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  • Articles  (20,986)
  • Polymer and Materials Science  (20,269)
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  • Articles  (20,986)
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  • 1
    Electronic Resource
    Electronic Resource
    Surface chemical sensitivity of polyaniline doped with palladium or platinum compounds This paper is part of the special issue: Part II of the Proceedings of the International Conference, Towards Molecular Electronics, TME'97, 23-28 June 1997,Śrem, Poland, edited by Prof. Jerzy J. Langer (Adv. Mater. Opt. Electron. 8, 213-284 (1998)) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 295-302 
    Details
    ISSN: 1057-9257
    Keywords: conductive polymers ; polyaniline ; palladium dopants ; platinum dopants ; catalytic hydrogenation ; active centres ; catalyst aging ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The chemical and structural surface-aging effects brought about by the presence of water in emeraldine base (EB) polyaniline (PANI) doped with Pd or Pt protonic acids were studied. IR spectroscopy, XRD, XPS and heterogeneous catalytic hydrogenation (alkyne→alkene→alkane) were applied to characterise the PANI-Pd and PANI-Pt. Interpretation of the results gave the surface characteristics, structure, chemical catalytic activity and stability mainly of PANI-Pd specimens. The unique form of catalytically active centres therein was the surface complex [PdCl4]2- with Pd 3d5/2 BE=337·7 eV. The most promising among the PANI-Pd catalysts studied were those dried in a slow, long procedure (3 months, zeolite 5A). Copyright © 1998 John Wiley & Sons, Ltd.
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  • 2
    Electronic Resource
    Electronic Resource
    Remote plasma-enhanced CVD of silicon nitride films: effects of diluting nitrogen with argon. Part II: effect of nitrogen plasma parameters on layer characteristics (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 23-29 
    Details
    ISSN: 1057-9257
    Keywords: remote PECVD ; silane ; nitrogen ; silicon nitride ; argon dilution ; hydrogen content ; stoichiometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: In Part I we reported the results of an emission spectroscopic study of the plasma obtained in an SiH4-N2-Ar mixture. It was shown that argon in metastable electronic excited states provides a high concentration of atomic nitrogen. In this part we report the results of a study of the influence of argon dilution on the growth rate, composition and properties of silicon nitride films. The exact influence of nitrogen dilution with argon depends on the process parameters and on the method of coupling of the RF power, but it is found in general that a high concentration of atomic nitrogen leads to changes in the relative amounts of Si-Hj and N-Hi bonds and in the Si/N ratio of deposited films. In particular, it is shown that hydrogen incorporation can be reduced and improved stoichiometry can be obtained. © 1998 John Wiley & Sons, Ltd.
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular conductors and magnets: different strategies and achievements (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 61-76 
    Details
    ISSN: 1057-9257
    Keywords: magnetic molecular materials ; conducting molecular materials ; polyoxometalates ; TTF ; ET ; conducting polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The different approaches used by the authors for the synthesis of new molecular materials exhibiting simultaneously magnetic and conducting properties are presented here. The aim is to prepare materials where a magnetic and a conducting sublattice coexist and/or interact in order to obtain either coexistence of properties or coupling between them. The strategy described is a hybrid one that combines various types of inorganic metal complexes with planar organic π-electron donors of the TTF family or with organic matrices made of conducting polymers. There are four main combinations: (i) magnetic polyoxometalates with organic donors - this strategy has already produced more than 10 radical salts where a magnetic character coexists with a conducting or semiconducting one; (ii) small magnetic anions with organic donors - in this case one of the most promising results has been the synthesis of one of the very few known examples of magnetic molecular metals; (iii) ferro- and ferrimagnetic oxalate-bridged bimetallic layers with organic donors; (iv) magnetic polyoxometalates incorporated into electrodeposited films of conducting polymers. © 1998 John Wiley & Sons, Ltd.
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of dopant counter-anion on tribological properties of polypyrrole (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 87-91 
    Details
    ISSN: 1057-9257
    Keywords: friction coefficient ; wear coefficient ; tribology ; conducting polymers ; 2,6-naphthalenedisulphonate (2,6-NDS) ; 1,5-naphthalenedisulphonate (1,5-NDS) and 2-naphthalenesulphonate (NS) polypyrroles ; sliding test ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: It is known that, with careful control of conditions, polypyrrole films with counter-ions of toluene sulphonic acid sodium salt and methane phosphonic acid sodium salt can be produced with friction coefficients comparable with or even better than PTFE. Here we now report a systematic study of polypyrrole with various planar anions for tribological bearing applications. Thus naphthalene disulphonate-doped polypyrrole has a kind of laminar structure with very good adhesion to the surface. Polymer films were electrodeposited on glass lenses and tested in a friction apparatus for friction and wear measurements. The film orientation was measured by low-angle X-ray diffraction and the surface structure was evaluated by both AFM and SEM for different film thicknesses. The friction coefficient and wear rate of such bearings were measured under loads up to 5 N and at speeds up to 30 mm s-1 and were found to be 0·06 and 0·04 nm mm-1 respectively. © 1998 John Wiley & Sons, Ltd.
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  • 5
    Electronic Resource
    Electronic Resource
    Redox reactions on TCNQ-modified self-assembled monomolecular films (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 121-128 
    Details
    ISSN: 1057-9257
    Keywords: self-assembly ; charge transfer ; electron-conducting monolayers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Suitably modified mono- and bimolecular films, including bilayer lipid membranes (BLMs), offer exceptionally good opportunities for probing electric field effects on charge transfer and redox reactions in biosensor and molecular electronics research and development.This work presents the redox reactions of tetracyano-p-quinodimethane (TCNQ) molecules incorporated in a self-assembled octadecanethiol monolayer (SAM) on polycrystalline gold electrodes, depending upon the type of supporting electrolyte cations and their concentration. Our results show that TCNQ-modified Au-SAM electrodes exhibit selectivity versus alkali metal cations in aqueous supporting electrolyte (∽10 kJ mol-1 difference between K+ and Li+ and between Cs+ and K+). The slope of the ‘calibration curves’ for Li+ and K+ is about 59 mV per decade of concentration of the analyte. The explanation of this behaviour is based on the Donnan potential model; however, an ion-pairing effect can also be involved. Our preliminary results show also that the TCNQ molecules within the octadecanethiol monolayer may act as a molecular redox device. © 1998 John Wiley & Sons, Ltd.
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  • 6
    Electronic Resource
    Electronic Resource
    Stoichiometric deviations along an ingot of CuGaSe2 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 147-155 
    Details
    ISSN: 1057-9257
    Keywords: synthesization ; chalcopyrite ; CuGaSE2 single phase ; X-ray diffraction ; stoichiometric deviations ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The dependence of the structural parameters on compositional deviations of CuGaSe2 has been studied. These deviations have been induced along an ingot by a single fusion of the components at 1150 °C and subsequent slow cooling in a stationary ampoule in a vertical furnace. All along the sample a single chalcopyrite phase is present and a compositional gradient along the ingot was found by energy-dispersive analysis of X-rays (EDAX) measurements, the upper part being rich in Ga (series B) and the lower part in Cu (series A), with Cu/Ga ratios of 0·95 and 1·1 respectively. A hypothesis of the existence of two phases in the melt is proposed to explain these facts. The unit cell parameters, anion displacement and Cu and Ga occupation numbers in their sublattices were analysed by X-ray powder diffraction and Rietveld refinement methods. In series A the occupation numbers are near stoichiometry, while in series B a Cu defect appears. In both series, changes in unit cell parameter are related to changes in Cu content, suggesting the presence of a fraction of Cu ions either as interstitials or at Ga sites when Cu is in excess, or of Cu vacancies in its sublattice when there is a Cu deficiency. © 1998 John Wiley & Sons, Ltd.
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of a planar chiral waveguide structure by a modified ATR method (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 195-199 
    Details
    ISSN: 1057-9257
    Keywords: chiral waveguides ; preparation of modified ATR method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Chiral properties of planar waveguide structures with a core layer formed by a poly(methyl methacrylate) (PMMA) host matrix doped with chiral santonin were investigated by means of a modified attenuated total reflection (ATR) method. Distinct modification of the observed ATR spectra was revealed for right and left circularly polarised incident beams. From comparison of the experimental spectra with theoretical curves, the following specific rotation was obtained: [α]20633=11,200 deg cm2 g-1 (santonin/ PMMA mass ratio 2:1). The origin of the observed optical activity and its influence on the waveguide dispersion characteristics are briefly discussed. © 1998 John Wiley & Sons, Ltd.
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  • 8
    Electronic Resource
    Electronic Resource
    Preface (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 213-213 
    Details
    ISSN: 1057-9257
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: No abstract
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  • 9
    Electronic Resource
    Electronic Resource
    Some new synthetic low-dimensional semiconductors based on inorganic units (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 263-267 
    Details
    ISSN: 1057-9257
    Keywords: semiconductors ; low-dimensional systems ; crystal structure ; optical properties ; photoluminescence ; Raman spectra ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The structural, optical and related properties (i.e. photoluminescence and resonance Raman spectra) of some synthetic (i.e. unconventional) low-dimensional semiconductor systems such as K2Cd3S4, [CH3SC(NH2)=NH2]3PbI5 and [H3N(CH2)6NH3]BiI5 are reported. They are compared with the properties of the corresponding higher-dimensionality systems. A blue shift of the excitonic bands and an enhancement of their binding energy and intensity were observed by decreasing the dimensionality or the size of the materials active part. The results are similar to those obtained from conventional semiconductors by decreasing the dimensionality or the size and are attributed to quantum confinement of excitons. © 1998 John Wiley & Sons, Ltd.
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  • 10
    Electronic Resource
    Electronic Resource
    Nitrogen dioxide gas-sensing studies on dip-coated films of novel chromophoric siloxane copolymers employing azo derivatives as side-chains (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 309-316 
    Details
    ISSN: 1057-9257
    Keywords: optical gas sensing ; polysiloxane ; azobenzene ; NO2 ; molecular modelling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Siloxane copolymers having as side-chains azobenzene derivatives bearing different electron-withdrawing and donating substituents were deposited as thin films by dip coating, and their behaviour upon exposure to 100 pm NO2 was studied by UV/visible spectroscopy. Electron-donating substituents at the ortho positions on the aromatic rings in the azo unit have significant influence on the absorbance changes produced by exposure to NO2, and this is explained by modelling, which suggests that interaction between the electrophilic nitrogen atom in NO2 and the electron clouds of the azobenzene skeleton is responsible for the sensing process, rather than the formation of a Wheland intermediate or other product of chemical reaction. Especially effective substituents are methoxy groups in either aromatic ring ortho or the azo linkage, which also produce a significant increase in intensity of the long-wavelength n-π* transition. This moves the optical interrogation signal to a wavelength range of particular benefit for potential applications. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 11
    Electronic Resource
    Electronic Resource
    Influence of polyaniline on electrode materials (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 303-308 
    Details
    ISSN: 1057-9257
    Keywords: polyaniline ; emeraldine base ; carbon fluoride ; lithium cells ; aprotic solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Polyaniline (PANI) has been used for modification of the electrochemical behaviour of a carbon fluoride ((CFx)n) cathode in a lithium cell. PANI and (CFx)n powders were carefully mixed and the electrochemical properties and kinetic parameters of the composite (CFx)n-PANI cathode were evaluated by galvanostatic and potentiodynamic techniques. An increase in exchange current has been found for electrodes with addition of polyaniline in the form of emeraldine base (EB). During the reduction process of carbon fluoride using 1 M lithium perchlorate solution in organic solvent, the ternary intercalation compound CLixF is formed and then irreversibly decomposed into carbon and lithium fluoride. The insertion of lithium cations into the (CFx)n layered structure is diffusionally controlled, hence improvement in electronic properties of this fluoride material by the presence of conducting PANI chains and enhancement of discharge performance were found for 25% addition of PANI. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 12
    Electronic Resource
    Electronic Resource
    Demonstration of unimolecular electrical rectification in hexadecylquinolinium tricyanoquinodimethanide (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 229-245 
    Details
    ISSN: 1057-9257
    Keywords: unimolecular rectifier ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Asymmetries in the macroscopic and the nanoscopic DC electrical conductivity through Langmuir-Blodgett multilayers and monolayers of γ-(n-hexadecyl)quinolinium tricyanoquinodimethanide (HDQ-3CNQ, 1) are due to a transition from the ground-state zwitterion to a probably neutral excited-state conformer, thus confirming without a shadow of a doubt the rectification of electrical current by a single molecule. © 1998 John Wiley & Sons, Ltd.
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  • 13
    Electronic Resource
    Electronic Resource
    Theory of organic field effect transistors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 285-294 
    Details
    ISSN: 1057-9257
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Field effect transistors with an organic material as active layer are at present essentially used to determine the mobilities in these materials. Until now, in analysing the measured current characteristics, only the simplest (Shockley) model has been used which accounts neither for this type of thin film transistor (TFT), which operates in depletion and accumulation, nor for the nature of the carriers. Starting from two-dimensional simulations for the analogous silicon TFT, we have developed an analytical model for the TFT that accounts for several peculiarities of the current characteristics of this type of transistor. In addition, a first modification has been developed which describes the situation when the charged states are polarons and bipolarons, as is the case in organic materials. Applications to published experimental current characteristics show that a general reanalysis is needed. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 14
    Electronic Resource
    Electronic Resource
    Electrically conducting and fluorising self-assembled monomolecular layers (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 31-37 
    Details
    ISSN: 1057-9257
    Keywords: self-assembled monomolecular layers ; chemical modification ; ATR/FTIR' electrical conductivity ; fluorescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Self-assembled monomolecular layers have been formed on a glass substrate with 3-aminopropyltriethoxysilane. The amino groups were chemically modified with either salicylaldehyde or 4-formylpyridine, then a TCNQ-pyridine CT complex was formed on a limited area of the surface, making a molecular conductive channel. This area is electrically conducting and we have observed it with the aid of SEM and direct measurements. ATR/FTIR and fluorescence spectroscopy were also used to monitor the monomolecular layer formation and modification processes. © 1998 John Wiley & Sons, Ltd.
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  • 15
    Electronic Resource
    Electronic Resource
    Electronic structure, insulator-metal transition and superconductivity in κ-ET2X salts (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 53-60 
    Details
    ISSN: 1057-9257
    Keywords: organic conductors ; electron correlations ; dielectric-metal transition ; superconductivity ; Fermi surface ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The electronic structure and superconductivity of layered organic materials based on the bis(ethylenedithio)tetrathiafulvalene molecule (BEDT-TTF, hereafter ET) with essential intra-ET correlations of electrons are analysed. Taking into account the Fermi surface topology, the superconducting electronic density of states (DOS) is calculated for a realistic model of κ-ET2X salts. A d-symmetry of the superconducting order parameter is obtained and a relation is found between its nodes on the Fermi surface and the superconducting phase characteristics. The results are in agreement with the measured non-activated temperature dependences of the superconducting specific heat and NMR relaxation rate of central 13C atoms in ET. © 1998 John Wiley & Sons, Ltd.
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  • 16
    Electronic Resource
    Electronic Resource
    Low-pressure-induced conformational transition in doped polypyrrole: optical and IR spectra (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 81-85 
    Details
    ISSN: 1057-9257
    Keywords: conducting polymers ; polypyrrole ; optical absorption ; pressure ; piezochromism ; conformation ; infrared spectra ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: A pressure dependence of the optical absorption spectra of BF-4-doped polypyrrole has been observed at pressures below atmospheric pressure. The two absorption bands at photon energies of 1·2 and 3·0 eV depend on the pressure: a decrease in the high-energy absorption is accompanied by an increase in the low-energy absorption and its shift towards lower energies. The Fourier transformation infrared reflection spectra also depend on the pressure in this region of pressures. The results are interpreted as a pressure-induced conformational transition of the polypyrrole chain. © 1998 John Wiley & Sons, Ltd.
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  • 17
    Electronic Resource
    Electronic Resource
    Electrosynthetic immobilisation of proteins for bioanalysis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 101-105 
    Details
    ISSN: 1057-9257
    Keywords: biosensor ; protein immobilisation ; protein modification ; electrochemistry ; nitrotyrosine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Use of electrosynthetic methodology allows the production of hen egg-white lysozyme (HEWL) either mononitrated at tyrosine 23 or bisnitrated at tyrosines 20 and 23, but never nitrated at tyrosine 53. This is a different sequence from that obtained by the chemical nitrating agent tetranitromethane, and when reduced by dithionite, the selectively modified enzyme can be anchored at pH 5 via the unique aromatic amino group to magnetic beads or other suitable matrices. HEWL so immobilised loses less than 10% of cell-wall lytic activity compared with the approximately 50% loss of activity when immobilised by conventional methodology at pH 9 via essentially random reaction at lysine residues and other functionalities which are nucleophilic at this pH. This result offers promise as a general method for selective protein immobilisation in biosensors and similar applications. © 1998 John Wiley & Sons, Ltd.
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  • 18
    Electronic Resource
    Electronic Resource
    Conference Report: Molecular Electronics-Science and Technology. 14-18 December 1997, Humacao, Puerto Rico (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 157-160 
    Details
    ISSN: 1057-9257
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 19
    Electronic Resource
    Electronic Resource
    Optical assessment of a fouling-resistant surface (PHEMA/ benzalkonium chloride) after exposure to a marine environment (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 187-193 
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    ISSN: 1057-9257
    Keywords: antifouling ; biofouling ; hydrogel ; benzalkonium chloride ; ultraviolet-visible spectroscopy ; underwater optics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: A hydrogel based on poly(2-hydroxyethyl methacrylate) (PHEMA) containing benzalkonium chloride (BAK) can be used as an environmentally acceptable, fouling-resistant material in the marine environment. The loaded hydrogel system is transparent and has the potential to be used in the protection of optical ports in underwater instruments. Ultraviolet-visible (UV-vis) spectroscopy was used to study the optical properties of the material after a marine exposure period. The optical transmittance of PHEMA/ BAK was higher for 10 weeks than that detected for poly(methyl methacrylate) (PMMA), a material currently used in commercial instruments, which confirmed the superior fouling resistance of the PHEMA/ BAK combination. The UV-vis spectroscopic method was quick, relatively cheap and accurate enough to allow the effects of the development of marine fouling on transparent surfaces for use in marine underwater optical applications to be monitored. © 1998 John Wiley & Sons, Ltd.
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  • 20
    Electronic Resource
    Electronic Resource
    Photoluminescence measurements of GaAs grown by liquid phase epitaxy from Ga-Bi solution (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 9-12 
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    ISSN: 1057-9257
    Keywords: LPE growth ; Ga-Bi solution ; ‘purification effect’ ; photoluminescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Thick, intentionally undoped GaAs epitaxial layers grown by LPE from Ga-Bi solution with different contents of Bi in liquid solvent (from 0 to 82 at.%Bi) were studied by photoluminescence (PL) at temperature &helvbi;T&helvbd;=2 K. The dependence of the photoluminescence spectrum on the content of Bi in solution was analysed. © 1998 John Wiley & Sons, Ltd.
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  • 21
    Electronic Resource
    Electronic Resource
    A robust gel-bilayer channel biosensor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 47-52 
    Details
    ISSN: 1057-9257
    Keywords: ligand gated ; channel protein ; biomembrane ; biosensor ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We demonstrate a novel protective configuration for a gated channel biosensor. The bilayer membrane containing the channel proteins is formed by a simple self-assembly technique ensuring continuous coverage of the interface between two slabs of agarose gel by a biomimetic lamella in a fluid state. The gel protects both membrane surfaces from mechanical shock and contact with low-energy media while allowing diffusion of biomolecules up to 10 MDa in weight. The technique has been demonstrated using both dioleoyl-phosphatidylcholine (DOPC) and a phosphatidylcholine lipid cross-linked with a short polysiloxane chain (PSPC). The conductance per unit area of the channel-free membrane produced by this method was less than 25 S m-2 for DOPC and 2 S m-2 for PSPC, and the bilayer nature of the barrier in both cases has been demonstrated by measurement of the capacitance. The applicability to sensors has been confirmed using gramicidin-D, a 1·1 kDa unilamellar lipid bilayer pore former, and partially confirmed using valinomycin, a selective ion transporter. On incorporation of gramicidin the membrane conductance increased by over an order of magnitude. © 1998 John Wiley & Sons, Ltd.
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  • 22
    Electronic Resource
    Electronic Resource
    [TTF]2[Fe(tdas)2]: a molecular conductor containing magnetic counter-ions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 93-96 
    Details
    ISSN: 1057-9257
    Keywords: ithiolene ; tetrathiafulvalene ; molecular conductor ; molecular magnetism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The salt [TTF]2[Fe(tdas)2] has been prepared by electocrystallisation and its conductivity and magnetic properties are reported. The X-ray structure has been determined. © 1998 John Wiley & Sons, Ltd.
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    Preface (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 45-45 
    Details
    ISSN: 1057-9257
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: No Abstract
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    Optimisation of the electrochemical bath for growing device-quality CuInSe2 thin films (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 1-8 
    Details
    ISSN: 1057-9257
    Keywords: electrodeposition ; copper-indium-selenide ; thin films ; layer-by-layer deposition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The electrochemical bath used for growing device-quality CIS (CuInSe2) thin films by co-deposition as well as layer-by-layer (LBL) deposition was characterised and optimised with respect to the film properties. The bath composition was varied by changing the Cu, In and Se ion concentrations in specific ratios in both co-deposition and LBL deposition. The film properties were analysed using techniques such as SEM (scanning electron microscopy), EPMA (electron probe microanalysis), AES (Auger electron spectroscopy) and XRD (X-ray diffraction). The structural, morphological and compositional properties of the films were characterised and their variation is attributed to the bath composition and growth conditions. © 1998 John Wiley & Sons, Ltd.
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    Remote plasma-enhanced CVD of silicon nitride films: effects of diluting nitrogen with argon. Part I: effect on nitrogen plasma parameters studied by emission spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 13-22 
    Details
    ISSN: 1057-9257
    Keywords: remote PECVD ; silane ; nitrogen ; silicon nitride ; argon dilution ; emission spectroscopy ; metastable states ; atomic nitrogen ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: In a series of two papers we describe the effect of argon dilution of the nitrogen passed through the RF discharge region on the plasma composition, growth rate and some characteristics of silicon nitride films deposited by remove PECVD. In this part we report the results of an emission spectroscopic study of the plasma obtained in an SiH4-N2-Ar mixture. It is shown that argon in metastable electronic excited states plays an important role during the RPECVD of silicon nitride films by providing a high concentration of atomic nitrogen which is necessary for the promotion of film growth. In Part II the influence of argon dilution on the growth rate, composition and some properties of silicon nitride films deposited by capacitively and inductively coupled remote PECVD is discussed. © 1998 John Wiley & Sons, Ltd.
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    Low-pressure-induced conformational transition in doped polypyrrole: electrical conductivity (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 77-80 
    Details
    ISSN: 1057-9257
    Keywords: conducting polymers ; polypyrrole ; electrical conductivity ; pressure ; conformation ; glass transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We describe the observation of a pressure-induced variation in the electrical conductivity of BF-4-doped polypyrrole at pressures below atmospheric pressure. We also show that there are anomalies in the temperature dependence of the electrical conductivity in cyclic measurements at temperatures of 240 and 310 K. The pressure effect is interpreted as a pressure-induced order-disorder conformational transition. The anomalies in the temperature dependence are attributed to the glass transition and melting of the polymer. © 1998 John Wiley & Sons, Ltd.
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    Melting of conducting organic composites based on TCNQ and methyl-TCNQ salts studies by IR spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 97-99 
    Details
    ISSN: 1057-9257
    Keywords: TCNQ salts ; IR spectra ; melting ; charge transfer, electron-phonon coupling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The infrared spectra (400-7000 cm-1) of three composites based on salts of tetracyano-p-quinodimethane (TCNQ) and methyl-TCNQ with N-alkyl-isoquinolinium cations are measured as a function of temperature (up to about 450 K). The influence of composite melting on the charge transfer and vibrational bands is studied. It is found that melting causes an irreversible transition into a new phase. © 1998 John Wiley & Sons, Ltd.
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    Conformational properties of quasi-particles in poly(p-phenylene vinylene) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 111-119 
    Details
    ISSN: 1057-9257
    Keywords: PPV ; conjugated polymers ; quasi-particles ; ab initio calculation ; infrared spectra ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We investigate the quasi-particle conformational defects (excitons, polarons and bipolarons) in phenylene vinylene oligomers (PVOs) consisting of up to 12 repeat units. The conformations are determined by minimisation of the total Hartree-Fock energy calculated at 3-21G level. The Hartree-Fock calculations of the excited states are followed by the CI-Singles calculation. The bond length alternation along the oligomer chain is discussed. On the basis of these results the vibrational transitions are calculated. To correct the basis set truncation error, the vibrational frequencies are multiplied by a uniform scaling factor. The types of vibrations are assigned. The theoretical spectra are in good agreement with the experimental infrared vibrational spectrum of poly(p-phenylene vinylene) (PPV). © 1998 John Wiley & Sons, Ltd.
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    Microstructural characterisation of nanocrystalline GaN prepared by detonations of gallium azides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 135-146 
    Details
    ISSN: 1057-9257
    Keywords: gallium nitride ; nanocrystallites ; detonation ; gallium azide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R3N)Ga(N3)3 (R=CH3, C2H5, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m2 · g-1. © 1998 John Wiley & Sons, Ltd.
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    Determination of the electroaffinity and potential barrier heights at polymer/ metal interfaces of poly(4,7-benzothiophene vinylene) (PBTV) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 181-186 
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    ISSN: 1057-9257
    Keywords: poly(4,7-benzothiophene vinylene) ; polymer interfaces ; conjugated polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: In this paper we determine the LUMO level position of poly(4,7-benzothiophene vinylene) (PBTV), a heterocyclic poly(phenylene vinylene) (PPV) analogue, using tunnelling current measurements. We compare the energy level positions with those measured for PPV and determine their shifts. The experimental results are compared with theoretical predictions and good agreement is observed. © 1998 John Wiley & Sons, Ltd.
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    Peculiarities of radiative recombination in amorphous molecular semiconductors doped with polymethine dye (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 201-209 
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    ISSN: 1057-9257
    Keywords: amorphous molecular semiconductors ; electron-hole pairs ; excitons ; photoconductivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Processes of charge carrier photogeneration and recombination are investigated in films of poly-N-epoxypropylcarbazole doped with polymethine dye. Films with blocking contacts were illuminated with light from either the region of dye absorption or beyond this region. The kinetics of accumulation and relaxation of electron-hole pairs with lifetimes greater than tens or hundreds of seconds was studied. It is presumed that the reason for the growth of recombination luminescence intensity in an external electric field is connected with the increase in efficiency of radiative recombination stimulated by electrons captured from photogenerated excitons. © 1998 John Wiley & Sons, Ltd.
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    Molecular design and properties of side chain liquid crystal polymers for applications in optoelectronics (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 247-262 
    Details
    ISSN: 1057-9257
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The synthesis of a number of side chain liquid crystalline polymers for quadratic non-linear optical (NLO) applications is reported. The active chromophore is a charge transfer (CT) biphenyl derivative which possesses mesogenic properties itself. The liquid crystalline behaviour of these polymers was established by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. The active chromophores were oriented by the standard corona poling technique and the degree of axial ordering was determined as a function of poling conditions by linear optical absorption. Growth of the second-harmonic generation (SHG) signal was used to probe the induction of polar order. These experiments clearly indicated that liquid crystallinity results in an enhancement of the polar order over that of isotropic materials. The second-order NLO susceptibility tensor components d31 and d33 were measured by the SHG technique. The ratio d33/ d31 was found to be much larger than 3, in agreement with molecular statistical models. Values of d33 up to 30-35 pm V-1 were obtained at 1064 nm fundamental wavelength. These values are essentially not resonance-enhanced, since the chromophore absorption occurs below 350 nm. © 1998 John Wiley & Sons, Ltd.
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    Thin films of novel polysiloxane copolymers substituted with stilbene and biphenylene side-chains: response to nitrogen dioxide (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 317-324 
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    ISSN: 1057-9257
    Keywords: gas sensing ; nitrogen dioxide ; stilbene ; biphenyl ; UV-visible spectroscopy ; thin films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Thin films of a selection of stilbene and biphenyl side-chain substituted liquid crystal polymers based on polysiloxanes were deposited using an automated dip-coating technique and exposed to either 100 ppm NO2 gas and/or concentrated nitric acid vapour, the consequent effect being monitored by changes in the UV-visible spectra of the material. No effective response to NO2 was observed from the biphenylene analogue, but the stilbene derivatives showed spectral changes to suggest that an interaction occurs between the vapour and the bridge position of the stilbene side-chain. The stilbenes also show a marked pre-conditioning phenomenon upon exposure to nitric acid vapour prior to exposure to nitrogen dioxide. This procedure gives a material that has a more reversible response on exposure to NO2 gas than an anagolous film that has not been pre-treated. Copyright © 1998 John Wiley & Sons, Ltd.
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    Microstructuring of As40S60 wafers exposed to soft X-raysSome of the results were presented at the 2nd International Conference on Photo-Excited Processes and Applications  -  ICPEPA '95, Jerusalem, Israel (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 129-133 
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    ISSN: 1057-9257
    Keywords: As-S wafers ; X-ray exposure ; microstructuring ; bulk optic element ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The possibilities of ‘resistless’ microstructuring of As36·1S63·9 wafers by soft X-ray irradiation and wet alkaline etching have been investigated. Scanning electron microscopy is used to study the influence of the exposure and processing parameters on the depth and acuity of the patterned structures. Structures 1 μm wide are obtained by irradiation with an energy flux of 2000 mJ cm-2, followed by etching in a solution of pH 10·8 at a temperature of 23°C for a processing time of 18 min. It is established that by X-ray irradiation and suitable processing of As36·1S63·9 wafers, microstructures of a depth up to 0·65 μm could be patterned. The structured wafers could be used as diffraction elements for IR optics. © 1998 John Wiley & Sons, Ltd.
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    Information-processing capabilities of chemical reaction-diffusion systems. 1. Belousov-Zhabotinsky media in hydrogel matrices and on solid supports (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 163-171 
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    ISSN: 1057-9257
    Keywords: chemical-based computing ; reaction-diffusion systems ; polymer materials for chemical computing ; Belousov-Zhabotinsky media ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Promising potentialities are opened up by the use of polymer materials for the elaboration of information-processing devices based on reaction-diffusion media. In this work, features of image processing by Belousov-Zhabotinsky media formed on the basis of hydrogel matrices and using catalyst immobilisation on the surface of solid supports have been investigated. Such active media structures have been found to improve significantly the quality of images in the course of their processing by the media. The spatial resolution of the media increases considerably in going from liquid Belousov-Zhabotinsky media and media functioning in polymer matrices to media based on catalyst immobilisation on the surface of solid supports. © 1998 John Wiley & Sons, Ltd.
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    Optical absorption behaviour of metal/semiconductor hybrid nanoparticle composites (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 173-180 
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    ISSN: 1057-9257
    Keywords: coated hybrid particles ; nanoparticle composites ; surface plasmon resonance ; optical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Semiconductor/metal hybrid nanoparticle composites have been prepared in a glass host by a modified melt/quench process and examined with respect to their optical properties. The coated hybrid nanoparticles exhibit surface plasmon resonance absorption spectra which are red-shifted compared with that of a dispersion of homogeneous Ag nanoparticles in the same host. The position of the plasmon resonance was a sensitive function of the heat treatment schedule. A theoretical model based on effective medium theory for the coated hybrid particles was used to describe the shift of the plasmon position in the optical spectra as a function of the coating thickness. The calculated absorption spectra of the coated hybrid particles agree well with the experimental results. © 1998 John Wiley & Sons, Ltd.
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    Optical spectra of C60 and C70 complexes: their similarities and differences (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 215-228 
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    ISSN: 1057-9257
    Keywords: fullerene ; fullerides ; charge transfer complexes ; spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Some possible uses of vibrational and electronic spectroscopies in characterising the basic interactions in C60 and C70 complexes are pointed out. We report on the wealth of infrared spectra of (usually) single crystals of C60 and C70 clathrates and complexes with organic donors. The changes in the spectral parameters of the complexes in comparison with those of the neutral fullerene molecules are attributed to redistribution of the charge on the spherical C60 or elongated C70 molecules in their compounds. Some general considerations on the origin of the IR, NIR, VIS and UV spectral variations are also given. © 1998 John Wiley & Sons, Ltd.
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    Towards the application of charge transfer salts and conducting polymer wires to electronic devices and sensors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 269-276 
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    ISSN: 1057-9257
    Keywords: organic charge transfer salts ; conducting polymers ; electronic properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We are exploring the electronic properties of novel materials such as conducting polymer-coated polyester fibres and charge transfer complexes configured in resistive, gated (FET) and diode configurations. In this paper we will consider several areas where we are attempting to make sensors and/ or primitive devices from molecular materials. Our most successful result so far is the temperature-dependent resistivity of polypyrrole-coated polyester fibres. Here we find that the conductivity is thermally activated and produces a reliable, highly sensitive indicator of temperature in a cryogenic environment. Using parallel configurations of fibres, sensors with different limiting resistances can be fabricated. We have also placed insulated electrical gates on single crystals of various metallic and insulating charge transfer salts and have attempted to alter the charge transfer character by the application of high electric fields. With polymethylmethacrylate (PMMA) insulating layers, gate voltages up to 150 V have been acquired with no leakage or heating. Similar measurements on diode devices fabricated from charge transfer complexes with different electronic structures are also in progress, and our preliminary results will be presented. Prospects and plans for developing these materials into viable sensors and devices are discussed. © 1998 John Wiley & Sons, Ltd.
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    Charge transfer complexes involving calix[4]resorcinarenes: potential candidates for non-linear optics (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 277-284 
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    ISSN: 1057-9257
    Keywords: calix[4]resorcinarenes ; charge transfer (CT) complexes ; tetracyanoquinodimethane (TCNQ) ; tetracyanoethylene (TCNE) ; non-linear optical (NLO) materials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Lipophilic calix[4]resorcinarenes - condensation products of resorcinol and lauryl aldehyde comprising four resorcinol units - form electron donor-acceptor complexes with electron acceptors tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) in organic solvents. Their formation was confirmed by EPR and UV-vis spectroscopy, except for compounds c1 and c3 which did not form charge transfer (CT) complexes with TCNE. Titration experiments involving calixarenes and electron acceptors indicated the presence of species of different stoichiometries. Complexes with ligands c1-c4 were characterised spectroscopically. CT bands appeared in most cases. © 1998 John Wiley & Sons, Ltd.
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    Reactivity ratios and sequence determination of acrylonitrile/hexyl methacrylate copolymers by one and two dimensional NMR spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2005-2015 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acrylonitrile/hexyl methacrylate copolymers of different monomer composition were prepared by photopolymerization using uranyl ions as photosensitizer. The copolymer composition data were used to calculate the comonomer reactivity ratios according to the Kelen Tüdős (KT) and the error-in-variables model (EVM) method. The reactivity ratios obtained from the EVM method are rA = 0.14 ± 0.03 and rH = 1.32 ± 0.17. The microstructure was obtained in terms of distribution of A and H centred triad sequences from 13C{1H} NMR spectra of the copolymers. The copolymerization mechanism was determined by using Cheng's methodology. It was found that the Markov second order model gave a good fit to the experimental data. The complex and overlapping proton and carbon signals of A/H copolymers were assigned to various compositional and configurational sequences with the help of inverse HETCOR experiments.
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    The effect of temperature on the polymerization of propene with dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. Modeling of kinetics (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1989-2004 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Propene polymerizations were performed using the two ansa-zirconocene catalyst systems dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. The polymerization rate was observed by continuously monitoring the monomer consumption. Reaction rate profiles were obtained in the temperature range from 40°C to 130°C at pressures between 1 and 2.5 bar and catalyst concentrations from 4.6 · 10-6 M to 4.2 · 10-5 M. Isotacticity, as measured by NMR, melting point and molecular weight decreases markedly at higher temperatures. Small amounts of 1,3-inserted monomer (〈1 mol-%) was observed at polymerization temperatures above 80°C. No 2,1-inserted monomer was detected. A kinetic model was developed that describes the polymerization rate for Me2Si(Ind)2ZrCl2 as the catalyst over the entire observed temperature range, and the polymerization rate for Me2Si(2-Me-Ind)2ZrCl2 in a limited temperature range. The model includes an activation reaction, latent sites that may revert to active sites and a permanent deactivation that is second order with respect to the active sites. The activation energy for the propagation reaction was found to be 37 kJ/mol for Me2Si(Ind)2ZrCl2 and 32 kJ/mol for Me2Si(2-Me-Ind)2ZrCl2/MAO. Several kinetic models are compared and discussed.
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    Preparation of poly(lactic acid)-grafted amylose through the trimethylsilyl protection method and its biodegradation (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2017-2022 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biodegradable poly(lactic acid)-grafted amylose was synthesized using a trimethylsilyl (TMS) protection method. Tetrahydrofuran soluble, mostly trimethylsilyl protected amylose was prepared and reacted with potassium tert-butoxide to give the corresponding alkoxide. Poly(lactic acid)-grafted amyloses were obtained by ring-opening anionic polymerization of lactide using the polymeric alkoxides as initiators and subsequent removal of the TMS groups. The obtained graft copolymers show biodegradability and a microphase-separated morphology.
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    Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2051-2061 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the mixed surfactants sodium dodecyl sulfate (SDS) and nonylphenol polyethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) on the styrene (ST) miniemulsion polymerization in the presence of dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) was investigated. Both Ostwald ripening and creaming could not be neglected for the miniemulsions stabilized by SDS/NP-40 in combination with DMA upon aging at 35°C, whereas no appreciable Ostwald ripening and creaming were detected for the SMA containing miniemulsions. For both the DMA and SMA containing polymerizations at 80°C, the rate of polymerization (Rp) decreases with increasing NP-40 concentration ([NP-40]). Incorporation of a small quantity of the extremely water-insoluble blue dye into the reaction system was applied to probe the particle nucleation loci. For the DMA containing polymerizations with [NP-40] = 0, 1.25, and 2.50 mM and the SMA polymerization with [NP-40] = 0 mM, homogeneous or micellar nucleation can not be ignored. On the other hand, the more hydrophobic SMA in combination with SDS/NP-40 effectively retards the particle nucleation occurring in the aqueous or micellar phase.
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    Crystallization kinetics and melting behavior of poly(butylene adipate), poly(butylene isophthalate) and their copolymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2063-2070 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior and the isothermal crystallization kinetics of poly(butylene adipate), poly(butylene isophthalate) and their random copolymers were investigated by means of differential scanning calorimetry. Multiple endotherms, commonly observed on the melting polyesters, were found to be influenced by crystallization temperature and composition. By applying the Hoffman-Weeks method to the isothermally crystallized samples, the equilibrium melting temperatures of the homopolymers were obtained. From calorimetric results on samples with different degree of crystallinity, the equilibrium melting enthalpy of poly(butylene isophthalate) was calculated and the presence of a crystal-amorphous interphase in copolymers was evidenced. Isothermal melt crystallization kinetics was analyzed according to the Avrami equation. As expected, the introduction of a comonomer was found to decrease the overall crystallization rate of the polymers. Values of Avrami exponent close to three were obtained for all the samples, independently of composition and crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. In the case of poly(butylene isophthalate), the dependence of the rate of crystallization on Tc shows a maximum at an undercooling of approximately 60°C.
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    Preparation, properties and biodegradation of stereoregular copolymers of (R,S)-3-butyrolactone and 4-butyrolactone (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2079-2085 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers obtained from the copolymerization of (R,S)-3-butyrolactone ((R,S)-3-BL) and 4-butyrolactone (4-BL) catalyzed by isobutylaluminoxane were compared in structure and properties to copolymers having the same types of repeating units produced by Alcaligenes eutrophus when grown with an appropriate substrate or substrate or substrate mixtures. Copolymers with 4-BL contents up to 33 mol-% were prepared and characterized by 1H NMR, 13C NMR, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The copolymers had a sequence distribution of 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units which were non-random in that very few, if any, sequences of more than two successive 4-HB units were present. The 3-HB units are believed to be separated into isotactic (R) and (S) blocks, but thermal analysis by DSC showed that both the glass transition temperatures and melting temperatures decreased in a regular manner with increasing contents of 4-HB units. Number average molecular weights of the copolymers (Mn) ranged from 7000 to 15000. Biodegradation tests with a bacterial hydrolase showed that the biodegradation rates increased with increasing contents of 4-HB units, as is the case for the equivalent bacterial copolymers.
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    Preparation of side-chain liquid-crystalline polymers via pyridylphenol hydrogen bonding (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2101-2105 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of side-chain liquid-crystalline polymers via pyridyl-phenol hydrogen bonding complexation was prepared by using non-liquid-crystalline precursors, such as poly[(4-vinylpyridine)-co-(butyl acrylate)] and 4-(4′-nitrophenylazo)phenol, 4-(4′-methoxyphenylazo)phenol or 4-(phenylazo)phenol. The association by hydrogen bonding was confirmed by means of FTIR. While the hydrogen bonds are weakened, and some dissociation occurs at the isotropization temperature, complete dissociation needs much higher temperature. The hydrogen bonds re-form as the complex is cooled to room temperature. The nematic liquid crystallinity of the polymer complexes was shown by means of wide-angle X-ray diffraction (WXRD) and polarized optical microscopy (POM). The different substitution groups of azophenol give isotropization temperatures of the polymer complexes in the following sequence: —NO2 〉 —H 〉 —OCH3.
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    Tailored rigid-flexible block copolymers, 4Part 3: cf. ref.3. Synthesis and properties of diblocks of poly(p-benzamide) and poly(m-benzamide) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2087-2094 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers were prepared by the condensation of rigid benzoyl-terminated poly(p-benzamide) and flexible anilino-terminated poly(m-benzamide) prepolymers. The use of two monomers of the AB type and of end-capped prepolymers resulted in the formation of diblock molecules uncontaminated by triblock or multiblock sequences. Moreover, selective extraction techniques in N,N-dimethylacetamide (DMAc) with varying amounts of LiCl resulted in the complete elimination of unreacted prepolymers, as evidenced from material balance and 1H NMR data. The above extraction technique also allowed a fractionation of the copolymers in terms of their rigid/flexible compositional distribution ratio. The molecular weight-intrinsic viscosity dependence of poly(m-benzamide) determined in a nonaggregating solvent using light scattering yielded a persistence length of 8 Å, suggesting a relatively large chain flexibility. A tailored copolymer with a fraction β of flexible residues = 0.70 was fractionated, determining the solubility, the viscosity, and the critical composition for mesophase formation in DMAc/LiCl and in 96% H2SO4 solutions. The results, in line with those previously reported for a related system, reveal that the addition of the flexible segment has a little effect on the critical concentration of poly(p-benzamide), whereas the biphasic gap is strongly reduced. Moreover, the solubility of the copolymer is substantially increased over that of the rigid homopolymer. The net result is an unexpected widening of the range of stability of the pure mesophase, with significant implications from both a fundamental and an applied standpoint.
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    Synthesis and characterization of a new polymer containing an electron accepting perfluoro group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2107-2112 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly{oxy-4,4′-octafluorobiphenylyleneoxy-alt-[1,4-phenylenevinylene(3-trimethylsilyl-1,4-phenylene)vinylene-1,4-phenylene]} (PFSi) was synthesized and characterized to investigate its thermal, optical, electrical and xerographic properties. An LED (light emitting device) using PFSi as the light emitting layer exhibits maximum emission for blue light, but a high turn-on voltage. The origin of the low device performance was examined by investigating the photoconducting behavior. PFSi shows a high photoconductivity in the presence of electron acceptors such as 5-nitroanthranilonitrile (5NAN), and the photoconductivity of PFSi is improved by introducing charge transport materials such as triphenylamine (TPA).
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    Synthesis and phase behavior of side-chain liquid crystalline polymers with pendant quinoline rings bearing either a polar or a non-polar end group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2095-2099 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Four methacrylate monomers, 2a-2d, containing a quinoline ring with a NO2 or a OCH3 group at the end of the mesogen were synthesized and polymerized. The copolymers with six methylene units as spacer, 3b-3d, showed a smectic phase induced by electron donor-acceptor interactions of the side groups. The homopolymer with eleven methylene units as spacer and methoxy end group, 3f, showed a smectic phase induced by the large length of the spacer. The copolymers with eleven methylene units, 3g-3i, showed a smectic phase induced by both the electron donor-acceptor interactions of the side groups and the large length of the spacer.
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    Molecular character of sharkskin phenomenon in metallocene linear low density polyethylenes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2113-2118 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of molecular weight on sharkskin dynamics is systematically studied using three metallocene-catalyzed linear low density polyethylenes (mLLDPE) of different molecular weights. A new experimental method is developed to enable in-situ characterization of the time scale τ on which sharkskin forms on the extrudate. This laser scattering technique directly measures the periodic variation of the refracted light of the rough sharkskin-like extrudate surface. It is found that τ increases with molecular weight as strongly as the overall molecular chain relaxation time, τ*, determined from oscillatory shear measurements. The observed molecular weight dependence provides additional support for the recently proposed interfacial stress growth/relaxation mechanism for sharkskin formation.
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    Synthesis and properties of poly(dimethyldiphenylsilylenemethylene) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2119-2127 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The novel polycarbosilane poly(dimethyldiphenylsilylenemethylene) (PDMDPSM) (2) was prepared by H2PtCl6-catalyzed ring-opening polymerization (ROP) of 1,1-dimethyl-3,3-diphenyl-1,3-disilacyclobutane (1). Polymerization in bulk at elevated temperature afforded high molecular weight PDMDPSM (Mw = 577000) with monomodal molecular weight distribution and regularly alternating SiR2/CH2 backbone structure. NMR spectroscopy revealed that a minor fraction of the monomer units is incorporated irregularly during polymerization in bulk, leading to structural units of the type —SiPh2—CH2—SiPh2— and —SiMe2—CH2—SiMe2—. The amount of regularly alternating dimethyl- and diphenylsilylenemethylene units increases when the polymerization is performed in solution at lower temperatures. PDMDPSM shows a glass transition temperature (Tg) at 50°C, which lies between the TgS of poly(methylphenylsilylenemethylene) (PMPSM) and poly(diphenylsilylenemethylene) (PDPSM), demonstrating the stiffening effect of the SiPh2 groups. Thermogravimetric analysis (TGA) evidenced nearly identical thermal stability of PDMDPSM and PMPSM.
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    Supramolecular structures of poly(p-phenylenes) with oxyethylene side chains and their mixtures with lithium salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2129-2140 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of poly(p-phenylenes) with linear and branched oxyethylene side chains was synthesized. Microphase separation in the solid state causes polymers with linear side chains to form supramolecular structures, which consist of main chain layers separated by an amorphous side chain matrix. If mixed with lithium salts such as lithium triflate (LiOTf) or lithium bis(trifluoromethanesulfone)imide (LiNTf), the polymers form solid solutions. The experimental data suggest that the layered structures undergo a one-dimensional swelling in the direction perpendicular to the main chain layers when blended with LiOTf and that this salt is only incorporated into the side chain matrix. The observed melting point depression in polymer-LiNTf mixtures is explained by the assumption that the salt species are incorporated both into the side chain and the main chain microphase.
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    Dielectric relaxation and relationships of local molecular mobility in linear and comb-like thermotropic polymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2147-2152 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric behavior of several thermotropic linear and comb-like polymers with flexible spacers and mesogenic fragments with different structure has been studied in a frequency range from 60 Hz to 1 MHz in the bulk state (below the glass transition temperature). Two regions of dipole relaxation caused by local mobility were detected. It was shown that the relaxation parameters of the first process virtually do not change with increasing spacer length and have similar values in polymers with different structure. In the case of the second process, in increase in spacer length considerably increases the mobility of kinetic elements.
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    Sequential reordering in condensation polymers, 5Parts 1-4: refs.4-7. Preparation and characterization of copolymers via transesterification of a polycaprolactonepoly(2,2-dimethyltrimethylene carbonate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2153-2164 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A blend of polycaprolactone (PCL) and poly(2,2-dimethyltrimethylene carbonate) (PDTC) containing catalytic amounts of dibutyltin dimethoxide was prepared from solution. The blend was then subjected to melt-mixing at 200°C and samples were taken after different times. According to thermal analysis data, with the increase of reaction time a gradual loss of the crystallizability of the blend components is observed, and after 70 min at 200°C the system becomes completely amorphous. 13C NMR data suggest that the loss of crystallizability of the blend is accompanied by an abrupt decrease in PCL and PDTC sequence lengths reaching after 70 min at 200°C an average length of about two repeating units each. These effects are explained by transesterification reactions between the lactone and carbonate units.
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    Ge- and sn-containing poly(p-xylylene): synthesis, structure and thermal behavior (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2179-2184 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Block copolymers of unsubstituted poly(p-xylylene)(PPX) and Ge- or Sn-organic bridged PPX (GePPX and SnPPX) were prepared by pyrolysis of specially synthesized organometallic p-cyclophane precursors followed by deposition and polymerization of the thus produced p-xylylene monomers. The copolymer structure and thermal behavior were investigated depending on deposition temperature (10 and -196°C). The copolymer PPX-GePPX obtained from solid monomers deposited at -196°C (2a) consists of long quasi-independent PPX and GePPX blocks and has paracrystalline structure. Thermal treatment of 2a near 160°C yields crystalline regions of PPX along with paracrystalline aggregates of GePPX. Pyrolysis of this system near 300°C in an inert atmosphere results in the formation of Ge crystals in PPX matrix. In contrast, the copolymer PPX-GePPX produced by simultaneous deposition and polymerization at 10°C (2a′) contains shorter blocks of PPX and GePPX than the copolymer deposited at -196°C. Copolymer 2a′ turns to the amorphous state during thermal treatment, and its pyrolysis does not lead to Ge-crystal formation; hence the supramolecular structure of the polymer plays an important role in inorganic phase formation. The copolymer PPX-SnPPX (2b) is formed only at a deposition temperature of -196°C; deposition at 10°C yields oligomeric resins. The structure of 2b is nearly the same as that of 2a; pyrolysis of 2b in air results in SnO2-crystal formation in a PPX matrix.
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    PVC modification with pyridine groups. Synthesis, characterization and transformation to ionomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2199-2204 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification of PVC with 4-mercaptopyridine is described. The content of pyridine groups in the products is measured by NMR and IR spectroscopy. The degree of modification depends on the reaction conditions, and values of up to 70% are achieved without degradation or other appreciable side reactions. The tertiary amino groups in the polymer can be alkylated with iodides of varying chain length to form quantitatively quaternary pyridinium salt groups, leading to PVC ionomers and polyelectrolytes.
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    Free radical polymerization of a sugar residue-carrying styryl monomer with a lipophilic alkoxyamine initiator: synthesis of a well-defined novel glycolipid (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2193-2197 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Controlled free radical polymerization of N-p-vinylbenzyl-2,3,5,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-D-gluconamide (Ac-VLA) was achieved by the nitroxide-mediated free radical polymerization with a lipophilic alkoxyamine “initiator” with a dioctadecyl group in 1,2-dichloroethane at 90°C. The polymerization proceeds in a “living” fashion, providing Ac-VLA polymers with low polydispersity. The hydrolysis of the polymers results in well-defined glycopolymer-carrying amphiphiles, viz., artificial “glycolipids”.
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    Living ring-opening isomerization polymerization of 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole with sulfonate initiators (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2237-2246 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic ring-opening isomerization polymerization of a bicyclic pseudourea, 2,3,5,6-tetra-hydroimidazo[2,1-b][1,3]oxazole (1), was examined. The polymerization of 1 with methyl trifluoromethane-sulfonate or p-toluenesulfonate proceeds even at -40°C and gives poly(1,3-oxazolidin-2-one-1,3-diylethylene) (2) in high yield. Postpolymerization experiments revealed that the present polymerization proceeds in a “living” fashion. The mechanism of the polymerization was determined from in situ 1H NMR measurements as well as kinetic analysis, which proved that the polymerization proceeds via ionic propagating species, although the apparent propagating species in the polymerization with methyl p-toluenesulfonate is covalent.
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    Radiation-induced radical formation and crosslinking in aqueous solutions of N-isopropylacrylamide (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2229-2235 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To investigate chain-initiating and crosslinking mechanisms, radical formation in dilute aqueous solutions of N-isopropylacrylamide (NIPAAm) and poly-NIPAAM was studied using electron pulse radiolysis with optical detection at room temperature. Several transients of NIPAAm generated by reactions with electrons, hydroxyl radicals and hydrogen atoms were observed. Electron attachment to the carboxyl group (ke = 9.0 x 109 dm3 · mol-1 · s-1) forms the radical anion, which undergoes fast and reversible protonation (pKa = 7.8) at the carboxyl oxygen. At pH 〉 pKa, slow and irreversible protonation of the electron adduct at the vinyl group leads to the α-carboxyalkyl radical CH3(.CH)CONHCH(CH3)2, which is also formed by addition of H atoms to NIPAAm (kH = 7.3 × 109 dm3 · mol-1 · s-1). Addition of OH radicals (kOH = 5.4 × 109 dm3 · mol-1 · s-1) forms CH2(OH)(.CH)CONHCH(CH3)2. Hydrogen abstraction was not observed in the case of NIPAAm monomer, but it was found for the reaction of OH radicals with thermally polymerized NIPAAm. Semi-empirical quantum chemical calculations support the assignment of the observed spectra to the radicals. A reaction mechanism for the formation of crosslinks is discussed.
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    A novel modification of poly(L-lysine) leading to a soluble cationic polymer with reduced toxicity and with potential as a transfection agent (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2565-2575 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chemical modification of poly(L-lysine) by hydrogen transfer addition of N,N-dimethylacrylamide to the primary amino groups results in new water soluble derivatives with reduced cell toxicity which maintain basic properties. Kinetic studies on the addition reaction were performed using model compounds, and a reliable kinetic model was obtained which proved to be valuable also in the case of poly(L-lysine). A peculiar feature of the addition reaction of poly(L-lysine) on N,N-dimethylacrylamide is that, starting from partially protonated poly(L-lysine), the reaction stops after that all the unprotonated units originally present have reacted. Toxicological studies on modified poly(L-lysine) in comparsion with parent poly(L-lysine) showed that the modifying reaction leads to a reduction in toxicity.
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    Synthesis, characterization and hydrolysis of poly[styrene-co-(6-methylene-1,4-oxathiepane-7-one)] and poly[styrene-co-(6-methylene-5-methyl-1,4-oxathiepane-7-one)] (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2577-2582 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Vinylic-type polymers bearing ester groups inside the polymer backbone have been synthesized by free radical copolymerization of styrene (St) and 6-methylene-1,4-oxathiepane-7-one (MOTPO) or 6-methylene-5-methyl-1,4-oxathiepane-7-one (MMOTPO). The addition-fragmentation ring-opening polymerization of both MOTPO and MMOTPO leads to the formation of ester linkages located inside the vinylic polymer backbone. A strong decrease of the molar mass of the copolymer has been observed when the copolymers were dissolved in a mixture of THF and water in the presence of sodium hydroxide. This decrease can be attributed to the hydrolysis of the ester linkages, as followed by size exclusion chromatography (SEC). The molar mass of the degraded polymer samples was correlated with the number of ester linkages in the backbone, showing that only a fraction of these ester groups have been hydrolyzed.
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    Unique morphologies found in freeze-dried poly(ethylene oxide) prepared from dilute solutions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2597-2600 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Freeze-dried particles of poly(ethylene oxide) (PEO) were prepared from sublimation of a 1 × 10-2 wt.-% solution of PEO in benzene in an ice-salt bath. After isothermal crystallization at 318.2 ± 0.1 K for 2 h, an unusual planar zigzag form of PEO was found. A variety of unique spherulite-like morphologies were also observed, and their formation is discussed on the basis of the interaction between solvent molecules and segment of the polymer chains.
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    Effect of filler on kinetics and energy of activation of phase separation in poly(methyl methacrylate)/poly(vinyl acetate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2609-2612 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of a filler on the rate and energy of activation of phase separation was studied for binary poly(methyl methacrylate)/poly(vinyl acetate) blends (system with LCST) using light scattering. It was found that the rate of phase separation of the filled blends at close quench depth ΔT = T-Ts is much lower as compared with the unfilled one at close quench depth. The activation energy for the filled blends is lower than that of unfilled blends. The drop of the rate of phase separation and of the activation energy in filled systems is explained by the formation of a border layer at the interface with solid where molecular packing is less dense and molecular mobility is restricted in comparison with unfilled polymer. Equal rates of phase separation or the equilibrium state may be achieved at higher quench depth for the filled blend.
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    Reduction of the cationic growing center of polyisobutylene by activated magnesium. Block copolymerization of isobutylene with tert-butyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2619-2623 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transformation of the tert-chlorine end group of poly(isobutylene) into a terminal Grignard group was studied with the motivation of producing a PIB macroanion. The reduction of the terminal tert-chlorine group was completed within 30 min at room temperature by using activated magnesium (Mg*) prepared by the reaction of MgCl2 with lithium naphthalenide. The efficiency of the transformation was 28%, which was determined by end-group analysis of the polymer obtained after quenching the reduction with methyl 2-phenylacetate in the presence of CeCl3. The terminal carbanion prepared by this method initiated the polymerization of tert-butyl methacrylate (TBMA) to give a block copolymer consisting of an anionically and a cationically polymerizable monomer.
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    The characterization of the interfacial reaction in polyamide 1010/poly(propylene)-graft-(glycidyl methacrylate) blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2631-2634 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Binary blends of polyamide 1010/poly(propylene) and polyamide 1010 (PA1010)/poly(propylene)-graft-(glycidyl methacrylate) (PP-g-GMA) were prepared. The epoxy groups in PP-g-GMA react with the amino end-groups in PA1010, thus a PA1010-graft-PP copolymer is formed and acts as a compatibilizer between PA1010 and PP-g-GMA. The reaction was confirmed by electron spectroscopy for chemical analysis (ESCA) and attenuated total reflection (ATR)-FTIR spectroscopic analysis, and also evaluated by the stability of the suspension obtained by dissolving the blends in formic acid and by the morphologies of the blends.
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    Structure-property relationships of core-shell type waterborne polyacrylate-polyurethane microemulsions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2635-2640 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Different cross-linking types of core-shell types waterborne polyacrylate-polyurethane (PAC-PU) microemulsions, in which polyurethane acts as the shell of the latex particles and a copolymer of acrylate monomers as the core, were synthesized. In the anionic polyurethane film. there is a certain degree of softhard phase mixing and different extents of short-range order of the hard segments. The introduction of a polyacrylate core increases the soft-hard phase separation in the polyurethane and breaks the short-range order of the hard segments in polyurethane to some extent. The hard segments in the shell and the core cause a widened tan δ peak. This peak shifts to higher frequencies as the core-shell ratio increases and also when a Type A or Type B cross-linking structures exist. The cross-linking structure, especially Type B, improves the soft-hard separation and the phase mixing of the core and the hard segments in the shell and at the same time breaks the short-range order in the hard segments. The cross-linking structure does not affect the thermogravimetric properties of the PAC-PU films.
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    An approach to hyperbranched polymers with a degree of branching of 100%Dedicated to the memory of Prof. Dr. Reimund Stadler (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2655-2664 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: General guidelines for the design of monomers for the synthesis of hyperbranched polymers without linear units are presented. The synthesis of one monomer fulfilling these requirements and the first results of the polymerization of this monomer are described. 4-(3-Maleimidopropoxy)-4′-methoxybenzaldehyde azine was used as a monomer of the AB2-type in a “criss-cross” cycloaddition with the maleimide group as A-function and the azine as two B-groups. Melt condensation of this monomer gave a polymer (Mn = 5700) which showed 1H and 13C NMR spectra corresponding well to the expected completely branched structure.
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    Swelling behavior of polyelectrolyte gels in the presence of salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2665-2670 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling behavior of weakly crosslinked polyelectrolyte gels based on sodium methacrylate (PMA) and diallyldimethylammonium chloride (DADMAC) in aqueous medium was studied in the presence of different types of salts (NaCl, arginine hydrochloride, cetylpyridinium chloride (CPC), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (SDBS)). It is shown that, starting from some characteristic concentration of a salt, a further increase of the salt concentration results in the shrinking of the gels. This characteristic concentration is defined by the gel parameters (polymer concentration in the gel that is a function of the monomer concentration at the conditions of hydrogel synthesis) and does not depend on the kind of salt used, except for the system polyelectrolyte gel/oppositely charged surfactant (PMA-CPC and DADMAC-SDS or SDBS). It is shown that the initial rate of gel shrinking for all studied systems, including the system gel/oppositely charged surfactant, is determined by the salt concentration and the gel parameters. For the systems PMA-CPC and DADMAC-SDS the gel collapse is a two-step process.
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    Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2677-2681 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The halide-free combination of Ni(acac)2 and DAD(diazadiene, ArN=CH—CH=NAr, where Ar = 2,6-C6H3(i-Pr)2) is active for ethylene polymerization in the presence of methylaluminoxane (MAO). The performance of this new catalytic system was evaluated with respect to activity and polymer structure. The degree of branching of the obtained polyethylenes is substantially influenced by the polymerization conditions. The activation mechanism was investigated by 1H NMR. MAO is proposed to participate in the ligand exchange process.
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    Effect of a triblock PCL-PDMS-PCL copolymer on the properties of immiscible poly(vinyl chloride)/poly(2-ethylhexyl acrylate) blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2699-2708 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Miscibility, thermal, mechanical and morphological properties of poly(vinyl chloride)/poly(2-ethylhexyl acrylate), (PVC/PEHA) blends containing 1-10 wt.-% of the triblock copolymer polycaprolactone-block-poly(dimethylsiloxane)-block-polycaprolactone (PCL-PDMS-PCL, Tegomer) were investigated by several techniques. Binary blends of PVC/PEHA are found to be immiscible according to differential scanning calorimetry and viscosity measurements. The effect of Tegomer addition on the properties of blends was examined. Ternary blends of PVC/PEHA/Tegomer exhibited a single Tg behaviour and viscosity measurements indicate some compatibility. Stress-strain results showed that Tegomer has a synergetic effect on the flexibility of the blends. FTIR analysis confirms the specific interactions between the components in ternary blends of PVC/PEHA/Tegomer. Morphological properties of the blends were examined by scanning electron microscopy.
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    Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning auger electron microscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2709-2715 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Scanning Auger electron microscopy (SAM), which is one of the best surface analytical methods, was applied to achieve basic understandings of the surface distribution of titanium species on supported Ziegler catalysts. Three different types of supported Ziegler catalysts were prepared by grinding MgCl2 with TiCl4 (Cat-A), by grinding MgCl2 with ethyl benzoate (EB) followed by the reaction with TiCl4 (Cat-B), and by reacting TiCl4 with a mixture of Mg(OEt)2 and dibutyl phthalate (DBP) (Cat-C). The SAM analysis revealed that the titanium species were scattered over the surface of Cat-A, while the distribution of the titanium species was rather even on the surface of Cat-B. In the case of Cat-C, the titanium species were found to exist evenly on the surface, and all particles of the catalyst showed a similar tendency. Hence, the influence of the preparation method of the catalyst on the distribution of the titanium species is clearly observed by SAM. Models of the catalyst particles obtained by different preparation methods were proposed on the basis of the results.
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    Crosslinked poly(styrenesulfonamide) with iminoacetic acid chelating groups for hard-water treatment (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2731-2735 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chlorosulfonated polystyrene-DVB (10%) copolymer (in beads form, 720-840 μm) has been modified with triethylenetetramine (TETA) to give the corresponding polymeric sulfonamide. By treating with the potassium salt of chloroacetic acid in water, amino groups of the polymer have been carboxymethylated almost quantitatively. The resulting material with iminoacetic acid pendant groups has very efficient chelating ability for Ca(II) and Mg(II) ions in ppm levels. The chelating polymer can be regenerated ten times by acid leaching without losing its original reactivity. It is suitable for removal of calcium and magnesium ions to supply soft water.
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    Bis(4-monosubstituted-5(4H)oxazolinones) as coupling agents for block copolymer synthesis: reaction with hydroxy-terminated oligomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2747-2753 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The bulk chain-coupling reactions between hydroxy-terminated poly(oxytetramethylene), poly(oxyethylene), or poly(ε-caprolactone) and several bis(4-monosubstituted-5(4H)oxazolinones) were studied. The polyaddition reaction proceeds rapidly and without side reactions when a catalytic amount of Ti(OBu)4 is used in the case of poly(oxytetramethylene) or poly(ε-caprolactone). On the other hand, the efficiency of the chain extension was much lower in the case of poly(oxyethylene). An explanation involving the coordination of poly(oxyethylene) oxygen atoms at the active sites of tetrabutoxytitanium is put forward. High molar mass block copolymers were synthesized by the chain-coupling reaction of mixtures of α,ω-dihydroxy-poly(oxytetramethylene) and -poly(ε-caprolactone) with bis(oxazolinones). The differential scanning calorimetry (DSC) study of the block copolymers revealed the existence of a microphase separation between the two blocks when the starting polymers have Mn ≥ 1000. For lower molar mass polymers amorphous products were obtained.
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    Determination of the content of extended chain segments in isotropic and uniaxially stretched polyethylenes by raman spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2767-2776 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectrum of polyethylene is known to be mainly sensitive to the conformational state of the polymer chain. At room temperature, most of the vibrations of the polyethylene Raman spectrum are intrinsically reflecting only one-dimensional order along the chain length. Based on the latter, we propose a straightforward quantitative procedure for the calculation of the content of extended (all-trans) and non-extended chain segments by using the C—C asymmetric stretching, the —CH2— twisting and the —CH2— wagging vibrations. The applicability of this procedure is demonstrated by using a set of samples covering a wide range of densities which, in addition, were subjected to uniaxial stretching and annealing. The results suggest that a significant portion of extended chain segments is placed outside the crystalline domains. Besides, in stretched samples, an important increase in the extended chain segments content was found. This is likely caused by the presence of highly oriented chain segments in the non-crystalline regions. These further disappeared as the stretched samples were annealed.
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    Infrared spectra evaluation of syndiotactic polystyrene by dynamic infrared linear dichroism spectra and static difference spectra (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2797-2804 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Uniaxially drawn syndiotactic polystyrene (sPS) in various modifications has been analyzed by static difference polarization spectra and DIRLD (dynamic infrared linear dichroism) spectra during mechanical stretching. Both, derivative bipolar bands and monopolar bands, are observed as a hint to submolecular changes induced by the applied external strain. The lineshape features in the dynamic in-phase spectra are described on the basis of frequency shifts and absorption amplitude variations during the stretching cycle. The conformationally sensitive vibrational modes are most sensitive to the external perturbation. The different responses of the conformationally insensitive vibrational modes to the external perturbation are discussed.
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    Modification of poly(propylene) through grafting with dimethyl itaconate in solution (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2495-2500 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Functionalization of isotactic poly(propylene) (PP) with dimethyl itaconate (DMI) as functional polar monomer using 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101) as radical initiator was carried out in both boiling xylene and decalin as solvent media. The effect of DMI and the initiator concentration on the extent of grafting was studied by varying reaction time and temperature. It was found that temperature affects the percentage of DMI grafted onto PP, which is slightly higher for reactions carried out in xylene than in decalin. The results also show that the amount of DMI incorporated is proportional to the initial DMI and initiator concentrations used in the grafting reaction up to certain concentrations, and thereafter a decrease in the percentage of grafting (G in wt.-%) was found. The maximum value of grafting obtained was 0.7 wt.-%. The melt flow index (MFI) values increase with increasing initial amount of initiator used in the grafting reaction. The degradation of the PP chain is higher when xylene is used as solvent. MFI values of 20-100 were found for modified PP compared with 11.4 for the unmodified polymer.
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    A novel observation in anionic ring-opening polymerization behavior of cyclic carbonates having aromatic substituents (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2489-2494 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The anionic ring-opening polymerization of six-membered cyclic carbonates having aromatic substituents, 5-methyl-5-phenyl-1,3-dioxan-2-one (1) and 5,5-diphenyl-1,3-dioxan-2-one (2), was carried out. The anionic homopolymerization of 1 readily proceeds to afford the corresponding polycarbonate, while 2 showed only a slight homopolymerizability. This is due to a rapid back biting reaction of the propagating polymer end to form 2. The conformational restriction of the adduct of 2 with an alkoxide, originating from the electrostatic repulsion between the alkoxide anion and the π electrons of the aromatic rings, might cause the rapid back biting reaction. The anionic copolymerization of 2 with 5,5-dimethyl-1,3-dioxan-2-one (3) proceeds to afford the copolymer. The anionic ring-opening polymerization of 1 was confirmed to be an equilibrium polymerization. Monomer 1 was regenerated up to the equilibrium monomer concentration by depolymerization of poly(1). A volume expansion (10.8%) was observed during the polymerization of 1.
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    Novel amphiphilic branched copolymers based on polystyrene and poly(ethylene oxide) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2501-2510 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Newly designed polystyrene (PS)/poly(ethylene oxide) (PEO) branched copolymers were obtained by a sequence of reactions involving both cationic and anionic polymerizations. Stars made of six PS-b-PEO arms and PS/PEO copolymers constituted of an inner PS part and an arborescent outer layer of PEO are two novel amphiphilic branched architectures that are described in this paper. The investigation of the solution properties of these copolymers by size exclusion chromatography (SEC) using tetrahydrofuran and an aqueous medium revealed that PS/PEO arborescent copolymers are more inclined to self-organize into unimicellar systems than their star homologues.
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    Solid-state photopolymerization of octadecyl sorbate to yield an alternating copolymer with oxygen (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2511-2516 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystals of octadecyl sorbate (ODS) were irradiated with sunlight or with a high-pressure Hg lamp to yield polymers with a molecular weight of 2.6-7.2 × 103. ESR spectroscopy confirmed that the propagating species is of allylic structure during the photopolymerization of ODS in the crystalline state, and that it is long-lived because of the immobility of the polymer chain produced. An alternating copolymer of ODS with oxygen is produced during the polymerization in air and the repeating unit of ODS in the resulting copolymer consists exclusively of 5,4-structure, when ODS crystals obtained by recrystallization from ethanol were used. Bulk polymerization of ODS provides a high molecular weight poly(ODS) with predominant trans-5,2-structure in the presence of a radical initiator in the melt. ODS crystals obtained from hexane or chloroform afford polymers consisting of both 5,4- and 5,2-structures.
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    Polyesters bearing furan moieties, 2Part 1: cf.ref.1. A detailed investigation of the polytransesterification of difuranic diesters with different diols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2755-2765 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A two-step transesterification procedure was applied to combinations of difuranic diesters and both aliphatic and furanic diols. The reaction parameters (including the nature of the catalyst) were varied in both phases of the process and the results compared with those published for similar systems based on aromatic diesters. The best results related to the first phase of the synthesis were obtained using Zn(AcO)2, Pb(AcO)2 or Ti(OBu)4 at 200°C with a large excess of diol. The second phase, which led to the actual polymer at 200-240°C, called upon the catalytic action of SnC2O4, Sb2O3 and Ti(OBu)4 and was prolonged until the viscosity of the media ceased to increase. Specific problems, related to some fragile moieties, limited the success of these polymerizations to a number of combinations which gave polyesters bearing regular structures and molecular weights in the tens of thousands.
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    Design, characterization and processing of cellulose-S-acetyl: a precursor to an electroactive cellulose (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2777-2783 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and characterization of Cell-SAc 3, a cellulose isopentyl (IP) ether with additional pendant S-acetyl (SAc) moieties (degree of substitution DSIP = 2.5, DSSAc = 0.4) are reported. Cell-SAc forms stable monolayers at the air-water interface once spread from dilute chloroform solution. The pressure-area isotherm of Cell-SAc is nearly identical to the parent Cell-IP 1, both exhibiting an expanded liquid phase at surface areas of 70 and 67 Å, respectively. The similarity of the two isotherms shows that the presence of the S-acetyl substituent does not result in an increase in the molecular area, at which the liquid-crystal analogous phase occurs. This observation suggests that the side-chains with the pendant S-acetyl group are oriented away from the water surface. Monolayers of Cell-SAc can be efficiently transferred onto silicon and hydrophobized glass or quartz substrates by a downstroke and upstroke technique. Resulting multilayers were characterized using X-ray reflection, FTIR, and UV-vis spectroscopy. The presence of S-acetyl moieties was found to increase the monolayer thickness relative to the parent Cell-IP. The cleavage of the S-acetyl group within the LB film is reported.
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    Tissue-compatible multiblock copolymers for medical applications, controllable in degradation rate and mechanical properties (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2785-2796 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A class of degradable, phase-segregated multiblock copolymers is presented. The new copoly(ester-urethane)s, termed DegraPolTM/btgc, consist of crystallizable poly[(3-R-hydroxybutyrate)-co-(3-R-hydroxyvalerate)]-segments and amorphous segments from ε-caprolactone, diglycolide and ethylene glycol. As junction unit an aliphatic diisocyanate, TMDI, is applied. The copoly(ester-urethane)s are thermoplastic elastomers (Tm = 120-136°C) and are processable without degradation. For medical applications, materials are needed in which the degradation rate and the mechanical properties are independently adjustable to the medical needs. The mechanical properties of DegraPolTM/btgc, e.g., elasticity and toughness, can be controlled by the weight fraction of crystallizable segment; the elastic moduli of DegraPol/btcg are adjustable between 50 MPa and 500 MPa and were only little influenced by the chemical structure and the composition of the soft segment. By insertion of ‘weak links’ in the form of easily hydrolyzable glycolyl-glycolate ester bonds into the amorphous segments, we attempted to synthesize degradable polymers in which the hydrolytic degradation rate can be controlled by the amount and the sequence distribution of these bonds. We report on the synthesis and on the thermal and mechanical properties of such polymers.
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    New chitin-based polymer hybrids, 3Part 2: cf. ref.4. Miscibility of chitin-graft-poly(2-ethyl-2-oxazoline) with poly(vinyl alcohol) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2805-2811 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility of blends of poly(vinyl alcohol) (PVA) with chitin-graft-poly(2-ethyl-2-oxazoline) (1) and poly(2-ethyl-2-oxazoline) homopolymer (PEtOZO) was investigated. Calorimetric results showed a single glass transition temperature (Tg) in the entire range of compositions for both blend systems, which indicated that PVA is miscible with both the graft copolymer 1 and PEtOZO. The Tg of PVA is also shifted to lower temperature upon blending with the graft copolymer 1. IR analysis revealed the existence of specific interactions via hydrogen bonding between the hydroxyl groups in PVA and the carbonyl groups in the poly(2-ethyl-2-oxazoline) side chain of graft copolymer 1. The results show that the interaction of graft copolymer 1 with PVA is increased by introduction of longer poly(2-ethyl-2-oxazoline) side chains. Thermal decomposition (TG) measurements supported the compatibility of PVA with graft copolymer 1 and with PEtOZO, and showed that the thermal stability of PVA is improved upon blending with 1 or PEtOZO.
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    Synthesis of novel oligomeric peroxides via condensation of dihydroperoxides with aromatic diols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1927-1933 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel oligoperoxides α-hydro-ω-hydroperoxyoligo(dioxydimethylmethylene-1,4-phenylene-dimethylmethylene) (BPB) (Tm = 143°C, Td = 176°C), α-hydro-ω-hydroxyoligo(dioxydimethylmethylene-1,4-phenylenedimethylmethylenedioxydimethylmethyleneethy lenedimethylmethylene) (EPB) (Tm = 100°C, Td = 175°C) and α-hydro-ω-hydroperoxyoligo(dimethylmethylene-2,6-naphthylenedimethylmethylene (NPN) (Tm = 137°C, Td = 177°C)), the products of condensation of tertiary diols with tertiary dihydroperoxides, were obtained. The structure of the oligoperoxides was confirmed by spectroscopic methods (IR, NMR). Their thermal properties were studied by differential scanning calorimetry (DSC), and the mechanism of the thermal decomposition of the oligomeric peroxides was proposed basing on the GC-MS analysis of the degradation products.
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    Liquid crystalline thermosets from triaromatic azomethine group containing diepoxides and 4,4′-methylenedianiline (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1935-1938 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Five triaromatic azomethine-linked diepoxides have been cured by reaction with 4,4′-methyl-enedianiline (MDA) in a molar ratio epoxide/amine of 1:1 and 2:1. The influence of the structure of monomers, of the molar ratio epoxide/amine, and of the curing conditions on the formation of liquid crystalline networks was studied. Initially a decrease of the clearing temperature was caused by mixing with the nonmesogenic diamine. The clearing point of the mixture increased with conversion, and thermosets with a liquid crystal order of the monomers were obtained from the 2:1 combinations. Curing occurs in two stages as revealed by DSC: first epoxy/amine reaction occurs, and at higher temperature homopolymerisation of residual oxirane takes place. This is due to non-homogeneous melting of the diepoxides in dynamic curing.
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    Vinylic polymerization of bicyclo[2.2.1]hept-2-ene by Co(II)-catalysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1951-1956 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The vinylic polymerization of bicyclo[2.2.1]hept-2-ene (norbornene) with Co(II) compounds, such as Co(II) stearate, substituted bis(1,3-diketo)cobalt(II), Co(dppe)Cl2, and the metallocene [η5-(C5Me5)Co-η2-Cl]2, in chlorobenzene activated with methylaluminoxane (MAO) is reported. MAO* synthesized by the hydrolysis of trimethylaluminium in chlorobenzene instead of toluene increases the catalytical activity strongly, and a turn over of 2.7 tons of poly(2,3-bicyclo[2.2.1]hept-2-ene) per mol cobalt per hour was achieved. The polymers obtained are amorphous (WAXS). They show weight-average molecular weights up to M̄w = 1.5 · 106 and are soluble in chlorobenzene, 1,2-dichlorobenzene, cyclohexane, and decahydronaphthalene.
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    Chain transfer by addition-fragmentation mechanism, 8.Part 7: cf. ref.1 Study of transfer agents designed to allow 1,5-intramolecular homolytic substitutions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2517-2526 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some substituted olefins and dienes bearing weak bonds located in appropriate locations were synthesized and added to vinylic monomer polymerization media, i.e., cumyl 4,6-heptadienyl peroxide (CHP), ethyl 5-cumylperoxy-5-methoxy-2-methylenehexanoate (ECMMH), 6-cumylperoxy-6-methoxy-3-methylene-2-oxoheptane (CMMOH), N-t-butyl-N-(2,2-diethoxyethyl)acrylamide (tBEEA), N-t-butyl-N-(2,2-diethoxyethyl)methacrylamide (tBEEMA). Chemistry aspects of synthesis and stability of the compounds are discussed. The thermolysis activation energies of the peroxidic compounds were estimated from DSC measurements to adapt the reaction conditions to the stability of these compounds. These compounds were tested as potential new chain transfer agents, involving a radical addition on activate unsaturation and a subsequent substitution on O—O or H—C bonds. In the first case, an oxyl radical was expelled and, in the second one, the generated carbon-centered radical was expected to evolve by a fast β-scission of the adjacent C—O bond to yield an alkyl radical. In both cases, these radicals would re-initiate efficiently the polymerization cycle. It was found that, in contrast to previously studied compounds allowing efficient 1,3-intramolecular homolytic substitutions (1,3-SHi), the transfer properties of these “1,5-substituted” compounds in the free radical polymerization of methyl methacrylate, styrene or butyl acrylate are poor in most cases. This behavior is discussed in terms of competition between intermolecular cross-addition reaction (copolymerization) and 1,5-intramolecular homolytic substitution (1,5-SHi).
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    Methacrylate networks containing chiral calamitic liquid crystalline side groups (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2247-2254 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A one-step copolymerization of ferroelectric methacrylate monomers leading to networks is presented. Oriented networks are obtained and electro-optical investigations are described. Smectic C* and another smectic phase are found in slightly crosslinked networks. For higher crosslinking densities, only the high temperature smectic C* phase was found. Electro-optical measurements were performed on the networks, and significant changes in the ferroelectrical properties were found. For crosslinking densities higher than 0.5 mol-%, switching times increased dramatically and the spontaneous polarization decreased. Networks with crosslinking densities of 2 mol-% did not exhibit ferroelectric properties.
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    Reactive groups on polymer coated electrodes, 8. Novel conducting polymer interfaces produced by electrochemical copolymerization of functionalized thiophene activated esters with 3-methylthiophene (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2255-2266 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the synthesis of two new functionalized thiophene activated esters and their electrocopolymerization with 3-methylthiophene, two types of redox active polymers have been prepared. FTIR studies of the resultant polymers reveal that both types of activated ester groups withstand the applied electrooxidative conditions and are correctly integrated into the corresponding polymers. The electrocopolymerization experiments show that the composition of the obtained polymers strongly depends on the ratio of the components in the reaction medium. With the increase of the ratios of pentafluorophenyl thiophene-3-acetate-3-methylthiophene or succinimido thiophene-3-acetate/3-methylthiophene, a higher concentration of functionalized thiophene units is incorporated into the polymer chains. The measurement of the conductivity on these polymeric films gave a value in the range of 10-3 to 10-2 S · cm-1, which is comparable to that of the unsubstituted polythiophene and consistent with the conjugation grade suggested by electrochemical and UV-vis spectroscopic data. As expected, the pendant reactive ester groups on the electrode surfaces react rapidly with different amino compounds without loss of the electroactivity of the polymers. Therefore, these novel polymeric materials can be used as electrode interfaces for further functionalizations, especially for the immobilization of amines, peptides, and enzymes.
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    Acetonitrile effects on quenching and photosensitized charge separation using partially quaternized poly(1-vinylimidazole)-bound ruthenium(II) complexes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2267-2274 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The acetonitrile effects on the quenching and photosensitized charge separation using two partially quaternized poly(1-vinylimidazole)-bound ruthenium(II) complexes, RuQPIm-19 and RuQPIm-44, wherein the numbers represent the degree of quaternization in molar percentage, have been investigated. The systems consist of RuQPIm-19 and RuQPIm-44 as photosensitizers, 1,1′-dimethyl-4,4′-bipyridinium (MV2+) and 1,1′-didodecyl-4,4′-bipyridinium (C12V2+) dications as electron acceptors (quenchers), and triethanolamine (TEOA) as a sacrificial electron donor. The photosensitized charge separation reaction proceeds through two processes, an interactive process and a direct process, i.e., the viologen is undergoing an interaction with these polymers and no interaction, respectively. The charge separation through the interactive process is less effective than that through the direct process, because the reaction through the interactive process is effective for both the forward and the back reactions. With the addition of acetonitrile, the rates of viologen radical formation decrease for RuQPIm-19 and RuQPIm-44, while the quenching efficiency decreases for RuQPIm-19 and increases for RuQPIm-44. In MV2+, the acetonitrile effect contributes to the interactive and direct processes for RuQPIm-19, while it contributes to only the direct process for RuQPIm-44, particularly the forward reaction for RuQPIm-19 and the back reaction for RuQPIm-44. In C12V2+, the interactive process through which the C12V2+ increases, leading to a decrease in the rates for viologen radical formation. Furthermore, these results indicate that the conformational changes in these polymers play an important role in the charge separation reactions.
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    Supramolecular dissociation of biodegradable polyrotaxanes by enzymatic terminal hydrolysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2311-2320 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Supramolecular dissociation of biodegradable polyrotaxanes via terminal hydrolysis by an enzyme (papain) in vitro was investigated in relation to their solution properties. The polyrotaxanes were synthesized by the introduction of L-phenylalanine (L-Phe) at both ends of an inclusion complex consisting of α-cyclodextrins (α-CDs) and amino-terminated poly(ethylene glycol) (PEG) via peptide linkages, followed by the hydroxypropylation of α-CDs. From static and dynamic light scattering studies, it was clarified that the polyrotaxanes form a loosely packed association but L-Phe-terminated PEGs form a tightly packed association. Further, the polyrotaxanes were found to maintain their rod-like structures in physiological conditions. In vitro degradation experiments using papain revealed that the terminal hydrolysis of the polyrotaxanes is completed and accompanied by the release of hydroxypropylated α-CDs, and this behavior is not affected by the association number of the polyrotaxanes. On the other hand, the terminal hydrolysis of L-Phe-terminated PEG is limited under similar conditions. From these results, the complete dissociation of the polyrotaxanes by hydrolysis is considered to be due to the loosely packed association, presumably related to the rod-like structure.
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    Modulated degradation of dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) in response to temperature (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2613-2618 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) were prepared, and their enzymatic degradation was examined at different temperatures. Although swelling ratios for the hydrogels are constant in a wide range of temperature, there is a drop of transmittance of the hydrogels in the swollen state in relation to the lower critical solution temperature of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide). Temperature-dependent enzymatic degradation was observed in these hydrogels to depend on the molecular weight of the grafts. The degradability of the hydrogel with shorter grafts is independent of temperature. In contrast, the degradability of the hydrogel with longer grafts increases with increasing temperature. Such a modulated degradation of hydrogels is considered to be due to a change in the entanglement between the grafted chain and dextran network by the hydration-dehydration behavior of the grafts.
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    Announcements (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2838-2838 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1998.021991225
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    Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenylene oxide)/chlorinated polyethylene blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2625-2630 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.
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    Cyclodextrins in polymer synthesis: Free radical polymerization of cyclodextrin complexes with N-methacryloyl-11-aminoundecanoic acid or N-methacryloyl-1-aminononane as guest monomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2641-2645 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The hydrophobic monomers N-methacryloyl-11-aminoundecanoic acid (1) or N-methacryloyl-1-aminononane (2) were incorporated as guests into the cavity of heptakis(2,6-di-O-methyl)-β-cyclodextrin (Me2-β-CD) as a host, yielding the water compatible monomers N-methacryloyl-11-aminoundecanoic acid/Me2-β-CD-complex (1a) and N-methacryloyl-1-aminononane/Me2-β-CD complex (2a). These complexes were polymerized radically in aqueous medium. The resulting polymers 1b and 2b which were obtained from the complexes 1a and 2a, are insoluble in water because of the unthreading of the cyclodextrin during the polymerization. The polymerization rate of 1a and 2a is high in comparison to the rate of the uncomplexed monomers 1 and 2 in solution. In addition, also the yields and viscosities of the polymers 1b, 2b prepared from complexed monomers in water are significantly higher than to the corresponding values of polymers 1c, 2c prepared in solution.
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    Synthesis and characterization of branched polypropenes obtained by metallocene catalysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2647-2653 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The homopolymerization of propene, 4-methyl-1-pentene, 1-octene and the copolymerization of propene with 4-methyl-1-pentene and 1-octene, respectively, was carried out with the isospecific metallocene catalyst system rac-[(dimethylsilylene)bis(2-methylbenzo(e)indenyl)]zirconium dichloride/methylaluminoxane at 30°C in toluene. By variation of the monomer ratio, it is possible to produce copolymers in the entire composition range. The activity, the amount of comonomer insertion, and the molecular masses obtained in the propene/1-octene copolymerization are significantly higher compared to the respective values of the system propene/4-methyl-1-pentene. It is possible to synthesize polymers with glass transition temperatures ranging from -65 up to 26°C. Whereas the incorporation of more than 20 mol-% 1-octene leads to amorphous polymers, the propene/4-methyl-1-pentene copolymers with less than 15 and more than 60 mol-% 4-methyl-1-pentene are semicrystalline. All melting points vary in the range from 50 to 225°C. Wide angle X-ray scattering measurements indicate an increase of the γ-modification compared to the γ-modification with increasing comonomer content and crystallization temperature. Typical supermolecular morphologies different from spherulites and known for the γ-phase of the isotactic polypropene homopolymer are observed for the copolymers by polarized light microscopy.
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    Sub-Tg annealing of the clathrate δ form of syndiotactic polystyrene (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2671-2675 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Amorphous films of syndiotactic polystyrene were crystallized in dichloromethane, to obtain samples in the clathrate δ form; successively the samples were either annealed at temperatures below the glass transition temperature (Tg) or extracted with acetone. The samples obtained show, in the X-ray analysis, crystalline structures tending toward the “emptied” δ form, free of solvent molecules, as already described for sPS. The study of the transport properties, diffusion and sorption of dichloromethane vapor, shows that the annealed samples are characterized by a slightly lower diffusion coefficient, but much higher sorption at low activity of the vapour. This high sorption is explained by the penetration of solvent molecules both into the amorphous and the “emptied” crystalline phase, producing again the clathrate form at low vapour activity. The high sorption capability makes these samples promising as sorption media to remove traces of polluting chlorinated solvents both in the liquid and in the vapour phase.
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    Synthesis of photoreactive α-4-azidobenzoyl-ω-methoxy-poly(ethylene glycol)s and their end-on photo-grafting onto polysulfone ultrafiltration membranes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2723-2729 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Covalent end-on grafting of poly(ethylene glycol) (PEG) onto a polysulfone (PSf) surface using α-4-azidobenzoyl-ω-methoxy-PEG (ABMPEG) is described. Photoreactive ABMPEG was synthesized by reacting monomethoxy-PEG (MPEG) with 4-azidobenzoyl chloride, yielding complete substitution of the hydroxyl groups. After adsorption from aqueous solutions, ABMPEG was photo-grafted under wet conditions onto PSf ultrafiltration (UF) membranes. Contact angle (CA) measurements showed the increased hydrophilicity of modified membranes and the irreversibility of the modification. Bovine serum albumin (BSA) adsorption decreased by 70% and the permeability decay after protein adsorption became less severe for the modified membranes compared to unmodified reference membranes.
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    Synthesis and electropolymerization of new p-nitrophenyl-functionalized thiophene derivatives (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2737-2746 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electrooxidative polymerization of three new p-nitrophenyl-functionalized thiophene derivatives leads to materials which show the electroactivities of both nitrobenzene and polythiophene. However, other than the reversible redox transition in solution, the nitro groups exhibit a complex nature of the cyclic voltammetric curve in the obtained solid polymeric films. It was found that the electrochemical behavior of the nitro groups has a dramatic effect on the conjugated π-electron systems of the substituted polythiophenes. Upon electrochemical addressing of the nitro groups the electroactivities of the corresponding polymers decrease rapidly compared to their analogous polymers without nitro groups. FTIR studies of these polymers revealed that after the reduction/oxidation process of the nitro groups still a large amount of electrolyte salt remains in the polymer films. As typical of functionalized polythiophenes, however, these new polymers can be switched under controlled conditions between their oxidized and neutral forms and exhibit the typical properties of electroactive polythiophenes, e.g., electrochromism.
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    Synthesis of side-chain liquid-crystalline polyesters using diethyl malonates with a mesogenic group and oligo(ethylene glycol)s and effect of specific interactions on their mesogenic behavior (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2329-2339 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Side-chain liquid-crystalline polymers were synthesized using malonic acid esters with a mesogenic group (1) linked through a hexamethylene spacer and oligo(ethylene glycol) (2n) as a flexible mainchain spacer. Polymers derived from 1 with a mesogen such as p-nitrophenylazophenoxy (1a) or 4-(4′-nitrophenylvinylene)phenoxy group (1b) form stable mesophases over a wide temperature range, through the increase of chain length of 2n decreases the thermal stability of the liquid-crystalline (LC) phases. LC polymers were obtained from 1 with a mesogen with p-substituted biphenoxy groups only when 2n with shorter chain length is employed. Copolymerizations were undertaken to see the effect of monomer pairs and copolymer compositions on the phase transition behavior of the copolymers formed, using three monomer pairs, 1a and 1 with the p-methoxybiphenoxy group as the mesogen, 1a and 1b, and 1a and 1 with the p-nitrobiphenoxy group as the mesogen. The copolymers formed from the first pair display a nematic phase over a much wider temperature range than the respective homopolymers. This was ascribed to the electron donor-acceptor interaction between the two mesogens in the monomer pair.
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