摘要
A mesogen-jacketed liquid crystal polymer,poly{2,5 -bis［(4′-hexyloxyphenyl)oxycarbonyl］styrene}(PHPCS),with number-average d molecular weight of 1.28×１０5 and polydispersity of 1.48 was prepared vi a 2,2,6,6 -tetramethyl-piperidinyloxy mediated free radical polymerization.The thermotr opic behavior was studied by a combination of differential scanning calorimetry, thermogravimetry,polarized optical microscope and wide-angle X-ray diffracti on.PHPCS was not crystalline over the entire temperature region studied.On hea ting,PHPCS first became an isotropic melt at glass transition temperature (T g) and then a mesophase at temperatures much higher than T g.On subseq uent cooling,the formed ordered phase disappeared above T g.Contrary to t heoretical predictions and previous experimental observations,the transition fr om isotropic melt to liquid crystalline phase was an endothermic process and th e order-disorder transition took place with concurrence of heat release.
A mesogen-jacketed liquid crystal polymer, poly {2,5-bis[(4'-hexyloxyphenyl) oxycarbonyl]styrene} (PHPCS) with number-averaged molecular weight of 1.28 x 10(5) and polydispersity of 1.48 was prepared via 2, 2, 6,6-tetramethyl-piperidinyloxy mediated free radical polymerization. The thermotropic behavior was studied by a combination of differential scanning calorimetry, thermogravimetry, polarized optical microscope and wide-angle X-ray diffraction. PHPCS was not crystalline over the entire temperature region studied. On heating, PHPCS first became an isotropic melt at glass transition temperature (T-g) and then a mesophase at temperatures much higher than T-g. On subsequent cooling, the formed ordered phase disappeared above T-g Contrary to theoretical predictions and previous experimental observations, the transition from isotropic melt to liquid crystalline phase was an endothermic process and the order-disorder transition took place with concurrence of heat release.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2003年第3期430-433,共4页
Acta Polymerica Sinica
基金
国家自然科学基金 (基金号 2 9992 5 90 - 4和 2 0 2 740 0 1)
教育部高等学校博士学科点专项基金 (基金990 0 0 136 )
教育部优秀青年教师教学与科研奖励基金资助项目
