Active Demulsification of Photoresponsive Emulsions Using Cationic–Anionic Surfactant Mixtures

• DOI: 10.1021/acs.langmuir.5b03912
• Publication Date: 2016-01-05T16:12:12Z
• Authors: Yutaka Takahashi; Nanami Koizumi; Yukishige Kondo
• Keywords: Sodium dodecyl sulfate; Cationic polymerization; Azobenzene

The influence of ultraviolet (UV) light irradiation on the emulsification properties mixtures an anionic surfactant, sodium dodecyl sulfate (SDS), and a photoresponsive cationic 2-(4-(4-butylphenyl)diazenylphenoxy)ethyltrimethylammonium bromide (C4AzoTAB), containing azobenzene group has been investigated. When n-octane aqueous SDS/trans-C4AzoTAB solution are homogenized, stable emulsions obtained in regions specific surfactant concentrations molar ratios mixed surfactants. for over week found to be oil-in-water (O/W) type. UV O/W leads coalescence smaller oil droplets into larger ones emulsions, i.e., demulsification. As result, phases fully separated by 90 min, even shorter than our previous result (6 h; Langmuir 2014 , 30 41 - 47 ). use microreactor shortens time required photoinduced demulsification 3.5 min. octane SDS/cis-C4AzoTAB no obtained. interfacial tension (IFT) between is higher that solution, indicating IFT increases with cis photoisomerization trans isomer. These results suggest isomerization due causes Ostwald ripening thereby reducing area water as increases. Subsequently, separate.