Molecular dynamics simulation study of water dynamics around synthetic polymer chain in aqueous solution: stereo-regular poly(acrylic acid) and poly(methacrylic acid)

Atomistic molecular dynamics simulations were performed to study the influence of tacticity and hydrophobicity on the dynamics of water surrounding uncharged stereoregular poly(acrylic acid) and poly(methacrylic acid). Intermolecular hydrogen bonding, dihedral dynamics of polymer, rotational dynamics, diffusion coefficient, residence time distribution and bridging of water molecules were used to characterise the water dynamics around solutes. The stereochemistry of the polymer chain influenced all of the estimated parameters used to evaluate water dynamics. The presence of hydrophobic moieties in polymer chains influences the rotational and hydrogen bond dynamics of water molecules. Solvation shells of different moieties of polymer chains significantly influence the residence time of bound water molecules. However, some water molecule/s exhibit a longer residence time. The backbone torsion dynamics of polymers considerably influenced the intermolecular hydrogen bond network in the polymer chain. When compared to the diffusion coefficients of water molecules in the second solvation shells and bulk water, the diffusion coefficients of water molecules in the first solvation shell of polymer chains are dramatically altered.