SOLVATION OF POLY(VINYL ALCOHOL) IN WATER, ETHANOL AND AN EQUIMOLAR WATER-ETHANOL MIXTURE - STRUCTURE AND DYNAMICS STUDIED BY MOLECULAR-DYNAMICS SIMULATION

Solutions of a 15-mer of poly(vinyl alcohol) in water, ethanol and a 1 /1 (mole fraction) mixture of water and ethanol have been studied by m olecular dynamics simulations. The solvent structure near the solute i s analysed in terms of radial distribution functions and hydrogen bond ing. Results indicate a preferential solvation by water molecules. Hyd rogen-bond life time analysis shows that solvent-solute hydrogen bonds are slightly longer-lived than solvent-solvent hydrogen bonds. Howeve r, the separation in time scales is not large enough to support the no tion of a solvent-decorated polymer. An analysis of the polymer dynami cs shows that the gauche <----> trans transitions of backbone dihedral angles are at least an order of magnitude slower than the renewal of intramolecular hydrogen bonds along the polymer chain. No coupling is observed between the two. (C) 1997 Elsevier Science Ltd.