Rod-like micelles of octadecyltrimethylammonium bromide and their freezing upon solubilised styrene polymerisation

Abstract

The association of octadecyltrimethylammonium bromide (C₁₈TABr) in ethanol/water (10/90 wt%) solvent has been studied using light-scattering measurements. With the help of sodium 2-naphthalenesulfonate (SNphs), C₁₈TABr formed rod-like micelles. Styrene was solubilised into the templating C₁₈TABr micelles with a mole ratio of SNphs to surfactant (n_SNphs/n_C18TABr) of 0.5, which was examined by dynamic light-scattering (DLS) and UV-spectral measurements. Then the solubilised styrene was polymerised in situ. Dilution experiments were performed to test the freezing effect. It was found that the amount of solubilising styrene, represented as the mole ratio of styrene to surfactant (n_st/n_surf), should be greater than 2.7 so as to achieve a good freezing effect. In the case of n_st/n_surf = 4.4, well-frozen rod-like micelles were obtained and their morphologies were evinced by TEM images. These frozen micelles were stable even in the 400% dilution test.