Hydronium Ions Are Less Excluded from Hydrophobic Polymer-Water Interfaces than Hydroxide Ions.

The cloud point temperatures of aqueous poly(-isopropylacrylamide) (PNIPAM) and poly(ethylene) oxide (PEO) solutions were measured from pH 1.0 to pH 13.0 at a constant ionic strength of 100 mM.

Solvation free energies of alcohols in water: temperature and pressure dependences.

Solvation free energies * of amphiphilic species, methanol and 1,2-hexanediol, are obtained as a function of temperature or pressure based on molecular dynamics simulations combined with efficient free-energy calculation methods. In general, * of an amphiphile can be divided into and , the nonpolar and electrostatic contributions, and the former is further divided into and which are the work of cavity formation process and the free energy change due to weak, attractive interactions between the solute molecule and surrounding solvent molecules. We demonstrate that * of the two amphiphilic solutes can be obtained accurately using a perturbation combining method, which relies on the exact expressions for and and requires no simulations of intermediate systems between the solute with strong, repulsive interactions and the solute with the van der Waals and electrostatic interactions.