Cellulose-based polymeric emulsifier stabilized poly(N-vinylcaprolactam) hydrogel with temperature and pH responsiveness

Abstract

N-vinylcaprolactam (NVCL) is a temperature-responsive monomer, which is widely used for preparing responsive hydrogels. However, poor water solubility of NVCL necessitates the use of emulsifiers for better dispersion. Hydrolyzed epoxy soybean oil-grafted hydroxyethyl cellulose (H-ESO-HEC) polymeric emulsifier has excellent emulsifying properties, and the carboxyl groups afford pH-responsiveness to the hydrogels. A novel temperature- and pH-responsive cellulose-based hydrogel was prepared by combining NVCL and H-ESO-HEC. The hydrogel morphology, thermal stability, and swelling capacity were characterized, and it was also used as a dual-responsive drug preservative carrier. Scanning electron microscopy and thermogravimetric analysis confirmed the porous structure and good thermal stability, respectively, of the hydrogel. The hydrogel displayed a temperature- and pH-dependent swelling behavior and improved swelling capacity. The swelling behavior agreed well with the Korsmeyer-Peppas model and Schott's second-order kinetic model. The dual-responsive hydrogel has significant potential in the drug delivery systems owing to its biocompatibility and temperature and pH sensitivity.