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  • Polymer and Materials Science  (18)
  • 2015-2019
  • 1970-1974  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Poly α-ester degradation studies. IV. Rheological studies of polymer degradation (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2031-2043 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Farol-Weissenberg rheogoniometer has been used to follow molecular weight changes during the degradation of certain poly-α-esters in the melt state. By observing the change in melt viscosity at low shear rates it had been shown that the decomposition of the poly(isopropylidene carboxylate) is substantially first-order with respect to the molecular weight of the residual polymer. The derived kinetic parameters are in good agreement with those previously obtained by other techniques. This provides a substantial piece of supporting evidence for the view that degradation takes place predominantly by intramolecular ester interchange involving the formation of 1,1,4,4,-tetramethylglycollide. The introduction of β-chlorine atoms into the polymer structure leads to a more complex degradation pattern. Thus the presence of a single β chlorine atom per repeat unit, as in poly(3-chloro-2-methyl-2-hydroxypropionic acid) leads to a substantially similar dependence on molecular weight with the added complication of progressive crosslinking which becomes more apparent in later stages of the reaction. This crosslinking reaction plays an increasingly important part as the extent of chlorination of the polymer is increased. In addition, the presence of chlorine leads to an increased sensitivity of the degradation reaction to the presence of oxygen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110822
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  • 2
    Electronic Resource
    Electronic Resource
    The radical initiation of vinyl polymerization by α.α.α′.α′-Tetrasubstituted dibenzyls (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 157 (1972), S. 279-298 
    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: Im Temperaturbereich von 60 bis 100°C wird die radikalische Polymerisation von Styrol, Methylmethacrylat und Acrylnitril von α.α′-Dicyanodibenzylen ausgelöst, die in α-und α′-Stellung mit Ester-, Nitril-, Amid- oder Phenylgruppen disubstituiert sind. Bei 100 bis 110°C ist auch das α.α.α′.α′-Tetracarboxymethyldibenzyl aktiv. Vinylacetat und Vinylchlorid werden durch diese Initiatoren kaum polymerisiert.Fur die Polymerisation des Styrols wurden die Bruttogeschwindigkeitskonstanten Kp, für viele Dibenzyle und fur Peroxide vergleichbarer Aktivitat dilatornetrisch bestirnrnt. Norrnalerweise sind die Zeit-Urnsatz-Kurven rnit den Dibenzylen und den Peroxiden vergleichbar; das Tetracyanodibenzyl allerdings bewirkt nur eine unvollstandige Polymerisation.Der große Einfiuß von Substituenten in α-Stellung oder in den Phenylringen der Dibenzyle auf die Polymerisation des Styrols wird diskutiert. Dabei ist auch die Stereochernie wichtig. Die meso-Form des Dinitrildiesters ergibt eine 2.5- bis 3.5 ma1 schnellere Polyrnerisation als das dl-Isornere.Die Dissoziationsgeschwindigkeitskonstanten kd der Initiatoren wurden NMR-spektroskopisch aus der Linienbreite bestirnmt. Die Dinitrildiester sind gute Initiatoren, wahrend die α.α′-Dicyanodibenzyle rnit weiteren Nitril- oder Phenylgruppen in α- und α′-Stellung wenig geeignet sind. SchlieBlich wurde die 1.2-Addition einiger der Dibenzyle an Styrol im Ternperaturbereich von 120 bis 150°C rnit der Methode der chernisch induzierten KernPolarisation (CIDNP) untersucht.
    Notes: The radical polymerization of styrene, methyl methacrylate and acrylonitrile is initiated by α.α′-dicyanodibenzyls α.α′-disubstituted with ester, nitrile, amide or phenyl groups in the temperature range 60 to 100°C and by α.α.α′.α′-tetracarboxymethyldibenzyl at 100 to 110°C. Vinylacetate and vinylchloride show a low reactivity.The overall polymerization rate constants Kp have been determined dilatometrically for styrene initiated by a large number of dibenzyls and comparable peroxides. The styrene polymerization curves are generally comparable with those of peroxides. A notable exception is tetracyanodibenzyl.The strong influence of α- and ring-substituents in the dibenzyls on the styrene polymerization rate is discussed. The stereochemistry is also important : the meso α.α′-dicyanodibenzyls α.α′-disubstituted with ester groups give a 2.5 to 3.5 fold faster polymerization than their dl isomers.The initiator efficiency is related to the kd values, determined from NMR line width measurements. The α.α′- dicyanodibenzyls α.α′-disubstituted with ester groups are good initiators, while those with phenyl groups and nitrile groups are inefficient.Relevant to initiation and termination, the 1.2-addition of some of the dimers to styrene at 120 to 150°C has been studied with chemically induced dynamic nuclear polarization (CIDNP).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021570128
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of residual side chain blocking groups and side chain charge on polypeptide conformation in aqueous solution (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 835-843 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD) spectrum of poly-L-lysine and poly-L-glutamic acid has been investigated in the presence of a small percent of side-chain blocking groups. The blocking groups benzyl, methyl, and carbobenzoxy show qualitatively similar effects. Less than five mole percent of aromatic blocking groups alters the CD spectrum. Consequently, unsuspected blocking groups may account for the variation observed in CD spectra of these polymers. A weak CD band at 235-240 nm was observed for the disordered unblocked polymer even in the absence of electrolyte. Viscosity data indicate that in salt-free solutions these chains at neutral pH still behave as random coils though with reduced conformational freedom, in contrast to some polyelectrolytes which behave as rigid rods in the absence of electrolyte. The viscosity data bring into question the relevance of isolated molecule conformational calculations to experimental CD spectra.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120412
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  • 4
    Electronic Resource
    Electronic Resource
    Electrostatic interactions in polyglutamic acid (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 845-856 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy estimates were made for completely charged polyglutamic acid with different assumptions concerning the placement of side chain charge. Viewed as a helix, the minimum energy structure is somewhat affected by the side-chain charge placement. The average energy of the chain viewed as a random coil is equal to or less than the average energy of the chain viewed as a helix. Unlike the polyacrylate chain, nearest-neighbor charge interaction is shown to increase the chain dimensions. Although the calculations are approximate there is little evidence to suggest that isolated polyglutamate molecules in the absence of added electrolyte should behave as rods or that there are significant amounts of locally ordered structures. Presently no experimental results exist under conditions appropriate to isolated molecular calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120413
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  • 5
    Electronic Resource
    Electronic Resource
    Development of blood-compatible elastomers. III. Hematologic effects of avcothane intra-aortic balloon pumps in cardiac patientsThe intra-aortic balloon pump treatment of cardiac patients at the Massachusetts General Hospital was supported in part by U.S. Public Health Service Contract No. PH43-67-1443 (MIRU). (1972)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 129-154 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: As of this date, tri-segmented intra-aortic balloons made from Avcothane-51 elastomer were applied in the counterpulsation treatment of about 80 cardiac patients. The combined effects induced by the implanted elastomer and the hemodynamics of pumping are analyzed by means of hematologic changes observed in a set of 28 patients who were treated at the Massachusetts General Hospital for an average period of about 4 days, and represent a widely diversified group in terms of their clinical conditions. In no case were, any significant adverse hematologic effects induced by this assist device whether the hosts had been anticoagulated or not heparinized at all. While platelet levels were somewhat affected by the assist device, the particular conditions of the patient appear to have an effect of at least, equal magnitude. In addition to platelet levels steadily decreasing with pumping time, changes in platelet levels similar to the pattern of “platelet tide” occurred with about equal frequency. Monitored in terms of erythrocyte counts and plasma hemoglobin levels, no significant degree of hemolysis could be detected. Leukocyte counts in patients having above-normal levels at the beginning of pumping returned to normal while in other cases there were no significant changes. Fibrinogen, one of the plasma proteins most sensitive to foreign surfaces, showed levels increasing from subnormal to normal as a function of pumping time. The overall in vivo performance of Avcothane-51 balloons appers to be consistent with the state of the surfaces of recovered devices, showing only the presence of occasional adherent platelets upon examination by scanning electron microscopy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820060410
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  • 6
    Electronic Resource
    Electronic Resource
    Cationic copolymerization of tetrahydrofuran with epoxides. I. Polymerization mechanism in the presence of a glycol (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 265-279 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerization of several epoxides and their copolymerization with tetrahydrofuran have been studied. The polymerizations were carried out by use of BF3·O(C2H5)2 as catalyst in the presence of 1,4-butanediol. Variations of catalyst and 1,4-butanediol ratio and concentration affect polymerization rate, molecular weight, and the formation of cyclic oligomers. The latter is also influenced by monomer fed ratio in the case of the copolymerizations. These effects are discussed, and some observations are made concerning the mechanism, particularly with respect to the role of the 1,4-butanediol. Mayo-Lewis monomer reactivity ratios were determined. The ratios found differed from previously published figures.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.150090202
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  • 7
    Electronic Resource
    Electronic Resource
    Cationic copolymerization of tetrahydrofuran with epoxides. III. Synthesis of block copolymers (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 295-298 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerization of various cyclic ethers by BF3·O(C2H5)2 in the presence of polymeric glycol leads to the formation of hydroxyl terminated block copolymers. Where poly(oxyethylene glycol) is used as the polymeric glycol, fission of the poly(oxyethylene glycol) chain occurs, and block copolymers, containing shorter ethylene oxide unit sequences are obtained. With poly(oxypropylene glycol), on the other hand, the polymer chain remains intact. This may be due to the steric influence of the pendant methyl groups. The cyclic oligomers formed as by-products in the polymerizations are easily removed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.150090204
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  • 8
    Electronic Resource
    Electronic Resource
    Cationic copolymerization of tetrahydrofuran with epoxides. II. Characterization and gel-permeation chromatography of by-products formed during polymerization (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 281-294 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclic oligomers formed as by-products in the polymerization of propylene oxide. 1,2-butylene oxide, and n-propyl glycidyl ether, and in the copolymerization of these monomers with tetrahydrofuran have been studied by gel-permeation chromatography and otherwise and their structures have been determined. Some of the physical properties of the cyclic oligomers are described.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.150090203
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  • 9
    Electronic Resource
    Electronic Resource
    Phenolic resins for solid-phase peptide synthesis: Copolymerization of styrene and p-acetoxystyrene (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 2017-2025 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Details are given of the synthesis and purification of p-acetoxystyrene and its solution and suspension copolymerization with styrene. Reactivity ratios, evaluated by the Tidwell-Mortimer method, were r1 (p-acetoxystyrene) = 1.18, and r2 (styrene) = 0.88 for (bulk) solution copolymerization. Corresponding values of the reactivity ratios for suspension copolymerization were, within experimental error, indistinguishable from unity. Thus the copolymer composition is governed simply by the monomer feed composition. Use of a specially designed reactor vessel permits convenient suspension copolymerization of styrene, p-acetoxystyrene, and divinylbenzene to give crosslinked resins having comparatively narrow particle size distributions. Acetoxy groups in the crosslinked resin are cleaved by hydrazine hydrate under very mild conditions to give crosslinked polystyrenes having phenolic groups which, in turn, provide a useful alternative to the more usual chloromethylated polystyrene resins for solid-phase peptide synthesis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.170120915
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  • 10
    Electronic Resource
    Electronic Resource
    Carboxyl-stabilized emulsion polymers (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 2493-2499 
    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: An emulsion polymerization process is reported for the production of high-solids, surfactant-free styrene/butadiene latices. With this procedure latices require no surfactants, for stabilization is built into the emulsion particles by means of copolymerized acid monomers. This “pH variable” method is a two-step, batch-on-batch polymerization. In the first step, all the ingredients are present in the reaction mixture; however, only enough styrene and butadiene is added to reach a low solids content. This step, carried out at low pH, produces a carboxylated seed latex. On raising the pH of this low-solids emulsion, the copolymerized carboxyl groups ionize, and the now highly charged latex particles provide an expedient locus for the generation of stable, highsolids latices. Neutralizing the carboxyl groups of the seed latex before adding the remaining monomers induces the highly hydrophilic carboxyl anions to remain on the surface of the latex particle, nearer to the aqueous environment of the surrounding media. Hence, the maximum stabilization capacity of the acid monomers is utilized. The process was evaluated to ascertain the effects of the following variables: the particle size and solids content of the first step, the nature of the base used to raise the pH, the pH of the dispersion prior to the second step, and the effect of the acid monomer on the latex stability.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1974.070180827
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