MECHANICAL AND OPTO - ELECTRICAL CHARACTERIZATION OF CHITOSAN - A MARINE BASED BIOMATERIAL

Abstract

Mechanical, electrical and optical properties of chitosan thin films extracted from the squid gladius found along the coastal areas of Kilifi and Mombasa were investigated in this study. The films were prepared by the solution cast technique. The room temperature ionic conductivity of the film was measured by the two electrodes conductivity measurement technique and was found to be ca.1525μScm − 1. DMA analysis showed two dynamic processes; the beta relaxation process which generally seemed to increase with frequency and chitosan concentration and the alpha relaxation process (Tg). The temperature range between these two transitions (30 - 120oC ) gave an insight of the operating temperature range of the biomaterial. Arrhenius plots gave the activation energy of the biomaterial at ca.259kJ/mol which increased with chitosan concentration. Structural characteristics of the sample were discussed on the basis of the DMA, AFM, X-ray, infrared and NMR analysis data. DMA results showed that the material under investigation is viscoelastic with very low mechanical damping which means its rigidity and resistance to deformation is very high. X-ray diffraction indicated the molecular form at two strongest peaks; 2θ ≈ 10.5o and 2θ ≈19.8o with minor reflections at 2 '6o and 2θ ≈35o and crystalline structure with an index of ca:66%. A DDA value of ca:75% was obtained from the integral values of proton NMR. Optical properties obtained from the UV vis absorbance spectra gave the optical density of the material at about 0.8, the absorption coefficient of ca.2.909 and the band gap of ca.2.75eV. The refractive index of the chitosan thin films was determined by the real and apparent depth method using a traveling microscope. To determine the relaxation time and frequency, the permittivity of the material was plotted as a function of frequency and gave a value of ca:1:58μs. Measured value indicates the dielectric loss decreases with increasing frequency and temperature. The activation plot confirms that the relaxation processes follow the Arrhenius law and gave the activation energy of the squid pen gladius at ca.54.7kJ/mole. Key Words: Tapping mode AFM, Deacetylation, Biomaterial, Cantilever.