MiS Preprint Repository

We investigate the conformational changes of the polymer induced by a change of the strength of polymer solvophobicity and the co-solvent pressure in the bulk solution. We describe the polymer in solution by the Edwards model, where the partition function of the polymer chain with a fixed radius of gyration is described in a field-theoretical manner within random phase approximation.

The polymer-co-solvent and the co-solvent-co-solvent interactions are treated in the framework of the mean-field approximation. We obtain the total Helmholtz free energy of the solution as a function of radius of gyration and the average co-solvent concentration within gyration volume. We obtain a system of coupled equations with respect to the radius of gyration of the polymer chain and the cosolvent concentration within the gyration volume. Varying the polymer solvophobic strength at high co-solvent pressure in the bulk we show that the coil-globule transition occurs accompanied by local co-solvent evaporation within gyration volume. On the other hand, varying the co-solvent pressure in the bulk we show that globule-rod transition of polymer chain can take place accompanied by co-solvent wetting transition within gyration volume.