Characterization of Triton X-100 and its oligomer (Tyloxapol) micelles vis-à-vis solubilization of bisphenol A by spectral and scattering techniques

Abstract

Abstract The purpose of this study was to investigate the micellar characteristics and solubilization efficiency of the oligomeric surfactant Tyloxapol and compare these with the corresponding standard monomeric surfactant Triton X-100 using spectral and scattering techniques. The focus has been to determine the solubilization of the commercially important compound bisphenol A (BPA, also an endocrine disruptor) in these two nonionic surfactants and its effect on the micellar structures in solution. 5% Triton X-100 in water at 30 °C forms ellipsoidal micelles ( R h (DLS) ≈ 5.5 nm, R a (SANS) ≈ 6.3 nm, R b (SANS) ≈ 2.0 nm, N agg ∼ 287), whereas small spherical micelles ( R h (DLS) ≈ 3.4 nm, R c (SANS) ≈ 2.1 nm, N agg ∼ 16) are formed by Tyloxapol. BPA solubilized to a greater extent in Tyloxapol micelles than Triton X-100 micelles; the molar solubilization ratio and micelle–water partition coefficient were higher than for Triton X-100 micelles. BPA induced micelle growth was seen for both the surfactants which resulted in a noticeable change in phase behaviour, viscosity and shape/size of the micelles. Small spherical Tyloxapol micelles transform into ellipsoidal ones while the ellipsoidal Triton X-100 micelles transform to short rods/stretched ellipsoidal structures. Micellar/phase behaviour for BPA solubilized micelles was markedly dependent on the pH of the solution.