Configuration effects of ortho, meta, and para linkages on liquid crystallinity during thin-film polymerization of poly(ester-amide)s

By in situ thin-film polymerization conducted on a heating stage of a polar izing microscope, we have investigated the effects of monomer structures on the formation of liquid crystallinity. Three polymerization systems studie d are 2,6-acetoxynaphthoic acid (ANA)/acetoxy acetanilide (AAA)/phthalic ac id (PA), ANA/AAA/ isophthalic acid (IA) and ANA/AAA/terephthalic acid (TA). In the three systems, PA, IA, and TA may create an ortho, a meta, and a pa ra linkage, respectively. The formation of liquid crystallinity was found s trongly dependent on the straightness and configuration of monomeric units. For ANA/AAA/PA and ANA/AAA/IA systems, there exists the critical ANA conte nt to yield the Liquid crystalline phase. Below this critical content, eith er amorphous phase forms or crystallization occurs during polymerization. E xperimental data also indicate that defect density in the polymerization pr oduct reduces with increasing ANA content. Surprisingly, for the first time , we have observed that the ANA/AAA/PA system has a higher tendency to yiel d liquid crystallinity than the ANA/AAA/IA system. For the ANA/AAA/TA syste m, the polycondensation reaction is incomplete if the TA content is too hig h because of the low reactivity and the high melting point of TA. Polymeriz ation of the ANA/AAA/TA system does not yield totally random copolymers bec ause the liquid crystal phase appears before all TA crystals disappear duri ng the polymerization. (C) 2000 John Wiley & Sons, Inc.