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

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 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 trans-cis 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 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).

Reversible Control of Surface Wettability of Polyimides Having Azobenzene Group on Their Side-chain by UV-Vis Light Irradiation

“…In this paper, the authors have firstly investigated reversible control of surface wettability of polyimides having azobenzene group on their side-chain by UVVis light irradiation. It is previously reported that the reversible trans-cis isomerization of azobenzene groups through UV-Vis irradiation is accompanied by fast and large changes in both geometry dipole moment [18,19], and this fact is expected to affect the reversible wettability change (Fig. 1).…”

Toward efficient water/oil separation material: Effect of copolymer composition on pH‐responsive wettability and separation performance

“…[1][2][3] One such smart material is the stimuliresponsive polymeric surface with tunable wettability under different external conditions, 4 such as pH, 5-8 electric potential, 9,10 light, [11][12][13][14] temperature, [15][16][17][18] and gas. 19 This feature enables the material to have applications in many areas, including controlled release platform, 20 ion pump, 21 and water/oil separation.…”

“…Compared with the polymer grafting, functional polymer coating that can be used directly would be more attractive in industrial fields because of its simple implementation process. [12][13][14][15] More recently, Yuan and Luo et al fabricated two types of smart fiber membranes by depositing pH-responsive copolymer fibers on a stainless steel mesh (SSM) through electrospinning for controllable oily water separation. 19,24 Poly(acrylic acid) (PAA) is a typical pH-sensitive hydrophilic polymer with pKa 5 4.7.…”

Nanoindentation of Films of Perfluorotridecyl, Perfluorodecyl, and Perfluoroheptyl End‐Functionalized Polystyrene at the Micron Scale

“…Their tendency toward self‐assembly and low‐surface free energies also makes them promising components in photoresponsive materials …”