Synthesis in aqueous media of poly(ethylene phosphoric acids) by mild thermolysis of homopolymers and block copolymers based on tert-butyl ethylene phosphate

Abstract

Poly(ethylene phosphoric acid)s (PEPA)s of different compositions, namely homopolymers, and diblock and triblock copolymers containing poly(ethylene glycol) monomethyl ether, l-lactide, and ε-caprolactone blocks, can be quantitatively obtained by mild thermolysis of polymers based on tert-butyl ethylene phosphate in aqueous media at 80 °C. Thermolysis of poly(tert-butyl ethylene phosphate) in the presence of sodium acetate gave a PEPA with a narrow molecular weight distribution (Ð = 1.10). The salt-like reaction product can be concentrated without the formation of three-dimensional gels. All starting poly(tert-butyl ethylene phosphate) containing homopolymers and block copolymers were effectively prepared with phenolate–Mg catalysts, i.e., [(BHT)MgBu(THF)]2 and [(BHT)Mg(OBn)(THF)]2 (BHT = 2,6-di-tert-butyl-4-methylphenolate). In the synthesis of polyphosphate–polyester block copolymers, the polyphosphate macromonomer inhibits further polymerization of ε-caprolactone. We therefore failed to obtain a copolymer BnO(tBuOEP)n-b-(εCL)mH using a coordination Mg catalyst.