Molecular weight dependence of the heats of hydration of some oligomeric ethylene oxides and their methoxyl derivatives

The molecular weight dependence of the heat of hydration of the oligomeric ethylene oxides and their monomethoxyl and dimethoxyl derivatives has been studied using microcalorimetry. In all cases the molar heat of hydration decreased rapidly at low molecular weights reaching an asymptote at molecular weights in excess of 400. Equivalent values were obtained between oligomers and blends of the same average molecular weight. The data followed the Flory relationship relating the property of a polymer to the reciprocal of its molecular weight. However, the gradient for the oligomeric ethylene oxides was different from that of the two methoxyl derivatives suggesting a change in chain configuration. (C) 1993 John Wiley & Sons, Inc.