Abstract
Chitosan-Ammonium dichromate polymer(CT-AD) was prepared and irradiated by UV light with a high pressure mercury lamp. It was found that CT-AD polymer, having crosslinking structure, undergoes a photodecomposition reaction. Owing to the photodecomposition reaction the solubility differential of the polymer is readily obtained. After development the soluble parts of the polymer were washed out and positive image was obtained. Characteristic curves of CT-AD polymer were made and showed in Fig. 1. These curves indicate that the more the incident energy of UV light was irradiated on the polymer, the more the soluble parts of the polymer were obtained. The influence of the content of AD in the film on the photosensitivity of the film was displayed in Fig. 2. Soluble parts of CT-AD polymer which were obtained after UV exposure decrease when AD content in the film increases. Thickness of the film is an important factor which influences the development process. In oder to investigate the mechanism of the photodecomposition reaction, UV irradiation of CT-AD polymer in HAc water solution was carried out for different periods of time and after irradiation the UV spectra (Fig.4) and the electric conducvivity (Fig.5) of the solutions were measured. The ammonium dichromate solution was also irradiated by UV light at the same time, it exhibits the absorption at 250, 350, 400nm, when the pH<7 (Fig.3). The UV spectrum of the CT-AD polymer in olution indicates that the absorption peaks shift from 266.2 to 250, 360.2 to 350nm, which are in accord with the absorption peaks of UV spectrum of the AD solution at pH<7. The enhanced electric conductivity proves the transition of dichromate ions to the solution. The mechanism of photodecomposition of CT-AD polymer is dependent initially on the transition of chromium from a high to low state of oxidation, followed by a decomposition of CT-AD polymer.
