ИСТИНА

Polymer micelles from AB-diblock copolymers (A is hydrophobic block, B is water soluble block) with homogeneous A-core and homogeneous B-corona were the subject of intensive study. A challenging task is a creation of hierarchically organized polymer micelles with the core or corona further subdivided onto structural domains with different properties and composition [1]. To solve this task we have prepared mixed polymer micelles from AB and AC diblock copolymers (A and C are hydrophobic blocks, B is ionic block). In aqueous media these block copolymers spontaneously self-assemble into joint micelles with hydrophobic A-core and segregating amphiphilic BC-corona. The structure and properties of micelles were studied as a function of corona composition  = [B]/([C]+[B]), both theoretically and experimentally. Mixed micelles demonstrated a remarkable inflection in structure near  ~ 0.5. Above this point aggregation number (m) and micelle dimensions coincided with those of individual AB-micelles. When  decreased below 0.5, dramatic growth of aggregation number was observed, accompanied by growth in micelle size and stretching B-chains. Scaling relationships between micelle characteristics and  were obtained from three-layered model of mixed micelles (A-core; shell from collapsed C-blocks, wrapping the core; the outer B-corona) via minimization of micelle free energy, taking into account electrostatic, osmotic, volume and surface contributions. Theoretical estimations predicted dramatic influence of  on aggregation number, m ~b^-3. This result is in general agreement with experimental data and confirms the correctness of the core–shell–corona model (Fig. 1). The inflection in micelle structure entails drastic changes in micelle ability to form soluble complexes with oppositely charged polymeric or amphiphilic complexing agents [2].