Some characteristic features of dilute aqueous alkali solutions of specific alkali concentration (2.5 mol p1) which possess maximum solubility power against cellulose

Abstract

Some structural features of aqueous(aq.)alkali solutions with specific concentration (2.5 mol l−1), in which cellulose shows maximum swelling or dissolution, were investigated by analysing electrical conductivity, 1H and 23Na NMR, solvation and Raman spectra of aq. alkali, especially aq. sodium hydroxide. Cellobiose solution in aq. alkali was also subjected to 1H NMR and specific rotatory angle measurements to elucidate the dissolved state of cellulose. It was found that in the specific alkali concentration, electrical conductivity, 1H and 23Na chemical shifts and 1H relaxation time became smaller and the number of solvated water molecules per 1 mole of alkali hydroxide became larger than those simply expected from their alkali concentration dependence in the outside range of specific alkali concentration. Raman spectra revealed that the peak giving maximum intensity of OH-deformation is energetically weakest at the specific concentration of aq. alkali. When cellobiose was added to the aq. alkali solution it was found that proton chemical shift of the system becomes larger especially at 4°C over the all alkali concentration range and its dependence on alkali concentration was almost linear. Based on these experimental facts some structure models of aq. alkali solution with specific concentration and the dissolved state of cellulose in the alkali solution were proposed. © 1988 The Society of Polymer Science, Japan.