Amphiphilic Graft Copolymers in Selective Solvents: Molecular Dynamics Simulations and Scaling Theory

Abstract

Intramolecular structures in amphiphilic graft copolymers with hydrophilic side chains and hydrophobic backbone have been studied by molecular dynamics simulations. In accordance with earlier theoretical predictions [Borisov, O.; Zhulina, E. Macromolecules 2005, 38, 2506−2514], we have found that balance of repulsive and attractive intramolecular interactions may result in the pearl-necklace-type conformations. The globular “pearls” are formed by collapsed segments of the main chain comprising multiple spacers; these pearls are stabilized against aggregation by repulsive interactions of the hydrophilic grafts. The size of the pearls is controlled by the intramolecular hydrophilic−hydrophobic balance, whereas the total number of pearls in the graft copolymer depends on the length of the main chain. For graft copolymer with relatively long spacers we have observed intramolecular conformational transition from pearl-necklace structure to unimolecular cylindrical micelle upon a decrease in the solvent quality for the main chain. The results of simulations, in particular behavior of polymers of finite chain length, are rationalized on the basis of revised and extended scaling theory.