Role of Tacticity in Determining Polymer-Water Interactions*

We present quantification of the nature of hydrogen bond dynamics and functional group expression for three tactic forms of the common polymer, poly(methyl methacrylate) (PMMA). Using all-atom molecular dynamics simulations with validated potentials, the response at the water interface of isotactic, syndiotactic, and atactic forms was quantified in terms of hydrogen bond participation, interaction energies, and relaxation times. The relaxation and reorientation of carbonyl groups, the key determinant of tactic PMMA-water interactions, was also computed. We found that the atactic form exhibits cooperative effects based on hydrogen bond participation and carbonyl group orientation. Similarly, the isotactic form undergoes the largest change in orientation, which we hypothesize would be functionally reflected in contact angle hysteresis measurements. The observed subtle changes in physical interaction with water provide a platform for stereocomplexed coatings and membranes that can utilize differentials in participation rates, packing, and surface expression for designer adhesion, wettability, compatibility, and selectivity applications.