Amphoteric, Sulfonamide-Functionalized Polysoaps: CO2-Induced Phase Separation for Water Remediation

Amphoteric polysoaps have been prepared via statistical RAFT copolymerization using either methacryloyl sulfacetamide (mSAC) or methacryloyl sulfmethazine (mSMZ) and 4-hexylphenyl methylacrylamide (4HPhMA). These copolymers form pH- and CO2-responsive polymeric micelles capable of sequestering hydrophobic molecules in water. The composition and structure of the respective copolymers can be changed to tailor the onset and extent of CO2-dependent phase behavior. When CO2 is introduced into the system, resulting in carbonic acid formation, the pH drops below the pK(a) of the sulfonamide units along the copolymer backbone, and phase separation occurs. Purging with N-2 results in an increase in pH and redissolution of the polysoap; this process can be repeated multiple times. The mSMZ polysoaps, which show complete phase transitions using this reversible process, were especially efficient in removing the model contaminants pyrene and 9-anthracenemethanol from water. The feasibility of recovering and reusing these copolymers is demonstrated, pointing to the potential utility of such CO2-responsive systems in water treatment and related environmental remediation applications.