Temperature-induced coil-globule transition of polypropylene oxide in aqueous solutions*

Polypropylene oxide (PPO) is a biocompatible polymer which is used in a wide range of industrial to biomedicalapplications, e.g. as a component of the commercial family of Pluronics. Using all-atom molecular dynamics simulations with modified OPLS forcefield we study the conformational changes of PPO in aqueous solutions as a function of temperature. We analyzed the temperature induced change in the PPO radius of gyration and correlate it with the polymer hydration properties, such as hydrogen bonding, hydration number, solvent accessible surface area, etc. We found that the coil-globular transition is accompanied by a noticeable reduction in polymer-water hydrogen bonding. We also estimate the heat capacity change as a function of temperature, which exhibits a maximum at the transition point and compare it with experimental data.