Chapter 2: The Chemistry of CO₂-triggered Switchable Materials

CO₂-switchable materials, regardless of whether they are solvents, solutes, surfactants, or surfaces, switch between one state and another due to a reversible chemical reaction between the material and the CO₂. However, not all such materials use the same chemical reaction for the switching process. If we classify the reactions based upon the product formed, the reactions include those that form bicarbonates, alkylcarbonates, carbamates, ureas, CO₂-Lewis base adducts, and iminoboronate cleavage products. The material in its CO₂-absent state may, depending on the reaction, be a neutral or anionic species and in its CO₂-present state may be neutral, cationic, or anionic. Which of the reactions is most appropriate for a given application depends greatly on the temperature and whether or not water is present in the system, but should also take into consideration the potential effects of the materials on health, safety, and the environment.