Showing papers by "Pijush Ghosh published in 2017"

Insights on Water Dynamics in the Hygromorphic Phenomenon of Biopolymer Films

Abstract: Water-responsive biopolymer thin films with engineered matrix characteristics can accomplish desirable shape changing properties such as self-folding. Self-folding response of chitosan film is experimentally characterized by its total folding time and rate of folding. Here, atomistic simulation is employed to investigate the molecular mechanism responsible for modified self-folding behavior observed in nanoparticle reinforced chitosan films. The nanocomposite system is solvated with water content varying from 10% to 100% of total mass of the system. The free volume available for diffusion of water molecules is affected by the flexibility of glycosidic linkages present in chitosan chains. The increase in mobility of water molecules with increase in water content decides the rate of folding. A separate molecular system is modeled with confined region between nanoparticles densified with chitosan chains and water molecules. The thickness of confined region is determined from the critical distance of influenc...

Surface dissimilarity affects critical distance of influence for confined water

Abstract: Water at interfaces and under nano-confinement is part of many natural processes. The behavior of this water is greatly influenced by the nature of the surfaces it is in contact with and the confinement distance. The objective of this study is to understand the behaviour of confined water between dissimilar (X–Y) surfaces under varying confinement spacing. The surfaces considered were hydrophilic in nature and the combinations were considered based on crystal structure and surface energy. The critical distance of influence of mineral substrates on the water molecules was determined by applying time-averaged static properties such as interfacial layer density and orientation and dynamic properties such as diffusion. It was observed that dynamic properties provide a higher value of critical distance compared to static properties for dissimilar surface combination. The reason for this disparity is probed in terms of mineral–water and water–water interactions. The disproportion of strong and weak H-bonds was observed to be significant in determining the dynamic behaviour of interfacial layer. We applied hydrophilic surface combinations of tricalcium silicate (C3S) and dicalcium silicate (C2S) for our investigations.