Hybrid Hydrogels for pH Indicator

Abstract

Hybrid hydrogels were prepared by copolymerization of 2-hydroxyethyl methacrylate and diallyldimethylammonium chloride mixed with alginate, bromothymol blue, and fume silica. The polymerization reaction occurred by free radical polymerization using potassium persulfate and N,N,N/, N/−tetramethyethylenediamine as a redox initiator and N,N/−methylenebisacrylamide as a crosslinker. The results showed that the hydrogels responded to pH and exhibited color change. The bromothymol blue ionization was the main reason for the color change of the hydrogels. Also, the alginate and fume silica incorporated in the hydrogels moved the color from light shade to dark shade. The alginate, fume silica, and diallyldimethylammonium chloride affected the swelling property of the hydrogels. The alginate and fume silica increased water absorption. However, the diallyldimethylammonium chloride decreased the swelling property. The hydrogel can be used as a sensor to detect acids or bases, such as urine, causing irritation in the elderly or bed-bound patients.