Synthesis And Characterization Of Azobenzene Hydroxypropyl Cellulose With Photochromic Property

Cellulose is the most abundant natural polymer which is renewable, has good mechanical strength, biocompatibility and biodegradation properties. Its extensive applications can alleviate the problems of increasing scarcity of fossil resources and pollution of petroleum products. Hydroxypropyl-cellulose (HPC) is a kind of important cellulose derivatives. Compared to cellulose, HPC shows good solubility in some common solvents including water, while maintains film-forming property, environmental friendliness and biodegradability, making it a better starting material for the preparation of some functional cellulose materials. In this work, azo-HPC was synthesized in HPC/N,N-Dimethylacetamide (DMAc) solution under mild conditions. This thesis includes following two aspects:(1) Three different azobenzene including hydroxy azobenzene (PA),4-(2,3-epoxypropoxy) azobenzene (OA) and4-(2-bromo-ethoxy) azobenzene (BA) were synthesized. azo-HPCa and azo-HPCb were homogeneously prepared in HPC/DMAc/O A solution and HPC/THF/BA solution, respectively. The structure of PA, OA, BA, and azo-HPC were characterized by NMR, FTIR, and Element analysis. The thermal properties of OA, BA, and azo-HPC were characterized by TG and DSC. The results showed that the glass transition of azo-HPC is obviously observed in20-50℃, and the thermal stability of azo-HPC is better than that of OA and BA.(2) The photochromic property of PA, OA, and azo-HPC in DMAc was investigated by UV-Vis test. The result showed that strong and weak absorption peaks of PA, OA, and azo-HPC appear at300-400nm and400-500nm, respectively. They showed reversible trans-cis-trans transition when their solutions were irradiated by successive irradiation of UV and visible light. Dynamic test showed that the degree of conversion linearly changed with time at the initial ultraviolet irradiation, while the conversion rate was slow at the later process. In addition, the results showed that azo-HPC/DMAc solution had a faster dark recovery rate and smaller energy loss.