Atomistic insights on the LCST behavior of PMEO2MA in water by molecular dynamics simulations

Abstract

Fully atomistic molecular dynamics simulations of poly(2-[2-methoxyethoxy]ethyl methacrylate) (PMEO(2)MA) in water at temperatures below and above its lower critical solution temperature (LCST) were performed to improve the understanding of its LCST behavior. Atomic trajectories were used to calculate various structural and dynamic properties. Simulation results show that PMEO(2)MA undergo a distinct coil-to-globule transition above LCST. Detailed analyses of the number of first hydration shell water molecules around various atomic regions are revealed that the water solubility of PMEO(2)MA below LCST is mainly provided by the hydrophobic hydration around the side chain carbon atoms. This is achieved by the cage-like water network formations which are disrupted when the temperature is increased above LCST, accompanied by significant amount of water molecule release and local water-ordering reduction, which leads to the LCST phase transition. Furthermore, other analyses such as the number of hydrogen bonds and hydrogen bond lifetimes suggest that intermolecular hydrogen bondings between polymer and water molecules have little effect on the phase transition. Our results will contribute to a better understanding on the LCST phase transition of oligo(ethylene glycol) methyl ether methacrylate (OEGMA)-based homopolymers at atomistic level that will be useful when designing homo- and co-polymers of OEGMAs with desired properties. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 429-441