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 β-diiminate (BDI) zinc-based catalysts, BDI^CF3(1)-ZnEt and BDI^CF3(2)-ZnEt ((BDI^CF3(1))H = [CH(CCF₃NC₆H₄-2,6-C₂H₅)₂] and (BDI^CF3(2))H = [CH(CCF₃NC₆H₄-2,6-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 α,ω-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 ²⁹Si NMR spectroscopy, ¹H NMR spectroscopy, ESI-MS, GPC, and DSC.