General Strategy for Making CO₂-Switchable Polymers

By discovering that poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) in water can react with carbon dioxide (CO₂) and have its lower critical solution temperature (LCST) reversibly tuned by passing CO₂ and argon (Ar) through the solution, we describe a general strategy for imparting a CO₂-switchable LCST or water solubility to polymers of broad interest like poly(N-isopropylacrylamide) (PNIPAM) and poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMEO₂MA). We show that by easy copolymerization incorporating DMAEMA as a CO₂-responsive trigger into PNIPAM or PMEO₂MA, their LCST can effectively be switched by the gases. Two examples of applications were further demonstrated: upon CO₂ or Ar bubbling at a constant solution temperature, hydrogels could undergo a reversible volume transition and block copolymer micelles could be dissociated and reassembled. This study opens the door to a wide range of easily accessible CO₂-switchable polymers, enabling the use of CO₂ as an effective trigger for smart materials and devices.