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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of amino-terminated telechelic polybutadiene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1353-1359 
    Details
    ISSN: 0887-624X
    Keywords: telechelic polybutadiene, synthesis and characterization ; telechelic polybutadiene, end-group analysis ; telechelic polybutadiene, transformation of amidino into amino end-groups ; amino-terminated telechelic polybutadiene, functionalities of two ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Butadiene was polymerized with water-soluble 4,4′-azobis(amidinopropane)dihydrochloride initiator in an ethanol-water medium at 60°C. Important variables, such as the initiator concentration, monomer concentration, solvency, and polymerization time and temperature were studied. 13C-NMR studies showed that no observable chain transfer to ethanol occurred during the polymerization. The conversion of monomer to polymer was significantly increased while maintaining a relatively narrow molecular weight distribution by intermittent feed of the initiator. The amidino end-groups of the polymer were transformed into amino groups by reduction using lithium aluminum hydride in THF, so that amine-terminated polybutadiene was obtained. The amino functionality of the polybutadiene was determined by titration to be 2.0. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330817
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  • 2
    Electronic Resource
    Electronic Resource
    On-line monitoring, modeling, and model validation of semibatch emulsion polymerization in an automated reactor control facility (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1553-1571 
    Details
    ISSN: 0887-624X
    Keywords: seeded emulsion polymerization ; gel effect ; radical entry ; particle size sensor ; semibatch model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The modeling of the semibatch emulsion polymerization of styrene and its validation against data obtained from a reactor facility is presented. The model, which describes the growth of a monodisperse polystyrene seed as neat monomer is fed to the reactor, incorporates recent findings in radical diffusion and kinetics. The current controversy surrounding radical absorption into particles is handled by considering absorption via propagation, diffusion, and collision in the model. Simulation results including weight fraction polymer inside the particles and particle diameter are compared to data obtained from a custom-designed and built automated reactor control facility capable of on-line density and on-line particle diameter measurements. Good agreement between simulation results and experimental data are obtained for any of the three absorption mechanisms considered by varying only one adjustable parameter located in the absorption rate coefficient relation. A sensitivity analysis of the model to this adjustable parameter, using the program ODESSA, is also presented and shown to be an important tool in the validation procedure. Lastly, an analysis of the dynamics of the process shows the variety of phenomena that can be obtained in a semibatch reactor including regions that exhibit pseudosteady states, autoacceleration of the rate, and limiting conversion. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1553-1571, 1998
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Calorimetric monitoring of emulsion copolymerization reactions (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 2907-2913 
    Details
    ISSN: 0887-624X
    Keywords: calorimetric monitoring ; emulsion copolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approach for monitoring both the overall conversion and the cumulative copolymer composition in emulsion copolymerization systems via calorimetric measurements was developed. The approach was checked by carrying out batch emulsion copolymerizations of methyl methacrylate/n-butyl acrylate, n-butyl acrylate/vinyl acetate, and methyl methacrylate/vinyl acetate and comparing calorimetric based estimations with off-line determinations of both the overall conversion and the cumulative copolymer composition. A good agreement was achieved for most of the cases studied. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080311204
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  • 4
    Electronic Resource
    Electronic Resource
    Particle growth in butadiene emulsion polymerization, 2.Part 1: cf.3. Gamma radiolysis (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 635-640 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the emulsion polymerization of butadiene at 60°C in Smith-Ewart interval III were investigated using gamma radiation to produce initiating species. The aim of this work was to determine radical desorption rate coefficients through monitoring non-steady state kinetics. The acquired data of the average number of radicals per particle (n) were in good agreement with data obtained from chemically initiated experiments. It was shown that the approach to steady state is kinetically determined and that thermal background initiation is negligible in the butadiene emulsion polymerization. While radical desorption rate coefficient data was determined with high uncertainty, the results are consistent with the transfer diffusion mechanism of radical exit.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950220
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  • 5
    Electronic Resource
    Electronic Resource
    New approach for the estimation of kinetic parameters in emulsion polymerization systems. II. Homopolymerization under conditions where n̄ 〉 0.5 (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 2187-2197 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new approach for the estimation of kinetic parameters in emulsion polymerization systems in which the average number of radicals per particle exceeds 0.5 is presented. The approach uses the time evolution of the conversion in chemically initiated systems and is based on a model that includes fundamental parameters such as the propagation rate constant, kp, the termination rate constant in the polymer particles, kt, the rate coefficient for initiator decomposition, kI, and the entry, ka, and exit, kd, rate coefficients. It was found that kp, kt, kI, ka, and, under some circumstances, kd can be accurately estimated provided that termination in the aqueous phase is significant. When the extent of the aqueous phase termination is negligible, only kp, kt, and kI can be estimated. The effect of both the experimental noise level and the run-to-run irreproducibility on the accuracy of the estimates was studied. In addition, it was found that significant inaccuracies resulted from the poor determination of the exact time when polymerization begins. A method to circumvent this problem was proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451215
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  • 6
    Electronic Resource
    Electronic Resource
    Deformational dynamics and nmr relaxation of supercoiled DNAs (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1023-1056 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and internal dynamics of supercoiled pUC 8 DNA (2717 bp) are examined by dynamic light scattering, and the magnitude and uniformity of its torsional rigidity are determined using time-resolved fluorescence polarization anisotropy of intercalated ethidium dye. Neither measurement gives any indication of an appreciably reduced bending or twisting rigidity, or anomalously rapid internal motions. For 31P, in supercoiled pUC 8, we measure T2 = (2.0 ± 0.5) × 10-3 s. This lies within the range of present theoretical estimates obtained using normal rigidities. The proton linewidths observed for pUC 8 and pBR322 (4363 bp) DNAs are within a factor of 2-3 of those similarly estimated assuming ordinary rigidities.According to Bendel, Laub and James [(1982) J. Am. Chem. Soc. 104, 6748-6754], supercoiled pIns36 DNA (7200 bp) exhibits an astonishingly long T2 = 1.17 s for 31P, a slowest rotational relaxation time, τ = 5 × 10-9 s, and an enormously reduced bending rigidity. Serious questions raised by these findings are examined here. The 5 × 10-9 s slowest rotational relaxation time is shown to be physically inadmissible.The nmr relaxation theory developed previously by Allison, Shibata, Wilcoxon, and Schurr [(1982) Biopolymers 21, 729-762], is modified to incorporate new results for deformable filaments, which directly introduce the highly nonexponential tumbling correlation function for reorientation of the local helix axis. Essential requirements for a complete calculation of R2, including estimation of the tumbling correlation function and evaluation of the still unknown DIP/CSA cross-term, are described in detail. Slow coil-deformation modes analogous to the Rouse-Zimm modes of linear DNAs are shown to make an important, if not dominant, contribution to the R2 relaxation rate. Geometrical parameters in the theory are chosen to provide good agreement with literature data for 600-bp linear DNA. Using this theory and an informed guess for the tumbling correlation function, we find that the 31P-nmr relaxation data of Bendel et al., if correct, necessarily impose on their DNA one or more extreme properties, such as enormously reduced bending or twisting rigidities. In contrast, the same theory yields reasonable agreement with the T2 reported here for 31P in supercoiled pUC 8 DNA when its rigidities are assumed to be quite ordinary.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240609
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  • 7
    Electronic Resource
    Electronic Resource
    On the role of magnesium ions in RNA stability (1998)
    New York : Wiley-Blackwell
    Biopolymers 48 (1998), S. 113-135 
    Details
    ISSN: 0006-3525
    Keywords: divalent cations ; magnesium ; RNA ; ion binding ; RNA folding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Divalent cations, like magnesium, are crucial for the structural integrity and biological activity of RNA. In this article, we present a picture of how magnesium stabilizes a particular folded form of RNA. The overall stabilization of RNA by Mg2+ is given by the free energy of transferring RNA from a reference univalent salt solution to a mixed salt solution. This term has favorable energetic contributions from two distinct modes of binding: diffuse binding and site binding. In diffuse binding, fully hydrated Mg ions interact with the RNA via nonspecific long-range electrostatic interactions. In site binding, dehydrated Mg2+ interacts with anionic ligands specifically arranged by the RNA fold to act as coordinating ligands for the metal ion. Each of these modes has a strong coulombic contribution to binding; however, site binding is also characterized by substantial changes in ion solvation and other nonelectrostatic contributions. We will show how these energetic differences can be exploited to experimentally distinguish between these two classes of ions using analyses of binding polynomials. We survey a number of specific systems in which Mg2+-RNA interactions have been studied. In well-characterized systems such as certain tRNAs and some rRNA fragments these studies show that site-bound ions can play an important role in RNA stability. However, the crucial role of diffusely bound ions is also evident. We emphasize that diffuse binding can only be described rigorously by a model that accounts for long-range electrostatic forces. To fully understand the role of magnesium ions in RNA stability, theoretical models describing electrostatic forces in systems with complicated structures must be developed. © 1999 John Wiley & Sons, Inc. Biopoly 48: 113-135, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the urinary polymer-related material from rats given poly[biguanide-1,5-diylhexamethylene hydrochloride] (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2591-2605 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die gastrointestinale Absorption von Poly(biguanid-1,5-diylhexamethylen-hydrochlorid) (1) in Ratten beträgt nur 5,6% einer einzigen oralen Dosis, und auch nach Langzeitbehandlung liegen die Konzentrationen im Gewebe höchstens bei 0,3 μg g-1. Durch cinfache chromatographische und spektroskopische Methoden konnte gezeigt werden, daß die im Harn ausgeschiedenen Substanzen in kleinen Mengen aus 1-Oligomeren mit zwer Cyanguanidino-Endgruppen bestehen, sowie aus Spuren von 3,3′-Dicyano-1,1′-hexamethylendiguanidin (8a) und einer Verbindung, die für 1-(6-Aminohexyl)-3-cyanoguanidin (2) gehalten wird, und die bei der Synthese von 1 entsteht. Die Bestandteile von 1 werden demnach in Ratten nicht metabolisiert.
    Notes: Gastro-intestinal absorption in rats of poly[biguanide-1,5-diylhexamethylene hydrochloride] (1) amounts to only 5,6% of a single oral dose, and after chronic administration, tissue concentrations do not exceed 0,3 μg g-1. It has been shown by simple chromatographic and spectroscopic methods that urinary polymer-related material consists of small amounts of 1-oligomers, with two cyanoguanidino end groups, as well as the trace constituents, 3,3′-dicyano-1,1′-hexamethylenediguanidine (8a) and a compound which is considered to be 1-(6-aminohexyl)-3-cyanoguanidine (2) that is formed during the synthesis of 1. Hence, the constituents of 1 are unmetabolized in rats.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770902
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  • 9
    Electronic Resource
    Electronic Resource
    Anionic syntheses of terminally functionalized ethylene oligomers (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 4205-4226 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic procedures for preparation of terminally functionalized linear ethylene oligomers are described. The preferred synthetic method is anionic oligomerization of ethylene with n-butyllithium-tetramethylethylenediamine and electrophilic substitution of the living oligomer so-formed. Conditions and procedures for subsequent chemistry to elaborate the end groups of these oligomers are described. These procedures afford strictly linear ethylene oligomers which contain a wide variety of end groups and which range in molecular weight from 1000 to 4500 (Mn). The product oligomers were characterized spectroscopically as toluene-d8 solutions at 110°C using multinuclear NMR, FT-IR, fluorescence, and UV-visible spectroscopies as appropriate. Alternative stepwise approaches to such oligomers are also discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271226
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  • 10
    Electronic Resource
    Electronic Resource
    Modification of polyolefin surfaces with iron cluster oxidants (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 389-396 
    Details
    ISSN: 0887-624X
    Keywords: polyethylene ; polypropylene ; oxidation ; biodegradation ; C—H bond activation ; functionalization ; XPS ; ATR-IR ; surface ; Gif ; oxidase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe3O(OCOCH3)6(C6H5N)3.5 and FeCl3 • 6H2O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300306
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