Cyclodextrins modify the properties of cationic polyacrylamides

The hydrodynamic diameter (D-h) of cationic polyacrylamides (c-PAM) in water can either decrease or increase dramatically in the presence of small amounts of beta-cyclodextrin (beta-CD). It is proposed that the CD partially disperses the charge on the polymer thereby promoting associations within or among neighboring polymer strands. Turbidity measurements show that beta-CD enhances the c-PAM induced flocculation of wood pulp fibers, which is in keeping with previous observations on sludge dewatering. The CD-polymer combinations that are the most effective for fiber flocculation are also those for which Dh Of the polymer is reduced the most. In situations where the CD compacts the c-PAM, the fiber network associated with the c-PAM is also compacted giving rise to a tighter floc. (C) 2009 Elsevier Inc. All rights reserved.