Stereospecific polymerization of alpha-(menthoxymethyl)acrylate

Abstract

Novel alpha-(alkoxymethyl)acrylates bearing a chiral substituent, racemic and optically active benzyl alpha-(menthoxymethyl)acrylates ((+)- and (-)-BMnMA), were synthesized and polymerized by radical and anionic methods. The effects of the chiral substituent on the stereoregularity and chiroptical property of the obtained polymers were investigated. 13CNMR spectra of the polymers obtained by anionic polymerization of the racemic monomer showed sharper peaks than that of the radically obtained polymers, indicating that the former polymers possessed higher stereoregularity than the radically obtained polymers. The polymers prepared from optically pure (-)-monomer with anionic initiators had low solubility in common organic solvents. However, the THF-soluble parts were highly isotactic, and exhibited lower specific rotation ([alpha]25(365) = -92 degrees) than those of the monomer ([alpha]25(365) = -226 degrees) and the radically obtained polymer ([alpha]25(365) = -201 degrees). The circular dichroism (CD) spectra of the copolymers prepared from a (+)- and (-)-monomer mixture with various optical purity suggested that the highly isotactic (-)-polymer may possess a chiral helical conformation.