Regioselective and Alternating Copolymerization of Carbonyl Sulfide with Racemic Propylene Oxide

We report the first example of a regioregular and fully alternating poly (propylene monothiocarbonate) (PPMTC) from the well-controlled copolymerization of two asymmetric monomers, carbonyl sulfide and racemic propylene oxide, using (Salen)CrCl in conjunction with bis(triphenylphosphoranylidene)ammonium chloride. The maximum turnover of frequency of this catalyst system was 332 h –1 at 25 °C. The contents of monothiocarbonate and tail-to-head linkages of PPMTC were up to 100% (based on 1 H NMR spectra) and 99.0% (based on 13 C NMR spectra), respectively. PPMTC samples have number-average molecular weight ( M n ) up to 25.3 kg/mol with polydispersity index of 1.41. The very low decomposition temperature of 137 °C and high refractive index of 1.63 of PPMTC make it a potential scarifying optical adhesive.