Synthesis of cellulose-based superabsorbent hydrogels by high-energy irradiation in the presence of crosslinking agent

• Cellulose derivative based hydrogels were prepared by radiation-induced crosslinking.
• N,N’-methylene-bis-acrylamide was used as a crosslinker to improve gel properties.
• The crosslinker improved the gel fraction at the expense of lower water uptake.
• The gelation occurred at milder conditions in the presence of crosslinking agent.
• The sensitivity to ionic strength decreased with the equilibrium water uptake.

Superabsorbent hydrogels were prepared from aqueous solutions of four cellulose derivatives (carboxymethylcellulose Na-salt – CMC, methylcellulose – MC, hydroxyethylcellulose – HEC and hydroxypropylcellulose – HPC) by gamma irradiation initiated crosslinking. CMC was used for the majority of the measurements. N,N’-methylene-bis-acrylamide (MBA) crosslinking agent was used to modify the gel properties. The crosslink density increased with the MBA concentration, leading to an improved gel fraction and lower water uptake. The crosslinking efficiency was the highest up to 1 w/wpolymer% MBA concentration. Very high MBA content (10 w/wpolymer%) led to a heterogeneous gel structure. Gelation also occurred under milder conditions in the presence of MBA: good gel properties were achieved at significantly lower doses and solute concentrations as compared to crosslinker-free solutions. The time required to reach maximum water uptake increased with the degree of swelling in equilibrium. Swelling properties of CMC gels with lower water uptake showed lower sensitivity to the ionic strength of the solvent.