The effect of pressure to 125 kbar has been measured on the O–H (or N–H) stretching frequency in a number of hydrogen bonding solids. Some data were also obtained on C–H stretching frequencies and on peak widths. For the hydrogen bonding peaks the initial shift is to lower energy. In a number of cases the direction reverses after shifts of 200–300 cm−1. The C–H frequencies increase in energy at all pressures. The results can be reproduced quite well by a simple model which adds a repulsion from the surroundings to Lippincott's model of an isolated H bond. The regularities observed among a number of substituted phenols are discussed in terms of substituent effects. The C–H bands broadened slightly with pressure while the bands involved in hydrogen bonding broadened substantially. These observations are discussed briefly in terms of a configuration coordinate model.

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Nanoparticle organic hybrid materials (NOHMs) are self-suspended liquid-like nanoparticle-based functional materials consisting of a surface-functionalized inorganic nanocore and oligomeric or polymeric chains. They often exhibit complex intermolecular and intramolecular interactions among their constituents, resulting in versatile physicochemical characteristics that range from glassy solids to solvent-free nanoparticle fluids. A variety of applications involving NOHMs have been investigated thus far, including thermal management fluids, lubricants, magnetic fluids, nanocomposites, electrolytes, water treatment and biomass pretreatment chemicals, and CO 2 capture solvents. In particular, NOHMs have recently been recognized as a promising CO 2 capture and utilization medium. To capture CO 2 more effectively, a variety of specific functional groups of strong chemical affinity to CO 2 can be added to the polymeric canopy (enthalpic contribution), and various steric considerations induced by attractive/repulsive interactions among the nanocores and canopies can be introduced (entropic contribution). These occur while maintaining negligible vapor pressure and enhanced thermal stability. Here, we investigated the canopy dynamics of NOHMs with different-sized SiO 2 nanocores, aiming to reveal the hidden nature of the entropic interaction occurring in NOHMs. Pulse-field gradient nuclear magnetic resonance spectroscopy (with 1 H) was employed to investigate the canopy dynamics of the NOHMs synthesized using 7, 12, and 22 nm SiO 2 particles, and these results were compared with those from a ternary mix of all three sizes of SiO 2 nanocores. The self-diffusion coefficient and thermal diffusivity were also evaluated.

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