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  • 1
    Electronic Resource
    Electronic Resource
    Poisson's ratio of poly(vinyl alcohol) gels (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 3092-3096 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00064a016
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  • 2
    Electronic Resource
    Electronic Resource
    Critical behavior of the intrinsic viscosity of poly(vinylalcohol) solutions near the gelation point (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7310-7313 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The critical behavior of intrinsic viscosity near the gelation point was experimentally examined for poly(vinylalcohol) (PVA) solutions. The constant of the Huggins equation for viscosity (k') for PVA clusters was higher than that of linear PVA. The intrinsic viscosity ([η]) for PVA clusters was smaller than that of linear PVA at lower polymer concentrations, at which PVA solutions were prepared and cooled. The critical exponent of [η] was found to be 0.20. The weak divergence of [η] resembles the critical behavior of Zimm clusters predicted by the 3D percolation theory, or that of Rouse clusters by the classical theory of the Flory–Stockmeyer type. The critical behavior of [η] of PVA solutions, however, may be considered to be close to Zimm clusters of the 3D percolation theory rather than that of Rouse clusters by the classical theory, because Zimm clusters are more preferable than Rouse clusters for the description of the critical behavior of [η].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459403
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  • 3
    Electronic Resource
    Electronic Resource
    Small angle x-ray scattering study on role of trapped entanglements in structure of swollen end-linked poly(dimethylsiloxane) networks (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9105-9111 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Amorphous structure of swollen end-linked poly(dimethylsiloxane) (PDMS) network has been investigated by means of small angle x-ray scattering (SAXS) technique as a function of molecular mass of precursor PDMS (Mp) and junction (cross-link) functionality. The Mp dependence of the SAXS profiles for tetra-functional PDMS networks shows a striking crossover at around Mp(approximate)Mc where Mc represents the critical molecular mass to form entanglement couplings in the PDMS melt. These results strongly suggest that structure of swollen end-linked networks significantly depends on whether precursor chains are well entangled or not before end-linking, and that when precursor chain is long enough to form entanglement couplings, trapped entanglements formed in cross-linking (instead of cross-links) play a major role in elementary mesh of the resulting networks. For the networks of Mp(very-much-greater-than)Mc, the correlation length for the network structure is fairly small and comparable to that of dynamic density fluctuation for the solutions of the precursor polymer, and in addition, no appreciable effect of junction functionality on long-range network structure is observed. These observations imply that the contribution of cross-link to static heterogeneity in network structure is screened by trapped entanglement dominant in number. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481521
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  • 4
    Electronic Resource
    Electronic Resource
    Crossover of the concentration dependence of swelling and elastic properties for polysiloxane networks crosslinked in solution (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 3352-3359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the preparation concentration dependence of the polymer volume fraction and the elastic modulus of the equilibrium swollen polydimethylsiloxane networks in toluene. The networks were prepared by the end-linking method in solution with a wide range of concentration. The network samples were attempted to be as small amount of structural defects as possible. The crossover has been observed for the preparation concentration dependence of the degree of equilibrium swelling and the elastic modulus. The crossover concentrations agree with each other, and are almost identical with the boundary concentration between the semidilute and the concentrated regime for the end-to-end distance of the polymer chain. The theoretical predictions which describe the experimental results have been derived as a function of the polymer volume fraction of preparation and swollen state, considering the effect of trapped entanglements on the elasticity and the concentration regime of preparation and swollen state. The good agreements of the theoretical predictions with the experimental results suggest that the trapped entanglements contribute to the elastic modulus together with the chemical crosslinks, and the crosslinking points moves affinely relative to the global polymer network on swelling. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471018
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  • 5
    Electronic Resource
    Electronic Resource
    Elastic modulus and equilibrium swelling of networks crosslinked by end-linking oligodimethylsiloxane at solution state (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 4833-4840 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the degree of equilibrium swelling and the elastic modulus of networks prepared by end-linking oligo(dimethylsiloxane)s (ODMS) in solution as a function of polymer concentration at crosslinking. The molecular weight of ODMS is so low that entanglement couplings are not formed in uncrosslinked state. It has been found from the preparation concentration dependence of elastic modulus in preparation state that trapped entanglements are formed by the introduction of crosslinks, and those considerably contribute to elastic modulus, even if the prepolymers are not entangled in uncrosslinked state. The experimental results for preparation concentration dependence of the degree of equilibrium swelling and the elastic modulus of equilibrium swollen networks are compared with the theoretical predictions by the two theories, i.e., the affine model and the c* theorem. It has been clearly shown that the affine model describes well the experimental results, while the discrepancies between the experimental results and the predictions by the c* theorem are considerable. These results strongly suggest that preparation concentration should be regarded as a reference state, and the displacement of crosslinks moves affinely on swelling, while the complete disinterpenetration of network chains in equilibrium swollen state, which is a postulate of the c* theorem, does not occur. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472320
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  • 6
    Electronic Resource
    Electronic Resource
    Investigations of ferroelectric-to-paraelectric phase transition of vinylidenefluoride trifluoroethylene copolymer thin films by electromechanical interferometry (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6367-6375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrostrictive and piezoelectric properties for a 1.3 μm thick film of a vinylidenefluoride/trifluoroethylene copolymer exhibiting a ferroelectric-to-paraelectric phase transition have been investigated as a function of temperature by means of electromechanical interferometry. The electrostriction remarkably increases in the vicinity of the phase transition temperature according to a sharp increase in the dielectric constant. For the unpoled sample in the ferroelectric phase with a polydomain structure in which the local spontaneous polarization is macroscopically cancelled out, the dependence of the electrostriction on the square of the applied electric field is nonlinear in the ferroelectric phase, while it is linear in the paraelectric phase. A theoretical model which takes into account the nonlinear dielectric constant can quantitatively explain the nonlinear contribution to the electrostriction in the vicinity of the ferroelectric–paraelectric phase transition, but it underestimates the contribution in the ferroelectric phase. Interactions within and/or between the ferroelectric domains in the polydomain structure are expected to contribute significantly to the nonlinear electrostriction. For poled samples a pronounced inverse-piezoelectric effect is measured. The achieved polarization and its temperature dependence are almost the same as for thicker films reported in earlier studies, obtained by different experimental techniques. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371699
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  • 7
    Electronic Resource
    Electronic Resource
    GPC analysis of polymer network formation 2. Bifunctional PPG prepolymer/crosslinker system (1997)
    Springer
    Polymer bulletin 38 (1997), S. 461-468 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Size distribution of polymer clusters in pre-gel state has been measured by means of gel permeation chromatography (GPC) for crosslinking system between bifunctional prepolymer and trifunctional crosslinker. Experimental chromatograms have been obtained at various degree of conversion, and compared with theoretical chromatograms predicted by the Flory-Stockmayer model. Experimental size distribution at low conversion is well described by the theory. On the other hand, experimental chromatograms at higher conversions show a long tail in lower elution volume region which is unexpected by the theory. This result suggests that clusters with relatively linear structure which is not predicted by the theory are formed. The formation of the clusters with fairly linear structure is estimated to originate from unequality in reactivity of sites in crosslinker which is due to steric hindrance by the reacted sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050074
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  • 8
    Electronic Resource
    Electronic Resource
    Stress-strain behavior of segmented polyurethaneureas under pure shear deformation (1996)
    Springer
    Rheologica acta 35 (1996), S. 288-295 
    Details
    ISSN: 1435-1528
    Keywords: Segmented polyurethane ; elasticity ; shear ; strain energy density function ; Poisson's ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Elastic properties of segmented polyurethaneureas (SPUs) under pure shear deformation were investigated. Data were analyzed by using strain energy density function (W). The values of the derivatives of W with respect to the invariants of the strain tensor (I i ; i = 1, 2, 3 ) at zero strain limit were also estimated theoretically and were compared with those estimated by experiment. The limiting value of the derivative with respect to I 1 (∂W/∂I 1) was shown theoretically to be 5 G/8, while the derivatives with respect to I 2 and I 3 (∂W/∂I 2 and ∂W/∂I 3 were respectively-G/8 and -3G/8. The theoretical prediction could explain the asymptotic behavior of the derivatives of SPUs as well as isoprene rubber (IR) reported by Kawabata et al. at small I 1 limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366915
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  • 9
    Electronic Resource
    Electronic Resource
    Elastic properties of real elastomers at small deformationsPoster presented at the “International Symposium on Advanced Network-Polymers, Kansai University” (ISANKU), at Kansai University, Suita, Osaka, Japan, on December 5-6, 1995. (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 197-203 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Elastic properties of real elastomers were examined by using partial derivatives of the strain energy density function (W) with respect to the invariant (Ii, i=1,2,3) of deformation tensor. The values of the derivatives at zero strain limit for styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and butadiene rubber (BR) were compared with those derived from the theory shown in the previous paper, where compressibility of the materials was taken into account. The asymptotic behavior of the derivatives for isoprene rubber (IR) and segmented polyurethaneurea (SPU) was also compared with those of the three types of rubbers. It was shown that the theoretical predictions for the limiting value agreed fairly well with the experimental values of the elastomers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400118
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and viscoelastic properties of segmented polyurethane blends (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1563-1568 
    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: Structure and viscoelastic properties of segmented polyurethanurea (SPU) blends were investigated. The glass transition temperature (Tg) of poly(tetramethylene glycohol) (PTMG) in a soft-segment block of the component SPU increased with decreasing molecular weight of PTMG. The blend samples showed two Tgs of PTMG in the temperature dispersions of the loss modulus (E″) and loss tangent (tan δ). The value of E′ in the leathery region for the blend specimens was trongly affected by the morphology. The blends were considered to have a morphology where PTMG differing in molecular weight was localized. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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