Self-assembled structures of amphiphiles regulated via implanting external stimuli

Abstract

This review article has summarized recent achievements of manipulating amphiphilic molecules and their self-assembled structures via different external stimuli.

pH-responsive fatty acid self-assembly transition induced by UV light

“…These modifications at the molecular scale lead to a change in packing parameter, which in turn change the morphology of the self-assembled microstructure [14][15][16]. In aqueous solution, a pH change can be obtained by either manually introducing additives or by the use of CO 2 [2,3,15,[17][18][19]. For instance, erucic acid forms worm-like micelles in aqueous solutions at high pH because all the fatty acid molecules are in a deprotonated state [19].…”

“…Light irradiation as external stimulus displays many advantages in comparison to the injection of CO 2 or the addition of chemical additives. UV light is a non-invasive trigger which avoids direct contact with the system and which can be remotely and accurately controlled with a micrometer scale resolution [3,6]. In a previous study, UV light was used to induce a pH jump in a mixture of 12-hydroxystearic acid and choline hydroxide in aqueous solution by using a photoacid generator to release protons under UV irradiation [20].…”

“…Variations in pH modify the solubility or ionization state of the surfactant, inducing a change in the morphology of the self-assembly, which in turn tunes the macroscopic properties [2][3][4]. For instance, fatty acids are a simple class of pH responsive surfactants which can be isolated from plant oils or waste-by-products such as tomato peels [8,9].…”

“…Surfactant morphology can be easily controlled by changing environmental conditions (pH, ionic strength, temperature, etc.) or by applying external stimuli (light, magnetic or electric field) to tune the strength of these non-covalent interactions and change the self-assembled microstructure [2][3][4][5][6][7].…”

“…For 1/2 < p < 1, bilayer structures like vesicles or lamellar phases are present in solution. The self-assembled structures are driven by various non-covalent interactions, including hydrogen bonding, electrostatic interactions, hydrophobic interactions and van der Waals interactions [2,3]. Surfactant morphology can be easily controlled by changing environmental conditions (pH, ionic strength, temperature, etc.)…”