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Poly(azobenzene acrylate-co-fluorinated acrylate) Spin-Coated Films: Influence of the Composition on the Photo-Controlled Wettability

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journal contribution
posted on 30.07.2013, 00:00 by Sanae Abrakhi, Sébastien Péralta, Odile Fichet, Dominique Teyssié, Sophie Cantin
The wetting properties of spin-coated films of copolymers based on azobenzene and fluorinated units have been investigated. The copolymers, denoted as poly­(Azo-co-AcRf6), have been synthesized by free-radical polymerization of different proportions of acrylate monomers bearing either an azobenzene group or a semifluorinated side chain. The UV–visible spectroscopy analysis of the different spin-coating films through a cycle of UV and visible light irradiation indicates the reversible transcis isomerization of azobenzene groups. Simultaneously, atomic force microscopy shows that surface roughness does not exceed 1 nm. Advancing and receding contact angles of water and diiodomethane have been measured before and after UV photoirradiation of the different surfaces. In particular, a decrease in the advancing contact angles has been observed upon transcis isomerization of azobenzene groups. Switching variations up to 50° have been evidenced without any introduction of surface nanoroughness. Surface free-energy evaluations have been deduced from these measurements, including dispersive and polar components. The results show that, through surface composition and UV photoirradiation, a large range of surface free-energies can be obtained, from 7 to 46 mN·m–1.