Sanae Abrakhi

Université de Cergy-Pontoise, 95001 CEDEX, Ile-de-France, France

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Publications (3)9.62 Total impact

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    ABSTRACT: 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 semi-fluorinated 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 trans-cis isomerization of the azobenzene groups. Simultaneously, Atomic Force Microscopy shows that surface roughness doesn't 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 of the advancing contact angles has been observed upon trans-cis 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.
    No preview · Article · Jun 2013 · Langmuir
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    ABSTRACT: Monolayers of a cellulosic polymer bearing cinnamate groups were characterized at the air-water interface by combining isotherm measurements, Brewster angle microscopy, and infrared-visible sum-frequency generation (SFG) spectroscopy. This spectroscopic technique was used to detect the photochemical behavior of the cinnamate groups upon UV photoirradiation of the monolayers. From the disappearance of the C═C mode and the absence of a change in the C═O mode, it could be concluded that isomerization is the dominant photoreaction for a monolayer of this polymer. This conclusion was corroborated by a comparison of the spectra of the monolayer after irradiation with spectra measured for monolayers spread from preirradiated solutions, for which it is known that isomerization is the main process.
    No preview · Article · May 2012 · The Journal of Physical Chemistry B
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    ABSTRACT: The photochemical behavior of photosensitive materials obtained by spin-coating or network synthesis of a cellulosic polymer bearing photo-cross-linkable cinnamate groups was investigated. First, cinnamate groups were grafted on a cellulose acetate butyrate polymer, with different grafting densities. The photochemical properties of the polymers were studied in solution by UV–visible and 1H NMR spectroscopy. Then spin-coated films and networks were prepared and characterized as a function of the number of cinnamate groups per cellulosic unit. The water-wetting properties of both surfaces were studied by dynamic contact angle measurements, before and after photoirradiation, and subsequent heating. The surfaces obtained by the two methods have significantly different behaviors that can be assigned to the distinct photochemical pathways of the cinnamate groups upon irradiation depending on the sample preparation. Indeed, dimerization reaction is evidenced as the main process in the spin-coated films while the expected isomerization is predominant at the surface of the polymer networks.
    No preview · Article · Mar 2011 · Colloid and Polymer Science