A “catalyst switch” strategy for the sequential metal-free polymerization of epoxides and cyclic esters/carbonate
J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis
47(12), 3814-3822, (2014)
Block polymers, Catalysts, Esters, Ethers, Cyclic carbonates, Ethylene oxides, Metal-free synthesis, Organic catalysts, Phosphazene base, Polyether chains, Sequential polymerization, Trimethylene carbonate
A “catalyst switch” strategy was used to synthesize well-defined polyether–polyester/polycarbonate block copolymers. Epoxides (ethylene oxide and/or 1,2-butylene oxide) were first polymerized from a monoalcohol in the presence of a strong phosphazene base promoter (t-BuP4). Then an excess of diphenyl phosphate (DPP) was introduced, followed by the addition and polymerization of a cyclic ester (ε-caprolactone or δ-valerolactone) or a cyclic carbonate (trimethylene carbonate), where DPP acted as both the neutralizer of phosphazenium alkoxide (polyether chain end) and the activator of cyclic ester/carbonate. This work has provided a one-pot sequential polymerization method for the metal-free synthesis of block copolymers from monomers which are suited for different types of organic catalysts.
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