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Thermotropic liquid-crystalline polyesters containing biphenyl mesogens in the main chain: The effect of connectivity

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Title Thermotropic liquid-crystalline polyesters containing biphenyl mesogens in the main chain: The effect of connectivity
 
Creator RANGANATHAN, T
RAMESH, C
KUMAR, A
 
Subject para,para'-bibenzoic acid
mesophase properties
aromatic polyesters
flexible spacers
polymers
4,4'-dihydroxybiphenyl
homopolyesters
liquid-crystalline polymers
biphenyl mesogens
ab approach
odd-even effect
effect of connectivity
polyesters
structure-property relations
 
Description A homologous series of main-chain thermotropic liquid-crystalline polyesters containing-rigid biphenyl mesogen and flexible methylene spacers were synthesized with the AB-type self-polycondensation approach. The polyesters were characterized with H-1 NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized light optical microscopy, and X-ray diffraction. These polyesters, containing trimethylene spacers on the acid side and various spacers on the alcohol side of the biphenyl mesogen, showed an odd- even effect in the transition temperatures and mesophase type. The even members showed higher transition temperatures than the odd ones. A normal smectic mesophase was observed for the even members, whereas the odd-membered counterparts exhibited a tilted smectic mesophase. To study the effect of connectivity, the mesophase characteristics of these polyesters were compared with those of the isomeric AB-type polyesters without any methylene spacer on the acid side of the biphenyl moiety. The mesophase characteristics were insensitive to whether the mesogen was connected to a carboxyl unit or a methylene unit. (C) 2004 .
 
Publisher JOHN WILEY & SONS INC
 
Date 2011-08-16T16:27:36Z
2011-12-26T12:55:02Z
2011-12-27T05:43:34Z
2011-08-16T16:27:36Z
2011-12-26T12:55:02Z
2011-12-27T05:43:34Z
2004
 
Type Article
 
Identifier JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 42(11), 2734-2746
0887-624X
http://dx.doi.org/10.1002/pola.20109
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9554
http://hdl.handle.net/10054/9554
 
Language en