CHIRALITY OF POLYVINYL COMPOUNDS .18. PREPARATION AND CHARACTERIZATION OF NEW OPTICALLY-ACTIVE COPOLYMERS WITH MAIN-CHAIN CHIRALITY CARRYING NAPHTHYL CHROMOPHORES

Optically active copolymers were obtained by radically initiated asymmetric cyclocopolymerization of two new monomers, 3,4-O-cyclohexylidene-D-mannitol 1,2;5,6-bis-O-[(4-vinylnaphthyl-1)]boronate] (2) and 3 4-O-cyclohexylidene-D-mannitol 1,2;5,6-bis-O-[(2-vinylnaphthyl-1)boronate] (3), with comonomers (e.g. methyl methacrylate) and subsequent splitting off the chiral D-mannitol template. The copolymers are optically active due to the chirality of the configuration of the main chain. Because of the spatial proximity of the two naphthalene units in the side chain of the copolymers circular dichroism (CD) spectra show strong CD with exciton couplets. The configurations of the (4-vinylnaphthyl-1)boronic acid and (2-vinylnaphthyl-1)boronic acid diad, respectively, in the copolymer chains could be determined with the aid of the ''exciton chirality method''. In both cases the diads possess (S,S) configuration. The mechanisms of cyclopolymerization of the two monomers are discussed on the basis of their conformations of lowest energy obtained by calculations with semiempirical methods (AM1).