Chapter 7: CO₂-switchable Surfactants

Conventional surfactants stabilize dispersions (emulsions, foams, and suspensions) even when those dispersions are no longer wanted. That problem is typically solved in industry by the addition of extra chemicals such as demulsifiers, strong acids, or high loadings of salts, all of which increase environmental impact and work to counteract the surfactants added earlier. Alternatively, a surfactant that can be “switched off” when the dispersion is no longer needed can avoid the environmental impacts of those additional chemicals. This chapter reviews CO₂-switchable surfactants, including cationic, anionic, nonionic, gemini, and other examples, and describes their applications. Methods for designing these species to avoid ecotoxicity are included.