Synthesis and liquid-crystal-aligning properties of novel aromatic poly(amide imide)s bearing n-alkyloxy side chains

摘要

Novel aromatic poly(amide imide)s (m-PAIs, m = 8, 12, 16) containing preformed isophthalamide unit and pendent n-alkyloxy (-O-n-CmH2m+1, m = 8, 12, 16) side chains were prepared in thin films by polymerization of pyromellitic dianhydride (PMDA) with N,N-bis(4-aminophenyl)-5-(n-atkyloxy)isophthalamides (m-DAs) obtained from N,N'-bis(4-nitrophenyl)-5-(n-alkyloxy)isophthalamides (m-DNs). The m-PAI films were tough, flexible and transparent with inherent viscosities in the 1.25-1.67 dL/g range in DMAc and soluble in DMAc and NMP on heating. In TGA m-PAIs began to degrade around 440 degrees C and in DSC no phase transitions were detected. In X-ray diffractometry the m-PAIs appeared amorphous with loosely developed layered crystalline structure. In liquid crystal (LC)-aligning performance measured using 4-n-pentyl-4-cyanobiphenyl (5CB) on thin film surfaces rubbed with standard velvet fibers, the m-PAIs showed homogeneous LC alignment parallel to the rubbing direction with 2.5-17.5 degrees pretilt angles, depending on the rubbing density and n-alkyloxy side chain length. (c) 2007 Wiley Periodicals, Inc.