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  • 1
    Electronic Resource
    Electronic Resource
    Design and characterization of thermosetting polyimide structural adhesive and composite matrix systems (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2943-2954 
    Details
    ISSN: 0887-624X
    Keywords: phenyl ethynyl ether imides ; amorphous or semicrystalline morphology ; volatile free thermosetting matrix ; structural adhesives ; composites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fully cyclized, organo soluble, phenylethynyl-terminated, ether-imide oligomers of 2-10,000 g/mol (Mn) were prepared by the reaction of 2,2′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-propane dianhydride (bisphenol-A dianhydride, BPADA) with a stoichiometric excess of either para, meta, or isomeric mixtures of phenylene diamine and phenylethynylphthalic anhydride (4-PEPA) endcapper. High para-containing oligomers produced semicrystalline powders, but the all meta isomer was completely amorphous. The lower molecular weight oligomers displayed an attractive low viscosity melt and were cured to very high gel content networks at 350-380°C for 30-90 min. The cured 3000 g/mol oligomers showed a (DSC) glass transition temperature (Tg) of 267°C and produced tough, solvent-resistant films. Excellent adhesion to surface-treated titanium alloys was achieved, as judged by single-lap shear measurements. Resin infusion molding was conducted, which permitted low-void, graphite-fabric composite panels to be prepared. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2943-2954, 1997
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Catalytic chain transfer for molecular weight control in the emulsion homo- and copolymerizations of methyl methacrylate and butyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 859-878 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of catalytic chain transfer in semi-batch emulsion polymerization has been studied for two monomers, viz, methyl and n-butyl methacrylate. Two different catalytic chain transfer reagents were used with different water solubilities: cobaloxime boron fluoride (COBF), which was found to partition approximately equally between organic and aqueous phases, and tetra-phenyl cobaloxime boron fluoride (COPhBF), which was found to reside predominantly in the organic phase. The difference in hydrophilicity between the two transfer agents was found to affect the polymerization mechanism. COBF exhibited superior transfer behavior in all cases, whereas the restricted mobility of the COPhBF had a deleterious effect on the efficiency of the transfer mechanism. The best results were achieved under monomer flooded conditions using COBF. MALDI-TOF mass spectrometry analysis shows catalytic chain transfer to be the dominant mechanism initiating and stopping chain growth as none of the chains appear to have initiator fragment end groups. Analysis of copolymers by MALDI-TOF mass spectrometry reveals both molecular weight and composition data. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 859-878, 1997
    Additional Material: 21 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of solvent on the homo-propagation rate coefficients of styrene and methyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2311-2321 
    Details
    ISSN: 0887-624X
    Keywords: styrene ; methyl methacrylate ; pulsed-laser polymerization ; “living” free radical ; propagation rate coefficient ; solvent effects ; benzyl alcohol ; N-methyl pyrrolidinone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The free radical propagation rate coefficients of both Methyl Methacrylate (MMA) and Styrene (STY) have been measured using Pulsed-Laser Polymerization. The effect of solvents on the propagation rate coefficient, kp, is reported for several solvents, namely, bromobenzene, chlorobenzene, dimethyl sulphoxide, diethyl malonate, diethyl phthalate, benzonitrile, and benzyl alcohol, at 26.5°C. This preliminary data indicated that benzyl alcohol (BzA) had a large effect on the MMA propagation reaction. As earlier work indicated that N-methyl pyrrolidinone (NMP) would also have a large effect on the kp of MMA, Arrhenius parameters were evaluated for both MMA and STY at two different concentrations of monomer in BzA and NMP. BzA had a significant effect (at 95% confidence) increasing both the activation energy (Ea) and the preexponential factor (A) for MMA and STY. In NMP, a similar trend is observed for MMA polymerization; however, while a solvent effect on STY was observed, the effect on Ea and A was too small to discern with confidence. A series of additional experiments was performed to evaluate the influence of camphorsulfonic acid (CSA) as an additive in STY polymerization. There was no effect of CSA on kp, confirming that the strong effect CSA has on “living” radical polymerization of styrene does not originate from complexation leading to an accelerated propagation step but rather by altering the ratio of active-to-dormant chains in the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2311-2321, 1997
    Additional Material: 12 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of porous hydrogel structures by polymerizing the continuous phase of a microemulsion (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 219-226 
    Details
    ISSN: 0959-8103
    Keywords: microemulsion ; hydrogel ; poly(2-hydroxyethyl methacrylate) ; equilibrium water content ; oxygen permeability ; scanning electron microscopy ; 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: A series of microemulsions have been formulated, with 2-hydroxyethyl methacrylate (HEMA) or HEMA/water/propanol mixtures as the continuous phase and methylcyclohexane as the discontinuous phase. The effect of surfactant type was investigated with the utilization of both anionic and nonionic surfactants. The microemulsion continuous phase was polymerized by UV radiation and a thermal post-cure. The resultant polymers were extracted to remove the discontinuous phase and the surfactant. On swelling, the majority of the polymers became opaque, although transparent PHEMA hydrogels were synthesized with an improved equilibrium water content (EWC). The cause of opacity was shown by field emission scanning electron microscopy (FESEM). The breakdown in the microemulsion on polymerization is caused by unfavourable interactions between the PHEMA and the stabilizing surfactants causing agglomerization of the discontinuous phase. All the hydrogels were found to have higher water retention than PHEMA, with EWCs of up to 70%. The modified polymers also demonstrated an increased rate of water diffusion into the matrix. A preliminary study of oxygen permability revealed that a significant improvement had been made over standard PHEMA membranes. The porous structure of the PHEMA gels has been shown to be dependent on the type of surfactant used during synthesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360301
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol-gel reaction (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 181-190 
    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: Nanocomposites were produced via sol-gel reactions for tetraethylorthosilicate within the cluster morphology of perfluorosulfonic acid films. Small-angle x-ray scattering revealed that the polar/nonpolar nanophase-separated morphological template persists despite invasion by the silicon oxide phase. Scanning electron microscopy (ESEM-EDAX) studies have indicated that the greatest silicon oxide concentration occurs near the surface and decreases to a minimum in the middle. Optical and ESEM micrographs revealed a brittle, surface-attached silica layer at high silicon oxide contents. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550120
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  • 6
    Electronic Resource
    Electronic Resource
    Crystallization behavior and mechanical properties of a nylon-6, -6/6, and -12 terpolyamide (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 2237-2245 
    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: Composition, tacticity, and processing history can affect the morphology of semicrystalline polymers. Although homopolyamides are a family of polymers well known for semicrystalline character, through copolymerization or multicomponent copolymerization significant changes in materials' crystalline and thermal properties can occur. Due to chain irregularities introduced by terpolymerization, differential scanning calorimetry shows RDG 114T, a commercial polyamide of nylon-6, -6/6, and 12, to have an atypically low Tm and exhibit interesting recrystallization behavior. Specifically, the polyamide is wholly amorphous upon cooling from the melt, and since its Tg is about 20°C (due to the presence of plasticizers), chain ordering is found to occur over time at room temperature. Since the polyamide's morphology is time-dependent, the tensile properties of the polymer are also found to vary with ambient aging. For instance, Young's moduli for an amorphous and 7-day room temperature-annealed sample are 1.3×102 and 2.8×102 MPa, respectively. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Frictional properties of polyolefins treated with fluoroelastomer processing aids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1465-1476 
    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: A friction measurement system was designed that made possible the measurement of the friction coefficient between a polymer melt and a metal die wall. The shear stresses developed in the capillary rheometer and the friction coefficient measured in the friction measurement system were compared in an attempt to understand the mechanism of fluoroelastomer processing aids (FPA) in the extrusions of polypropylene (PP) and linear low-density polyethylene (LLDPE). The apparent viscosity drops of LLDPE treated with FPA were larger than those of PP treated with FPA. The friction coefficient drops of LLDPE treated with FPA were also larger than those of PP treated with FPA. High viscosity FPA showed a moderate friction coefficient drop in the actual extrusion of PP even though it showed only a poor effect in the capillary rheometer. The frictional forces were calculated from the friction coefficient measurement made during extrusions of FPA-treated and untreated samples. © 1995 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070551011
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  • 8
    Electronic Resource
    Electronic Resource
    The Quest For Extra-Large Pore, Crystalline Molecular Sieves (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1745-1750 
    Details
    ISSN: 0947-6539
    Keywords: large-pore materials ; materials science ; molecular sieves ; zeolites ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The definition and reasons for desiring extralarge pore, crystalline molecular sieves are ennumerated. A historical perspective on the development of these materials is presented with emphasis on critical features important for practical application. Based on the known physiochemical properties of extra-large pore materials, several avenues for their synthesis are suggested. Finally, a few issues of concern when dealing with this class of materials are presented.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031104
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  • 9
    Electronic Resource
    Electronic Resource
    Application of dielectric spectroscopy and DSC to the study of relaxations in some copolymeric hydrogels (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 397-404 
    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: The nature of water in copolymeric N-vinyl pyrrolidone/methyl methacrylate hydrogels has been investigated using dielectric thermal analysis (DETA) and differential scanning calorimetry (DSC). Dielectric tan δ measurements are reported over a frequency range 500 Hz-20 kHz and a temperature range of -140 to +20°C. The observed complex relaxations were attributed to the mobility of water and the relaxation processes of the copolymer matrix. In addition DSC was used to measure the melting endotherm of water in gels partially swollen to a pseudoequilibrium. The resultant data were fitted to a two-phase approximation model. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560310
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  • 10
    Electronic Resource
    Electronic Resource
    A Novel Sensitive Colorimetric Assay for Visual Detection of Solid-Phase Bound Amines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2787-2791 
    Details
    ISSN: 1434-193X
    Keywords: Solid-phase peptide synthesis ; Disperse Red 1 ; p-Nitrophenyl ester ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new simple and efficient method for the detection of incomplete coupling reactions during solid-phase peptide synthesis is decribed. Using p-nitrophenyl ester 1 (NF31), free amino groups can be visually detected on the resin by direct coloring of the beads. A specific feature of the assay resides in the possibility of detection of sterically hindered primary amines.
    Additional Material: 3 Ill.
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