The coil–globule transition of aqueous polymers is of profound significance in understanding the structure and function of responsive soft matter. In particular, the remarkable effect of amphiphilic cosolvents (e.g., alcohols) that leads to both swelling and collapse of stimuli-responsive polymers has been hotly debated in the literature, often with contradictory mechanisms proposed. Using molecular dynamics simulations, we herein demonstrate that alcohols reduce the free energy cost of creating a repulsive polymer–solvent interface via a surfactant-like mechanism which surprisingly drives polymer collapse at low alcohol concentrations. This hitherto neglected role of interfacial solvation thermodynamics is common to all coil–globule transitions, and rationalizes the experimentally observed effects of higher alcohols and polymer molecular weight on the coil-to-globule transition of thermoresponsive polymers. Polymer–(co)solvent attractive interactions reinforce or compensate this mechanism and it is this interplay which drives polymer swelling or collapse.

水性聚合物的线圈-球转变对于理解响应性软物质的结构和功能具有深远的意义。特别是，两亲性助溶剂（例如醇类）导致刺激响应性聚合物膨胀和塌陷的显着效果在文献中引起了激烈的争论，并经常提出相互矛盾的机制。使用分子动力学模拟，我们在此证明醇类通过类似表面活性剂的机制降低了产生排斥性聚合物-溶剂界面的自由能成本，该机制令人惊讶地在低醇浓度下驱动聚合物崩溃。这种迄今被忽视的界面溶剂化热力学的作用对​​于所有线圈 - 球转变都是常见的，并合理化实验观察到的高级醇和聚合物分子量对热敏聚合物的线圈到小球转变的影响。聚合物-（共）溶剂的吸引相互作用加强或补偿了这种机制，正是这种相互作用导致聚合物膨胀或坍塌。