Static Investigation of the Influence of Polymer Molecular Weight and Loading in the Gas Chromatographic Determination of Poly(dimethylsiloxane) Interaction Parameters

Activity coefficients and interaction parameters determined by a static method are reported for benzene and hexane at infinite dilution in five samples of poly(dimethylsiloxane) in the molecular weight range 3350–89000 at 303 K. A small but significant variation of these properties is shown to occur with benzene if the polymer loading on a relatively inert solid support is reduced below ca. 20 wt %. The variation is attributed to adsorption at the surface of the support and the gas-liquid interface. An appreciable variation of the solution properties with polymer molecular weight is found. However, this variation is not sufficient to explain the differences between results of other workers, which are probably best explained by difficulties in determining the amount of polymer used in the gas-liquid chromatographic measurements.