Preparation, swelling and electro-mechano-chemical behaviors of a gelatin–chitosan blend membrane

Abstract

Swelling, states of water, morphology, stability in the aqueous solution, and electro-mechano-chemical bending behaviors of the gelatin–chitosan blend system were studied in order to clarify the potential use of this blend system as an actuator. The gelatin–chitosan blend system was prepared in order to avoid dissolution of the pure chitosan in an aqueous medium and the rigidity and easy degradation of the pure gelatin in the swollen state. The blend systems showed improved material properties: the vacuum-dried blend sample at the G75/C25 (w/w, gelatin–chitosan) ratio showed ∼6 times swelling (in distilled water, at neutral pH and room temperature), ∼5 times stability (in distilled water), and ∼6 times bending (at 6 V/53 mm and in a 0.02 M NaCl aqueous solution) as compared to pure gelatin. These enhanced properties could be explained by the introduction of free –OH, –NH₂, and –NHOCOCH₃groups of the amorphous chitosan in the blend and the network structure through the electrostatic interactions between the ammonium (–NH₃⁺) ions of the chitosan and the carboxylate (–COO⁻) ions of the gelatin. The scanning electron microscopy (SEM) micrographs of the surfaces of the blend films showed homogeneous and smooth surfaces due to the good miscibility between gelatin and chitosan. However, a different morphology from the fractured surface was found between the pure gelatin and blend systems which showed condensed and foliaceous morphologies, respectively. The leafy morphology indicates a large and homogeneous pore structure, which would cause increased ion diffusion into the gel and might lead to increased bending.