Aggregation of Hydrophobic-Amphiphilic Block Copolymers

We analyze the aggregation of locally amphiphilic copolymers with blocky architecture and uniformly distributed amphiphilic moieties in terms of a mean-field theory. Locally amphiphilic structure is characteristic of many thermoresponsive polymers, both linear and grafted, which endows them with local surface activity. Self-assembly of such copolymers exhibits a rich diversity of morphologies, which are analyzed in the present work in the limit of high surface activity of amphiphilic dimers with solvophilic/polar pendants. Depending on the composition and architecture of the copolymer and also sizes and interaction parameters of the solvophilic/polar pendants, we build morphological diagrams of copolymer solutions. Copolymers with small volume pendants form precipitates with internal voids containing these pendants. For moderate volume pendants, a lamellar structure (or large vesicles) is observed at smaller fractions of amphiphilic monomer units in the chain and micelles are formed at larger fractions of these units. For large polar pendants, copolymers of both types mainly form granular branched compound micelles. The type and sizes of micelles depend on the monomer distribution along the chain, and the blocky architecture favors micellization and formation of spherical particles. Micelles of macromolecules with sufficiently long side chains have adjacent outer layers saturated with the polar groups, and the size of hydrophobic domains of such micelles is independent of the side chain lengths. For shorter side chains, their length determines the size of domains formed by the amphiphilic blocks of the block copolymers and the thickness of discs or layers and the radius of beads formed by the regular copolymers.