Dual-responsive polymers synthesized via RAFT polymerization for controlled demulsification and desorption

Intelligent polymers responsive to the environment have aroused widespread interest in many applications of materials and interfaces. However, sensitive control of the oil-water interface remains a major challenge, using reversible self-assembly of macromolecules induced by external stimuli. Here, we synthesized a new amphiphilic triblock copolymer responsive to pH and UV light via reversible addition–fragmentation chain transfer (RAFT) aqueous polymerization. Poly(methacrylic acid) (PMAA) acts as the hydrophilic block; poly(N, N-dimethyl aminoethyl methacrylate) (PDMAEMA) and poly(methacrylamide azobenzene) (PMAAAB) are the hydrophobic blocks with responsiveness. The as-synthesized polymer was measured regarding UV–vis transmittance and contact angle to verify the tunable amphiphilicity and wettability by the double stimulation. The newly developed dual-responsive polymer was applied for oil/water separation and controlled dye release, where methylene red (MR) was chosen as the representative adsorbate. With the synergic stimulation of pH and UV light, efficient separation for oil-in-water emulsions (separation efficiency: 66.8% in 15 min) and excellent desorption for adsorbed dyes (desorption efficiency: 93.8% in 15 min) are achieved.