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  • Polymer and Materials Science  (11)
  • Earth Resources and Remote Sensing
  • 1990-1994  (11)
  • 1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Thermogravimetric analysis of poly(alkyl methacrylates) and poly(methylmethacrylate-g-dimethyl siloxane) graft copolymers (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1747-1753 
    Details
    ISSN: 0887-624X
    Keywords: poly(methyl methacrylate) ; polydimethylsiloxane ; thermogravimetric analysis (TGA) ; graft copolymers ; poly(alkyl methacrylates) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal stabilities of various poly(alkyl methacrylate) homopolymers and poly(methyl methacrylate-g-dimethyl siloxane) (PMMA-g-PSX) graft copolymers have been determined by thermogravimetric analysis (TGA). As expected, the thermal stabilities of poly(alkyl methacrylates) were a function of the ester alkyl group, and polymerization mechanism. In particular, thermally labile linkages, which result from termination during free radical or nonliving polymerization mechanisms, decrease the ultimate thermal stabilities of the polymers. However, graft copolymers, which were prepared by the macromonomer technique with free radical initiators, exhibited enhanced thermal stability compared to homopolymer controls. A more complex free radical polymerization mechanism for the macromonomer modified polymerization may account for this result. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320917
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  • 2
    Electronic Resource
    Electronic Resource
    Hindered lithium dialkylamide initiators for the living anionic polymerization of methacrylic esters (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2425-2430 
    Details
    ISSN: 0887-624X
    Keywords: anionic ; polymerization ; living ; methyl methacrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium diisopropylamide is an efficient initiator for the anionic polymerization of methyl methacrylate in polar solvents at -78°C. Predictable molecular weights based on the initiator concentration were obtained, yields were quantitative, and molecular weight distributions were relatively narrow (〈1.30). The presence of an amino end group and confirmation of the initiation mechanism were confirmed by potentiometric titration using HClO4. Number-average molecular weights determined by titration agreed well with values determined by SEC. Other lithium dialkylamides that contain larger alkyl groups such as lithium diisobutylamide were less efficient initiators. This was attributed to the more nucleophilic anion due to less steric hindrance near the nitrogen atom. Molecular weight distributions were significantly broadened (〉2.0), and molecular weight control was not achieved. However, polymer yields were quantitative. In all cases, PMMA stereochemistry was indicative of a solvent-separated lithium counterion, and triad compositions were identical to organolithium initiated homopolymers, i.e., 78% syndiotactic, 20% heterotactic, and 2% isotactic. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321303
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of long-range2 13C-1H coupling constants of 95% uniformly 13C-labeled polysaccharide from streptococcus mitis J22 (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 1327-1338 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coaggregation of Streptococcus mitis strain J22 in the early stages of dental plaque formation has been shown to result from interaction of cell wall polysaccharides with lectins on the surface of other oral bacterial species. This bacterium was grown in a medium containing 13C as the sole carbon source. We have isolated the lectin receptor polysaccharide from this strain with full enrichment in 13C and have determined a number of two-bond and three-bond 13C-1H coupling constants from measurements of the offsets in two-dimensional homonuclear nmr spectra [exclusive correlated spectroscopy (E-COSY) method]. A scheme for reliable extraction of these coupling constants from homonuclear Hartmann-Hahn and nuclear Overhauser effect spectroscopy spectra is tested in model compounds. We interpret the three-bond coupling across the glycosidic linkage in terms of dihedral angles in order to provide conformational information to supplement molecular modeling and nuclear Overhauser effect data. We show that the E-COSY method works well even for coupling constants smaller than the nmr line width and that a number of the 3JCH across the glycosidic linkage are in the range of 1-2 Hz, which is much smaller than many previously reported values. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360341005
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  • 4
    Electronic Resource
    Electronic Resource
    A thermally stimulated current/relaxation map analysis of the relaxation processes in aromatic polyester, liquid crystal polymer film (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 587-608 
    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: Thermally stimulated current (TSC) and relaxation map analysis (RMA) have been applied to the examination of dynamics of thermally induced relaxation processes in highly oriented, wholly aromatic, polyester liquid crystalline polymer films. Films of two compositions were examined. A primary distinction in composition was the difference in level of 6-hydroxy-2-napthoic acid. Following an analysis protocol developed by Sauer et al., it was found that values of activation enthalpy were well above the zero entropy value at temperatures well below the Sauer “Tg.” This indicates a high level of cooperativity in rotational relaxation processes even at low temperatures. Cooperative rotational relaxation domains were postulated to account for this behavior. The persistence of cooperativity above the Sauer “Tg.” is evidence that these materials did not undergo a conventional glass transition at any temperature in the range-80 to 200°C. The behavior of these materials as a model system of “loosely bundled rods” was examined using a modified Barker-Crine analysis. This type of model behavior seemed to fall off at relatively low temperatures. The occurrence of rotational processes at high temperatures with little or no loss in orientation suggests that polymer chains are physically constrained to maintain their relative positions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530511
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  • 5
    Electronic Resource
    Electronic Resource
    Acetals as nucleating agents for polypropylene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 591-596 
    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: Nucleating agents increase the impact strength, tensile strength, and tensile elasticity modulus of semicrystalline polymers. Nucleating agents also decrease product cycle times, resulting in a cost savings per product unit. We have synthesized and tested 15 compounds as nucleactors for polypropylene. Of these, trinapthylidene sorbitol, tri-(4-methyl-1-naphthylidene)sorbitol, tri-(4-methoxy-1-naphthylidene) sorbitol, and dibenzylidene xylitol are efficient nucleators of polypropylene. Trinaphthylidene sorbitol (tns) has two major diastereomers: The “S” diastereomer yields a faster crystallization rate for polypropylene than does the commercial nucleator dibenzylidene sorbitol (Millad 3905). Crystallization rates are 208 and 88, respectively (t-1.05 min-1 × 1000). The “R” diastereomer, however, is a poor nucleator and interferes with the nucleating activity of the “S” diastereomer. A 52/48 mixture of diastereomers does not nucleate polypropylene, even at twice the concentration. This is first time that the importance of stereochemistry has been demonstrated in the nucleating action. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520502
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  • 6
    Electronic Resource
    Electronic Resource
    Methacrylate-based block ionomers I: Synthesis of block ionomers derived from t-butyl methacrylate and alkyl methacrylatesDedicated to Professor Maurice Morton to commemorate the establishment of the Maurice Morton Institute of Polymer Science at the University of Akron. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 205-216 
    Details
    ISSN: 0959-8103
    Keywords: block ionomer ; anionic polymerization ; methacrylates ; 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: Diblock and triblock copolymers of t-butyl methacrylate (tBMA) with 2-ethylhexyl methacrylate (EHMA) and n-hexyl methacrylate were prepared via alkyl lithium initiation and sequential addition techniques in THF at -78°C. The tBMA blocks were quantiatively and selectively hydrolyzed to afford poly(methacrylic acid) (PMAA) blocks which were then neutralized with alkali metal bases to form block ionomers. The unhydrolyzed copolymers had a phase mixed morphology as evidenced by thermal analysis while the hydrolyzed and neutralized polymers were multiphase materials. The carboxylic acid and ioncontaning triblock copolymers formed gels in nonpolar solvents which could be disrupted by the addition of polar additives. Certain carboxylic acid and ioncontaining EHMA/tBMA diblock copolymers also showed this behavior. The triblock ionomers did not show thermoplastic flow prior to degradation, except at the lowest ionic content studied (2%).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210330212
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  • 7
    Electronic Resource
    Electronic Resource
    Monolayer formation of chitin derivatives containing PMMA side-chains (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 303-307 
    Details
    ISSN: 0959-8103
    Keywords: monolayer formation ; PMMA-grafted chitin derivative ; phase transition ; accessible monolayer to lysozyme ; 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 monolayer behaviour of poly(methyl methacrylate) (PMMA)-grafted chitin derivatives was studied on an air-water interface by measuring surface pressure-area isotherms. The formation of a stable monolayer indicates the well-defined packing and orientation of the chitin derivative, which can be regulated by the main-chain length under appropriate experimental conditions. The isotherms exhibit a transition point from a liquid expanded phase to a condensed phase at a surface pressure of approximately 15mN/m for almost all monolayers examined. The transition pressure decreases with increase of temperature from 10 to 20°C. The properties of the sub-phase affected the formation of a monolayer greatly. The collapse of a surface film takes place at lower pressure on the sub-phase of a 0.1 M NaCI solution. After introducing lysozyme at a concentration at 2.4 × 10-8M to the sub-phase, the monolayer showed an extensively expanded phase with a longer transition region. This indicates that the monolayer was degraded by the lysozyme, resulting in a disordered structure. The results are contrasted with those of an aqueous phase where N-acetylglucosamine residues may be inaccessible to lysozyme so that the degradation of the chitin derivative occurs at a very slow rate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350401
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  • 8
    Electronic Resource
    Electronic Resource
    Photoswitch based on bacteriorhodopsin Langmuir-Blodgett films (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 4 (1994), S. 219-224 
    Details
    ISSN: 1057-9257
    Keywords: Bacteriorhodopsin ; Langmuir-Blodgett films ; Differential response ; Photoswitch ; Photoalarm ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Langmuir-Blodgett (LB) films of bacteriorhodopsin (bR) without addition of lipids were deposited on indium tin oxide (ITO) conductive electrodes. A sandwich photocell with a juction structure of ITO/bR/electrolyte/ITO has been constructed in which the bR LB film was put into contact directly with an aqueous electrolyte immobilized in an agar gel. Under visible light irradiation a transient photocurrent due to a change in light intensity can be observedl showing the property of vision-imitative material. It can be used as a multiple optical switch, since it gives positive and negative transient photocurrnts during application and removal of light irradiation respectively and has a photoresponse repeatedly in the same direction when the light intensity increases or decreases stepwise. A photoalarm consisting of the bR photocell and an amplifier was set up by utilizing the switching function of the bR LB film.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860040305
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  • 9
    Electronic Resource
    Electronic Resource
    Structure and properties of liquid crystalline naphthalenediol copolyesters (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1913-1921 
    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: Thermotropic liquid crystalline copolyesters with 1.4-, 1.5-, and 2.7-naphthalenediol (NDO) units were prepared by molten-state copolycondensation. It was found that the chain structure of the copolyesters is almost the same as the structure of recurring moieties of five units. The copolyesters have a glass transition temperature above 381 K, decomposition temperature above 703 K, and melting temperature between 513 and 559 K and their melts exhibit nematic texture and stir opalescence. The copolyester melts show a usual rheological behavior depending on the NDO unit content, but much lower extrudate swell. Light-scattering patterns of the copolyester films with low crystallinity are clearly asymmetric and therefore indicate the existence of preferred orientation of the copolyester chains. Scanning electron microscopy observation suggests that the as-spun fibers of 2.7-NDO-containing copolyesters were highly oriented and fibrillated. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070511107
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  • 10
    Electronic Resource
    Electronic Resource
    Cure kinetics of different molar ratios of 4,4′-bismaleimidodiphenylmethane and bisphenol A dicyanate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 105-112 
    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: Bismaleimide-triazine (BT) resins are thermosets derived from the addition polymerization of different molar ratios of 4,4′-bismaleimidodiphenylmethane (BM) and bisphenol A dicyanate (BA). The possible cross-linking reactions involved in the formation of BT resins are addition polymerization of BM, cyclocrimerization of BA, and heteropolymerization between BM and BA. Fourier-transform infrared spectroscopy reveals that cyclotrimerization of BA occurs during the cure of a 1 : 2 molar ratio of BM to BA (as 1M2A). No sign of cyclotrimerization is observed for the case of the 1 : 1 molar ratio of BM to BA (as 1M1A). A dynamic differential scanning calorimeter (DSC) is employed to study the cure kinetics. The apparent activation energy evaluated from the Prime method is increased with the content of the BM component in the starting mixture. The different pattern of activation energy with fractional conversion (α) indicates the different chemical nature for the cure reactions of 1M1A and 1M2A. The empirical rate functions thus evaluated are 2.32 × 105 + 5.62 α 105α - 8.61 × 105α2 and 6.07 × 105 + 1.06 × 106α - 1.66 × 106α2s-1 for the cure reactions of 1M1A and 1M2A, respectively. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530111
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