THE PRESSURE VOLUME TEMPERATURE PROPERTIES OF POLYETHYLENE, POLY(DIMETHYL SILOXANE), POLY(ETHYLENE GLYCOL) AND POLY(PROPYLENE GLYCOL) AS A FUNCTION OF MOLECULAR-WEIGHT

The pressure-volume-temperature (PVT) properties of a number of polymer liquid samples as a function of molecular weight have been investigated. The polymers studied included polyethylene (PE), poly(dimethyl siloxane) (PDMS), poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). The properties of the end-groups and their effect on the density, compressibility, thermal pressure coefficient and expansivity as a function of their concentration are discussed. The specific volume exhibits a clear 1/M(n) dependence for those molecules with weakly interacting end-groups, i.e. PE and PDMS. The specific volume is found to be independent of M(n) for PEG and PPG, which can hydrogen-bond to each other. The data sets have been compared using equation-of-state theories.