ANOMALOUS CONFORMATIONAL BEHAVIOR OF SHORT POLY(OXYETHYLENE) CHAINS IN WATER - AN FT-IR SPECTROSCOPIC STUDY

Conformational behavior of short poly(oxoethylene) (POE) chains in water has been studied by FT-IR spectroscopy. The spectra of aqueous solutions of CH3(OCH2CH2)(m)OCH3 with m = 2-6 were measured for various concentrations by using a horizontal ATR accessory. The observed spectra show that, with increasing water fraction, the population of the gauche conformation about the OC-CO bond increases, but the direction of the conformational preference is reversed for lower concentrations. The observed maximum of the gauche population is interpreted as a consequence of anomalous enhancement of the gauche population in a specific concentration region. This effect is more significant for shorter POE chains, These observations suggest that there exist some specific interactions, which highly favor the gauche conformation of the O-CH2-CH2-O segment, for limited composition regions of the binary systems of short POE chains and water.