The pH and temperature dual-responsive micelle transition in the mixture of hydrotrope potassium phthalic acid and quaternary ammonium surfactants cetyltrimethylammonium bromide

摘要

A facile and effective route to prepare a pH and temperature dual-responsive surfactant micelle has been introduced based on hydrotrope potassium phthalic acid (PPA) and quaternary ammonium surfactants cetyltrimethylammonium bromide (CTAB). The system can be switched between viscoelastic solution and water-like fluid by adjusting pH values. In this paper, different binding abilities between the hydrotrope and surfactants have been demonstrated during the process of adjusting pH because the hydrotrope has different ionization degrees with the pH variation. And with the aid of rheological measurements and cryo-TEM observation, we discussed the different effects of the hydrotrope on surfactants at various pH values in detail and analyzed the possible aggregate transition mechanism of CTAB-PPA system induced by pH. Besides, this CTAB-PPA system has temperature-responsive property when pH < 2.50. The temperature sensitivity and reversible control of rheological properties may greatly facilitate practical applications of such responsive viscoelastic solution.