Liquid crystalline poly(β‐aminoester)s containing different mesogenic groups

Abstract Four series of new poly(β‐aminoester)s based on different mesogenic units and amino spacers were prepared and their properties examined. The polymers were obtained by a Michael‐type polyaddition reaction of the diamines piperazine ( 5a ), 2‐methylpiperazine ( 5b ), N,N ′‐dimethylhexamethylenediamine ( 5c ), and 4,4′‐trimethylenedipiperidine ( 5d ) to diacrylates containing the anisotropic group, trans ‐4,4′‐vinylenedi‐ p ‐phenylene diacrylate ( 1 ), 4‐(4‐acryloyloxybenzylideneamino)phenyl acrylate ( 2 ), 4,4′‐diphenylylene diacrylate ( 3 ), and 4,4′‐azoxydi‐ p ‐phenylene diacrylate ( 4 ). The mesophase behaviour of the resulting polymers 6–9 was strongly influenced by the nature of both the anisotropic and spacer groups. The 4,4′‐azoxydi‐ p ‐phenylene unit appeared to be the most efficient in promoting liquid crystal properties, whereas no mesophases could be observed in polymers incorporating the 4,4′‐biphenylylene unit. Doping of poly(β‐aminoester)s, based on 4,4′‐azoxydi‐ p ‐phenylene units, with a low‐molar‐mass cholesterogen allowed to obtain cholesteric structures extending over wide ranges of temperature. The molecular weight of the polymers was found to play a role in determining thermotropic mesomorphism by affecting the melting temperature of the polymer. In this context, some non‐macromolecular model compounds were analyzed in respect of their thermal behaviour.