A NOVEL OBSERVATION IN ANIONIC RING-OPENING POLYMERIZATION BEHAVIOR OF CYCLIC CARBONATES HAVING AROMATIC SUBSTITUENTS

The anionic ring-opening polymerization of six-membered cyclic carbona tes having aromatic substituents, 5-methyl-5-phenyl-1,3-dioxan-2-one ( 1) and 5,5-diphenyl-1,3-dioxan-2-one (2), was carried out. The anionic homopolymerization of 1 readily proceeds to afford the corresponding polycarbonate, while 2 showed only a slight homopolymerizability. This is due to a rapid back biting reaction of the propagating polymer end to form 2. The conformational restriction of the adduct of 2 with an alkoxide, originating from the electrostatic repulsion between the alk oxide anion and the pi electrons of the aromatic rings, might cause th e rapid back biting reaction. The anionic copolymerization of 2 with 5 ,5-dimethyl-1,3-dioxan-2-one (3) proceeds to afford the copolymer. The anionic ring-opening polymerization of 1 was confirmed to be an equil ibrium polymerization. Monomer 1 was regenerated up to the equilibrium monomer concentration by depolymerization of poly(1). A volume expans ion (10.8%) was observed during the polymerization of 1.