Synthesis and characterization of highly elastic superabsorbent natural rubber/polyacrylamide hydrogel

A hydrogel based on natural rubber (NR) was developed. NR was simultaneously incorporated within NR-graft-polyacrylamide (NR-g-PAM) hydrogel to form, via physical chain entanglement, a freely mobile secondary polymer network. A semi-interpenetrating polymer network (semi-IPN) was formed. The amount of NR in the hydrogel was varied from 0 wt% to 50 wt% to optimize both mechanical and physical properties. The water absorption capacity of a hydrogel with 30 wt% of NR (30NR) was 15,200%. The compressive modulus of 30NR was 106.5 kPa, 650% higher than that of a pure PAM hydrogel. The formation of the semi-IPN structure improved mechanical properties while maintaining the adsorption performances of the hydrogels. NR-g-PAM hydrogels at all NR contents adsorbed cationic and anionic azo dyes. 30NR removed 90% of methylene blue (MB) from aqueous solution in less than 24 h with a maximum adsorption capacity of 538.3 mg g(-1). Fitting the experimental data from 30NR to theoretical adsorption isotherms and the results of thermodynamic study indicated a monolayer adsorption of MB on a homogeneous surface via physisorption and the adsorption process was endothermic. This hydrogel showed reusability for MB removal, with efficiency as high as 70% on the 10th cycle. The NR-g-PAM hydrogels were photodegradable upon exposure to heat, UV light, and moisture. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A hydrogel based on natural rubber was developed and optimized by varying the NR content, showing improved mechanical and adsorption properties for dye removal. The formation of semi-IPN structure enhanced the performance of the hydrogel, making it suitable for the removal of methylene blue.