A facile route to obtain an acidic hydrogel containing lactate moieties

The idea to develop hydrophilic lactic acid-based polyelectrolyte was presented. A facile route was utilized to prepare smart hydrogels that contained lactate units and carboxylic groups. The hydrogels were obtained through the radical cross-linking reaction between an unsaturated lactate-contained macromonomer and acrylic acid (AA)/itaconic acid (IA) monomer pair. The structure and performances of the hydrogels were characterized with thermogravimetric analysis, dynamic thermal analysis, scanning electron microscopy, swelling tests and adsorption measurements. The equilibrium swelling ratios of the hydrogels in acidic (pH 3.6) and basic (pH 11.5) media reached 25.3 and 62.3 respectively. The pH-sensitive swelling behaviors of the hydrogel confirmed that the hydrogels contained carboxylic groups and they were hydrophilic. The metal ions including calcium, copper, lead and cerium ions were bound into the hydrogels, which also confirmed the existence of the carboxyl groups. Moreover, the swelling ratio and adsorption capacity of the gel prepared from monomer pair were significantly higher than those obtained in absence of IA, which suggested that the properties of the hydrogels could be controllable by simply adjusting the ratio of AA/IA. In addition, the weight loss percentage of the hydrogel was around 37% after two-week in vitro degradation, which indicated the hydrogel contained lactate units.