Photoresponsive Foams Generated by a Rigid Surfactant Derived from Dehydroabietic Acid

Abstract

Innovation in the structure of surfactants is crucial to the construction of a surfactant-based system with intriguing properties. With dehydroabietic acid as a starting material, a nearly totally rigid azobenzene surfactant (R-azo-Na) was synthesized. The trans-R-azo-Na formed stable foams with half-lives of 636, 656, 976, and 872 min for 0.3, 1, 2, and 4 mmol·L aqueous solutions, respectively. Under UV light irradiation, a fast collapse of the foams was observed, showing an in situ response. The excellent foam stability of trans-R-azo-Na leads to the extremely high photoresponsive efficiency. As revealed by dynamic surface tension and pulsed-field gradient NMR methods, an obvious energy barrier existed in the adsorption/desorption process of trans-R-azo-Na on the air/water interface. The foams formed by trans-R-azo-Na are thus stable against coarsening processes. The results reveal the unique photoresponsive behavior of a surfactant with a rigid hydrophobic skeleton and provide new insights into the structure causing aggregation of surfactants.

Phase Behavior and Aggregation in a Catanionic System Dominated by an Anionic Surfactant Containing a Large Rigid Group

“…[27] Song and co-workersr eported an absolutelyr igid surfactant (R-azo-Na) that has high foaming ability and efficient light responsiveness. [28] They also found that an anionic surfactant (C 12 biphNa) containing ab iphenyl group can form rigid nanowire-like aggregatesw ith b-CD, and hydrogels were thus obtained. [29] In our previousw ork, an ovel anionic surfactant, N-dodecylmaleimidepimaricc arboxylate (C 12 -MPA-Na, Scheme 1), synthesized from rosin, spontaneously self-assembled sequentially into large spherical micelles, annular micelles, andt hreadlike micelles with increasing concentration.…”

“…However, rigid surfactants in mixtures of catanionic surfactants have rarely been reported despite the fact that rigid surfactants have intriguing properties. It has recently been reported that surfactants with a nonplanar rigid hydrophobic group show interesting interfacial properties and unique aggregation behavior due to a strong hydrophobic effect and large molecular volume . The aromatic groups in the surfactants N10TAB and N10‐6‐10N partially overlap with the flexible alkyl chain, which prompts the formation of vesicles at quite low concentration .…”

“…The aromatic groups in the surfactants N10TAB and N10‐6‐10N partially overlap with the flexible alkyl chain, which prompts the formation of vesicles at quite low concentration . Song and co‐workers reported an absolutely rigid surfactant (R‐azo‐Na) that has high foaming ability and efficient light responsiveness . They also found that an anionic surfactant (C 12 biphNa) containing a biphenyl group can form rigid nanowire‐like aggregates with β‐CD, and hydrogels were thus obtained .…”

“…It has recently been reportedt hat surfactants with an onplanar rigid hydrophobic group show interesting interfacialp roperties and unique aggregation behavior due to a strong hydrophobic effect and large molecular volume. [27][28][29][30] The aromatic groups in the surfactants N10TAB andN 10-6-10N partially overlap with the flexible alkyl chain, which prompts the formation of vesicles at quite low concentration. [27] Song and co-workersr eported an absolutelyr igid surfactant (R-azo-Na) that has high foaming ability and efficient light responsiveness.…”

CO2‐responsive polymer surfactant formed by noncovalent binding between dimethyl‐dodecylamine and alginate

“…In recent years, switchable surfactants have been studied extensively. Common stimuli are pH, temperature, light, magnetic field, oxidants/reductants and CO 2 . These switchable surfactants can be used to stabilize emulsion or foam which has to be demulsified or defoamed at a specific desired stage.…”