All-Atom Molecular Dynamics Simulations of the Temperature Response of Poly(glycidyl ether)s with Oligooxyethylene Side Chains Terminated with Alkyl Groups.

Recently, experimental investigations of a class of temperature-responsive polymers tethered to oligooxyethylene side chains terminated with alkyl groups have been conducted. In this study, aqueous solutions of poly(glycidyl ether)s (PGE) with varying numbers of oxyethylene units, poly(methyl(oligooxyethylene)_n glycidyl ether) (poly(Me(EO)_nGE)), and poly(ethyl(oligooxyethylene)_n glycidyl ether) (poly(Et(EO)_nGE) (n = 0, 1, and 2) were investigated by all-atom molecular dynamics simulations, focusing on the thermal responses of their chain extensions, the recombination of intrapolymer and polymer–water hydrogen bonds, and water-solvation shells around the alkyl groups. No clear relationship was established between the phase-transition temperature and the polymer-chain extensions unlike the case for the coil–globule transition of poly(N-isopropylacrylamide). However, the temperature response of the first water-solvation shell around the alkyl group exhibited a notable correlation with the phase-transition temperature. In addition, the temperature at which the hydrophobic hydration shell strength around the terminal alkyl group equals the bulk water density ( T CRP ) was slightly lower than the cloud point temperature ( T CLP ) for the methyl-terminated poly(Me(EO)_nGE) and slightly higher for the ethyl-terminated poly(Et(EO)_nGE). It was concluded that the polymer-chain fluctuation affects the relationship between T CRP and T CLP . [ABSTRACT FROM AUTHOR]