Group 13 metal compounds as catalyst for the homopolymerization of epoxides

The ring-opening polymerization (ROP) of epoxides, namely cyclohexene oxide (CHO), propylene oxide (PO), and tert -butyl glycidyl ether ( t BuGE) catalyzed by Group 13 (Al, Ga, In) metal initiators is reported. These polymerization reactions were performed under solvent-free conditions and in the presence of chloroform (CHCl 3 ) and toluene. InCl 3 was the most efficient catalyst for the polymerization in the presence of CHCl 3 , and monomer loading up to 10,000 equivalents. It was observed that though the polymerization rate was slow in the presence of a solvent, the polymerization was much more controlled than in solvent-free conditions, producing exceptionally high molecular weights with narrow dispersities. The highest molecular weight of the polymer attained was 136.3 kg/mol, with CHO as the monomer. The order of reactivity for the epoxides was found to be CHO > t BuGE > PO. The polymerization reaction proceeds through an activated chain-end mechanism as established from the MALDI-TOF analysis of the polymer. These polymers were found to be atactic.