Acid-Labile Surfactants Based on Poly(ethylene glycol), 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)-CoOBzF(5) 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 H-1-, C-13- 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 H-1-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.