Statistical thermodynamics of water-mediated interactions
Abstract
The unique solvent properties of water arise from its capacity to structurally respond to solutes with a wide range of attractive strengths, resulting in its propensity to mediate solute conformation and aggregation behavior. A variety of solutes are investigated through their molecular interaction energies and entropies which compose the free energies (ΔG), enthalpies (ΔH), and entropies (ΔS) of hydration. Connections between fundamental thermodynamic perturbation and linear response theories form a unified perspective of polar, non-polar, and ionic hydration for small, molecular solutes, and resolve an entropic mystery surrounding the apparent insensitivity of experimental hydration entropies to solute electrostatic forces. From this theoretical foundation, hydration thermodynamic signatures of non-polar hydration are extended to the nanoscale with n-alkane polymer chains and spherical oil drops. Theoretical predictions and molecular dynamics simulations support a crossover from hydrophobic (Δ G > 0) to hydrophilic (ΔG < 0) hydration for model spherical oil drops, and a similar conformation-dependent crossover is also found to accompany the folding of n-alkane C100 chain into its globular state.
Degree
Ph.D.
Advisors
Ben-Amotz, Purdue University.
Subject Area
Physical chemistry
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