The Cationic Ring Opening Polymerization of Oxetane and Other Cyclic Ethers

The homopolymerization of oxetane in the presence of boron trifluoride etherate (BF 3 OEt 2 ) and ethanediol (HOCH 2 CH 2 OH) as an initiator system gave polymer with a molecular weight in the range of 4000-7000. Previous work has shown that a side reaction such as the formation of cyclic oligomers, particularly tetramer often occurs in large quantities. In contrast during copolymerizations between specific combination of cyclic ethers, cyclic oligomers were found in smaller amounts and in some instances almost eliminated. The difference in behaviour between homo and copolymerization was ascribed to a change in the structure of the propagating end