| Popis: |
A study of the effect of Li, Na, Mg, Ca, Sr, Ba, La perchlorates and Li chloride and nitrate on the viscosity of 22% secondary cellulose acetate (CA) solutions in acetone, aqueous acetone mixtures and DMF shows that on increasing the amount of salt dissolved, the higher the valency of the cation, the greater the extent to which solution viscosity increases. This is the result of the formation of donor-acceptor bonds between cations of salts and donor solvents and between cations and donor groups of the CA chain; as a consequence solution cross linking increases. The anions are unable to provide solvated complexes with donor solvents (DMF and acetone) and therefore have no effect in practice on the viscosity of CA solutions in these solvents. In the presence in the solution of fairly large amounts of water the dependence of solution viscosity on the amount of salt added is expressed by a curve with a maximum, which is due to the competing ordering action of Mg 2+ cations and the disorganizing effect of perchlorate of the anion. |
