title: Reversible Photoinduced Switching of Permeability in a Cast Non-Porous Film Comprising Azobenzene Liquid Crystalline Polymer.
abstract: Permeation characteristics of an azobenzene-containing liquid crystalline (LC) non-porous film are investigated using a metallic corrosion method. Thin films (300 nm) are fabricated by the solution casting of an azobenzene side-chain LC polymer on freshly polished carbon steel coupons. Coated coupons are treated under the following conditions: a) gradual annealing at a cooling rate lower than 1 °C · min(-1) from 150 °C (above its Tg ) to room temperature, and b) irradiation at 465 nm (20 mW · cm(-2) ) with either circularly polarized light (CPL) or non-polarized light (NPL). The morphology of these films is characterized using X-ray diffraction, polarized optical microscopy, and transmission measurements. The results suggest that the annealing treatment resulted in the formation of a polydomain structure consisting of locally ordered small smectic domains that lack mutual orientation. Ordered micro domains are surrounded by disordered phases. CPL and NPL irradiation generates a monodomain orientated structure and an isotropic liquid crystal glass, respectively. The permeability of these non-porous films treated by CPL, NPL, and annealing are found to be 6.14 × 10(-4) , 1.92 × 10(-2) , and 1.56 × 10(-3) cm(3)  · m(-2)  · d(-1) . An orientation-dependent structure model is constructed to explain the permeation phenomenon, considering the ordered phase is impermeable, only the disordered phase is accessible to penetrating molecules. Fast switching of gas permeation is demonstrated by alternative irradiation of the film with CPL and NPL, which results in an approximately 30-fold difference in the permeability of the non-porous film.
authors.affiliation: School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, P. R. China. jianliu@swust.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
authors.forename: Mingle
authors.initials: M
authors.lastname: Wang
authors.affiliation: State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
authors.forename: Mingling
authors.initials: M
authors.lastname: Dong
authors.affiliation: State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
authors.forename: Liude
authors.initials: L
authors.lastname: Gao
authors.affiliation: State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Tian
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D050866:Liquid Crystals; D008567:Membranes, Artificial; D010539:Permeability; D055668:Photochemical Processes; D011108:Polymers / Q000737:chemistry*; D016062:Porosity
chemical_list: D001391:Azo Compounds; D008567:Membranes, Artificial; D011108:Polymers; C009850:azobenzene