Lactic Acid-Derived Copolymeric Surfactants with Monomer Distribution Profile-Dependent Solution and Thermoresponsive Properties

We report the synthesis and solution properties of novel biobased thermoresponsive amphiphilic copolymers prepared using N,N-dimethyl lactamide acrylate (DMLA) and ethyl lactate acrylate (ELA) as hydrophilic and hydrophobic monomers, respectively. Copolymers with similar overall molecular weight but different monomer distribution profiles, such as random, diblock, triblock, and random-blocks, were prepared using photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization activated by a Zn-based photoredox catalyst. The synthesized polymers show interesting self-assembly and thermoresponsive behavior in water, depending on the monomers distribution along the chain. Different critical solution temperatures, in the range of 13-70 °C, were observed by tuning the monomers molar ratio and distribution. The formation of aggregates of various types was proven by transmission electron microscopy (TEM). The prepared polymers also display different surface activity with the fully random copolymer being significantly more surface active than block systems. A study of emulsion stabilization was performed with oils of various polarity, showing promising results for applications of these novel polymers as biobased surfactants and water/oil (w/o) emulsion stabilizers.