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Main chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB-type self-polycondensation route: FT-IR and XRD studies

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Title Main chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB-type self-polycondensation route: FT-IR and XRD studies
 
Creator RANGANATHAN, T
GOWD, EB
RAMESH, C
KUMAR, A
 
Subject infrared temperature
2,6-tolylene diisocyanate
molecular-weight
flexible spacer
blowing agents
6 methylene
polymers
polyesters
polyethylene
foams
ft-ir
liquid-crystalline polymers
polyurethanes
xrd studies
 
Description The detailed mesophasic characterization of main chain liquid crystalline polyurethanes containing biphenyl mesogen, which were synthesized by the novel AB-type self-polycondensation approach, was carried out by using Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM), variable temperature X-ray Diffraction (XRD), and Fourier Transform Infrared (FT-IR) spectroscopic studies. The type of mesophase present in these polymers was identified to be the smectic A phase by POM and XRD studies. The smectic layer thickness was found to increase as the length of the spacer increased. The effect of temperature on the hydrogen bonding was analyzed by FT-IR studies. The curve-fitting analysis of the NH stretching and C=O stretching modes of vibrations indicated a gradual decrease in hydrogen bonding during the transition from the crystalline state to the mesophase. The mesophase to isotropic liquid transition was then accompanied by the complete disappearance of the hydrogen bonding. The biphenyl bands also showed changes during phase transitions due to the coupling of biphenyl vibration modes with the urethane linkage attached to it. (c) 2005 .
 
Publisher JOHN WILEY & SONS INC
 
Date 2011-08-16T08:41:07Z
2011-12-26T12:54:51Z
2011-12-27T05:43:10Z
2011-08-16T08:41:07Z
2011-12-26T12:54:51Z
2011-12-27T05:43:10Z
2005
 
Type Article
 
Identifier JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 43(9), 1903-1912
0887-624X
http://dx.doi.org/10.1002/pola.20668
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9445
http://hdl.handle.net/10054/9445
 
Language en