Studies on arylidene and azobenzene Based photochromic liquid Crystalline polymers

Abstract

newlineThe objective of the present investigation is to synthesize two series newlineof novel dual functional main chain liquid crystalline polymers containing newlinephotocrosslinkable chalcone and photoisomerizable azobenzene group from newlinep hydroxybenzaldehyde and vanillin respectively Series I II The newlinehighlight of this work is the synthesis of the hitherto unreported benzilidene newlinecontaining alkanone polyesters carrying the azomoiety in the main chain The newlinephotocrosslinking behaviour of these polymers is compared with that of the newlinevanillylidene containing alkanone polyesters The influence of the main chain newlineazo moiety and the effect of the methylene spacer in both these cases are also newlineassessed The chalcone moiety was prepared by the reaction of newlinecycloalkanones pentanone and hexanone with p hydroxybenzaldehyde I newlineand vanillin II separately in absolute ethanol with a Lewis acid catalyst to newlineyield four different monomers newlineThe methylene spacers were introduced into the chalcone derivative newlineby the nucleophilic displacement of bis benzylidene and bis vanillylidene newlinewith various m bromoalkanols m 6 8 10 in dry DMF 4 4 azobenzenedi newlinecarboxylic acid was prepared from 4 nitrobenzoic acid and D glucose in the newlinepresence of sodium hydroxide The acid synthesized was converted to acid newlinechloride on reacting with thionyl chloride and purified by vacuum distillation newlineThe polymers were synthesized by the solution polycondensation method by newlinereacting with the 4 4 azobenzendicarbonylchloride and the arylidene newlinemonomers at ambient temperature in chloroform in good yield newline newline