Smart material from chitosan hydrogel containing barakol

Abstract

Some polymer hydrogels consisting of an elastic cross-linked network and fluid filling the interstitial spaces of the network can change their volume and shape reversibly in response to several external physiochemical factors and so-called Wintelligent or smart materialsW. However, they are often made of expensive materials or by a difficult process and desired properties such as responsiveness, reversibility and mechanical strength are still unsatisfactory. This thesis proposes a novel electric-sensitive polymer hydrogel prepared from chitosan, poly (acrylic acid), barakol and crosslinking agents. Its swelling behaviors were investigated by immersion of the hydrogel fims in NaCl aqueous solution and applying an electric field. Bending speed, bending angle and reversibility were among observed characteristics. The effects of several parameters including the ratio of the component materials, concentration of the surrounding solution and electric potential being applied were studied. In addition, the hydrogel films were characterized by Fourier transform infrared spectroscopy. Their thermal properties were characterized by differential scanning calorimetry (DSC). Their mechanical properties were characterized by testing tensile strength and elongation at break. The results showed that the performance of the proposed smart material was comparable to those in the literature for most key characteristics and better in terms of bending speed and reversibility. Since both chitosan and barakol can be extracted from natural organisms widely available in Thailand, the proposed smart material is cheaper and easier to prepare than those in the literature. The use in electric-sensitive polymer hydrogel is a novel application of barakol. Interestingly, the present of barakol significantly improved the bending speed of the hydrogel films. The most probable explanation is that barakol helped move sodium ions and chloride ions into the hydrogel films more easily and therefore increased the electric sensitivity.