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We have studied the ionic conductivity and the dipolar reorientational dynamics of aqueous solutions of a prototypical deep eutectic solvent (DES), ethaline, by using dielectric spectroscopy on a broad range of frequency (MHz-Hz) and for temperatures ranging from 128 to 283 K. The fraction of water in the DES was varied systematically to cover different regimes, starting from pure DES and its water-in-DES mixtures to the diluted electrolyte solutions. Depending on these parameters, different physical states were examined, including low viscosity liquid, supercooled viscous liquid, amorphous solid and freeze-concentrated solution. The ionic conductivity and the reorientational relaxation both exhibited characteristic features of glassy dynamics that could be quantified from the deviation from Arrhenius temperature dependence and non-exponential decay of the relaxation function. A transition occurred between the water-in-DES regime, (< 40 wt %), where the dipolar relaxation and ionic conductivity remained inversely proportional to each other, and the DES-in-water regime, (> 40 wt %), where a clear rotation-translation decoupling was observed. This suggests that for low water content, on the timescale covered by this study (~10 -6 s to 1 s), the rotational and transport properties of ethaline aqueous solutions obey classical hydrodynamic scaling despite these systems being presumably spatially microheterogeneous. A fractional scaling is observed in the DES-in-water regime, due to the formation of a maximally freeze-concentrated DES aqueous solution coexisting with frozen water domains at sub-ambient temperature.

We have investigated the dynamics of water confined in mesostructured porous silicas (SBA-15, MCM-41) and four periodic mesoporous organosilicas (PMOs) by dielectric relaxation spectroscopy. The influence of water−surface interaction has been controlled by the carefully designed surface chemistry of PMOs that involved organic bridges connecting silica moieties with different repetition lengths, hydrophilicity, and H-bonding capability. Relaxation processes attributed to the rotational motions of nonfreezable water located in the vicinity of the pore surface were studied in the temperature range from 140 to 225 K. Two distinct situations were achieved depending on the hydration level: at low relative humidity (33% RH), water formed a nonfreezable layer adsorbed on the pore surface. At 75% RH, water formed an interfacial liquid layer sandwiched between the pore surface and the ice crystallized in the pore center. In these two cases, the study revealed different water dynamics and different dependence on the surface chemistry. We infer that these findings illustrate the respective importance of water−water and water−surface interactions in determining the dynamics of the interfacial liquid-like water and the adsorbed water molecules as well as the nature of the different H-bonding sites present on the pore surface.

The temperature dependence of the structure of water confined in hydrophilic mesostructured porous silica (MCM-41) and hydrophobic benzene-bridged periodic mesoporous organosilicas (PMOs) is studied by Raman vibrational spectroscopy. For capillary filled pores (75% relative humidity, RH), the OH stretching region is dominated by the contribution from liquid water situated in the core part of the pore. It adopts a bulklike structure that is modestly disrupted by confinement and surface hydrophobicity. For partially filled pores (33% RH), the structure of the nonfreezable adsorbed film radically differs from that found in capillary filled pores. A first remarkable feature is the absence of the Raman spectral fingerprint of low-density amorphous ice, even at a low temperature (−120 °C). Second, additional bands reveal water hydroxyl groups pointing toward the different water/solid and water/vapor interfaces. For MCM-41, they correspond to water molecules acting as weak H-bond donors with silica and dangling hydroxyl groups oriented toward the empty center of the pore. For benzene-bridged PMO, we found an additional type of dangling hydroxyl groups, which we attribute to water at the hydrophobic solid interface.

The mechanism of devitrification of racemic ibuprofen (RS-IBP, C 13 H 18 O 2 ) was analyzed by low-wavenumber Raman spectroscopy (LWRS). This study shows the capabilities of LWRS to provide detailed new structural information, with respect to X-ray diffraction data, on the atypical crystallization process of a molecular material (RS-IBP) composed of a majority of hydrogen atoms. The conversions of Raman intensity into reduced intensity and Raman susceptibility were presented. The combination of these two types of spectrum representation reflecting the fast relaxational dynamics and the structural organization, respectively, has clearly revealed the high degree of disorder of Phase II. Additionally, Phase II was described as an early transient and metastable step of crystallization toward Phase I, from a deeply quenched liquid state. Analyzing the isothermal and nonisothermal crystallization has revealed two types of conversion of Phase II into Phase I, a solid-solid transformation and a crystallization of Phase I after melting of Phase II, respectively.

Using the Milling-Assisted Loading (MAL) solid-state method, for loading a poorly water-soluble drug (ibuprofen, IBP) within SBA-15 matrix has given the opportunity to manipulate the physical state of drugs for optimizing bioavailability.MAL method makes it easy to control and analyze the influence of the degree of loading on the physical state of IBP inside SBA-15 matrix with an average pore diameter of 9.4 nm. It was found that the density of IBP molecules in an average pore size has a direct influence both on the glass transition and the mechanism of crystallization. Detailed analyzes of the crystallite distribution and melting by Raman

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