Copolymerization of epoxides and five-membered cyclic carbonates in the presence of zinc coordination catalysts

Alkylene oxides like ethylene oxide (1a) and propylene oxide (1b) were reacted with alkylene carbonates like ethylene carbonate (2a) and propylene carbonate (2b) in the presence of catalysts based on diethylzine and polyphenols (pyrogallol, 4-tert-butylcatechin) and catalysts based on diethylzinc-phenol at temperatures in the range of 35–100°C. Reaction products were characterized by means of elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy and molecular weight determinations. The products appeared to be the respective low-molecular-weight copolymers – polyoxyalkylene-co-(alkylene carbonate)]s: polyoxyethylene-co-(ethylene carbonate)] (3 aa) , polyoxyethylene-co-(propylene carbonate)] (3 ab) , polyoxypropylene-co-(ethylene carbonate)] (3 ba) and polyoxypropylene-co-(propylene carbonate)] (3 bb). Copolymers obtained with diethylzinc-polyphenol catalysts were of higher molecular weight than those obtained with diethylzinc-phenol catalysts. They contained more than 50 mol-% of alkylene oxide units. Predominant head-to-tail arrangement of these units including those connected via carbonate linkages was observed by means of NMR spectroscopy in the case of 3 bb.