Block copolymerization of 3,3‐dimethyl‐2‐oxetanone. II. Synthesis of polydimethylsiloxane‐containing copolymers

Carboxy‐terminated polydimethylsiloxanes (PDMSs) have been prepared by anchoring the functional end group on the main chain via a hydrolytically stable SiC bond. The neutralized carboxy‐terminated PDMSs are effective initiators of the 3,3‐dimethyl‐2‐oxetanone (or pivalolactone) block copolymerization. The yield of block copolymers depends on the initiation efficiency of the carboxylate end groups, but this limit can be overcome by the use of more than one carboxylate group per end chain, and “palm‐tree” structures are obtained. The ability to crystallize of poly(3,3‐dimethyl‐2‐oxetanone) is significantly depressed when this polyester is engaged in PDMS‐rich block copolymers, but the observed heterophase morphologies (350 Å) are uniformly fine.