Synthesis, characterization, and swelling behaviors of chitosan-g-poly (acrylic acid-co-acrylamide) superabsorbent using tetraallylammonium bromine as crosslinker

Here, copolymerization of acrylic acid (AA) and acrylamide (AM) onto chitosan (CTS) was performed using 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) as the initiator and tetraallylammonium bromine (TAAB) as the crosslinker. The structure of the superabsorbent was characterized via Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and atomic force microscopy. The reaction conditions were optimized by an orthogonal experiment, and the water absorbency in different solutions was investigated at 80 ℃. The optimal conditions for the preparation of P(AA-AM)/CTS were as follows: The mass ratios of AM to AA, CTS to AA, VA-044 to AA, TAAB to AA were 20, 7, 0.05, 0.18%, respectively. The superabsorbent showed excellent temperature resistance, and the swelling ratio reached 371.2 g/g in distilled water at 80 ℃. Next, the sensitivity of P(AA-AM)/CTS to various salt concentrations was measured and the results showed that P(AA-AM)/CTS was most sensitive to BaCl 2 , whereas KI had the least influence on water absorbency. Additionally, P(AA-AM)/CTS had different swelling capacities in various pH solutions. The gel showed excellent pH responsiveness; a pH reversible property was observed between pH 2 and 7 as well as pH 7 and 12.