The polymerisation of methacryloyl surfactant vesicles by Fenton's reagent and their characterisation and stability to alcohol and detergents

Abstract

The cationic double chain surfactant hexadecyl [11-(methacryloyloxy) undecyl] ammonium bromide (methacryloyl surfactant) has been used to make polymerisable vesicles in aqueous solution. Polymerisation was initiated using Fenton's reagent (hydrogen peroxide and ferrous ions) at room temperature. Fenton's reagent is shown to give vesicles with a very high degree of polymerisation, as by the loss of olefinic hydrogen atoms by proton NMR spectroscopy, over a wide range of experimental conditions (hydrogen peroxide to ferrous ion and surfactant to hydrogen peroxide molar ratios). The polymerised vesicles ranged in size (peak diameter of the equivalent normal weight distribution) from 120 to 260 nm as measured by photon correlation spectroscopy. The stability of the vesicles to disruption by ethanol and the non-ionic detergents Triton X-100 and octyl glucoside was investigated from absorbance and size measurements. It has been found that for both unpolymerised and polymerised surfactant vesicles the optical absorbance curves at 400 nm pass through maxima as a function of the concentration of additive. For polymerised vesicles the absorbance maxima are broader and sufficiently different from those of unpolymerised vesicles to be used as a diagnostic test for polymerisation. The origin of the absorbance behaviour is discussed in terms of vesicle fusion/aggregation and disruption.