Tailoring Amphiphilic Copolymers for Improved Aqueous Foam Stability

Amphiphilic copolymers of various-molecular-weight (MW)poly(ethyleneglycol) (PEG) were synthesized via reversible addition-fragmentationchain transfer (RAFT) polymerization. The first PEG series, poly(ethyleneglycol)monomethacrylate (PEGMA, average Mn 200 and 400 MW), containedan -OH terminal group, and the second series, poly(ethyleneglycol) monomethyl ether monomethacrylate (PEGMMA, average Mn 200,400, and 1000 MW), possessed an -OCH3 terminal group.A total of five PEG-functionalized copolymers contained the same hydrophobicmonomer, butyl acrylate (BA), and were successfully reproduced viaa one-pot synthesis. The resulting PEG-functionalized copolymers providea systematic trend of properties including surface tension, criticalmicelle concentration (CMC), cloud point (CP), and foam lifetime basedon the average MW of the PEG monomer and final polymer properties.In general, the PEGMA series produced more stable foams with PEGMA200demonstrating the least change in foam height with time over a 10min period. The important exception is that at elevated temperatures,the PEGMMA1000 copolymer had longer foam lifetimes. The self-assemblingcopolymers were characterized by gel permeation chromatography (GPC), H-1 nuclear magnetic resonance (NMR), attenuated total reflectionFourier transform infrared (FTIR-ATR), CMC, surface tension, dynamiclight scattering (DLS), as a foam using a dynamic foam analyzer (DFA),and foam lifetime at ambient and elevated temperatures. The copolymersdescribed highlight the importance of the PEG monomer MW and terminalend group for surface interaction and final polymer properties forfoam stabilization.