Molecular dynamic simulation study on structure of water in crosslinked poly(N-isopropylacrylamide) hydrogels

The arrangement of water molecules within poly(N-isopropylacrylamide) (P-NIPAM) gels was analysed using molecular dynamic (MD) simulations of P-NIPAM polymer chains crosslinked by N,N'-methylenebisacrylamide (BIS) molecules in an aqueous solution. The generation of the polymer was performed in three steps, first the crosslinker molecules were placed randomly, then the crosslinkers were connected by NIPAM monomer chains, and finally the water molecules were inserted. We extracted simulation trajectories from simulations, with N, V and T fixed, for different polymer concentrations at 285, 300 and 325 K. The trajectory data were used for analysis of the polymer-water structure and for determination of the diffusion coefficients, which were compared with experimental data.