Supercooled Water in PVA Matrixes. II. A Molecular Dynamics Simulation Study and Comparison with QENS Results

Abstract

Molecular dynamics (MD) simulations were carried out to elucidate the dynamic behavior of water confined in poly(vinyl alcohol), PVA, hydrogels. Model topology is supported by experimental network parameters, and simulation results are compared to an incoherent quasielastic neutron scattering (QENS) investigation carried out on PVA hydrogels.1 From the QENS dynamic scattering law (part I), 1 a random jump model was adopted for the description of water diffusion to extract a microscopic diffusion coefficient and a residence time between two "jumps". In the present work, consistently with this framework, water diffusion parameters as diffusion coefficients and residence times have been evaluated using the mean square displacement of water in a time window of 10 ps and the time autocorrelation function of water hydrogen bonds. The calculated parameters are in good agreement with the experimental ones, giving confidence to this approach. Further developments are in progress to take into account a more realistic description of hydrogel structure in the molecular dynamics simulations.

Long-term physical evolution of an elastomeric ultrasound contrast microbubble

“…Undoubtedly, the shell hydration, that causes the swelling of the PVA structure [12,27,43], also contributes to the actual MBs' shell thickness as well as to the rheology and acoustics of aged PVA MBs. It has been reported that the water structured among crosslinked PVA chains can exert a significant influence on the stiffness and the stability of the polymer matrix [54][55][56]. The way in which the long-term modifications in the structural and mechanical properties of the PVA MBs disclosed here reflect a different dynamic of the water confined on the shell surface is an aspect that remains unclarified.…”

Molecular Modeling and Dynamics Studies of Hexanal Release from Polyvinyl alcohol - Cyclodextrin Nano-fiber Composite for Extending Shelf-life of Mango

“…From this result, it shows that when the temperature is increased, the hexanal release from the PVA-β cyclodextrin composite is induced when there is a low relative humidity in the environment. The water molecules got destructured when there is a high temperature (Chiessi et al, 2005), and there are changes in the polymer conformation. This confirms our data that at a high temperature of 33°C, water molecules get destructured rapidly, and due to the polymer chain conformation, hexanal is released quickly at low relative humidity level.…”

Computing thermomechanical properties of dry homopolymers used as raw materials for formulation of biomedical hydrogels

“…This property is crucial for the formulation of multicomponent material such as that used in contact lens. Three patents [4,40,41] dealing with the utility of this parameter on the design of contact lens materials are given as examples. Moreover, from the semi IPN structure obtained from polymerized MMA-monomer and PMMA-polymer, Vuorinen et al [42] stated that the formation of a IPN bond is linked to the difference between the solubility parameter of the polymer and the monomer.…”

“…Among them, force field transferability, size models, and sampling are among the most important factors. United [4][5][6][7] or All [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] atoms force fields were extensively used during the last 20 years to study phase behavior [8,9], structures [10][11][12], PVA models has been shown by Noorjahan and Choi in 2013 [22]. They observed a drop from 6, 3, and 2.5 MPa respectively for atactic, isotactic, and syndiotactic PVA when the degree of polymerization was increased from 50 to 400 monomer units.…”