Abstract: Polyacrylic acid/activated carbon composite hydrogel(PAA/AC) was prepared by free radical solution polymerization of acrylic acid(AA) using ammonium persulfate as an initiator and N,N′-methylene-bis-acrylamide as a crosslinker in the presence of activated carbon. The equilibrium swelling degree and the dynamics of the gels swelling in distilled water, saline and buffer solutions with different pH were studied. The results showed that the activated carbon enhanced the swelling capacity of PAA gel effectively, the PAA/AC hydrogel exhibits higher equilibrium degree of swelling(SWeq) than PAA hydrogel over the range of pH investigated, and the SWeq of PAA/AC is about 303 and 60(g/g) in distilled water and saline, respectively, which is about 2.4 times higher than that of PAA hydrogel. The mechanism of the swelling was also discussed, and the results showed that the aggregated structure of the polymer chains might be destroyed by the intervention of the activated carbon, which caused a decrease in interactions among polymer chains and an increase in the swelling capacity of PAA/AC gel. The glass transition temperatures(Tg) and cross sectional morphologies of PAA and PAA/AC gels were measured by differential scanning calorimetry(DSC) and scanning electron microscope(SEM), respectively, and the results further proved a decrease in the interactions among polymer chains.

Key words: Activat carbon, Composite hydrogel, Equilibrium swelling degree, Swelling mechanism, Fick&, rsquo, s law