Crosslinked DADMAC polymers as cationic super absorbents

Abstract

Abstract Loosely crosslinked cationic polyelectrolytes (polyquats) with super-water-sorption abilities are presented, for the first time. Hydrogels obtained by radically initiated copolymerization of N , N -diallyl, N , N -dimethyl ammonium chloride (DADMAC) with N -vinyl 2-pyrrolidone (NVP) in presence of N , N , N ′, N ′-tetraallyl piperazinium dichloride (TAP) as crosslinker showed reasonably high equilibrium swelling ratios, as high as those for poly(acrylic acid)-based super absorbents. The highest swelling ratios (up to 360) were attained by fully cationic hydrogels derived from DADMAC and 0.5% TAP. The hydrogels with 0.5–5% crosslinkers exhibited rapid expansion in neutral water, so that the equilibrium swelling values were attained within 2–3 min. The crosslinking densities of the gels were estimated by Flory-type swelling model using “phantom network elasticity” for the elastic contribution. This estimation revealed low crosslinking efficiencies of TAP (0.24–0.35) due to its double cationic charge. In the study “the salt effect” and effects of the comonomer ratios and crosslinker contents on the swellings were also investigated.