Small-angle neutron scattering study of poly(methyl methacrylate-block-sodium acrylate-block-methyl methacrylate) and poly(sodium acrylate-block methyl methacrylate-block-sodium acrylate) triblock copolymers in aqueous solutions

Small-angle neutron scattering experiments were made on poly(methyl methacrylate-block-sodium acrylate-block-methyl methacrylate) [p(MMA-b-NaA-b-MMA)] and p(NaA-b-MMA-b-NaA) solutions by varying the composition and the concentration of the polymer with and without 1 M NaCl added. Scattering curves could be evaluated by assuming that the polymers aggregate into polydisperse micelles. The experiments support the expectation that in the case of the p(MMA-b-NaA-bMMA) block sequence the hydrophilic blocks form closed loops connected by both ends to the micellar cores; in the case of the p(NaA-b-MMA-b-NaA) block sequence they float freely in the solvent. The micellar cores exert considerable stability against dilution and added electrolyte. The interaction of charged micelles could be. formally described in terms of volume exclusion and the Derjaguin-Landau-Verwey-Overbeek potential