SYNTHESIS AND CHARACTERIZATION OF NEW METHYL-SUBSTITUTED AZOMETHINE-SILOXANE LIQUID-CRYSTAL MACROCYCLES - INFLUENCE OF THE METHYL-SUBSTITUTION ON THE CYCLE FORMATION

This article is devoted to the synthesis of new methyl-substituted azo methine-siloxane macrocyclic dimers. They have been obtained by an int ramolecular interiminination reaction of linear polydimethylsiloxane-b lock-polyazomethine main-chain liquid crystal polymers. The reaction h as been studied on mono-, di- and tetramethyl-substituted azomethine m oities to estimate the influence of methyl-substitution on the feasibi lity of the reaction. Specific conditions (diluted solution, strong ac id catalysis, recrystallization) led to pure macrocyclic dimers, which have been characterized by SEC, C-13 NMR and X-ray crystallography. T his reactional process is the first step for synthesis of substituted liquid crystal macrocyclic structures, which constitute a new family i n the liquid crystal polymer field.