环丁烷基聚酰亚胺液晶取向膜的制备及光控取向研究

Preparation of cyclobutane-based polyimide alignment films and the photoalignment research

采用1,2,3,4-环丁烷四酸二酐(CBDA)分别与芳香族二胺单体,包括4,4′-二氨基二苯甲烷(MDA)、3,3′-二甲基-4,4′-二氨基二苯甲烷(DMDA)、3,3′,5,5′-四甲基-4,4′-二氨基二苯甲烷(TMMDA)、3,3′-二甲基-5,5′-二乙基-4,4′-二氨基二苯甲烷(DMDEDA)、1,1-双(4-氨基-3,5-二甲基苯基)-1-苯基甲烷(PTMDA)以及1,1-双(4-氨基-3,5-二甲基苯基)-1-(3′-三氟甲基苯基)甲烷(TFMDA)通过低温溶液缩聚法制备了聚酰胺酸(PAA)型液晶取向剂。采用该系列PAA取向剂装配了液晶盒。测试结果显示,PAA高温固化后形成的聚酰亚胺(PI)取向膜具有良好的耐热稳定性,5%失重温度均超过了450℃。经过波长为254 nm的线性偏振紫外光(LPUV)辐照后,该系列PI取向膜对液晶分子具有良好的取向效果,预倾角(θ_(p))为0.28~0.47°。装配的液晶盒的残余直流电压(RDC)最低可达364 mV。

A series of poly(amic acid)(PAA)alignment agents are prepared from 1,2,3,4-cyclobutane tetracarboxylic dianhydride(CBDA)and various aromatic diamines,including 4,4′-methylenedianiline(MDA),3,3′-dimethyl-4,4′-diaminodiphenylmethane(DMDA),3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane(TMMDA),3,3′-dimethyl-5,5′-diethyl-4,4′-diamino-diphenylmethane(DMDEDA),1,1-bis[(4-amino-3,5-dimethyl)phenyl]-1-phenylmethane(PTMDA),and 1,1-bis[(4-amino-3,5-dimethyl)phenyl]-1-(3′-trifluoromethylphenyl)methane(TFMDA),respectively via low-temperature polycondensation procedure.Liquid crystal(LC)minicells are fabricated by using the prepared PAAs as the alignment agents.The polyimide(PI)alignment films obtained by thermally curing of the PAAs exhibits good thermal stability with the 5%weight loss temperatures higher than 450℃.The PI alignment films show good alignment ability to the LC molecules after exposure by the linear polarized ultraviolet light(LPUV)(wavelength:254 nm).The LC molecules show the pretilt angles(θ_(p))in the range of 0.28-0.47°.The LC minicells show low residual direct current voltage(RDC)features with the RDC values as low as 364 mV.