Multistimuli-Responsive Foams Using an Anionic Surfactant

Abstract

In this work, we report a novel class of a commercially available surfactant which shows a multistimuli-responsive behavior toward foam stability. It comprises three components-a hydrophobe (tristyrylphenol), a temperature-sensitive block (polypropylene oxide, PO), and a pH-sensitive moiety (carboxyl group). The hydrophobicity-hydrophilicity balance of the surfactant can be tuned by changing either the pH or temperature of the system. At or below pH 4, the carboxyl functional group is dominantly protonated, resulting in zero foamability. At higher pH, the surfactant exhibits good foamability and foam stability marked with a fine bubble texture (∼200 μm). Foam destabilization could be achieved rapidly by either lowering the pH or bubbling CO gas. At a fixed pH in the presence of salt, increasing the temperature to 65 °C resulted in rapid defoaming because of the increased hydrophobicity of the PO chain. This stimuli-induced stabilization and destabilization of foam were found to be reversible. We envisage the use of such a multi-responsive foaming system in diverse applications such as foam-enhanced oil recovery and environmental remediation where spatial and temporal control over foam stability is desirable. The low-cost commercial availability of the surfactant further makes it lucrative.

Photo-Switchable Surfactants for Responsive Air–Water Interfaces: Azo versus Arylazopyrazole Amphiphiles

“…[1][2][3][4] The responsiveness can be reached by different stimuli such as light, [5][6][7][8][9][10][11][12][13][14] temperature, 15,16 pH, 17,18 magnetic or electric fields, 19 or through a combination of these factors to yield multiresponsive systems. 3,[20][21][22] In particular, light as a stimulus to trigger interfacial and material responses has the advantage that it can be controlled precisely in time and space, thus offering material control in four dimensions. In order to change the properties of a fluid interface, photoresponsive surfactants that can undergo E/Z photo-isomerization reactions have been studied in previous works but were concentrated on azobenzene surfactants for light responsive emulsions, [23][24][25] organogels, 26 vesicles, 27 microgels 28 and foams.…”

Hydroxypropyl cellulose as a green polymer for thermo-responsive aqueous foams

“…Aqueous foams responding to external stimuli such as light,5 magnetic fields9 or temperature10–13 are subject of current research. Also first multi-stimuli responsive foams are reported in previous works 14,15. A major advantage of responsive interfaces is the ability to drive materials properties such as foam stability or foamability on demand and in a non-invasive way.…”

pH-Dependent Foam Formation Using Amphoteric Colloidal Polymer Particles

“…Moreover, the fragments of dried foams showed an iridescent character under white light. The pH-dependent formation of aqueous foams/bubbles using the polymer particles studied in this study should help in understanding the stability of foams/bubbles utilized in industry including food, textile, petroleum, cosmetic, pharmaceutical and personal care product sections [2,[59][60][61][62].…”