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  • Polymer and Materials Science  (112,478)
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  • 1
    Electronic Resource
    Electronic Resource
    Phase and orientational behaviors in liquid crystalline main-chain/side-group block copolymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 21-29 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystal ; block copolymer ; polyester block ; polymethacrylate block ; magnetic field ; X-ray diffraction ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase and orientational behaviors of a series of liquid crystalline (LC) AB-type diblock copolymers comprising thermotropic main-chain (MC) polyester and side-group (SG) polymethacrylate blocks were investigated by X-ray diffraction. The MC and SG blocks were phase separated and gave rise to their individual mesophases that coexisted at equilibrium. The samples were oriented by using either a magnetic field or a mechanical field. In magnetically aligned samples both the MC and SG microphases were oriented with their smectic planes orthogonal to the magnetic field direction, independent of the copolymer composition. Mechanically aligned, fiber samples showed different orientations of the MC and SG smectic planes for different sample compositions. In this case the disposition of the smectic planes of the MC and SG blocks was driven by the relative length of the two blocks. Some features of the X-ray patterns of the copolymers were compared to those of the MC and SG homopolymers. In addition, the MC smectic domains crystallized on annealing without affecting the orientation that had been achieved by applying a magnetic field. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 21-29, 1998
    Additional Material: 11 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Smectic networks obtained from twin LC epoxy monomers - mechanical deformation of the smectic networks (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 31-38 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystals ; thermosets ; smectic epoxy ; nematic ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Deformation experiments were carried out for densely crosslinked smectic-like networks obtained from diepoxy monomers with twin mesogen architecture. For the initially unoriented smectic networks, the network could be aligned up to an orientation parameter of 0.35 by applying 8 MPa of external stress in the rubbery regime. X-ray diffraction measurements revealed that the deformed smectic network possesses both smectic-A like and smectic-C like structure. It is thought that after extension domains initially oriented parallel to the external stress displayed a smectic-A-like structure, whereas domains initially tilted with respect to the tensile direction showed a stress-induced smectic-C like structure. A smectic network oriented under a.c. electric fields with an orientation parameter of 0.4 had a smectic-A like structure and possessed linear elasticity in the rubbery regime. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 31-38, 1998
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological study on poly-p-phenylenebenzobisoxazole (PBO) fiber (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 39-48 
    Details
    ISSN: 0887-6266
    Keywords: poly-p-phenylenebenzobisoxazole ; X-ray scattering ; transmission electron microscopy ; Young's modulus ; tenacity ; crystal size ; orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies. Crystal size, orientation of the crystal, fibrils, microvoids, and fine structure were discussed. It was found that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal (160 Å) and the transverse (110 Å) directions. Crystal modulus estimated by extrapolation to perfect orientation on the plot of the fiber modulus as a function of fiber orientation (Northolt's method) shows discrepancy from the crystal modulus directly obtained by X-ray scattering. This discrepancy means that the Northolt's model is insufficient to describe the Young's modulus of PBO fiber. Microvoids elongated to the fiber direction were examined by small-angle X-ray scattering and transmission electron microscopic methods. The diameter of the microvoids was 20 Å to 30 Å and the fiber had a very thin microvoids-free layer (0.2 μm). Preferential orientation of the a-axis of crystal in the fiber was also confirmed. Summarizing these results, a structure model of the PBO fiber was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 39-48, 1998
    Additional Material: 16 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of ion content in ionomer on the ion conductivity of polymer electrolytes based on the P(MMA-co-LiMA)/PEG/LiCF3SO3 blend (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 991-997 
    Details
    ISSN: 0887-6266
    Keywords: poly(methyl methacrylate-co-lithium methacrylate)(P(MMA-co-LiMA)) ; ionomer ; polymer electrolyte ; ion content ; ion conductivities ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have prepared polymer electrolytes composed of poly(methyl methacrylate-co-lithium methacrylate) ionomer (P(MMA-co-LiMA)), low molecular weight PEG, and LiCF3SO3 salt. The ion groups in P(MMA-co-LiMA) could enhance the miscibility between the MMA units and PEG in the polymer electrolytes. This miscibility enhancement made the pathway of ion transport less tortuous, and consequently led to the increase in ion conductivity. The maximum ambient ion conductivities in these systems were measured to be in the range of 10-4-10-5 S/cm. The polymer electrolytes became transparent at the higher ion content owing to the enhanced miscibility. The mechanical stability of the polymer electrolytes was also improved through the introduction of ion groups into the PMMA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 991-997, 1998
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Moisture transport studies on newly developed aromatic and aromatic/aliphatic copolyester thin films (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1025-1035 
    Details
    ISSN: 0887-6266
    Keywords: polymer thin films ; thermosets ; microelectronics ; moisture ; physical aging ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In polymers for microelectronics applications, moisture is known to have a deleterious effect upon device reliability. In this paper, the moisture transport behaviors of a newly developed family of all-aromatic and aromatic/aliphatic copolyester thermosetting films were described. The moisture uptake as a function of temperature, relative humidity, sample thickness, and processing conditions were presented via conjugate moisture sorption tests.1 It was found that the post curing near but below Tg resulted in an increase in both total moisture uptake and diffusion coefficient due to the effect of physical aging and the generation of sample defect volume. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1025-1035, 1998
    Additional Material: 18 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of sub-Tg relaxations on chromophore reorientation in corona-poled polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1013-1024 
    Details
    ISSN: 0887-6266
    Keywords: nonlinear optical polymer ; pressure ; chromophore reorientation ; poly(alkyl methacrylates) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Activation volumes for chromophore reorientation were measured for a series of guest-host polymeric materials, indicating a significant coupling between chromophore motion and the glassy α and β relaxation dynamics of the polymer host. The specific systems studied were formed by individually dissolving N,N-dimethyl-p-nitroaniline (DpNA), 4-(dimethylamino)-4′-nitrotolane (DMANT), 4-(diethylamino)-4′-nitrotolane (DEANT), and 1-((4-(dimethylamino)phenyl)ethynyl)-4-((4-nitrophenyl)ethynyl)benzene (DMAPEANT) in poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(isobutyl methacrylate) (PiBMA). In each of these systems, the isothermal, sub-Tg decay of the second-order optical susceptibility χ(2) was monitored as a function of pressure using second harmonic generation. In each system, the observed decay of χ(2) was represented by a stretched exponential equation from which the decay time τ0 and decay distribution width βKWW were determined. For each dopant molecule, the decrease in activation volume with the increasing size of the polymer host's alkyl side group and the pressure dependence of βKWW were indicative of partial coupling between chromophore rotation and the glassy β relaxation dynamics of the polymer host. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1013-1024, 1998
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    A quantitative model for the specific volume of polymer-diluent mixtures in the glassy state (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1037-1050 
    Details
    ISSN: 0887-6266
    Keywords: polymer glasses ; glass transition ; diluents ; antiplasticization ; mixtures ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mathematical model to describe the specific volume of glassy mixtures of a polymer and a low molecular weight diluent or additive is presented. The model is based on understandable physical assumptions and relies on parameters that can be determined experimentally or estimated from methods available in the literature. The predictions of the model show good agreement with the experimental data for mixtures of four polymers with diluents that in the pure state are liquid, glassy, or crystalline. The observed negative departure from volume additivity, as defined by simple additivity of the specific volume of the pure glassy polymer and the pure amorphous diluent, is the result of the relaxation of the excess volume of the glassy mixture relative to the equilibrium state caused by mixing two components with different glass transition temperatures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1037-1050, 1998
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Towards a better mixing of two incompatible polymers by casting from solution without compatibilizer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1051-1060 
    Details
    ISSN: 0887-6266
    Keywords: polymer mixtures ; film casting ; solvent selectivity ; incompatibility ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of polystyrene/poly(oxyethylene) (PS/POE) and polystyrene/poly-(methyl methacrylate) (PS/PMMA) have been obtained by casting from solution. Differential Scanning Calorimetry, Optical Microscopy, and Scanning Electron Microscopy showed that two incompatible polymers can present relatively good miscibility (formation of domains smaller than 5 μm) when the solvent from which the films are obtained does not present any noticeable selectivity towards the two polymers of the blends. An increase of the casting temperature increases the miscibility of PS and PMMA because the selectivity of the solvent used, towards these polymers decreases with increasing temperature. On the contrary, an increase of the casting temperature in the case of the PS and POE mixture decreases their miscibility because the selectivity of the solvent used increases with increasing temperature. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1051-1060, 1998
    Additional Material: 9 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Pressure-volume-temperature properties and free volume parameters of PEO/PMMA blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1061-1080 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; dilatometry ; free volume ; specific volume ; excess volume ; compressibility ; thermal expansivity ; equation of state ; scaling parameters ; crystallinity ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Melt-miscible polymer blends of poly(ethylene oxide)/atactic poly(methyl methacrylate (PEO/a-PMMA)) were prepared by melt-mixing and characterized by pressure-volume-temperature (PVT) dilatometry in the pressure and temperature range of 0 to 200 MPa and 20 to 200°C, respectively. The PVT data were analyzed in terms of two equations of state (EOS). The empirical Tait EOS was applied in the glassy, semicrystalline, and equilibrium melt state, and the Simha-Somcynsky EOS theory was applied in the equilibrium melt and glassy state. The Simha-Somcynsky EOS theory contains a free volume function. The temperature, pressure, and composition dependence of the free volume fraction h calculated from the Simha-Somcynsky EOS theory was studied. As a function of blend composition we observe that the free volume fraction, thermal expansivity, and compressibility all deviate mainly positively from linearity while the specific volume deviates mainly negatively from linearity. These findings are reconciled with composition-dependent free volume parameters, the free volume and cell volume as well as with self- and cross-interaction parameters derived from the Simha-Somcynsky EOS theory as applied to polymer mixtures. Moreover, the pressure dependence of glass and melting transitions as well as crystallization kinetics have been investigated. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1061-1080, 1998
    Additional Material: 18 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Inorganic/organic host-guest materials: Surface and interclay reactions of styrene with copper(II)-exchanged hectorite (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 673-679 
    Details
    ISSN: 0887-6266
    Keywords: scanning force microscopy ; hectorite ; polystyrene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Many important layered silicate-polymer nanocomposite materials may be synthesized using an in-situ polymerization process. Using this technique, organic monomers are intercalated into the interlayer regions of the hosts, where subsequent polymerization may then occur. In this paper, we report on the in-situ polymerization of styrene in Cu(II)-exchanged hectorite thin films. Scanning force microscopy (SFM) images of the polymer surface reveal that the surface polystyrene is generally aggregated into groups of elongated strands. SFM imaging of the interclay regions, in conjunction with X-ray diffraction (XRD) and electron spin resonance (ESR) data, indicates that approximately 20-30% of these regions contain polystyrene, with minimal reduction in the majority of Cu2+ sites observed. XRD data shows little or no intercalation of the monomer into the true intergallery regions. Instead, the polymer likely forms in intercrystallite or planar defect regions. In addition, two distinct phases of polymeric material are found within these defect regions, a highly polymerized polystyrene in addition to a polystyrene form exhibiting greater material stiffness. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 673-679, 1998
    Additional Material: 3 Ill.
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