Determination of the parameters of molecular-weight distribution of hydroxyethyl starches by diffusion-ordered NMR spectroscopy

The possibility of the application of diffusion-ordered NMR spectroscopy to the study of the molecular-weight distribution of hydroxyethyl starch is investigated. The use of regression equations relating these parameters to the coefficients of the self-diffusion of polymer macromolecules as a whole, namely, the average coefficient of self-diffusion D s and the coefficient of self-diffusion at the peak maximum D p, is proposed for the quantitative assessment of weight-average (M w) and number-averaged (M n) molecular weights and molecular weight at the peak maximum (M p). It is shown that the determination of M w, M n, M p based on the data on D s gives the best results. It was found that the values of polydispersity indexes found using diffusion-ordered NMR spectroscopy are independent of the choice of diffusion parameter D s or D p.