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  • 1
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Random and alternating thermotropic liquid-crystalline copolyethers have been synthesized from 4,4′-dihydroxybiphenyl and a 1/1 mol ratio of 1,5-dibromopentane and α,ω-dibromoalkanes by a two-phase (organic solvent-aqueous NaOH) phase-transfer-catalyzed polyetherification. Random copolyethers were prepared from α,ω-dibromoalkanes having six to twelve methylene units. Their phase behavior was compared with those of the perfectly alternating copolyethers containing five methylene units in one spacer and eight, nine, or eleven methylene units in the other, respectively. An odd-even dependence in thermal transitions has been observed in both oligomeric systems. In all cases, alternating copolyethers, even though comparatively lower in molecular weight, have given rise to higher melting and isotropization temperatures. Since the increase in the melting temperature is larger than the increase in the isotropization temperature, the thermal stability range of the mesophase has narrowed for alternating copolyethers with respect to their random copolyether counterparts.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1875-1882 
    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: Three new types of fillers for polypropylene are investigated. The first two were derived from burnt rice husk ash (RHA), whereas the third, a wood-based filler, was processed from oil palm trunk. One important characterization of the composites involves the checking for the actual filler content and filler distribution within the matrix. An analytical technique is described here for computation of the filler content in the composites based on a simple expression derives from thermogravimetric analyses. For filler with volatiles such as the black RHA, the derived expression was pf = 106(rb/mc), and for easily burnt fillers (wood-based), the expression was pf = 156(md/mc). The technique has shown good agreement and consistency between analyzed and actual filler contents and a uniform filler distribution within the polypropylene matrix. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 2913-2930 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermotropic liquid crystalline (LC) copolyethers have been synthesized from 1,9-dibromononane, a nonmesogenic bisphenol (4,4′-isopropylidenediphenol [BPA]) and a mesogenic bisphenol (4,4′-dihydroxybiphenyl [HB]) by a two-phase (organic solvent - aqueous NaOH) phase-transfer catalyzed polyetherification. LC polyethers were obtained for copolymers containing as much as 70 mol % BPA. Optical polarizing microscopy and DSC have revealed smectic mesomorphism for all the copolyethers. The influence of both copolymer composition and microstructural changes, including the nature of the chain ends, upon the mesomorphic properties of these copolyethers have been discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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