Water‐soluble acrylamide copolymers. X. Flocculation efficiencies of poly[acrylamide‐co‐N,N‐dimethylacrylamide], poly[acrylamide‐co‐methacrylamide], poly[acrylamide‐co‐N‐t‐butylacrylamide], and their cationic derivatives

A hydrated, 1% by weight Na‐kaolinite suspension in deionized water was prepared, completely characterized, and reproducible measures of flocculation efficiency were validated. Flocculation tests of copolymers of acrylamide (AM) with dimethylacrylamide (DMA), methacrylamide (MeAM), or N‐t‐butylacrylamide (NTBAM) with 1% Na‐kaolinite suspensions gave average settling rate rates which decreased as the proportion of DMA, MeAM, or NTBAM in the copolymer increased. However, for a similar weight‐average molecular weight and slightly lower 〈r_g〉, the copolymer from DMA‐co‐AM‐3 gave settling rates and supernatant turbidities comparable to similar types of commercial polymers. This new copolymer was also more resistant to changes in pH or the presence of an electrolyte than were the tested commercial polymers. Cationic derivatives of the new copolymers gave lower average settling rates and higher supernatant turbidities than those of Percol 721 (cationic PAM), probably because of their lower charge densities. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2090–2108, 2002; DOI 10.1002/app.10562