Modification of Rice Husk with Glycidyl Crosslined Microgel Latex for Preparation of Hybrid Hydrogel

Hypothesis: The main objective of this project was the development of a new method for converting natural polymers into hybrid hydrogels. The hybrid hydrogels are usually prepared through grafting of acrylic monomers onto pure polysaccharides, and this study was performed using rice husk to prepare semi-synthetic hybrid hydrogels.
Rice husk as a source of polysaccharide was modified with acrylic latexes that were prepared through inverse emulsion polymerization with the use of acrylic monomers such as acrylic acid, acrylamide and 2-acrylamido-2-methyl propane sulfonic acid. This process resulted in the conversion of low-value material into a value added semi-synthetic hydrogel product. Low absorbency under load (AUL) was the main weakness of hybrid hydrogels. The hybrid hydrogels were surface crosslinked through ethylene glycol diglycidyl ether (EGDGE) as surface crosslinker to improve AUL.
Findings: The effect of latex type on the swelling capacity of hybrid hydrogels was investigated. The chemical reaction between rice husk and acrylic latex was carried out in modification process of rice husk. The obtained semi-synthetic hydrogel constituted of 51% natural part and 49% synthetic part. Among the microgel latexes with different structures, the poly (NaAA-AA-AM-AMPS) was the most suitable polymer latex for the conversion of rice husk into hydrogel. The swelling of this hybrid hydrogel was 35.8 and 12.7g/g in distilled water and saline solution, respectively, whereas the unmodified rice husk showed no water absorption capability. AUL of surface crosslinked hybrid hydrogels was increased up to 27%. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). These hydrogels, which were prepared directly from natural polymers, showed great potentials in agricultural systems applications.