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  • Polymer and Materials Science  (20)
  • Surface physics, nanoscale physics, low-dimensional systems
  • 1995-1999  (20)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 299-305 
    ISSN: 0887-624X
    Keywords: polygluconamides ; stereoregular polyamides ; stereoregular nylons ; chiral polyamides ; chiral nylons ; aminoaldonic acids ; sugar polyamides ; carbohydrate monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two stereoregular polygluconamides, one (3) of polypeptide-type and the other (16) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D-glucosamine and D-glucose, respectively. The new polyamides were characterized by elemental analysis, and IR, 1H- and 13C-NMR spectroscopies. The molecular weights for 3 and 16 were estimated as 25,000 and 67,000, respectively, on the basis of viscosimetric measurements. Both polyamides display high optical activity; they are highly hydrophilic and readily soluble in water as well as in a variety of organic solvents including chloroform. Polyamide 16 is highly crystalline and yields resistant films with spherulitic texture. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1959-1968 
    ISSN: 0887-624X
    Keywords: optically active polyamides ; helical nylons ; nylon-3 ; poly(β-amide)s ; poly(β-aspartate)s ; poly(α-isobutyl-β-L-aspartate) ; stereoselective polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different polymerization methods were used for the preparation of poly(α-isobutyl-β-D,L-aspartate)s containing variable ratios of D- to L-aspartic units and the microstructure of the resulting stereocopolymers was examined by NMR spectroscopy. Anionic ring-opening polymerization in solution of enantiomeric mixtures of α-isobutyl-β-D- and L-aspartalactams was found to proceed stereoselectively rendering block copolymers composed of right- and left-handed helical sequences. Configurationally statistical copolymers were obtained instead when the enantiomeric lactam mixtures were polymerized in the bulk. Random stereocopolymers could be prepared also by polycondensation in solution of mixtures of pentachlorophenyl α-isobutyl-β-D and -L-aspartates. The conformation in solution and the crystal structure of the resulting copolymers were investigated in connection with their stereochemical configuration and these features compared with those displayed by optically pure poly(α-isobutyl-β-L-aspartate). © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1157-1167 
    ISSN: 0887-624X
    Keywords: zirconocene catalysts ; ethylene ; 1-hexene ; copolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The PM3(tm) semiempirical method has been used to optimize the structures for the reactants and transition states of the first and second ethylene insertion processes into zirconocene catalytic systems. The results obtained for these reactions are compared with calculations published in the literature performed at different ab-initio theoretical levels. The agreement between our calculations and those reported in the literature is satisfactory. Taking advantage of the reduced computational effort required in semiempirical calculations two additional processes related with the so-called comonomer effect were also studied: ethylene/1-hexene copolymerization, and chain termination reaction, both in the homopolymerization and in copolymerization of ethylene with 1-hexene comonomer. The calculated activation energies support some experimental findings such as the higher polymerization activities in the presence of comonomers and also the molecular weight reduction of the copolymers due to the more favorable β-elimination reactions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1157-1167, 1998
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 41-54 
    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: This article describes the hydrolytic degradation of a series of nylons based on methylated L-tartaric acid and diamines. These polytartaramides were prepared by a solution polycondensation process using bis(pentachlorophenyl)-2,3-O-dimethyl-L-tartrate and N,N′-bis(trimethylsilyl)alkanediamines with 6, 8, or 12 methylene groups. The stereoregular optically active polyamides obtained were soluble in chloroform and showed intrinsic viscosities between 1.0 and 2.7 dL g-1. The degradation of these polytartaramides in the form of discs has been investigated in buffered salt solutions of pH 2.3, 7.4, and 10.6, and at temperatures of 37, 55, and 70°C. The degradation was monitored by following the changes in molecular weight, mass loss, chemical constitution, and thermal properties. Our results show that these polytartaramides degrade slowly at 37°C, with a degradation rate highly depending upon the number of methylenes in the diamine unit of the polyamide. The pH of the medium has also a great influence on degradation, as well as the temperature, with an important hydrolysis rate enhancement at 70°C. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 1072-1074 
    ISSN: 1040-0397
    Keywords: Molecular recognition ; Phosphate ; Cyclodextrin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexation of phosphate ion by β-amino-cyclodextrin (host 1) was detected by voltammetric methods through the competitive displacement of water-soluble ferrocene derivatives from their complexes with host 1 in neutral aqueous media. The half-wave potential and the anodic peak current for oxidation of the ferrocene derivative were found to be sensitive to the phosphate concentration throughout a range which is determined, among other factors, by the concentration of host 1 and the binding constant between the selected ferrocene derivative and the β-amino-cyclodextrin host.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2379-2384 
    ISSN: 0887-6266
    Keywords: ultrasound degradation ; microwave degradation ; polyamides ; polypeptides ; polyglutamates ; polyaspartates ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 3133-3142 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report dynamic viscoelastic measurements of a series of binary blends of hydroxyethyl ether of starch and ethylene-vinyl acetate copolymer (EVA), which are correlated with the granular arrangement of the starch derivative within the EVA matrix and the adhesion between both phases, studied by scanning electron microscopy. The rheological properties are similar to those of polymers filled with solid spheres, although we found a minimum in the Newtonian viscosity and a maximum in the elasticity at low starch derivative concentrations, which have been attributed to a change in the density of chain entanglements.
    Additional Material: 11 Ill.
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  • 8
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A structural study was carried out on poly(α-butyl β-L-aspartate), which is a stereoregular nylon-3 derivative with an alkoxycarbonyl group attached to the β-carbon of the main-chain repeating unit. Two crystal forms, namely hexagonal and tetragonal, made of 13/4 and 4/1 helices, respectively, and bearing a structural resemblance to the polypeptide α-helix, were characterized by X-ray diffraction. Though these forms are basically identical to those previously reported for poly(α-isobutyl β-L-aspartate), the crystal transition from hexagonal to tetragonal known to take place in this polymer by effect of heating, was not observed in the present case. Modeling calculations revealed that although similar conformations are favoured for the two polymers in both crystal forms, the relative stability of the 13/4 helix to the 4/1 helix was found to be significantly reduced in the case of the butyl derivative. The presence of helical conformation in solution has been evidenced by both 1H NMR and circular dichroism and the helix-coil transition promoted by acids was investigated by means of these techniques.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Preparative temperature rising elution fractionation (TREF) on commercial linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) samples has been performed. The resulting fractions exhibited a bimodal and a unimodal distribution, respectively. Two LLDPE fractions of low (5 CH3/1000 C) and high (21 CH3/1000 C) short-chain branching content were solution-mixed with the LDPE central fraction (16 CH3/1000 C). Indirect evidence based on differential scanning calorimetry results suggest that the fractions with similar branch contents are more miscible than those with dissimilar ones.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 963-973 
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; crystal modulus ; mechanical properties ; force-field parametrization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A force-field suitable for the calculation of the mechanical properties of poly(ethylene terephthalate) and their relation with the molecular structure of the polymer has been developed. The force-field parameters were derived from quantum mechanical AM1 calculations and tested against thermodynamic and vibrational spectroscopy data available for a set of closely related small molecules. The crystal moduli of the two solid phases known for poly(ethylene terephthalate) were estimated by means of this new force-field considering both the isolated chain and the chain within the unit cell. Results were qualitatively consistent with reported x-ray data showing that the triclinic crystal form is stiffer than the mesomorphic phase provided that sample heterogeneities were taken into account. Although overestimated moduli resulted for both cases, divergences with experimental values were found to be slighter than those obtained by other theoretical methods. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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