Infrared spectroscopic study of conformational properties of short chain poly(oxyethylene)s in methanol and carbon tetrachloride

摘要

Conformational properties of short chain poly(oxyethylene)s (POEs), CH3(OCH2CH2),OCH3 with m = 1-4, in methanol and carbon tetrachloride were studied by infrared spectroscopy. The conformational changes of the C-C and C-O bonds of the POE chain with varying concentration were analysed by examining the intensity ratio of the relevant conformational key bands. With increasing solvent fraction, the gauche preference of the C-C bond and the trans preference of the C-O bond increase in methanol, while the conformational preference of these bonds in carbon tetrachloride is opposite to that in methanol. The observed conformational behaviour with varying concentration is consistent with the effects of dielectric properties of the medium, hydrogen bonding between the POE chain and the solvent, and structure of the solvent. The results for the methanol solutions are similar to those for the aqueous solutions, except for anomalous conformational preference of the C-C bond in water in low-concentration regions. This peculiar phenomenon in water may be explained by specific hydration structure around the POE chain. (C) 1998 Elsevier Science B.V. [References: 25]