STRUCTURAL-PROPERTIES OF CHARGED DIBLOCK COPOLYMER SOLUTIONS

Aqueous micellar solutions of ionic/neutral block copolymers have been studied by light scattering, small angle neutron scattering and small angle X-ray scattering. We made use of a polymer comprised of a short hydrophobic block (polyethylene-propylene) PEP and of a long polyelec trolytic block (polystyrene-sulfonate) PSSNa which has been shown prev iously to micellize in water. The apparent polydispersity of these mic elles is studied in detail, showing the existence of a few large aggre gates coexisting with the population of micelles. Solutions of micelle s are found to order above some threshold in polymer concentration. Th e order is liquid-like, as demonstrated by the evolution with concentr ation of the peak observed in the structure factor (q(peak) proportion al to c(1/3)); and the degree of order is found to be identical over a large range of concentrations (up to 20 wt%). Consistent values of th e aggregation number of the micelles are found by independent methods. The effect of salt addition on the order is found to be weak.