SYNTHESIS AND THERMOTROPIC PROPERTIES OF NEW POLYACRYLATES CONTAININGALKANOYL-SUBSTITUTED AZOBENZENE MESOGENS

The synthesis and characterization of a series of new polyacrylates 1, containing the azobenzene mesogen spaced from the backbone by a hexam ethylene segment and substituted in the 4-position by an alkanoyl chai n of variable length, together with those of the relevant precursors a re reported. Optical and X-ray analyses provided evidence for the pres ence of a smectic A mesophase in a fairly broad range of temperature i n both polymers and low molar mass compounds. In polyacrylates 1, the side-chain substituents were fully interdigitated in a smectic A, stru cture. The comparison of the transition parameters of polymers 1 with those of another series of polyacrylates 7 containing the azobenzene u nit substituted in the 4-position by an alkyloxy chain of variable len gth revealed that the replacement of an oxygen atom by a carbonyl grou p strongly enhanced the smectogenic character of the azobenzene group.