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.