An interplay of excluded-volume and polymer–(co)solvent attractive interactions regulates polymer collapse in mixed solvents

Cosolvent effects on the coil–globule transitions in aqueous polymer solutions are not well understood, especially case of amphiphilic cosolvents that preferentially adsorb and lead to both swelling collapse. Although a predominant focus literature has been placed role polymer–cosolvent attractive interactions, our recent work shown excluded-volume interactions (repulsive interactions) can drive preferential adsorption cosolvent collapse via surfactant-like mechanism. Here, we further study polymer–(co)solvent two kinds solutions, namely, good solvent (water)–good (alcohol) (GSGC) poor solvent–good (PSGC) which exhibit non-monotonic change radius gyration with addition cosolvent. Interestingly, at low concentrations, energetic oppose GSGC contrarily support PSGC indicating importance underlying chemistry. Even though alcohol molecules adsorbed polymer, trends concentrations dominated by polymer–water cases. Therefore, either reinforce or compensate mechanism, it is this interplay drives coil-to-globule solutions. These results have implications for rationalizing cononsolvency real systems such as polyacrylamides where understanding microscopic driving forces still debatable.