title: Synthesis and characterization of photochromic azobenzene cellulose ethers.
abstract: Photochromic azobenzene cellulose ethers were prepared by homogeneous etherification of cellulose with 2,3-epoxypropoxy-azobenzene (EA) in N,N-dimethylacetamide/lithium chloride solution. The EA with epoxy group could highly efficiently react with cellulose to synthesize 3-azobenzyloxy-2-hydroxypropyl-cellulose (Azo-cellulose) ethers with controllable degree of substitution (DS(azo)). The DS(azo) was in a range of 0.2-2.0 adjusted by the molar ratio of EA to anhydroglucose unit of cellulose. The Azo-celluloses with DS(azo)≥0.53 were soluble in aprotic solvents like dimethylsulfoxide. Their chemical structures and properties were characterized by elemental analysis, FT-IR, NMR, and thermogravimetric analysis. They showed reversible trans-cis-trans transition when Azo-cellulose/DMAc solutions were irradiated by successive irradiation of UV and visible light. The transition between trans- and cis- isomers could be effectively controlled by simply adjusting the irradiation time. The photo-stimulated trans-cis-trans conformational change induced conformation transition between rod-like shape of trans-isomer and skewed shape of cis-isomer.
authors.affiliation: Fujian Provincial Key Laboratory of Polymer Materials, College of Material Science and Engineering, Fujian Normal University, Fujian 350007, China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Li
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
authors.forename: Jiabao
authors.initials: J
authors.lastname: Weng
authors.forename: Biao
authors.initials: B
authors.lastname: Chen
authors.forename: Haiqing
authors.initials: H
authors.lastname: Liu
mesh_terms: D000081:Acetamides / Q000737:chemistry; D001391:Azo Compounds / Q000737:chemistry*; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects; D002482:Cellulose / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004987:Ethers; D018021:Lithium Chloride / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D055668:Photochemical Processes; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D013818:Thermogravimetry; D014466:Ultraviolet Rays
chemical_list: D000081:Acetamides; D001391:Azo Compounds; D001672:Biocompatible Materials; D004987:Ethers; D002482:Cellulose; C009850:azobenzene; D018021:Lithium Chloride; C013959:dimethylacetamide; D004121:Dimethyl Sulfoxide
keywords: Azo polymers; Cellulose; Photochemistry; Photochromic behavior