The influence of macromolecular architecture on the micellization in block copolymer/homopolymer blends

We investigate the micellar formation and micelle characteristics of block copolymers of varying architecture within homopolymer matrices. A series of symmetric (polyisoprene)$_{n}$(polystyrene)$_{n}$ (I$_{n}$S$_{n}$) miktoarm star block copolymers, with n identical pairs of arms, and a series of (polyisoprene)$_{2}$(polystyrene), I$_{2}$S, graft copolymers with constant total MW and varying composition, $f_{PS}$, are added to a low MW PI homopolymer matrix and the blends are investigated by small-angle X-ray and light scattering as a function of copolymer concentration and n or $f_{PS}$. The functionality of the junction point of the copolymer does not influence the characteristics of the I$_{n}$S$_{n}$ micelles, while $f_{PS}$ controls the behavior of the I$_{2}$S grafts. A simple thermodynamic model is developed that describes theoretically the micellization of A$_{n}$B$_{n}$ copolymers within B homopolymers and its predictions agree very well with the experimental data both qualitatively and quantitatively. Sponsored by NATO's Scientific Affairs Division, by the Greek GSRT and by the EU.