Cobalt(III)-Complex-Mediated Terpolymerization of CO2, Styrene Oxide, and Epoxides with an Electron-Donating Group

Terpolymerizations of CO2, styrene oxide (SO), and epoxides with an electron-donating group such as propylene oxide (PO) or cyclohexene oxide (CHO) were carried out by using Co(III)-salen complexes in the presence of an intra-or intermolecular nucleophilic cocatalyst. The resultant terpolymers have only one thermolysis peak and one glass transition temperature (T-g), which can be easily adjusted by controlling the proportion of styrene carbonate linkages. During the CO2/SO/PO terpolymerization, the monomer reactivity ratios (r(SO) = 0.18 and r(PO) = 2.25) evaluated by Fineman-Ross plot indicates a random distribution of the two kinds of carbonate units in the resultant polymer. Contrarily, the monomer reactivity ratios were found to be rSO 0.48 and r(CHO) = 0.79 in the CO2/SO/CHO terpolymerization, indicating that an alternating nature of the two different carbonate units predominantly exists in the resultant polycarbonate. The regioselective ring opening of SO has a significant effect on the reactivities of both SO and CHO during the terpolymerization with CO2. The matched reactivity is contributed to the enhanced regioselective ring opening of SO, caused by the attack of the dissociating polymer carboxylate anion, bearing a cyclohexene carbonate end unit. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 874-879