Computer simulations of comb-like macromolecules with responsive diblock copolymer side chains

Comb-like macromolecules having diblock copolymer side chains with inner (grafted to the backbone) responsive block and outer soluble block were studied using dissipative particle dynamics simulations. Like for thermoresponsive polymers, responsiveness of the inner block means variation of its solubility upon changing of external conditions leading to variation of the solvent quality. The collapse of single copolymers (regime of infinite dilution) and their self-assembly in solution were examined. The effects of grafting density and the composition of the side chains were considered. The results reveal three distinct regimes which are characterized by the different balance of interactions between solvophilic and solvophobic groups and by the number of intramolecular clusters in the single macromolecules. The solvent quality, at which the transition between the regimes occurs, depends on the molecular architecture. In the case of macromolecular ensemble, the increase in the grafting density not only requires poorer solvent to induce intermolecular aggregation but also changes the shape of the aggregates (micelles). Namely, the grafted macromolecules can form the continuous or branched cluster, as well as cylindrical micelles. In turn, the change of the side chain composition strongly influences the stability of the solution: the longer the responsive block, the sooner the macromolecules precipitate upon the block collapse. Graphical abstract