Size dependence of hydrophobic hydration at electrified gold/water interfaces

Hydrophobic hydration at metal/water interfaces actively contributes to the energetics of electrochemical reactions, e.g. CO2 and N2 reduction, where small hydrophobic molecules are involved. In this work, constant applied potential molecular dynamics is employed to study hydrophobic hydration at a gold/water interface. We propose an adaptation of the Lum–Chandler–Weeks (LCW) theory to describe the free energy of hydrophobic hydration at the interface as a function of solute size and applied voltage. Based on this model we are able to predict the free energy cost of cavity formation at the interface directly from the free energy cost in the bulk plus an interface-dependent correction term. The interfacial water network contributes significantly to the free energy, yielding a preference for outer-sphere adsorption at the gold surface for ideal hydrophobes. We predict an accumulation of small hydrophobic solutes of sizes comparable to CO or N2, while the free energy cost to hydrate larger hydrophobes, above 2.5-Å radius, is shown to be greater at the interface than in the bulk. Interestingly, the transition from the volume dominated to the surface dominated regimes predicted by the LCW theory in the bulk is also found to take place for hydrophobes at the Au/water interface but occurs at smaller cavity radii. By applying the adapted LCW theory to a simple model addition reaction, we illustrate some implications of our findings for electrochemical reactions.

Small-to-Large Length Scale Transition of TMAO Interaction with Hydrophobic Solutes

We report the effect of trimethylamine N-oxide (TMAO) on the solvation of nonpolar solutes in water studied with molecular dynamics (MD) simulations and free-energy calculations. The simulation data indicate the...

Multicomponent diffusion of interacting, nonionic micelles with hydrophobic solutes

Rigorous theory for gradient diffusion in hard-sphere suspensions is adapted to locally monodisperse, nonionic micellar solutions with solute, and effectively used to predict ternary diffusion matrices [D] acquired using the Taylor dispersion method.

Reversible Multilayered Vesicle-like Structures with Fluid Hydrophobic and Interpolyelectrolyte Layers

Hydrophobic blocks of amphiphilic block copolymers usually form glassy micellar cores with a rigid structure that limits their applications as nanocapsules for targeted delivery. We report here on the core/shell micelles with a soft core formed<br>by self-assembly of block copolymer composed of hydrophobic and polycation blocks, poly(lauryl acrylate)-block-poly(trimethylammonioethyl acrylate) (PLA-QPDMAEA), in aqueous solution. Using scattering, microscopy and spectroscopy techniques, we showed that such copolymer forms spherical and cylindrical core/shell micelles with a fluid-like PLA core and a positively charged shell, and that these micelles can encapsulate and release hydrophobic solutes. Moreover, we discovered novel vesicle-<br>like multicompartment structures containing both soft hydrophobic and interpolyelectrolyte (IPEC) layers formed by co-assembly of PLA-QPDMAEA core/shell micelles with another diblock copolymer composed of a hydrophilic block and polyanion block poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-PMAA). These complex structures were characterized by small-angle neutron scattering, supported by self-consistent field modeling that confirmed the formation of vesicle-like structures with dense PEO core, IPEC inner layer, PLA soft layer, IPEC outer layer and loose PEO corona. Due to their unique tunable properties, such multicompartment micelles with fluid and IPEC layers and hydrophilic corona can be used as nanocapsules with controllable thickness of each layer, charge and stability.<br>

Reversible Multilayered Vesicle-like Structures with Fluid Hydrophobic and Interpolyelectrolyte Layers

Hydrophobic blocks of amphiphilic block copolymers usually form glassy micellar cores with a rigid structure that limits their applications as nanocapsules for targeted delivery. We report here on the core/shell micelles with a soft core formed<br>by self-assembly of block copolymer composed of hydrophobic and polycation blocks, poly(lauryl acrylate)-block-poly(trimethylammonioethyl acrylate) (PLA-QPDMAEA), in aqueous solution. Using scattering, microscopy and spectroscopy techniques, we showed that such copolymer forms spherical and cylindrical core/shell micelles with a fluid-like PLA core and a positively charged shell, and that these micelles can encapsulate and release hydrophobic solutes. Moreover, we discovered novel vesicle-<br>like multicompartment structures containing both soft hydrophobic and interpolyelectrolyte (IPEC) layers formed by co-assembly of PLA-QPDMAEA core/shell micelles with another diblock copolymer composed of a hydrophilic block and polyanion block poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-PMAA). These complex structures were characterized by small-angle neutron scattering, supported by self-consistent field modeling that confirmed the formation of vesicle-like structures with dense PEO core, IPEC inner layer, PLA soft layer, IPEC outer layer and loose PEO corona. Due to their unique tunable properties, such multicompartment micelles with fluid and IPEC layers and hydrophilic corona can be used as nanocapsules with controllable thickness of each layer, charge and stability.<br>