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  • Polymer and Materials Science  (112,478)
  • Cell & Developmental Biology  (25,032)
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  • 101
    ISSN: 0887-6266
    Keywords: optically active polymers ; gel permeation chromatography ; laser light scattering ; GPC calibration ; rodlike conformation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By combining the offline static and dynamic laser light scattering (LLS) and gel permeation chromatography (GPC) results of a broadly distributed polymer sample, we were able to characterize a series of chiral binaphthyl-based polyarylenes and poly(aryleneethnylene)s in THF at 25°C. For each of the samples, we obtained not only the weight-average molar mass Mw, the second virial coefficient A2 and the z-average translational diffusion coefficient 〈D〉, but also two calibrations: V = A + Blog(M) and D = kD M-αD, where V, D, and M are the elution volume, the translational diffusion coefficient and the molar mass for monodisperse polymer chains, respectively, and A, B, kD, and αD are four calibration constants. Using these calibrations, we estimated the molar mass distributions of these novel polymers. We showed that using polystyrene to calibrate the GPC columns could lead to a smaller Mw. Our results indicate that all the polymers studied have a rigid chain conformation in THF at 25°C and the introduction of the  - NO2 groups into the monomer can greatly promote the polymer solubility in THF.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2615-2622, 1998
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  • 102
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2643-2651 
    ISSN: 0887-6266
    Keywords: poly(ethylene oxide) ; poly(methyl methacrylate) ; blends ; atomic-force microscopy ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The binary blend of poly(ethylene oxide)/atactic poly(methyl methacrylate) is examined using hot-stage atomic-force microscopy (AFM) in conjunction with differential scanning calorimetry and optical microscopy. It was found possible to follow in real time the melting process, which reveals itself to be nonuniform. This effect is ascribed to the presence of lamellae having different thicknesses. The crystallization process of poly(ethylene oxide) from the miscible melt is also followed in real time by AFM, affording detailed images of the impingement of adjacent spherulites and direct observation of lamellar growth and subsequent polymer solidification in the interlamellar space.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2643-2651, 1998
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  • 103
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2635-2642 
    ISSN: 0887-6266
    Keywords: polypyrrole film ; bending ; strain ; sorption isotherm ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sorption-induced bending and recovery motion of PPy films containing different dopant ions have been investigated, and the interaction between water vapor and PPy was studied from sorption isotherms and kinetics. It was found that the PPy/BF4 film exhibited the most rapid motion, and the initial speeds of bending and recovery motion were 7.9 and 5.9 mm s-1, respectively. The linear expansion coefficient of the film increased in order of PPy/DBS, PPy/TsO, PPy/ClO4, and PPy/BF4, which is consistent with the packing density of the PPy chains (φPPy). The dual-mode sorption model applied to the isothermal sorption of water vapor to the PPy demonstrated that the Langmuir's capacity constant increased in the same order with the φPPy, while the Henry's law constant was nearly constant. The sorption kinetics obeyed Fickian despite the dimensional change of the films, and the PPy/BF4 film had the largest diffusion coefficient of 3.13 × 10-8 cm2 s-1. The experimental results indicated that the kind of dopant ion was crucial to the thermodynamics and kinetics of sorption, and the quick and intensive bending motion of PPy/BF4 films was attributed to the fast diffusion of water vapor, which caused the large dimensional change of the film.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2635-2642, 1998
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  • 104
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2665-2669 
    ISSN: 0887-6266
    Keywords: dielectric permeability ; dipole correlation factor ; glass transformation ; correlation ; polarization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The generality of baric changes in static dielectric permeability of polymers for different temperatures of the sample is considered in the present work. It is shown that the initial growth of dielectric permeability is followed by its lowering that arises during the glass transformation of the sample. Formulas that reflect the changes of dielectric permeability under isothermal changes of pressure and isobaric changes of temperature of the sample are obtained. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2665-2669, 1998
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  • 105
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2653-2663 
    ISSN: 0887-6266
    Keywords: [60]fullerene ; styrene ; anionic copolymerization ; structural characterization ; sodium naphthalene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The novel C60-styrene copolymers with different C60 contents were prepared in sodium naphthalene-initiated anionic polymerization reactions. Like the pure polystyrene, these copolymers exhibited the high solvency in many common organic solvents, even for the copolymer with high C60 content. In the polymerization process of C60 with styrene an important side reaction, i.e., reaction of C60 with sodium naphthalene, would occur simultaneously, whereas crosslinking reaction may be negligible. 13C-NMR results provided an evidence that C60 was incorporated covalently into the polystyrene backbone. In contrast to pure polystyrene, the TGA spectrum of copolymer containing ∼ 13% of C60 shows two plateaus. The polystyrene chain segment in copolymer decomposed first at 300-400°C. Then the fullerene units reptured from the corresponding polystyrene fragments attached directly to the C60 cores at 500-638°C. XRD evidence indicates that the degree of order of polymers increases with the fullerene content increased in terms of crystallography. Incorporation of C60 into polystyrene results in the formation of new crystal gratings or crystallization phases. In addition, it was also found that [60]fullerene and its polyanion salts [C60n-(M+)n, M = Li, Na] cannot be used to initiate the anionic polymerization of some monomers such as acrylonitrile and styrene, etc.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2653-2663, 1998
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  • 106
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2671-2675 
    ISSN: 0887-6266
    Keywords: second normal stress difference ; melt rheology ; Doi-Edwards model ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Flow birefringence is used to study stress relaxation following step strain deformations of a well entangled polyisoprene melt. The optical method employs multiple light paths to fully sample the three-dimensional stress tensor, and hence provides measurements of all three independent shear material functions (shear stress and both first and second normal stress differences). Experiments are complicated by multiple orders in retardation. However, data show that the ratio of the second to the first normal stress difference is a strain thinning function, with magnitude intermediate between the predictions of the Doi-Edwards model with and without independent alignment. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2671-2675, 1998
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  • 107
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2677-2681 
    ISSN: 0887-6266
    Keywords: sulfonated SEBS ; viscosity property ; molecular aggregation ; freezing-thawing treatment ; shear-thickening ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dilute solution properties of lightly sulfonated hydrogenated styrene-butadiene-styrene block copolymer (S-SEBS) dissolved in tetrahydrofunan (THF) were studied by viscometry. The ring conformation in dilute regime can be deduced from the intrinsic viscosity data. It is believed that this special conformation results from the location of ionic group at both two-end blocks. The intermolecular aggregation can be observed when the solutions undergo the freezing-thawing process in the same concentration region. The extent of aggregation is affected by the freezing-thawing cycle times, water content in THF, and the counterion radii, etc. The properties of the aggregation equilibrium are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2677-2681, 1998
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  • 108
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2683-2689 
    ISSN: 0887-6266
    Keywords: interfacial tension ; square gradient theory ; equation-of-state theory ; polystyrene/poly(methyl methacrylate) blend ; polystyrene/poly(dimethyl siloxane) blend ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interfacial tension between immiscible polymer pairs was predicted by using a square gradient theory in conjunction with the Flory-Orwoll-Vrij equation-of-state expression for the free energy of mixing. The contact interaction parameter was determined by fitting the equation-of-state theory to experimental cloud points taken from the literature, and the square gradient coefficient was estimated from the relation derived from a scattering function. The modified square gradient theory could successfully predict both the magnitude and temperature dependence of interfacial tension between polystyrene and poly(methyl methacrylate), although no adjustable parameters were used in calculating interfacial tension. The molecular weight dependence of interfacial tension was also successfully predicted. The contribution of free volume on interfacial tension is analyzed for two systems: polystyrene/poly(methyl methacrylate) and polystyrene/poly(dimethyl siloxane) blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2683-2689, 1998
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  • 109
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2691-2702 
    ISSN: 0887-6266
    Keywords: surface segregation ; polyolefin copolymers ; deuterium labeling effect ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have examined the effect of deuterium labeling on surface interactions in mixtures of random olefinic copolymers [C4H8]1-x[C2H3(C2H5)]x. Based on surface segregation data we have determined a surface energy difference χs between pure blend constituents. In each binary mixture components have different fractions x1, x2 of the group C2H3(C2H5), and one component is labeled by deuterium (dx) while the other is hydrogenous (hx). The mixtures are grouped in four pairs of structurally identical blends with swapped labeled constituent (dx1/hx2, hx1/dx2). For each pair the surface energy parameter χs increases when the component with higher fraction x is deuterated, i.e., χs(dx1/hx2) 〉 χs(hx1/dx2) for x1 〉 x2. A similar pattern has been found previously for the bulk interaction parameter χ. This is explained by the solubility parameter formalism aided by the lattice theory relating the surface excess to missing-neighbor effect. χs has also an additional contribution, insensitive to deuterium swapping effect, and related to entropically driven surface enrichment in a more stiff blend component with a lower fraction x. Both enthalpic and entropic contributions to χs seem to depend on the extent of chemical mismatch between blend components. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2691-2702, 1998
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  • 110
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2703-2716 
    ISSN: 0887-6266
    Keywords: calorimetry ; dielectrics ; diffusion ; monoamine-triepoxide ; thermoset ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Calorimetry and dielectric relaxation spectroscopy during the growth of a polymer network in the stoichiometric mixture of a triepoxide with 4-chloroaniline have been performed in separate experiments to investigate the increase in the relaxation time with the number of covalent bonds. A comparison with the corresponding study of triepoxide-aniline and triepoxide-3-chloroaniline mixtures shows that steric hindrance of the amine group by chlorine slows the molecular dynamics and the relaxation time of the state containing a fixed number of bonds. The polymerization kinetics measured during ramp heating does not yield a reliable activation energy. A recent empirical relation between the relaxation time and the extent of polymerization, and the condition for the onset of diffusion-control kinetics have been examined using the data for these three polymerizing mixtures. The results show substantial deviations from the empirical relation and appear to conflict with our basic understanding of the polymerization process. It is shown mathematically that features attributed to the onset of diffusion-controlled kinetics can arise from thermochemical behavior alone, without reference to the molecular dynamics. An earlier theory for the change in the kinetics of an addition reaction from mass control to diffusion control has been considered, and is seen as relevant to the polymerization reactions. It is argued that the dielectric relaxation rate does not directly indicate the chemical reaction rate because the reorientational motion of the dipolar entities may not be coupled to the rotational and translational diffusion that brings the sterically hindered chemically reacting sites together. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2703-2716, 1998
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  • 111
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2737-2743 
    ISSN: 0887-6266
    Keywords: high-temperature zone-drawing ; high-tension multiannealing ; nylon 46 fiber ; high-modulus ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nylon 46 fibers produced by the high-temperature zone-drawing treatment were treated by repeating high-tension annealing treatments, that is, a high-tension multiannealing (HTMA) treatment to improve their tensile properties. The HTMA treatment was carried out at a repetition time of 10 times and treating temperature of 110°C under high tension (538.2 MPa) close to the tensile strength at break. Although the HTMA treatment was carried out at 110°C, which is much lower than the crystallization temperature of 265°C for nylon 46, the degree of crystallinity increased up to 59%. The orientation factor of crystallites increased dramatically up to 0.949 by the first high-temperature zone-drawing treatment and slightly during the subsequent treatments. This observation indicated that the orientation of crystallites due to slippage among molecular chains did not occur during the HTMA treatment. The treatments shifted the melting peak to slightly higher temperatures, and the HTMA fiber has a melting endotherm peaking at 285°C. The fiber obtained finally had a storage modulus of 12.5 GPa at 25°C. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2737-2743, 1998
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  • 112
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2745-2750 
    ISSN: 0887-6266
    Keywords: polymer blends ; hydrogen bonding ; small-angle neutron scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Deuterium-labeled polystyrene modified by random distributions of the comonomer p-(1,1,1,3,3,3-hexaflouro-2-hydroxyisopropyl)-α-methyl-styrene [DPS(OH)] has been blended with poly(butyl methacrylate) (PBMA) and studied with small-angle neutron scattering (SANS). Miscibility is induced via hydrogen bonding between the DPS(OH) hydroxyl group and PBMA carbonyl groups. The data suggest that the nature of the miscible-phase structure in these blends differs from that of the usual homopolymer blends at small scattering angles, which we attribute to the short-range site specific nature of the hydrogen bond interaction. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2745-2750, 1998
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  • 113
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2725-2735 
    ISSN: 0887-6266
    Keywords: blending ; polymorphism ; syndiotactic polystyrene (s-PS) ; amorphous polystyrene (a-PS) ; PPO ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray diffraction and optical microscopy characterization were performed to evaluate the phenomenon of alteration of polymorphism of syndiotactic polystyrene (s-PS) in the presence of other blending miscible polymers: poly(2,6-dimethyl-p-phenylene oxide) (PPO) or atactic polystyrene (a-PS). Both α and β crystal forms were observed in the neat s-PS sample, but only β-form crystal was found in miscible blends of s-PS with a-PS or PPO. The order and neighboring chain segments of neat s-PS are different from those of s-PS/PPO or s-PS/a-PS blends; thus, it is plausible that the greater randomness in the melt state of s-PS/a-PS or s-PS/PPO blends might be unfavorable for formation of α-form crystals from melts. The final spherulitic morphology the s-PS/a-PS or s-PS/PPO blends suggests that the amorphous-state miscibility of does not change much the spherulitic structure of s-PS. The radial growth rate is, in general, depressed with the presence of blending miscible polymers in s-PS of equal Tg or PPO of higher Tg. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2725-2735, 1998
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  • 114
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2751-2760 
    ISSN: 0887-6266
    Keywords: fatigue ; crazes ; polypropylene ; microscopy ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article reports initial results of an investigation whose aim is to characterize fatigue damage induced in semicrystalline polymers subjected to uniaxial high cycle fatigue. Herein we report results obtained from fatiguing tensile bars of high molecular weight compression-molded alpha-phase iPP. Samples were fatigued for up to one million cycles at a frequency of 2 Hz. During fatigue, in situ measurements of dynamic mechanical response and energy densities were recorded. Postmortem morphological studies were also conducted using SEM of etched surfaces and TOM. The results show that damage formation occurs in a regularly spaced array of crazes. This damage, its evolution, and energetics are discussed as they relate to the overall fatigue life of the material. A methodology to isolate the energy consumption for the formation of a single craze is given. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2751-2760, 1998
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  • 115
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    Macromolecular Rapid Communications 19 (1998), S. 131-133 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The isothermal crystallization process of a PCL/SAN blend (90/10 wt.-%) was investigated by using real time image analysis and hot stage optical microscopy. It was found that the growth rate of ringbanded spherulites in the isothermal crystallization process is not constant. Slow growth occurs in the bright bands, while fast growth is found in the dark bands. The radially unequal growth rate of ring-banded spherulites in PCL/SAN blends may be related to the convex band structure on the surface. This new discovery gives us the idea that rhythmic growth is effective in the growth process of ring-banded spherulites.
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  • 116
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    Macromolecular Rapid Communications 19 (1998), S. 145-148 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A transient periodic stripe domain pattern is observed during photo-induced director reorientation of a sample containing rod-like block copolymer vesicles in a low molecular weight nematic liquid crystal.
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  • 117
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    Macromolecular Rapid Communications 19 (1998), S. 163-166 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Slurry polymerizations of ethylene over vanadium catalysts (based on VCl4 and VOCl3) and their MgCl2(THF)2-supported equivalents were studied. Unsupported vanadium catalysts were found to be unstable while the vanadium active sites deposited on the MgCl2(THF)2 complex are stable. A sharply outlined correlation was found between the concentration of vanadium(III) and catalyst productivity. The high activity and stability of the vanadium catalyst when supported on the magnesium complex is attributed to the increase of resistance to reduction of active vanadium(III) to inactive vanadium(II) by an organoaluminium co-catalyst.
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  • 118
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    Macromolecular Rapid Communications 19 (1998), S. 185-190 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-oxyl terminated vinylbenzyl chloride macromonomers, available via controlled free radical polymerization, were used to synthesize AB-block copolymers of vinylbenzyl chloride and styrene with low polydispersity and different block lengths and block length ratios. The vinylbenzyl chloride blocks were quantitatively converted into cationic polyelectrolytes by reactions with tertiary amines. The micellization of the synthesized amphiphilic cationic block copolymers was investigated using different techniques such as static light scattering, ultracentrifugation and size exclusion chromatography.
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  • 119
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    Macromolecular Rapid Communications 19 (1998), S. 173-176 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel technique of preparation of multilayer assemblies consisting of a controlled number of molecular layers of various proteins arranged according to a predetermined architecture is described. The multilayers were formed by consecutive adsorption of polyanions and positively charged proteins below their isoelectric point and covalently crosslinked via protein amino groups. Polyanions were washed out from the crosslinked protein assembly by rinsing with buffer in which the net charge of the proteins was inverted.
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  • 120
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    Macromolecular Rapid Communications 19 (1998), S. 451-454 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microhardness (H) of gelatin dry cast films was measured in the 100-250°C range. A strong H increase with temperature from 330 MPa up to 450 MPa was observed in the first cycle. The H values reached in the subsequent cycles are higher than those obtained in the preceding ones, surpassing the hardness of all commercial synthetic polymers and soft metals. Results are discussed in terms of crosslinking between side-chain reactive groups.
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  • 121
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    Macromolecular Rapid Communications 19 (1998), S. 473-477 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ethylene oxide (EO) mobility in polystyrene-graft-[poly(ethylene oxide)] (PS-g-PEO) and polystyrene-graft-[stearyl poly(ethylene oxide)] (PS-g-SPEO) copolymers was evaluated by spin probe techniques. The ESR spectra indicate that 4-hydroxyl-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) is strongly biased to the PEO phase of the PS-g-(S)PEO membranes. The rotational correlation time τc can also be employed to assess the PEO mobility in PS-g-(S)PEO membranes. Although τc of PS-g-(S)PEO usually decreases with increasing surface density of EO, it is of interest that τc is rather high when the surface within a depth of at least 5 nm is fully occupied by SPEO (sample PS-g-SPEO-72.6).
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  • 122
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyisobutylene-graft-polystyrene (PIB-g-PSt) was synthesized by quasiliving atom transfer radical polymerization (ATRP) of styrene. The ATRP process was induced by an industrially produced poly-(isobutylene-co-p-methylstyrene-co-p-bromomethylstyrene) macroinitiator (PIB) in the presence of CuBr and 2,2′-bipyridine. Successful graft polymerizations were performed both in bulk and in xylene solution. Preliminary investigations indicate phase-separated morphology and thermoplastic elastomer (TPE) behavior of this new graft copolymer with certain PIB/PSt ratios. These materials are able to elongate to ca. 500% of their original dimension without any irreversible deformation.
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  • 123
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    Macromolecular Rapid Communications 19 (1998), S. 505-509 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Silica supported (butylcyclopentadienyl)2ZrCl2/MAO catalysts were synthesized according to the “incipient wetness” method from a solution of metallocene in a liquid monomer. The monomer was allowed to polymerize yielding a catalyst containing polyhexene (PH), polystyrene (PS) or polyoctadiene (PO). One catalyst containing no polymer was also synthesized. The catalysts were used to polymerize ethene at 70°C and 4 bar total pressure. The measured average activities were 5 300 kg PE/(mol Zr · h) for (BuCp)2ZrCl2/MAO/PH/SiO2, 8 600 kg PE/(mol Zr · h) for (BuCp)2ZrCl2/MAO/PS/SiO2, 3 400 kg PE/(mol Zr · h) for (BuCp)2ZrCl2/MAO/PO/SiO2 and 5 700 kg PE/(mol Zr · h) for (BuCp)2ZrCl2/MAO/SiO2. The polyhexene, polystyrene or polyoctadiene in the catalyst forms a protective layer around the active sites. Even after exposure to air for five hours these catalysts retain some polymerization activity.
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  • 124
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    Macromolecular Rapid Communications 19 (1998), S. 271-273 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Particles of semiconducting polyaniline and a copolyaniline bearing ionic substituents were synthesized. Electrorheological (ER) fluids using these particles were compared with each other with respect to their rheological properties and dielectric spectra. In the steady shear rheological experiment conducted at 3 kV/mm (DC) at 25°C, the copolymer system showed higher stress than the polyaniline system in the whole shear rate region. This result was interpreted in terms of the conductivities of the particles and their dielectric spectra. Especially, the different behavior in the high shear rate region can be related to the electrical relaxation phenomena observed in the dielectric spectra.
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  • 125
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    Macromolecular Rapid Communications 19 (1998), S. 549-552 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular chain conformation of the dried gel of syndiotactic polystyrene (sPS) in octadecyl benzoate solution was investigated. sPS gels form rapidly through solid-liquid phase separation. The obtained sPS chains are in the highly ordered all-trans TT skeletal conformation which is different from a twofold TTGG helical conformation that sPS assumes in normal solvents. The size of the solvent molecule is considered to play an important role in the formation of the conformation of sPS in solution.
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  • 126
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetics of polymerization of ε-caprolactone (CL) initiated with tin(II) octoate (Sn(Oct)2) in THF as a solvent at 80°C was studied. The results strongly indicate that polymerization initiated with Sn(Oct)2 proceeds on the tin(II)-alkoxide bond and are not compatible with a mechanism in which propagation was proposed to proceed by a nucleophilic attack of the …—OH ended macromolecules on the monomer-Sn(Oct)2 complex.
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    Macromolecular Rapid Communications 19 (1998), S. 631-634 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Soluble propeller-like polyarylates with M¯n ≈ 1 × 104 and melting in the range 200-220°C were synthesized via one-pot simultaneous Diels-Alder (using anthracene or (E,E)-1,4-diphenylbutadiene as enophile and the fumaroyl moiety as dienophile) and polycondensation reaction. Thermal properties of all polyarylates were evaluated. Decomposition occurs in two steps between approximately 300-400°C. The first step is due to retro-Diels-Alder reaction and the second one to main-chain decomposition.
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  • 128
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    Macromolecular Rapid Communications 19 (1998), S. 445-450 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The composition and molar masses of equimolar multicomponent copolyesters, obtained from 1,4-butandiol and mixtures of succinic, adipic, sebacic, and terephthalic acids were characterized by 13C NMR, size exclusion chromatography (SEC), matrix assisted laser desorption ionization-time of flight mass spectroscopy (MALDI-TOF-MS), and viscosimetry. These copolyesters were subjected to partial methanolysis, and the composition and sequence of the oligomers obtained in the methanolysis were determined by the analysis of their fast atom bombardment (FAB-MS) mass spectra. The comparison of the composition data obtained by FAB-MS and 13C NMR indicates that for copolymers containing sebacic units the methanolysis is a partially selective process, and that oligomers containing sebacic units accumulate in the residue.
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  • 129
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    Macromolecular Rapid Communications 19 (1998), S. 467-471 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel one-step synthesis of hydrophobically modified polyacrylamide (PAAm) is described. Triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PEO-PPO-PEO) are grafted onto PAAm in melts of acrylamide in the presence of benzoyl peroxide. The resulting PEO-PPO-PEO-g-PAAm graft copolymers are capable of self-assembly in response to temperature changes in aqueous media.
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    Macromolecular Rapid Communications 19 (1998), S. 493-497 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic initiation activity of derivatives of S-methylsulfonium salts has been evaluated in the cationic polymerization of glycidyl phenyl ether (1). These initiators are soluble in 1 and capable of initiating the cationic polymerization of 1 on heating, except for methyltetrahydrothiophenium tetrafluoroborate (6) (r.t. -160°C). Among them, methyldiphenylsulfonium tetrafluoroborate (4) shows moderate thermal latency, that is the polymerization of 1 occurs efficiently at 160°C but not below 80°C.
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  • 131
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The ionogenic polymers namely poly(N,N-diallyl-N-cetylammonium hydronitrate) (PDACA · HNO3) and poly(N,N-diallyl-N,N-dimethylammonium chloride)-block-poly(cetyl acrylate) (PDADMACl-block-PA-16) were synthesized via activation of the terminal double bond of the PDADMACl precursor and initiation of the polymerization of the acrylic monomer in alcohol solution. The microphase separated structure of a blend of both homopolymers and of the block copolymer was proved by differential scanning calorimetry (DSC) and X-ray diffraction measurements. Side chain crystallization in PDA-CA · HNO3 completely restricts the crystallization of the ionogenic backbones which, however, control the layered structure and the crystallization of the aliphatic chains. In PDADMACl-block-PA-16 crystalline polyacrylate blocks coexist with crystalline ionogenic blocks. The length of the polyacrylate block influences the ability of the ionogenic block to form the crystalline structure.
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    Macromolecular Rapid Communications 19 (1998), S. 553-556 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Paper was preserved by deposition of poly(cyclohexene oxide) polymerised in situ by a photoinitiated cationic process. The efficiency of the deposition, as function of parameters such as the used catalytic system and the reaction time, has been evaluated by detection of uncovered cellulose present at the sample surface determined by means of X-ray photoelectron spectroscopy. The percentage of uncovered cellulose detected was ranging from 1 to 40%.
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    Macromolecular Rapid Communications 19 (1998), S. 573-579 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of a new liquid crystalline block copolymer consisting of a polystyrene block and a side-chain liquid crystalline siloxane block is reported. The synthetic approach described is based on the anionic polymerization of styrene and cyclic trimethyltrivinyltrisiloxane monomers, followed by functionalization of the siloxane block with side chain mesogens. The siloxane block has a Tg well below 25°C and is designed to exhibit a chiral smectic C* phase at room temperature. These block copolymers are the first side-chain liquid crystalline block copolymers which contain both a high Tg glassy block and a low Tg liquid crystalline block.
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    Macromolecular Rapid Communications 19 (1998), S. 601-604 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic alkyl zirconocene complex Cp2Zr+Me[CH3B-(C6F5)3] is found to initiate the ringopening polymerization of 1,5,7,11-tetraoxaspiro[5,5]undecane under mild condition to give poly(oxypropylenepropylenecarbonate) with low polydispersity. The rate of the polymerization is first-order with respect to monomer and catalyst concentration. At high monomer concentration, the initial rate of polymerization becomes zero-order with respect to monomer concentration.
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    Macromolecular Rapid Communications 19 (1998), S. 613-617 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyglycolide (poly(hydroxyacetic acid)) with wide variability of pore size can be prepared by combination of a solid-state polymerization reaction and addition of sodium chloride crystals. The solid state reaction leads to a composite of polyglycolide and NaCl. The latter can be washed out with water leaving behind porous polyglycolide with interconnected pores in the micrometer range. To achieve a higher porosity and to induce larger pores, additional coarse sodium chloride was added before polymerization. This opens a way to functionally graded polyglycolide resembling natural bone that should have a potential as bone substituting material.
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  • 136
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    Notes: The synthesis of poly(thio- 1,4-phenylene) (PPS) at room temperature by the reaction of diphenyl disulfide with potassium persulfate (K2S2O8) in non-basic solvents, in the presence of trifluoromethanesulfonic acid, is reported. The reaction in chlorinated solvents, such as dichloromethane and tetrachloroethane, resulted in partial oxidation of sulfide to sulfoxide and sulfone. On the other hand, the polymerization proceeded well in nitrobenzene and the PPS formed was free of branches, crosslinks and thianthrene units. The molecular weight of the polymers formed in different solvents were in the range 2000-8000. The reaction proceeded under identical conditions with bis(2,6-dimethylphenyl) disulfide as well, but the polymer yield was lower.
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    Macromolecular Theory and Simulations 7 (1998), S. 91-96 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We present a macroscopic model for the behavior of smectic A liquid single crystal elastomers (LSCEs) under an external dilatory stress thus investigating the elastomeric analogue of the undulation instability in low molecular weight (LMW) smectic A liquid crystals. We show that the critical wavelength λc of the expected undulation pattern is given by an expression quite similar to that obtained for LMW smectic A phases. This result provides a possible explanation for the strong light scattering (high turbidity) observed by Nishikawa et al. very recently in thick samples of a smectic A LSCE above a certain threshold stress applied parallel to the layer normal in the experiments. We find that, in contrast to the critical wavelength λc, the threshold dilatation εc is dominated by the elastic properties of the smectic LSCE. Thus - as observed in the experiments by Nishikawa et al. -εc is found to be several orders of magnitude higher than in the LMW case.
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A procedure is developed that allows the calculation of chain-length distributions of polymers prepared by periodic modulation of the initiation process considering concomitant continuous initiation. For the case of a (pseudostationary) laser-pulse initiated polymerization process a closed solution could be derived for the pseudostationary radical concentration and for the chain-length distribution of dead polymer terminated by disproportionation or stabilized by chain-transfer to monomer or solvent. The analysability of the characteristic peaks appearing in the chain-length distributions of laser-pulse initiated polymers (which is the key for determining the rate constant kp) is only moderately influenced by continuous thermal radical formation if the extent of this side reaction is not pathologically large, i.e. as long as the amount of primary radicals created by the laser-pulse appreciably exceeds that produced in the dark reaction.
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    Macromolecular Theory and Simulations 7 (1998), S. 196-200 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
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    Macromolecular Theory and Simulations 7 (1998), S. 201-201 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: In a recent study we found the classical dynamics of a polyethylene (PE) chain to exhibit low dimensional chaos at temperatures as low as a few Kelvin. These results strongly suggest that classical molecular dynamic simulations in polymer systems can grossly overestimate vibrational motion, which consequently results in disordered structures. In contrast, quantum mechanical calculations using Internal Coordinate Quantum Monte Carlo (an improved method with an initial conjecture for the correct wave function) indicate that the quantum ground state for a three-dimensional model PE chain is far more rigid than determined from molecular dynamics (MD) simulations, even at energies as low as a small fraction of the ground state energy. This result casts uncertainty on the reliability of MD estimates of dynamical or structural quantities relevant to the study of some macromolecular systems.
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    Macromolecular Theory and Simulations 7 (1998), S. 59-63 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this note microgels with and without excluded volume interactions are considered. Based on earlier exact computations on Gaussian mircogels, which are formed by self-crosslinking (with M crosslinks) of polymer chains with chainlength N, Flory type approximations are used to get first insight to their behavior in solution. It is shown that two different types of microgels exist: A special type of branched polymer whose size scales as R ∝ N2/5/M-1/5, instead of R ∝ N1/2. The second type are c*-microgels whose average mesh sizes r are swollen and form self avoiding walks with a scaling law of the form r = a(N/M)3/5.
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    Macromolecular Theory and Simulations 7 (1998), S. 79-90 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We theoretically investigate polymer deformation and shear thinning, i.e., a decrease of intrinsic viscosity, in a dilute polymer solution as a function of the applied shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}. We use a bead-and-spring model with hydrodynamic interaction in the Rouse-Zimm framework, approximately accounting also for excluded-volume effects, and impose a constraint on the average mean-square spring length to prevent its stretching at large \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}. When suitably normalized, both the intrinsic viscosity [η] and the components of the mean gyration tensor 〈SS〉 depend on the single variable \documentclass{article}\pagestyle{empty}\begin{document}$ \xi = {{\dot \gamma \tau _1^{\left( 0 \right)} } \mathord{\left/ {\vphantom {{\dot \gamma \tau _1^{\left( 0 \right)} } {N^{1 - v} }}} \right. \kern-\nulldelimiterspace} {N^{1 - v} }} $\end{document} where τ(0)1 is the longest relaxation time for \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma = 0 $\end{document}, N is the number of chain springs and v is the Flory exponent. The full shear-rate dependence is obtained numerically, and compared with analytical results obtained under free-draining conditions both for low and for very large shear rates. The shortcomings of the theory are also discussed, in particular a substantial stretching under shear of the central springs, where the intramolecular tension is largest, with a corresponding strong contraction of the end springs due to the average character of the constraint.
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    Macromolecular Theory and Simulations 7 (1998), S. 521-549 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The spring-and-bead model proposed by Rouse and Zimm can theoretically treat the viscoelastic behaviour of polymers. In this paper, we first point out that the Rouse and Zimm matrices in the molecular theory of polymer viscoelasticities are equivalent to the adjacency matrix and admittance (or Kirchhoff) matrix in graph theory, respectively. In order to solve the eigen-value problems of Rouse and Zimm matrices, the matrices are first represented by their corresponding eigen-graphs, which reflect the topological structure of the real chain. Starting from the eigen-graph, instead of tedious mathematics, the eigen-value problems are solved by a series of simple graphic operations, such as cutting-off the bonds, removing the closed pathways, etc. The eigen-polynomial of Rouse and Zimm matrices and the viscoelastic properties of the chain are obtained by using the theorems given in this paper. It is also shown that the eigen-polynomial of the chain can be greatly reduced if the chain graph has elements of symmetry. As the Rouse theory of viscoelasticity is closely related to the conformational statistics of Gaussian chains, it is demonstrated that the graph-theoretic approach developed here can also be applied to solve the configurational properties of Gaussian chains, such as the distribution function of the radius of gyration and its moments, the shape of a Gaussian chain, etc. We have also demonstrated that the graph-theoretic approach developed here is also applicable to copolymeric chains.
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    Macromolecular Theory and Simulations 7 (1998), S. 591-598 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of nonlinearity on dynamics and the appearance of nonhomogeneous equilibrium states in a polyethylene crystal are analyzed. The role of different inputs into the nonlinearity of potentials of interaction is investigated theoretically by means of approximate equations. The solutions of these equations which describe equilibrium cracks, domain walls, bivacancies and vacancies are presented. The energies and elastic fields of these structural defects are calculated.
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    Macromolecular Theory and Simulations 7 (1998), S. 623-639 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent significant advances in theoretical liquid crystalline rheology are presented. Dynamic simulations are performed using a complete theory which include the three major effects of liquid crystalline materials: (1) short range order elasticity, (2) long range order elasticity, and (3) viscous flow effects. The results and discussions include rectilinear simple shear flow, complex non-linear phenomena such as defect texture generation and coarsening processes under quiescent and shear conditions, and pattern formation such as banded texture during and after cessation of flow. The complete theory predicts four in-plane (1-D orientation) flow modes and five out-of-plane (2-D orientation) flow modes in one-dimensional shear flow, depending on the magnitudes of R (ratio of short to long range order elasticity) and Er (Ericksen number: ratio of viscous to elastic force). The multistability of these flow modes is clearly explained in terms of degrees of freedoms in the nematic orientation. The number of degrees of freedom increases with increasing the spatial dimension of the system, and thus more complex orientation patterns arise in the higher dimension. Well-known defect structures arise and coarsen during simulations of the isotropic to nematic phase transition. The effect of shear flow on the defect generation process is to suppress the defect nucleation, and the simulations suggest a method of how to create defect-free nematic samples. The banded textures during and after cessation of flow are also captured by the complete theory.
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    Macromolecular Theory and Simulations 7 (1998), S. 355-357 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The average instantaneous shape of an unperturbed polyethylene chain is studied with a Monte Carlo technique. Different short-range interactions in the polyethylene chain are considered. The shape is evaluated as the ratio 〈L12〉:〈L22〉:〈L32〉, where L1≤L2≤L3 are the orthogonal components in the system of principal axes of gyration. Differences are found for different interactions in short- and medium-length chains, while for long chains all ratios converge to a common limit, which is about 1:2.7:12.0 for polyethylene chains.
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    Macromolecular Theory and Simulations 7 (1998), S. 391-397 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two new error-in-variables methods to estimate the reactivity ratios are developed. These are based on variants of the Skeist solution of the copolymerization equation. One method is suitable when one of the reactivity ratios is close to one and the other is for use when both ratios are close to one. In simulations, the latter is compared with an error-in-variables method based on the original Skeist solution. The results of the two error-in-variables methods and the extended Kelen-Tüdös method are given for a wide selection of reactivity ratios and error magnitudes.
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    Macromolecular Theory and Simulations 7 (1998), S. 407-419 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New models for the steric environment of Ti isospecific polymerization sites for poly(propylene) on MgCl2 microcrystals are proposed. They directly involve a donor molecule in order to obtain isospecific activable Ti atoms otherwise belonging to isolated adsorbed TiCl4 molecules or Ti2Cl8 dimers which are lacking of the required chirality for stereocontrol. The donor molecules able to attain at best this effect keep to some peculiar conformational rules settled by the authors in a previous theoretical-correlative study on highly active Lewis bases. The new 1,3-dimethoxypropane series suggested by the authors and recently patented by Montell has been examined in detail. Essentially three different types of closeness between Ti atoms and donor molecules can take place, in which different moieties of the diether compound help to build the ‘right’ steric environment in the site's neighbouring. In the three proposed models S1, S2, S3 the stereocontrol is attained through, respectively, one of the methoxy moieties, one of the methyls, and one of the central carbon atom substituents. New hypotheses on the role of Lewis bases in the preparation of isospecific heterogeneous Ziegler-Natta catalysts are discussed.
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    Macromolecular Theory and Simulations 7 (1998), S. 435-446 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work simulation calculations are presented describing the copolymerization of ethylene with acrylate monomers using sets of independently determined rate coefficients. The reaction scheme of the copolymerization which is implemented is derived logically from that of homopolymerizations. The simulation results are directly compared to experimental data achieved at 150°C and 2 000 bar in an almost ideally mixed vessel. Using the model without modification for copolymerizations with methyl acrylate and butyl acrylate the transferability was successfully tested. Both facts are in contrast to several studies presented in literature. Commonly at least some rate coefficients are adjusted and the model implementation is not standardized, especially when dealing with transfer to polymer reactions. Conversion, species concentrations and copolymer composition are well captured by the simulation model for an ideally mixed copolymerization vessel at several operation conditions using a uniform parameter set. This works out for both copolymerization systems. With respect to the molecular weight distribution based on the available data an estimation is possible. It is pointed out that for a precise description of the polymer properties the simulation model has to be refined. An important aspect for this purpose is to find sensors, enabeling the independent determination of the required rate coefficients.
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    Macromolecular Theory and Simulations 7 (1998), S. 399-405 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A correlative approach is illustrated in which some conformational features of Lewis bases used in Ziegler-Natta heterogeneous catalysts for isotactic poly(propylene) proved to be molecular descriptors strongly correlating with stereoregulating power and polymerization yield. They are both steric and statistical descriptors and have been obtained through the analysis of the entire rotational hypersurface of the considered compounds. The correlative study selected some of their values as necessary conditions for a good stereoregulating effect. Their calculation for new molecules led to the predictive evaluation of new chemical classes as efficient stereoregulating electron donors and to the choice of the most effective ones.
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    Macromolecular Theory and Simulations 7 (1998), S. 421-429 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We present a new method for describing photokinetics in the liquid crystalline or amorphous glassy state of polymers. A stochastic model has been developed in order to simulate the ordering process in azo side chain polymers which is induced by photoselective isomerization cycles. The dependence of the reorientation process on photochemical and thermal transition rate constants as well as the influence of matrix rigidity and cooperative interactions between the side chains is explained. With additional information about the molecular polarizabilities, the optical properties of the system, e.g. the evolution of birefringence, can be evaluated directly by this method.
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    Macromolecular Chemistry and Physics 199 (1998), S. 1807-1813 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Preparation, optical properties, and electrochemical redox behavior of poly(benzimidazole-4,7-diyl)s are reported. Dehalogenation polycondensation of 4,7-dibromobenzimidazole and its derivatives (2-heptyl and 2-phenyl derivatives) with zerovalent nickel complexes gives the corresponding polymers in 72-100% yield. Poly(benzimidazole-4,7-diyl) and its heptyl derivative have molecular weights of 1.3 × 104 and 3.8 × 104, respectively, as determined by light scattering measurements. In non-acidic solvents the polymers give rise to one absorption peak at about 300 nm, which is assigned to a π-π* transition occurring in the benzimidazole monomeric unit, and another absorption peak at a longer wavelength, which is considered to originate from the π-π* transition occurring in the π-conjugated main chain. The π-π* absorption peak, as well as the photoluminescence peak of the polymers, are shifted in acidic media due to protonation. The polymers are electrochemically active regarding reduction (or n-doping) and show electrochromism.
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  • 154
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    Macromolecular Chemistry and Physics 199 (1998), S. 2017-2022 
    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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  • 155
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    Macromolecular Chemistry and Physics 199 (1998), S. 1859-1864 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dichlorosilanes with ethyloligoglycoxypropyl substituents were synthesized from dichlorosilane and the respective allyl compounds. Wurtz-type coupling reaction led to a series of ether substituted polysilylenes with a distinct amphiphilic character. Formation of high molecular weight polymers becomes increasingly difficult as the length of the ether substituents is increased.
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  • 156
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A study of the effect of polymerization temperature on the microtacticity of poly(propylene) prepared using various MgCl2-supported catalysts has shown that, in almost all cases, an increase in temperature leads not only to higher proportions of isotactic polymer but also to increased stereoregularity of the isotactic fraction. The results indicate a greater relative increase in productivity, with increasing temperature, for highly isospecific as opposed to moderately isospecific centres. It is suggested that easier propagation after the occasional regioirregular (2,1-) insertion may contribute to this effect.
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  • 157
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    Macromolecular Chemistry and Physics 199 (1998), S. 1887-1893 
    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 novel poly(arylene ether ketone ketone)s were prepared from two novel oligomers and three different diacid chlorides via Friedel-Crafts polymerization. The oligomers 2,6-bis(4-phenoxybenzoyl)naphthalene and 5-tert-butyl-1,3-bis(4-phenoxybenzoyl)benzene were synthesized by Friedel-Crafts acylation of diphenyl ether with 2,6-naphthalenedicarbonyl dichloride and 5-tert-butylisophthaloyl dichloride, respectively, in the presence of AlCl3 as catalyst. Friedel-Crafts polymerization of either of these two novel oligomers with tert-butylisophthaloyl dichloride, isophthaloyl dichloride or 1,6-hexanedioyl dichloride gave six novel PEKK's, having Tg's in the range of 135--180°C, but only the naphthalene-based PEKKs displayed Tm's between 130 and 345°C. PEKK's containing the 5-tert-butylisophthaloyl group are soluble in polar solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N,N-dimethylformamide, THF, chloroform etc. Polymer PA1, which has a fully unsubstituted aromatic chain structure, is insoluble in common organic solvents and, moreover, shows polymorphism. Intrinsic viscosities and adhesion behavior of soluble PEKKs were also determined.
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  • 158
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    Macromolecular Chemistry and Physics 199 (1998), S. 1895-1900 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Trimethylsilylcellulose (TMSC) was prepared from commercial cellulose with a mixture of hexamethyldisilazane and chlorotrimethylsilane in the solvent system N,N-dimethylacetamide/lithium chloride. The soluble, highly silylated polymer (degree of substitution, DS 2.9) had a molar mass M̄w of 500 kg/mol and a molecular non-uniformity U = (M̄w/M̄n) - 1 of 2.9. In order to investigate the principal suitability of a continuous polymer fractionation for polysaccharides like cellulose derivatives and to obtain TMSC with different molecular weights and lower non-uniformity TMSC was fractionated by means of CPF (Continuous Polymer Fractionation), well-established in the field of synthetic polymers. The samples were fractionated using a mixed solvent, composed of toluene and dimethyl sulfoxide, and characterized by capillary viscometry, gel permeation chromatography (GPC), and GPC-light scattering coupling. The molar masses of the fractions range from 110 to 600 kg/mol and their U values vary between 0.9 and 1.9. The intrinsic viscosities of TMSC in tetrahydrofuran at 25°C and M̄w are related by [η] = K · Mwa, where K = 0.0089 mL/g and α = 0.82.
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  • 159
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    Macromolecular Chemistry and Physics 199 (1998), S. 1909-1915 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel one-pot syntheses of sulfur-containing polymers from a five-membered cyclic dithiocarbonate (5-phenoxymethyl-1,3-oxathiolane-2-thione (1)) and diamines were examined. Polydisulfides with M̄n 5400 ∼ 15800 were obtained in the oxidation polymerization of dithiols 2, which were obtained in situ by the reactions of 1 and diamines. When 1,12-dodecanediamine was employed, a polydisulfide with relatively high M̄n was obtained, while in the case of m-xylylenediamine, the polymerization was accompanied by intermolecular cyclization to give a polydisulfide with low M̄n. Polythiourethanes with M̄n 6500 ∼ 17200 were obtained in the polyaddition of 2 with 4,4′-methylenebis(phenyl isocyanate). The yields and M̄n values increase with increasing methylene chain length of 2. Polythioethers with M̄n 2600 ∼ 19900 were obtained by the polycondensations of 2 with α,α′-dibromo-p-xylene. The glass transition temperature (Tg) of the polymer decreases with increasing methylene chain length in the main chain.
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    Macromolecular Chemistry and Physics 199 (1998), S. 1927-1933 
    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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    Macromolecular Chemistry and Physics 199 (1998), S. 1939-1942 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The norbornene/ethylene copolymerization was studied using C2v- and Cs-symmetric metallocene catalysts in the presence of methylaluminoxane as a cocatalyst. The batch reactions were carried out at four different temperatures copolymerizing a constant amount of ethylene with the appropriate amount of norbornene. The activity decreases for the Cp2ZrCl2 catalyst and increases to a constant level for the [Ph2C(Flu)(Cp)]ZrCl2 catalyst when the norbornene/ethylene ratio in the reaction increased. The highest activities and the highest norbornene contents in the copolymers were achieved using the [Ph2C(Flu)(Cp)]ZrCl2. The microstructure of the copolymer determined with 13C NMR was observed to depend on catalyst, temperature and monomer ratio. Cp2ZrCl2 produces more norbornene blocks as a function of norbornene content in the copolymer and longer norbornene sequences than [Ph2C(Flu)(Cp)]ZrCl2. The correlation between the increasing norbornene content in the copolymer and the increasing glass transition temperature is more obvious for [Ph2C(Flu)(Cp)]ZrCl2.
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    Macromolecular Chemistry and Physics 199 (1998), S. 1951-1956 
    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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    Macromolecular Chemistry and Physics 199 (1998), S. 1973-1979 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, crystal structure and detatiled molecular mechanics calculations, including crystal packing interactions, of tetrahexylsubstituted sexithienylene are presented. Unexpectedly the molecule, which arranges in the P-1 space group, displays no herringbone arrangement, thienylenic rings are far from coplanarity and the alkylic side chains present different conformations. Molecular mechanics fully accounts for these findings. From crystal packing computations it is derived that different arrangements are unable to lower the packing energy, due to the closeness of two alkyl chains on the same side of the thienylenic backbone, which prevents interspersion of non-parallel molecules.
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    Macromolecular Chemistry and Physics 199 (1998), S. 2129-2140 
    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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    Macromolecular Chemistry and Physics 199 (1998), S. 2301-2310 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Propagation rate coefficients (kp) for the homopolymerization of cyclohexyl methacrylate (CHMA), glycidyl methacrylate (GMA) and 2-hydroxyethyl methacrylate (HEMA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique. Temperature was varied between -10 and 90°C and pressure up to 2500 bar. kp values for CHMA and GMA agree within the experimental accuracy of ± 20 per cent. They are by about a factor of 2.5 below kp of HEMA. The activation energies and activation volumes of kp of methacrylates studied so far, including linear and branched alkyl methacrylates, are close to each other: EA(kp) = (22 ± 2) kJ · mol-1 and ΔV≠(kp) = -(16 ± 2) cm3 · mol-1, respectively, indicating a pronounced family-type behavior.
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  • 166
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    Macromolecular Chemistry and Physics 199 (1998), S. 2321-2328 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new aromatic dicarboxylic acid, 4,4′-(2,6-naphthylenedioxy)dibenzoic acid (3), was synthesized by the fluoro-displacement reaction of p-fluorobenzonitrile with 2,6-naphthalenediol in the presence of potassium carbonate, followed by alkaline hydrolysis. A series of aromatic polyamides having inherent viscosities of 1.30-2.19 dL/g were prepared by the triphenyl phosphite activated polycondensation from the diacid 3 with sixteen aromatic diamines. Most of the resulting polymers were noncrystalline and readily soluble in a variety of polar solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP). Except for those polymers derived from p-phenylenediamine, benzidine, and 4,4′-bis(p-aminophenoxy)biphenyl, transparent, tough, and flexible films were cast from the DMAc or NMP solutions. The films had tensile strengths ranging from 70 to 91 MPa, elongations at break from 6 to 50%, and initial moduli from 1.35 to 2.32 GPa. The polyamides exhibit glass transition temperatures in the range of 178-300°C. Almost all polymers are stable up to 400°C, with 10% weight loss being recorded above 500°C, in air and nitrogen atmosphere.
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    Macromolecular Chemistry and Physics 199 (1998), S. 2341-2364 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The unique structure and reactivity of cellulose opens up various possibilities for the design of advanced materials based on this biomacromolecule. In the present feature the state of the art of selected cellulose functionalization reactions is discussed adequately considering own research results. In particular, new synthesis paths to ionic cellulosics, both with controlled functionalization patterns and unconventional combinations of different functional groups (hydrophilic-lipophilic), as well as new synthesis concepts are presented. An important approach to new cellulosics is the reaction via an induced phase separation with solid alkali hydroxide particles. Starting from solutions of cellulose in N,N-dimethylacetamide/LiCl or from organo-soluble cellulose derivatives of different hydrolytic stability dissolved in dimethyl sulfoxide, subsequent etherification and esterification yield cellulose products of unconventional functionalization patterns and properties. Not only reactions directed towards the hydroxyl groups - the primary reactive sites - is given attention but also nucleophilic displacement reactions at the carbon atoms appear as synthesis tool to new polysaccharide materials.
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    Macromolecular Chemistry and Physics 199 (1998), S. 2365-2378 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For poly(TMPS)Poly(oxydimethylsilanediyl-1,4-phenylene-dimethylsilanediyl). fractions and blends of fractions, it has been established experimentally that the isothermal spherulitic growth rate, G, and physical properties are strongly interrelated. Correlations also depend strongly upon molecular weight. Below the melt viscosity entanglement molecular weight Mc, G is very dependent upon molar mass whenever crystallized fractions are chain folded, brittle and lacking in tiemolecules. Above Mc, G is essentially constant, and polymers are tough and durable because of trapped entanglements, tie-molecules and the like, that are mostly located at lamellar interfaces. Growth rate measurements and other physical properties of poly(TMPS) are inconsistent with the claim that reptation is a viable process in the crystallization of this polymer. Selective chemical etching of poly(TMPS) crystal surfaces of moderate MW (≈35 × 103 Daltons) show an increase in crystallinity from ≈75% to 95% as the surface is removed, thus testifying to a less than ordered surface morphology. Notably, in melt crystallized high MW fractions, approaching 106 Daltons and beyond, the morphology is much less well organized than it is in moderate to low MW fractions. Trends in the physical properties of polyethylenes, polyisoprene and poly-(ethylene oxide) MW fractions are analogous in behavior to melt crystallized poly(TMPS) fractions over comparable molecular weights ranges, and consistent with a morphology that is dependent upon polymer chain length.
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  • 169
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The chain transfer coefficient (Cs) has been determined for 2-methyl-2-propanethiol (t-Bu-SH) in the solution polymerization of methyl methacrylate (MMA). Three different analytical methods were investigated. The Mayo and chain length distribution (CLD) methods yielded consistent Cs values of 0.12 and 0.13, respectively, at 60°C. A third, new approach to the evaluation of Cs values was also attempted using Matrix-Assisted-Laser-Desorption-Ionisation (MALDI) Time-Of-Flight Mass Spectrometry to analyse the end-groups of the polymer chains. The values of Cs obtained from MALDI analyses were not consistent with the other two methods and the relative intensities of the peaks with different end-groups were found to be dependent on the selection of cation.
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  • 170
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin films of methacrylic polymers, obtained by copolymerization of perfluorodecyl- and 2-ethylhexyl methacrylate, were prepared by spin coating or by the Langmuir-Blodgett (LB) technique. The permeability to water of these materials was studied by means of the attenuated total reflection (ATR) technique, revealing the strong dependence of the swelling phenomenon on the films' surface composition and structural order. The presence of polar groups on the film/air interface facilitates the wetting of the thin films.
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    Macromolecular Chemistry and Physics 199 (1998), S. 223-237 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: AB and ABA block copolymers are synthesized by direct living anionic polymerization where the A-block is a liquid crystalline side chain polymer (LC-block) and the B-block is an isotropic polymer (I-block). Similar to amphiphilic block copolymers with a “hydrophilic” water soluble segment and a “hydrophobic” water insoluble part, the LC/I block copolymers consist of the “nematophilic” LC-block that is soluble in a nematic solvent and the “nematophobic” segment that is insoluble in nematic solvents. The behaviour of these LC/I block copolymers and corresponding homopolymers is analyzed in dilute nematic solutions of low molar mass liquid crystals. The effects of varying molecular weight, chemical constitution of blocks and block length ratio are investigated. Copolymers with a high fraction of the I-block are insoluble in the nematic solvent as indicated by phase separation. Copolymers with a high fraction of the LC-block are completely soluble. If the weight fraction of the LC-block is in the range of 0.46 to 0.85, thermoreversible thread-like aggregates are formed in the nematic solvent. These thread-like aggregates have a uniform diameter of 2-3 μm and their long axis perfectly follows the director field of the nematic matrix. The formation of these structures is discussed in terms of copolymer concentration, temperature and influence of aligning surfaces. From simple geometrical packing arguments it can be assumed that these thread-like aggregates consist of bilayered vesicles. In contrast to the spherical shape of amphiphilic block copolymer vesicles in aqueous solution, the rod-like shape of vesicles in nematic solution is caused by the minimization of free elastic energy density of the nematic matrix.
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  • 172
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Small block copolymers consisting of a hydrophilic poly(ethylene glycol) block and a second, also hydrophilic, moiety which strongly interacts with alkaline earth ions were synthesized by diverse reaction sequences based on poly(ethylene glycol) monomethyl ethers (MW = 2000 and 5000 g/mol, respectively). These starting blocks were transferred to the poly(ethylene glycol) monomethyl monoglycidyl ether or to poly(ethylene glycols) with one terminal acid chloride group. Both intermediates were subsequently reacted with poly(ethyleneimine) (MW = 700 g/mol) and bromoacetic acid to yield poly(ethylene glycol)-block-poly[(N-carboxymethyl)ethyleneimine] (PEG-b-PEIPA, average MW = 3800 resp. 6800 g/mol) as a polymeric analog of EDTA. The terminal epoxy group is also convenient for the connection of simple pèptide sequences. For the desired purpose of ion binding, poly(aspartic acid) (PAsp) was applied, resulting in the block copolymer PEO-b-PAsp. A simple testing procedure concerning the inhibition of calcium carbonate precipitation was applied for the prepared structures. A comparison with commercial builders for water treatment such as poly[(acrylic acid)-co-(maleic anhydride)] or poly(aspartic acid) stresses the superb calcium carbonate crystallization inhibition efficiency (up to the 20 fold) of the double hydrophilic block copolymer stabilizers.
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    Macromolecular Chemistry and Physics 199 (1998), S. 2489-2494 
    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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    Macromolecular Chemistry and Physics 199 (1998), S. 2527-2532 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(styrene-co-acrylic acid) on sulfonation with concentrated sulfuric acid exhibits an unusual acid-base indicating property: an intense purple colour in alkali which changes sharply to yellow at the equivalence point. The acid-base indicating property of the polymer can not be explained by the simple structure of the sulfonated copolymer. On the basis of infrared and nuclear magnetic resonance studies it is suggested that the copolymer during sulfonation undergoes an internal Friedel Crafts acylation followed by cyclic dehydration leading to a conjugated structure. A possible mechanism is proposed for the colour change with change in pH. The copolymer was prepared also in form of spherical beads which can be used repeatedly as indicator in acid-base titrations.
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  • 175
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The atom transfer radical polymerization (ATRP) of styrene has been studied using complexes of copper carboxylates. Compared with systems employing copper halides as the catalyst, the use of the copper carboxylates resulted in faster polymerization rates and higher polydispersities. A ligand (dNbpy) to Cu(I) carboxylate ratio of 1 was sufficient to achieve the maximum rate of polymerization. The addition of a small amount of either Cu(II) or Cu(I) halide to the copper carboxylate system yielded polymers with better controlled molecular weights and lower polydispersities yet the polymerization still remained relatively fast.
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    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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  • 177
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    Macromolecular Chemistry and Physics 199 (1998), S. 2293-2299 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization of 1,2,3,6-tetrahydrophthalic anhydride (THPhA) as electrophilic monomer and N-(2-hydroxyethyl)ethyleneimineSystematic name: N-(2-hydroxyethyl)aziridine. as nucleophilic monomer in acetonitrile without initiator was investigated. The copolymers show low incorporation of THPhA in the main chain and preferential incorporation in the side chain by esterification reaction of the hydroxymethyl group. On the basis of the spectroscopic data a copolymer structure is proposed.
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  • 178
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    Macromolecular Chemistry and Physics 199 (1998), S. 2311-2320 
    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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  • 179
    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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  • 180
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    Macromolecular Chemistry and Physics 199 (1998), S. 2613-2618 
    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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  • 181
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    Macromolecular Chemistry and Physics 199 (1998), S. 2625-2630 
    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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  • 182
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    Macromolecular Chemistry and Physics 199 (1998), S. 2635-2640 
    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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  • 183
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    Macromolecular Chemistry and Physics 199 (1998), S. 2409-2416 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report an experimental investigation on long chain branching (LCB) in ethylene polymerization with the Dow Chemical's constrained geometry catalyst system, CGC-Ti/TPFPB/MMAO, using a continuous stirred-tank reactor (CSTR) at 140°C, 3.45 × 103 kPa, and a mean residence time (τ) of 4 min. The effects of the catalyst (CGC-Ti) and co-catalyst (TPFPB and MMAO) concentrations on the catalyst activity, polymer molecular weight, and shear thinning were systematically examined. The boron cocatalyst had a great influence on the CGC activity. Increasing the ratio TPFPB/CGC-Ti from 0.66 to 5 gave ethylene propagation rates from 1.65 × 103 to 1.36 × 104 L · mol-1 · s-1. The addition of MMAO appeared to be essential, most likely acting as an impurity scavenger. The LCB polyethylenes showed enhanced shear thinning properties. The melt flow index ratios I10/I2 were in the range of 6.96 to 23.4, with the I2 of 0.172 to 0.681 g/10 min. The weight-average molecular weight Mw was correlated to I2 using a power equation within narrow I10/I2 ranges. The exponential factors were in the range of 4.24 to 6.31. The experimental and calculated Mw's were in a good agreement.
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  • 184
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    Macromolecular Chemistry and Physics 199 (1998), S. 2511-2516 
    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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  • 185
    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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  • 186
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New poly(urea-imide)s having inherent viscosities of 0.26-0.57 dL/g were synthesized in two steps by ring-opening polyaddition of N,N′-dimethyl-N,N′-bis(aminophenyl)ureas to various aromatic tetracarboxylic dianhydrides giving poly(amic acid)s, followed by thermal cyclodehydration. All the poly(urea-imide)s showed amorphous patterns in the wide angle X-ray diffractograms. Most of the poly(urea-imide)s were soluble in organic solvents, especially phenolic solvents such as m-cresol and o-chlorophenol, and the polymers synthesized from the 3,4′-type diamine were more soluble than those from the 4,4′-type monomer. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the poly(urea-imide)s were in the range of 218-263°C and 455-500°C, respectively.
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  • 187
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    Macromolecular Chemistry and Physics 199 (1998), S. 463-470 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Group transfer polymerization (GTP) of methyl methacrylate (MMA) was carried out using potassium bibenzoate (KBB) in presence of 18-crown-6 as catalyst and 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene (MTS) as initiator in tetrahydrofuran (THF) at 25°C. The performance of this catalyst was compared with tetrabutylammonium bibenzoate (TBABB) catalyst. Broader polydispersity and lower initiator efficiency were observed for the polymers prepared using KBB/18-C-6 catalyst. Kinetic studies were conducted using both catalysts under identical conditions to better understand the effect of the countercation in GTP.
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  • 188
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    Macromolecular Chemistry and Physics 199 (1998), S. 471-488 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article summarizes recent experiments relating measurements of molecular orientation to bulk rheological behavior in liquid crystalline polymers (LCPs) under shear. The principal experimental techniques are flow birefringence and x-ray scattering. Since LCPs usually exhibit a “polydomain” texture, measurements of flow-induced orientation reflect both the local distribution of molecular orientation around the director and the heterogeneous distribution of director orientations in the sheared LCP. In model lyotropic solutions of poly(benzyl glutamate) (PBG) and hydroxypropylcellulose (HPC), there are clear structural signatures of a transition from director tumbling dynamics at low Deborah number to flow alignment at high Deborah number. Rheo-optical measurements of the full refractive index tensor in PBG allow the orientation predictions of microstructural theories for LCP rheology to be quantitatively tested. At low shear rates the two model materials differ: PBG solutions exhibit significant orientation, while HPC solutions show little orientation. This is correlated with the presence of so-called “Region I” shear thinning in HPC solutions. Conversely, in PBG solutions of high concentration, x-ray scattering measurements demonstrate that Region I arises from the presence of a hexagonal phase. The model systems are further differentiated in relaxation. Molecular orientation increases in PBG solutions, but decreases in HPC solutions upon flow cessation; these differences are manifested in the evolution of dynamic properties. Finally, structural investigations of a PBG solution and a nematic surfactant solution during step changes in shear conditions are used to interrogate tumbling dynamics at low shear rates and test microstructural tumbling models.
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  • 189
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the present work, a comparative study of the dynamic mechanical and dielectric properties of two related polymers, poly(pentachlorophenyl methacrylate) (PPCPM) and poly(phenyl methacrylate) (PPhM), was carried out. In both polymers a similar relaxational behaviour was observed. Dielectric relaxation measurements give an improved resolution as compared with that obtained from dynamic mechanical techniques for a given process. The polymers show a secondary loss peak at approximately room temperature and a prominent peak overlapped with the conductivity electrode polarization contributions at temperatures above the glass transition temperature, studied by dielectric relaxation measurements. The activation energy associated with the relaxation process at low temperature is about 77 kJ · mol-1 (which is similar to that observed in poly(alkyl methacrylates)) whose origin is attributed to the hindered partial rotation of the carboxymethyl group. An improved method of separating dipolar contributions from the non-dipolar ones was used to characterize the high temperature relaxation process and to obtain information from the diffusion coefficient of the conducting species.
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  • 190
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    Macromolecular Chemistry and Physics 199 (1998), S. 589-595 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When benzene/cyclohexane, toluene/cyclohexane and o-xylene/cyclohexane mixtures are subjected to pervaporation through a side-chain liquid-crystalline polymer (LCP) membrane in the liquid-crystalline state, the permeation rate increases with increasing temperature and the LCP membrane exhibits permselectivity for the aromatic hydrocarbon. The permeation rate and permselectivity of the LCP membrane for each mixture decreases with increasing molecular size of the aromatic hydrocarbon in the binary feed mixture.
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  • 191
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    Macromolecular Chemistry and Physics 199 (1998), S. 583-588 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The “living” free radical polymerization of styrene in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) affords low polydispersity polystyrene (PS). The thermal instability of the linkage of the TEMPO group of the PS, however, restricts the processing possibilities of the resin. Therefore, different methods were tried to remove the TEMPO end groups from the polystyrene. It was found that oxidation with m-chloroperbenzoic acid (MCPA) and heating in the presence of 2,6-di-tert-butyl-4-methylphenol give the best results while other reagents such as cumene hydroperoxide or lithium aluminium hydride only reduce the concentration of the TEMPO end groups in the final polymer. The product of the oxidation with MCPA was investigated with MALDI-TOF MS and with 1H NMR spectroscopy. It was found that a signal at 4 ppm commonly referred to the polystyrene end connected to the TEMPO group overlaps with an absorption caused by the Diels-Alder adduct of the thermally self-initiated polystyrene. Hence, the facile removal of the TEMPO group gives the opportunity to determine the degree of autopolymerization in a TEMPO based polystyrene.
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  • 192
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    Macromolecular Chemistry and Physics 199 (1998), S. 597-606 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of i-polypropylene and a semiflexible liquid crystalline polymer (iPP/LCP 90/10 and 80/20 w/w) were compatibilized with 2.5, 5 or 10 wt.-% PP-g-LCP copolymers. The crystal structure, crystallization behaviour and morphology of the compatibilized blends have been investigated by differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and optical microscopy. It is shown that the nucleation rate and crystallization rate of iPP strongly increased in the compatibilized blends in comparison to the uncompatibilized ones. In compatibilized blends, while iPP spherulites get smaller and crystallinity degree increases, the crystal growth mechanism of iPP remains unchanged. An assumption has been made about the mechanism of the compatibilization, using graft copolymers constructed of segments identical to the blended polymers: the PP segments of PP-g-LCP copolymers, if long enough, cocrystallize with bulk iPP, compatibilizing partially the two components; the LCP grafts of the copolymers cocrystallize with the bulk LCP or enter the amorphous phase of the blends. The miscibility of each part of the copolymer compatibilizers with the corresponding bulk component of the blend leads to a reduction of the interfacial tension and to a strong reduction of the dimensions of dispersed LCP phase. The compatibilized iPP/LCP blends display improved crystallization kinetics, enhanced degree of crystallinity and improved interphase adhesion. Consequently, an improvement of the mechanical properties and rheological characteristics should be expected for these blends.
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  • 193
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    Macromolecular Chemistry and Physics 199 (1998), S. 607-612 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Scope and limitation of the vinyl ether block copolymerization of isobutyl vinyl ether (IBVE) and 2-chloroethyl vinyl ether (CEVE) initiated by CH3CHIOR/ZnI2 were studied. These polymerizations exhibit the characteristics of a living polymerization. Di- and triblock copolymers were synthesized by sequential monomer addition (IBVE, CEVE). The poly(2-chloroethyl vinyl ether) (PCEVE) segment in those block copolymers is of particular interest because of the possibility to modify this segment by nucleophilic substitution of the chlorine. This strategy allows the synthesis of tailor made amphiphilic block copolymers.
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  • 194
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    Macromolecular Chemistry and Physics 199 (1998), S. 619-623 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal polymerizations of alkali and alkaline earth 4-vinylbenzoates (4-VBAs) in bulk were investigated. The relative reactivity of the alkali salts decreases in the following order: K 〉 Na 〉 Li, which is in reverse order to that of alkali methacrylates. In the polymerization of K-4-VBA at 240°C, the number-average molecular weight decreases with increasing reaction time, although the yield of polymer increases. The polymerization of the K salt proceeds as long as the crystallinity of the monomeric salt is maintained, and is terminated when there is no crystalline compound in the reaction mixture left. The relative reactivity of the alkaline earth salts decreases in the following order: Mg 〉 Ca 〉 Sr ≫ Ba. The polymerization of Mg-4-VBA proceeds rapidly at 240°C in the initial stage (30 min) and then levels off, however, the appearance of the reaction mixture still remains crystalline.
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  • 195
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The active sites precursors on a MgCl2-supported Ziegler catalyst and the correlation to catalyst stereospecificity were investigated in the initial stage of propene polymerization in terms of the interaction of a variety of ethoxysilanes with the structure (Me)nSi(OEt)4-n. The kinetic study using the stopped-flow technique indicated that the interaction of the catalyst with a variety of ethoxysilanes prevents formation of active sites, and the degree of inhibition depends upon the number of ethoxy groups. It is considered that the values of propagation rate constant on the isospecific active sites are essentially the same regardless of the structure of the ethoxysilane, but the ratio of the isospecific active sites to the total number of active sites depends on the number of ethoxy groups. The same tendency in the variation of the activity, the stereospecificity, and the kinetic parameters depending on the number of ethoxy groups attached to a silane atom was observed regardless of whether the ethoxysilanes were treated with the catalyst or with triethylaluminium before polymerization.
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  • 196
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    Macromolecular Chemistry and Physics 199 (1998), S. 625-632 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For the purpose of grafting conjugated molecules on metal or oxide electrodes (which is an essential step towards a new generation of reliable organic light emitting diodes), we have synthesized soluble oligocyclohexadienes (12 cyclic units) by anionic polymerization and functionalized them by carboxylic acids, thiol and siloxane. Aromatization of the oligomer to oligo(para-phenylene) (OPP) is carried out by dehydrogenation with chloranil. The adsorption of the carboxylic oligo(para-phenylene) derivatives on indium tin oxide powder is investigated by solution equilibration. In tetrahydrofuran (THF) an equilibrium constant of K = 21 500 1 · mol-1 and a maximum surface coverage (Nmax) of 4 μmol/m2 are obtained by using the Langmuir equation. A characteristic area of 40 Å2 per molecule is inferred from the surface density of absorbed oligo(para-phenylene), which indicates that a densely packed monolayer of vertically adsorbed molecules is formed.
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  • 197
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    Macromolecular Chemistry and Physics 199 (1998), S. 655-666 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Quinoid thiophene oligomers 6, 7 and 8 were prepared and characterized as model compounds of small bandgap polymers and were shown to have solid state bandgaps in the range of 1.31-2.15 eV and a lowest energy solution optical absorption maximum (λmax) of 480-676 nm. It was found that the bandgap and ionization potential decrease and electron affinity increases with increasing size of the quinoid oligomer. These results of the model compound studies are in agreement with theoretical predictions for the electronic properties of polythiophene with quinoid geometry and suggest that small bandgap polymers can be achieved by direct incorporation of quinoid structure in the polymer backbone.
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  • 198
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of MgCl2-supported Ziegler-Natta type catalysts containing different amounts of ethyl propionate (EP) as internal donor were prepared and tested in the propene polymerization in order to evaluate their activity and stereospecificity. These catalysts were obtained by treating chemically activated MgCl2 supports bearing variable ethyl propionate contents with TiCl4. The supports and the derived catalysts so prepared were characterized by elemental analysis, XRD and FT-IR techniques. The polymerization tests were carried out at 70°C and 7.5 atm using dimethoxydiphenylsilane as external donor and hydrogen as chain transfer reagent. A correlation between the procatalyst structure and composition and their activity as well as stereoselectivity was obtained. On processing the obtained results it was possible to evaluate the trend of both the activity and the stereoselectivity on the simultaneous changes of the Ti/Mg, Ti/EP and EP/Mg molar ratios. Actually, these catalysts show the best performance with a composition corresponding to the following molar ratios: Ti/Mg ≈ 0.03, Ti/EP ≈ 0.14 and EP/Mg ≈ 0.27. Finally, these studies confirm again that the active supports and the procatalysts are essentially based on a Cl-Mg-Cl chain structure model.
    Additional Material: 13 Ill.
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  • 199
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 677-686 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New director reorientation experiments with a series of different elastomers are presented. Elastomers with a permanent monodomain structure are stretched perpendicular to their initial director alignment. After a threshold strain is exceeded, stripe-domains are formed parallel to the external stress with alternating sense of rotation in each domain. With increasing network density the average spacing of the stripes decreases. The anisotropy of the polymer chains is varied both by changing the reduced temperature and by introducing smectic clusters via copolymerisation with a mesogen forming a smectic-A phase. The anisotropy of the network is analyzed by the isobaric expansion of the sample parallel to the director as a function of temperature. Reorientation experiments at different reduced temperatures show that the interval of strains, where the director rotates, depends on this anisotropy. The experiments on cybotactic-nematic elastomers reveal that smectic fluctuations give a significant contribution to the threshold. The results are compared to the theory of Warner and Terentjev, yielding a good qualitative agreement.
    Additional Material: 12 Ill.
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  • 200
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectra of the three title polymers have been determined for polymers of different tacticities. Assignments to the various possible HH/HT/TT and m/r dyad structures were made. These were facilitated by the use of optically active monomers in the case of 1 and 3. In the precursor polymers the cis double bonds in the HH dyads were less readily hydrogenated than those in the other types of dyad. Methyl substitution parameters are summarized for the hydrogenated polymers and their unsaturated trans precursors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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