Hydrogen dynamics in a time range from hundreds of femtoseconds to nanoseconds can be directly analyzed using neutron spectroscopy, where information on the inelastic and quasi-elastic scattering, hereafter INS and QENS, can be obtained. In this study, we applied these techniques to understand how the nanoscale mobility of the aqueous solution of polyacrylic acid (PAA) used in conventional glass ionomer cements (GICs) changes under confinement. Combining the spectroscopic analysis with calorimetric results, we were able to separate distinct motions within both the liquid and the GICs. The QENS analysis revealed that the self-diffusion translational motion identified in the liquid is also visible in the GIC. However, as a result of the formation of the cement matrix and its setting, both translational diffusion and residence time differed from the PAA solution. When comparing the local diffusion obtained for the selected GIC, the only noticeable difference was observed for the slow dynamics associated with the polymer chain. Additionally, over short-term aging, progressive water binding to the polymer chain occurred in one of the investigated GICs. Finally, a considerable change in the density of the GIC without progressive water binding indicates an increased polymer cross-linking. Taken together, our results suggest that accurate and deep understanding of polymer-water binding, polymer cross-linking, as well as material density changes occurring during the maturation process of GIC are necessary for the development of advanced dental restorative materials.
Water mobility through porous rock has a role to play in many systems, such as contaminant remediation, CO 2 storage, and oil recovery. We used inelastic and quasielastic neutron scattering to describe water dynamics in two different chalk samples that have similar pore volume (ranging from tens of micrometers to a few nanometers) but different water uptake properties. We observed distinct water populations, where the analysis of the quasielastic data shows that after the hydration process most of the water behaves as bulk water. However, the lack of quasielastic signal, together with the observation of a translational mode at 10 meV, imply that in chalk samples that take up less water confinement occurs mostly in the pore volume that is accessible with nitrogen adsorption measurements.
Alternation in various properties of n-alkanes (CnH2n+2) as a function of carbon content (n) is termed `odd-even effect'. Here, we report a comprehensive molecular dynamics simulation study on n-alkane systems...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.