Enantiopure Isotactic PCHC Synthesized by Ring-Opening Polymerization of Cyclohexene Carbonate

The ring-opening polymerization (ROP) of racemic trans -cyclohexene carbonate ( rac -CHC) and enantiopure trans -( R, R )-CHC is successfully carried out with various catalyst systems. Poly(cyclohexene carbonate) (PCHC) with a slight isotactic bias ( P m = ca. 60–76%) is obtained by ROP of rac -CHC catalyzed by zinc diaminophenolate, zinc β-diketiminate, yttrium bis(phenolate), or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with an alcohol as a co-initiator. Purely isotactic PCHC is synthesized for the first time via ROP of enantiopure ( R, R )-CHC with a zinc/benzyl alcohol catalyst system. All reactions proceed without decarboxylation, affording well-defined PCHCs with M n,NMR up to 17 000 g mol –1 and Đ M = ca. 1.2. Purely isotactic PCHC is semicrystalline, with T g = 130 °C, T c = 162 °C, and T m = 248 °C. DFT computations further highlight the significant favorable impact of the trans -cyclohexane ring-strain to enable the ROP of CHC, as opposed to meso -CHC which is unreactive.