ИСТИНА

In this work, the influence of pH and ionic strength of the surrounding medium on the structural characteristics (core radius, R(core), aggregation number, N(aggregation), hydrodynamic radius, R(hydrodynamic), corona thickness, D(corona)) of micelles generated in aqueous solution of polyisobutylene-block-poly(methacrylic acid) diblock copolymers (PIB(X)-b-PMAA(Y), where X and Y denote the number-average degrees of polymerization of the corresponding blocks: X = 20, Y = 100, 280; X = 25, Y = 350, 2850; X = 75, Y = 615, 1590) have been investigated by means of small-angle neutron scattering (SANS) and dynamic light scattering (DLS). The values of R(core) and N(aggregation) (obtained by means of SANS) were found to distinctly rise with decreasing pH or increasing concentration of NaCl. The sensitivity of these structural parameters to the variation of the conditions of the surrounding medium strongly suggests that the formed macromolecular assemblies are "dynamic" rather than "frozen" ones. The values of R(hydrodynamic) (obtained by means of DLS) as well as the values of D(corona) (obtained by means of a combination of SANS and DLS) were shown to rise with increasing pH or decreasing concentration of NaCl, indicating an expansion of micellar coronas upon rising apparent charge of the polyelectrolyte blocks.