title: Mechanical and transport properties of the poly(ethylene oxide)-poly(acrylic acid) double network hydrogel from molecular dynamic simulations.
abstract: We used atomistic molecular dynamics (MD) simulations to investigate the mechanical and transport properties of the PEO-PAA double network (DN) hydrogel with 76 wt % water content. By analyzing the pair correlation functions for polymer-water pairs and for ion-water pairs and the solvent accessible surface area, we found that the solvation of polymer and ion in the DN hydrogel is enhanced in comparison with both PEO and PAA single network (SN) hydrogels. The effective mesh size of this DN hydrogel is smaller than that of the SN hydrogels with the same water content and the same molecular weight between the cross-linking points (Mc). Applying uniaxial extensions, we obtained the stress-strain curves for the hydrogels. This shows that the DN hydrogel has a sudden increase of stress above approximately 100% strain, much higher than the sum of the stresses of the two SN hydrogels at the same strain. This arises because PEO has a smaller Mc value than PAA, so that the PEO in the DN reaches fully stretched out at 100% strain that corresponds to 260% strain in the PEO SN (beyond this point, the bond stretching and the angle bending increase dramatically). We also calculated the diffusion coefficients of solutes such as D-glucose and ascorbic acid in the hydrogels, where we find that the diffusion coefficients of those solutes in the DN hydrogel are 60% of that in the PEO SN and 40% of that in the PAA SN due to its smaller effective mesh size.
authors.affiliation: Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Seung Soon
authors.initials: SS
authors.lastname: Jang
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.forename: M Yashar S
authors.initials: MY
authors.lastname: Kalani
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D001692:Biological Transport; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000737:chemistry; D004058:Diffusion; D020100:Hydrogels / Q000737:chemistry*; D008968:Molecular Conformation; D008970:Molecular Weight; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D020100:Hydrogels; D012996:Solutions; D014867:Water; D011092:Polyethylene Glycols