Network formation in polyehtyleneglycol solutions. An intradiffusion study

Intradiffusion coefficients of binary mixtures, water-polyethyleneglycol (PEG) (molecular weight 200, 400, 2000, 3400, 10 000 Da), were measured by pulsed gradient spin echo (PGSE)-NMR to determine the mass and concentration effects. The properties of polydisperse samples are compared with those of oligomers, and the effect of polydispersity is discussed. The PEG diffusion coefficients approach a constant value at high concentration, indicating the formation of a dynamic network between water and PEG molecules. The stochiometry of this network is evaluated and compared with the result of a model derived from an extension of gelation theory. It was found that at infinite dilution limiting self and mutual diffusion coefficients are not equal: this has been interpreted as an effect of polydispersity.