ИСТИНА

Polymer-surfactant mixtures and macromolecules with amphiphilic monomer units can self-assemble into nanoparticles of various shapes in solution. The morphology of a collapsed state of macromolecules in a poor solvent is studied using the scaling mean-field theory [1] and, for macromolecules with hydrophobic backbone and polar side groups, by the molecular dynamics simulations as well. Surfactant molecules and amphiphilic monomer units are described as dimers consisting of hydrophobic (H) and polar (P) parts. There are surface activity of amphiphilic dimers together with solvent quality and macromolecule length that control the system morphology. For long hydrophobic macromolecules in the presence of a nonionic surfactant, we predict in theory the formation of a spherical globule (aggregation) or a necklace-like structure (solubilized state) only, whereas intermediate rod-like structures can be formed for shorter macromolecules. The morphology diagrams of single amphiphilic macromolecules contain regions of spherical particles (solid sphere, vesicle and onion-like structure), elongated particles (disc, torus, rod, and nanoworm), and the area of necklace conformations. Vesicles are found to be the most favorable structure type for sufficiently long macromolecules at a moderate amphiphilicity degree of monomer units. Besides, a lateral aggregation in nonionic polymer brushes (polymer layers grafted from a surface) interacting with amphiphilic dimer surfactants is studied using the scaling mean-field theory [2]. The pattern formation is analyzed in the limiting case of a very high degree of amphiphilicity of the surfactant molecules with large polymer-compatible H parts. The morphology diagrams comprise lamellae perpendicular to the grafting plane, polymer layers with pores of different types, and a homogeneous brush. It is predicted that the process of pore formation in a homogeneous brush caused by a temperature change can be a first-order phase transition and can be accompanied by a stepwise extension of the brush.