Photoresponsive Microemulsions

Abstract

Photoresponsive microemulsions have been made by addition of a photodestructible surfactant, sodium 4-hexylphenylazosulfonate (1), to AOT-stabilized water-in-heptane phases. Exposure of these samples to UV light led to changes in phase stability and droplet size, owing to breakdown of 1. Small-angle neutron scattering was used to follow this UV-induced shrinkage of the water nanodroplets: a maximum volume decrease was found to be in the order of 60%. Proton NMR of an UV-irradiated microemulsion shows that around 90% of the added 1 decomposes, to yield a mixture of 4-hexylphenol (∼37%) and hexylbenzene (52%).

Characterization of Microemulsion Systems Formed by a Mixed 1,3‐Dioxolane Ethoxylate/Octyl Glucoside Surfactant System

“…Use of triggerable surfactant in microemulsion systems has been of interest to our group for the release of nanoencapsulated materials. There have only been a few reports of use of triggerable surfactants for microemulsion formation to date [3,4]. An acid-cleavable alkyl ethoxylate referred to as ''CK-2,13'', 4-CH 3 O(CH 2 CH 2 O) 7.2 -CH 2 , 2-(CH 2 ) 12 CH 3 , 2-(CH 2 )CH 3 , 1,3-dioxolane forms microemulsion systems with behavior similar to those formed by linear alkyl ethoxylates (C i E j s), except that CK-2,13 undergoes apparent zeroth-order hydrolysis when in contact with buffer solution of pH \ 7, and is a less efficient amphiphile than C i E j s, i.e., has a high critical microemulsion concentration, presumably because of the stiffness in the molecule imparted by the 1,3-dioxolane ring and the broad molecular weight distribution of its ethoxylate groups [5][6][7].…”

Reversible Light‐Triggered Control of Emulsion Type and Stability

“…[3,20] In microemulsions, photodestructible surfactants were successfully used to change the phase stability and the droplet size. [21] However, surfactant destruction is not compatible with the concept of reversibility. The mixed surfactant/polymeric surfactant emulsifier system described herein appears unique, in the sense that it exhibits reversibility and high sensitivity.…”

Photorheology and rheokinetics of CTAB/chlorocinnamic acid micelles

“…Because light is easy to control and can be directed at a precise spot with resolution of a few micrometers, PR fluids have potential values in microscale applications, such as microfluidic devises, microvalves or flow sensors [8] . Recently PR fluids have been used in drag reduction and heat transfer enhancement [9] , control of surface tension [10~11] , microemulsion phase separation [12] and biological systems [13] .…”