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2014669 
Journal Article 
A Conventional Surfactant Becomes CO2-Responsive in the Presence of Switchable Water Additives 
Su, Xin; Robert, T; Mercer, SM; Humphries, C; Cunningham, MF; Jessop, PG 
2013 
Yes 
Chemistry: A European Journal
ISSN: 0947-6539
EISSN: 1521-3765 
19 
18 
5595-5601 
English 
23463681 
WOS:000318282200014 
We have developed a new benign means of reversibly breaking emulsions and latexes by using "switchable water", an aqueous solution of switchable ionic strength. The conventional surfactant sodium dodecyl sulfate (SDS) is not normally stimuli-responsive when CO2 is used as the stimulus but becomes CO2 -responsive or "switchable" in the presence of a switchable water additive. In particular, changes in the air/water surface tension and oil/water interfacial tension can be triggered by addition and removal of CO2 . A switchable water additive, N,N-dimethylethanolamine (DMEA), was found to be an effective and efficient additive for the reversible reduction of interfacial tension and can lower the tension of the dodecane/water interface in the presence of SDS surfactant to ultra-low values at very low additive concentrations. Switchable water was successfully used to reversibly break an emulsion containing SDS as surfactant, and dodecane as organic liquid. Also, the addition of CO2 and switchable water can result in aggregation of polystyrene (PS) latexes; the later removal of CO2 neutralizes the DMEA and decreases the ionic strength allowing for the aggregated PS latex to be redispersed and recovered in its original state. 
colloids; emulsion; stimuli-responsive; surface analysis; surfactants