Acid-labile surfactants based on poly(ethyleneglycol), carbon dioxide and propylene oxide: Miniemulsion polymerization and degradation studies

Partially degradable, nonionic AB and ABA type di- and triblock copolymers based on poly(propylene carbonate) and poly(ethylene glycol) blocks were synthesized via immortal copolymerization of carbon dioxide and propylene oxide, using mPEG or PEG as a macroinitiator, and (R,R)-(salcy)-CoOBzF₅ as a catalyst in a solvent-free one-pot procedure. The amphiphilic surfactants were prepared with molecular weights (M_n) between 2800 and 10,000 g mol^-1 with narrow molecular weight distributions (1.03-1.09). The copolymers were characterized using ¹H-, ¹³C- and DOSY-NMR spectroscopy and size exclusion chromatography (SEC). Surface-active properties were determined by surface tension measurements (critical micelle concentration, CMC; CMC range: 1-14 mg mL^-1). Degradation of the acid-labile polycarbonate blocks was investigated in aqueous solution using online ¹H-NMR spectroscopy and SEC. The amphiphilic polymers were used as surfactants in a direct miniemulsion polymerization for poly(styrene) (PS) nanoparticles with mean diameter of 270 to 940 nm. The usage of an acid-triggered precipitation of the emulsion simplified the separation of the particles from the surfactant and purification of the nanoparticles.