02086nas a2200229   4500008004100000022001400041245016400055210006900219260006800288300001400356490000700370520120800377653001001585653003201595653001801627653001601645100002001661700001701681700001501698700001601713856012701729       2005                        eng d  a0887-624X00aMain chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB-type self-polycondensation route: FT-IR and XRD studies0 aMain chain thermotropic liquid crystalline polyurethanes contain  a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY  a1903-19120 v433 a<p>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 Wiley Periodicals, Inc.</p>10aFT-IR10aliquid-crystalline polymers10apolyurethanes10aXRD studies1 aRanganathan, T.1 aGowd, E., B.1 aRamesh, C.1 aKumar, Anil  uhttps://library.ncl.res.in/content/main-chain-thermotropic-liquid-crystalline-polyurethanes-containing-biphenyl-mesogens-0