Aqueous Viscosity Enhancement through Helical Inclusion Complex Cross-Linking of a Hydrophobically-Modified, Water-Soluble, Cationic Cellulose Ether by Amylose

It has been found that combinations of a hydrophobically-modified, water-soluble, cationic cellulose ether, 3, and amylose (a linear polysaccharide isolated from potato starch) dissolved together in water at high temperature and carefully cooled afford increased solution viscosity over either polymer acting alone. The mode of viscosity enhancement has been attributed to formation of a cross-linked network created when the amylose forms a noncovalent, helical clathrate with the hydrophobic groups attached to 3 . Such an effect is not observed when 3 is replaced with a nonhydrophobic, water-soluble, cationic cellulose ether, 2, or when the amylose is replaced with either amylopectin or α-, β-, or γ-cyclodextrin. The resulting noncovalent, cross-linked clathrate network is pseudoplastic and temperature unstable. Heating the complex results in complete loss of solution viscosity, which then gradually rebuilds as the solution is recooled.