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  • 1
    Digitale Medien
    Digitale Medien
    Effect of methyl groups on the thermal properties of polyesters from methyl substituted 1,4-butanediols and 4,4′-biphenyldicarboxylic acid (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 493-504 
    Details
    ISSN: 0887-624X
    Schlagwort(e): butanediol ; 4,4′-biphenyldicarboxylic acid ; characterization ; liquid crystalline polymer ; methyl substitution ; nematic ; polyester ; smectic ; synthesis ; thermal properties ; X-ray analysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Results are reported on the effect of lateral methyl groups on the thermal properties of a series of polyesters prepared from diethyl 4,4′-biphenyldicarboxylate and various methyl substituted 1,4-butanediols. The diols were 1,4-butanediol; 2-methyl-1,4-butanediol; 2,2-dimethyl-1,4-butanediol; 2,3-dimethyl-1,4-butanediol; 2,2,3-trimethyl-1,4-butanediol; and 2,2,3,3-tetramethyl-1,4-butanediol. Apart from the tetramethyl derivatve, the transition temperatures of the methyl substituted polyesters were lower with respect of the unsubstituted polyester. On the basis of polarized photomicrographs, a smectic A mesophase was found for the unsubstituted polyester, whereas a nematic mesophase was observed for the 2-methyl substituted polyster. The 2,2-dimethyl, 2,3-dimethyl, and the 2,2,3-trimethyl substituted polyesters showed no liquid crystalline behavior. The 2,2,3,3-tetramethyl derivative displayed a birefringent melt phase although the DSC measurements were not unambiguous. A copolyester based on diethyl 4,4′-biphenyldicarboxylate, 1,4-butanediol, and 2,2,3,3-tetramethyl-1,4-butanediol showed a broad nematic mesophase. Further evidence for the nematic mesophase of this copolyester and the 2-methyl substituted polyester was provided by dynamic rheological experiments. Based on thermogravimetric analysis, it was concluded that the thermal stability was affected only when four methyl side groups were present in the spacer. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1995.080330316
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  • 2
    Digitale Medien
    Digitale Medien
    Curing ethylene-propylene rubber terpolymers with dimethacrylate monomers. II. Effect of unsaturation (1965)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 9 (1965), S. 1579-1584 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: In a previous paper it was shown that the vulcanization obtained with ethylene-propylene-diene terpolymer is equivalent or superior to that obtained with ethylene-propylene copolymer when a peroxide-dimethacrylate coagent cure system was used. In order to determine the effect of the unsaturation on the physical properties in the terpolymer, the terpolymer had been hydrogenated to remove the double bonds. Infrared spectra and bromination were used to check the extent of hydrogenation. Tensile strength, Shore A hardness, per cent elongation, and modulus indicated no decrease in vulcanization efficiency after hydrogenation. The data show that the unsaturation in the terpolymer does not contribute to the vulcanization cure with the peroxide-dimethacrylate coagent curing system.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1965.070090433
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  • 3
    Digitale Medien
    Digitale Medien
    A new instrument to assess animal joint stiffness in vitro (1985)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 19 (1985), S. 601-605 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820190512
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  • 4
    Digitale Medien
    Digitale Medien
    Synthesis of high-molecular-weight poly(L-lactide) initiated with tin 2-ethylhexanoatePresented in part at the annual meeting of the Dutch Foundation for Chemical Research (SON), Section Macromolecules, March 4-5, Lunteren, The Netherlands 1985. (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1809-1814 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The bulk polymerization of L,L-dilactide was studied as a function of polymerization temperature (Tp), time and concentration of catalyst (tin 2-ethylhexanoate). Poly(L-lactide) (PLLA), with the highest value of intrinsic viscosity ([η] = 13 dl · g-1; M̄v ≈ 1 · 106) and heat of fusion (ΔHm = 64,7 J · g-1), was synthesized at a low catalyst concentration (0,015 wt.-%) and at the lowest Tp studied (100°C), just above the melting point of L,L-dilactide (98°C). The ceiling temperature of PLLA was found to be 275°C, as deduced from an M̄v max. - Tp curve. The M̄w/M̄n ratios of as-polymerized PLLA samples ranged from 2 to 3. Fractions of PLLA with M̄v max. were already present at 50% conversion. The experimental results support a proposed nonionic insertion polymerization mechanism. Polymerization at 100-140°C resulted in early crystallization of PLLA leading to a rather untangled polymer and microporous (pores up to 100 nm) sample texture.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1987.021880804
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  • 5
    Digitale Medien
    Digitale Medien
    Hot drawing of surface growth polyethylene fibers, 2Part 1: cf.2. Effect of drawing temperature and elongational viscosity (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3351-3359 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A distinct improvement of the tensile properties of “surface growth” polyethylene fibers can be realised by drawing at elevated temperatures. The optimal drawing temperatures were found in the range of 120-150°C. Drawing in the hexagonal phase above 150°C does not lead to an increase of strength. Elongational viscosity measurements revealed extremely high values in the order of 1011-1012 Poise. Activation energies between 75-95 kJ/mol were determined from the temperature dependence of elongational viscosity. The observed drawing behaviour is discussed in relation to the morphological changes that occur during drawing.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1981.021821138
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  • 6
    Digitale Medien
    Digitale Medien
    A novel thermoset polymer optical fiberFinancial support from “Stichting Toegepaste Wetenschappen en Stichting Scheikundig Onderzoek Nederland” (STW-SON) is gratefull acknowledged. Thanks are due to H. J. Brouwer for building the experimental set-up for measuring the POF transmission losses and measuring the FEP surface topography with AFM. (1996)
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 45-48 
    Details
    ISSN: 0935-9648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/adma.19960080107
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  • 7
    Digitale Medien
    Digitale Medien
    (Co)polymers of L-lactide, 1. Synthesis, thermal properties and hydrolytic degradation (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1633-1647 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Copolymers of L-lactide with D-lactideAccording to IUPAC the name dilactide is preferred to lactide., glycolideIUPAC name: diglycolide., ε-caprolactone and trimethylene carbonate, and networks with spiro-bis-dimethylene-carbonate (2,4,7,9-tetraoxaspiro[5.5]undecane-3,8-dione) were prepared in bulk at standardized polymerization conditions. The properties of the nascent copolymers were evaluated with respect to the nature of the comonomer. Copolymerization with comonomers entailing low glass transition temperature simultaneously reduces the crystallinity. 300 MHz 1H nuclear magnetic resonance is shown to be a useful technique for the determination of the average monomer sequence lengths in ε-caprolactone and trimethylene carbonate copolymers. The presence of crystallizable L-lactide sequences, due to differences in monomer reactivity, has a large effect on the thermal properties of the copolymer as well as on the long-term degradation characteristics.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1994.021950515
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  • 8
    Digitale Medien
    Digitale Medien
    On the chain stiffness of poly(lactide)s (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 2219-2229 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(lactide)s (PLAs) are well known hydrolytically degradable polymers, that are widely used for biomedical applications. However, the intrinsic brittle nature of poly(lactide)s is still poorly understood. The stiffness of a polymer chain, expressed as the characteristic ratio C∞ plays an important role in the deformation mechanism of amorphous polymers. In order to investigate the effect of tacticity, high molecular weight poly(lactide) stereo-copolymers with D-lactide contents in the range 0-50 mol-% were synthesised. These polymers were used in light scattering and differential scanning calorimetry (DSC) experiments for the determination of the characteristic ratio C∞ and glass transition temperature Tg. The results of the light scattering experiments in acetonitrile indicate that the characteristic ratio C∞ for poly(lactide)s depends on the L/D-lactide ratio and increases with the tacticity of the polymer from 9.5 for racemic PDLLA to an estimated 11.8 for isotactic PLLA. These results are consistent with the observed brittle behaviour of poly(lactide) stereo-copolymers and agree well with predictions obtained from group contribution methods. The choice of the relevant bond length used for the calculation of the characteristic ratio from the scattering data is not as obvious as it may seem and remains a point of discussion. The tacticity of poly(lactide)s also influences the glass transition temperature, which varies from 54°C for racemic to 63°C for isotactic poly-(lactide).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1996.021970713
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  • 9
    Digitale Medien
    Digitale Medien
    (Co)polymers of L-lactide, 2.Part 1: cf. ref.9 Mechanical properties (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1649-1663 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of copolymerization of L-lactide with several lactones and cyclic carbonates and the processing variables in compression moulding of poly(L-lactide) homopolymers on the mechanical properties was investigated. Sharp maxima in the impact strength versus comonomer composition and heat of fusion were obtained, reflecting the important role of the presence of a crystalline fraction in the material. Crystalline domains increase the interconnectivity of a physical polylactide network and decrease the molecular weight between these physical crosslinks. The brittle strength concomitantly increases, and as the yield stress remains more or less constant, an increase in impact strength is observed. Very high crystalline as-polymerized poly(L-lactide) prepared with less active catalysts on the other hand has an extremely low entanglement density and therefore a low brittle tensile strength.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1994.021950516
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  • 10
    Digitale Medien
    Digitale Medien
    Copolymerization of dienes with acrylic and methacrylic acids (1953)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 10 (1953), S. 441-442 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1953.120100407
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