A guide to the selection of switchable functional groups for CO 2 -switchable compounds

• Published in: Physical chemistry chemical physics : PCCP Vol. 18; no. 28; pp. 19276 - 19288
• Main Authors: Alshamrani, A. K., Vanderveen, J. R., Jessop, P. G.
• Format: Journal Article
• Language: English
• Published: 2016
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/C6CP03302D

Many CO 2 -responsive species, including many of the CO 2 -switchable surfactants, solvents, solutes, gels, colloids, and surfaces, rely on the ability of CO 2 to lower the pH of water. Uncharged basic groups on the CO 2 -responsive species are therefore converted from a neutral state to a protonated cationic state (a bicarbonate salt), which causes dramatic and useful changes to the properties of the species. However, this switching process only works correctly if a basic group of appropriate basicity has been selected. This article presents a comprehensive guide to the selection of basic groups for CO 2 -switchable species for use in water. The appropriate basicity, as measured by the p K aH (the p K a of the protonated compound), is a function of the concentration of the switchable species, the temperature, the pressure of CO 2 , the presence or absence of an organic liquid phase, and the solubility of the neutral form of the compound.