title: Humidity responsive asymmetric free-standing multilayered film.
abstract: A humido-responsive free-standing film has been created using layer-by-layer assembly technique. Polyethylenimine (PEI) at high pH was assembled with poly(acrylic acid) (PAA) at low pH on a Teflon substrate to yield a micro-nanostructured surface that can be made superhydrophobic after being coated with a low surface energy compound. The resulting asymmetric free-standing film with one surface being superhydrophobic while the other is hydrophilic after detachment from the substrate can undergo reversible bending/unbending shape transitions when the environmental humidity is changed. The bending/unbending movement of the free-standing film can be ascribed to the different responses of these two surfaces to humidity.
authors.affiliation: MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Liyan
authors.initials: L
authors.lastname: Shen
authors.forename: Jinhong
authors.initials: J
authors.lastname: Fu
authors.forename: Ke
authors.initials: K
authors.lastname: Fu
authors.forename: Catherine
authors.initials: C
authors.lastname: Picart
authors.forename: Jian
authors.initials: J
authors.lastname: Ji
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D036103:Nanotechnology / Q000379:methods*; D011094:Polyethyleneimine / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011138:Polytetrafluoroethylene / Q000737:chemistry; D017155:Wettability
chemical_list: D000180:Acrylic Resins; D011108:Polymers; C006903:carbopol 940; D011138:Polytetrafluoroethylene; D011094:Polyethyleneimine