Synthesis of emulsion-templated poly(acrylamide) using CO2-in-water emulsions and poly(vinyl acetate)-based block copolymer surfactants

We present here a simple and generic method for producing inexpensive and biodegradable polymer surfactants for use in supercritical CO2. Low molecular weight (M-w < 7000 g/mol) hydroxyl-terminated poly(vinyl acetate) (PVAc-OH) was synthesized using optimized reaction conditions and isopropyl ethanol (IPE) as the chain transfer agent. Oligomeric PVAc-OH (OVAc-OH, M-w < 3000 g/mol) was then obtained by supercritical fluid fractionation. The OVAc-OH species was converted to the imidazole ester by reaction with carbonyl diimidazole (CDI) and CO2-soluble surfactants were produced by coupling these reactive blocks with poly(ethylene glycol) methyl ethers or poly(ethylene glycol) diols. The surfactants found to be extremely effective in the production of stable CO2-in-water (C/W) emulsions, which were then used as templates to produce emulsion-templated materials with unprecedentedly high levels of porosity for materials produced by this route. It was shown that these hydrocarbon surfactants can out-perform perfluorinated species in applications of this type.