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

Abstract

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 Ds and the coefficient of self-diffusion at the peak maximum Dp, is proposed for the quantitative assessment of weight-average (Mw) and number-averaged (Mn) molecular weights and molecular weight at the peak maximum (Mp). It is shown that the determination of Mw, Mn, Mp based on the data on Ds 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 Ds or Dp.