Stabilization of CO2-in-water emulsions by nonfluorinated surfactants with enhanced CO2-philic tails

摘要

Several amphiphilic nonfluorinated polymers, poly(vinyl acetate)-block-poly(dimethylaminoethyl methacrylate) (PVAc-b-PDMAEMA) and poly(vinyl acetate-alt-diethyl maleate) (PVDBM)-b-PDMAEMA with different ratios of CO2-philic and hydrophilic groups, were synthesized using RAFT/MADIX polymerization and ATRP. Stability measurements revealed that PVDBM8-b-PDMAEMA(22) could emulsify 80% CO2 in H2O, with stable CO2-in-water (C/W) emulsions observed for more than 48 h under 20.0 MPa at 25 degrees C, which was 20 times longer than PVAc-b-PDMAEMA did. The optimal degree of polymerization (DP) for CO2-philic groups in PVDBM-b-PDMAEMA was 8, because increasing the DP of PVDBM increased the CO2-philicity, whereas increased molecular weight limited the miscibility in water. Molecular dynamics simulations were applied to determine the hydrophilic/CO2-philic balance (HCB). It was found that enhanced CO2-philic tails widened the HCB range, and the optimal range of the HCB was varied with CO2-philic tail types. Both experimental and simulation results demonstrated that enhancing the CO2-philicty of surfactant tails can improve the stability of C/W emulsions.