Infrared spectroscopic study of conformational properties of a short-chain poly(oxyethylene) (C1E3C1) complexed with lithium halides in water

The conformation of a short-chain poly(oxyethylene), CH 3 (OCH 2 CH 2 ) 3 OCH 3 (C 1 E 3 C 1 ), complexed with LiX (X  Cl or Br) in water was studied by infrared spectroscopy. The effects of the cation and the anion on the conformation were examined on the basis of the observed spectra, in conjunction with reported molecular dynamics simulations and a proposed hydration structure model for ions. The cation Li + is coordinated to ether oxygens, resulting in disruption of the hydration structure favorable for C 1 E 3 C 1 molecules to be incorporated, and the anions Cl − and Br − break water structure, resulting in unfavorable hydration of C 1 E 3 C 1 with water. The anion Cl − alters the conformation of C 1 E 3 C 1 to a greater degree than Br − . The cation and the anion likewise distort the favorable conformation ( gauche for the C–C bond and trans for the C–O bond) of POE in water.