Micellization Behavior of an Amphiphilic Statistical Copolymer in Water-Methanol Mixtures

Sedimentation equilibrium measurements were made on an amphiphilic statistical copolymer p(AMPS/C6) made of sodium 2-(acrylamido)-2-methylpropane-sulfonate (AMPS) and n-hexyl methacrylate (C6), dissolved in water-methanol mixtures with 0.2 M LiClO4 and different methanol contents over a wide polymer concentration range. The experimental results were analyzed in terms of a micellar Solution theory for amphiphilic polyelectrolytes to estimate the aggregation number m of the micelle and the internal free energy change Delta(m)/m (per polymer chain) due to micellization. Both m and Delta(m)/m decreased with increasing the methanol content in the solvent. In addition, dynamic light scattering for the same copolymer system indicated that p(AMPS/C6) formed a uni-core star-like micelle in water-methanol mixture with the methanol mole fractions of 0 and 0.06.