SYNTHESIS AND RING-OPENING POLYMERIZATION OF OPTICALLY PURE MESOGENIC MALOLACTONATES

Optically pure malolactonate monomers containing biphenyl mesogenic groups with either an ethylene or a hexamethylene spacer were prepared from optically pure malic acid and polymerized with alkylaluminoxane catalysts to form a series of new chiral side chain liquid-crystalline polymers, which contained the chiral centres in the backbone. The mesogenic malolactonate monomers were determined to be optically pure by H-1 NMR spectroscopy of the beta-lactone complexed with a chiral europium shift reagent. Both the methylaluminoxane and isobutylaluminoxane catalysts gave polymers having bimodal molecular weight distributions, the latter catalyst yielded a larger amount of the higher molecular weight fraction than the former. The polymers showed high optical rotations, high degrees of isotactic stereoregularity, and enantiotropic liquid-crystalline properties, all of which were influenced by the molecular weight distribution. Copolymers of malolactonate monomers with different spacers were also prepared and characterized.