Temperature and pH responsive behaviours of CMC/AAc hydrogels prepared by electron beam irradiation

The temperature and pH-responsive characters of hydrogels prepared from aqueous solutions containing 4.2 and 25% (w/v) carboxymethyl cellulose (CMC) and acrylic acid (AAc), respectively under the effect of accelerated electrons was investigated. Even though the initial content of hydrogels solution is constant, the swelling in water and responsive characters were greatly dependent on electron beam irradiation dose. In this regard, the percentage swelling in water of the hydrogel prepared at 50 kGy is relatively higher than that prepared at 80 kGy. However, both hydrogels displayed super water absorbing behaviour at room temperature in the range of similar to 3500-4600%. The hydrogels exhibit a relatively low tendency to swell in methanol with respect to water, in which the overall swelling in water is similar to 12 times that in methanol. The deswelling of the hydrogels at 40 degrees C in water from the equilibrium swelling state at 25 degrees C showed a lower rate than the swelling process. The results showed that the CMC/AAc hydrogel prepared at 50 kGy has a temperature-response character within the temperature range 25 + 15 degrees C at any time of swelling, while the hydrogel prepared at 80 kGy, does not show this character within this range of temperature. While the swelling of CMC/AAc hydrogel prepared at 50 kGy was found to substantially increase with increasing pH values from 3 to 10, the hydrogel prepared at 80 kGy was found to display pH responsive character below and above 7. (c) 2005 Elsevier B.V. All rights reserved.