CO_2-based non-ionic surfactants: Solvent-free synthesis of poly(ethylene glycol)-block-poly(propylene carbonate) block copolymers

摘要

Copolymerization of carbon dioxide (CO_2) and propylene oxide (PO) is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic poly(ethylene glycol) (PEG) block and a nonpolar poly(propylene carbonate) (PPC) block. A series of poly(propylene carbonate) (PPC) di- and triblock copolymers, PPC-b-PEG and PPC-b-PEG-b-PPC, respectively, with narrow molecular weight distributions (PDIs in the range of 1.05-1.12) and tailored molecular weights (1500-4500 g mol~(-1)) is synthesized via an alternating CO_2/propylene oxide copolymerization, using PEG or mPEG as an initiator. Critical micelle concentrations (CMCs) are determined, ranging from 3 to 30 mg L~(-1). Non-ionic poly(propylene carbonate)-based surfactants represent an alternative to established surfactants based on polyether structures. Copolymerization of CO_2 and propylene oxide is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic PEG block and a nonpolar poly(propylene carbonate) block. The established (R,R)-(salcy)-CoOBzF_5 complex is used as a catalyst and bis(triphenylphosphine)iminium chloride as an ionic cocatalyst in the solvent-free synthesis. Non-ionic poly(propylene carbonate)-based surfactants represent an alternative to established polyether structures.