SELECTIVE SYNTHESIS OF STRUCTURALLY ISOMERIC POLY-BETA-ESTER AND POLY-DELTA-ESTER FROM BETA-(2-ACETOXY-ETHYL)-BETA-PROPIOLACTONE WITH AL AND ZN CATALYSTS

Results of an experimental study are presented which demonstrate that structurally isomeric polymers were formed by the ring-opening polymerization of beta -(2-acetoxy ethyl)- beta -propiolactone with (EtAlO)//n and Et(ZnO)//2ZnEt catalysts; specifically, the Al catalyst catalyzed normal polymerization which led to poly- beta -ester and the Zn catalyst formed isomerized poly- beta -ester as the main product. The polymer structure was determined by nuclear magnetic resonance (NMR), T//1-value, thermal decomposition product, and (T//g). The NMR studies for the monomer-catalyst systems indicated that the Al catalyst interacted predominately with the lactone group, whereas the Zn catalyst interacted with the side-chain ester group. These site-selective interactions could be related to the difference in the stereoregulation by the two catalysts during the poly( beta -ester)-forming polymerization process.