In Situ Generated ABA Block Copolymers from CO2, Cyclohexene Oxide, and Poly(dimethylsiloxane)s

Chain-transfer polymerization reactions with siloxanes, CO2, and cyclohexene oxide have been conducted, utilizing two beta-diiminate (BDI) zinc-based catalysts, BDICF3(1)-ZnEt and BDICF3(2)-ZnEt ((BDICF3(1))H = [CH(CCF3NC6H4-2,6-C2H5)(2)] and (BDICF3(2))H = [CH(CCF(3)NC(6)H4-2,6-CH-(CH3)(2))(2)]). The correlation between equivalents of siloxane and the corresponding molecular masses and glass transition temperatures is exhibited. Furthermore, the in situ preparation of ABA block copolymers from carbon dioxide, cyclohexene oxide, and alpha,omega-bis(hydroxymethyl)poly(dimethylsiloxane)s is presented. This reaction was found to strongly relate to a robust Lewis acid catalyst like the outlined complexes. The polymer properties can be tuned by varying the amount of chain-transfer agent or changing the catalyst. The resulting polymer structures and incorporation of siloxanes were revealed by Si-29 NMR spectroscopy, H-1, NMR spectroscopy, ESI-MS, GPC, and DSC.