Effects of solvent treatments on characteristics of superporous hydrogels

Abstract

The synthesis of an acrylamide-based superporous hydrogels (SPHs) was carried out by solution polymerization. SPHs were submerged in one of the organic solvents: diethyl ether, acetone, absolute ethanol, or hexane for 48 h. The characterization studies were performed by measurement of apparent density, porosity, swelling, mechanical strength, and scanning electron microscopy (SEM). The swelling ratio was calculated based on the mass of SPHs in the swollen state and in the dried state. The penetration pressure of the SPHs was measured from the force required for complete fracture of SPH. SPHs showed porosities of more than 60%. In double distilled water SPHs showed tremendous increase in equilibrium swelling capacity. But, when the same SPHs were placed in artificial gastric fluid for swelling, they showed very low equilibrium swelling capacity. The solvent treated SPHs showed good swelling characteristics in both the swelling media compared to that of SPH without solvent treatment. When an artificial gastric fluid was used as a swelling medium, ethanol- and hexane-treated SPHs showed higher penetration pressure compared to SPH without solvent treatment, while diethyl ether- and acetone-treated SPHs showed less penetration pressure. SEM images clearly indicate the formation of interconnected pore and capillary channels. The characterization studies revealed that the SPHs treated with solvents showed remarkable effects on their characteristics compared to SPH without solvent treatment. The results of the present study provide background for the selection of solvent for SPH treatment to improve characteristics that will lead to modification of the available SPH-based gastric retention devices.

Keywords: superporous hydrogel, solvent, scanning electron microscopy, swelling, penetration pressure