COMPUTER-SIMULATION STUDIES ON THE POLYMER-INDUCED MODIFICATION OF WATER PROPERTIES IN POLYACRYLAMIDE HYDROGELS

The interactions between polyacrylamide and SPC/E water molecules in p olymer gels and solutions were analyzed using computer simulations. Se veral polymer structures with different concentrations, connectivity c haracteristics, and pore sizes were used in order to investigate diffe rent polymer environments. It.was shown that the structure of water wa s strongly modified in the presence of the polymer. This polymer-induc ed modification could be characterized in a very detailed way using th e spatial distribution function, which considers both the distance as well as the orientation of the water molecules relative to the amide s ide groups. The dynamics of water, as manifested in the translational and rotational diffusion and residence probability of water is slowed down in the presence of the polymer. The strongest modifications are f ound in the shell of bound water, but also long-ranged effects were de tected. The hydrogen bonds in the vicinity of amide side groups become stronger and longer lived. By setting the partial charges in the amid e side groups to zero in some systems, artificial apolar polymer netwo rk model systems were defined, whose influence on the structure of wat er is remarkably different from the influence of the polar networks, a lthough their influence on the transport properties of the surrounding water molecules was found to be quite similar.