Synthesis, swelling and responsive properties of a new composite hydrogel based on hydroxyethyl cellulose and medicinal stone

In this study, a series of pH- and saline-responsive composite hydrogels were prepared by a facile free-radical graft copolymerization amongst hydroxyethyl cellulose (HEC), sodium acrylate (NaA) and medicinal stone (MS). Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric/Differential thermal analysis (TG/DTA) confirmed NaA was grafted onto HEC and MS participate in polymerization, and presented the improved thermal stability. Field emission scanning electron micro-scope (FESEM). Energy dispersive spectroscopy (EDS), Elemental map (EM) and Transmission electron microscopy (TEM) analyses revealed a better distribution of MS in the HEC-g-PNaA matrix. Introducing 10 wt% MS greatly enhanced the swelling capacity by 400% (from 162 to 810 g/g), and also enhanced by 117% (from 162 to 352 g/g) even MS content reached 50 wt%. Also, the initial swelling rate was improved by incorporating MS, but decreased with enhancing the ion strength. The highly reversible On-Off switching pH- and saline-responsive region of the hydrogel was clearly extended after forming composite. In addition, the intriguing "overflowing" swelling behaviour was observed in aqueous solution of dimethyl sulfoxide (DMSO). (C) 2011 Elsevier Ltd. All rights reserved.