Mara Camaiti (Institute of Geosciences and Earth Resources, National Research Council, Florence)
The proposal concerns the synthesis of perfluorinated compounds and their use for the restoration of artworks. The perfluorinated compounds proposed are new compounds designed according to particular expected physical chemical properties and will be used for the restoration of easel paints and for the protection of stones materials.
We propose to synthesize two families of perfluoroethers compounds, based on our know-how and expertises and characterized by the presence of polar groups such as hydroxyls that can change interactions with supports and physical characteristics: - a first family, PFE glycosides, combines the hydrophily of bio-sourced carbohydrate moiety to the hydrophoby brought by the perfluorinated chain. We proposed to use a methodology already managed in the Group of Cergy-Pontoise and allowing obtaining stable C-glycosides derivatives. We anticipate that the fluorinated analogues could present particular properties for applications in cultural heritage topics. For now, we start the synthesis from D-glucose. β-D-C-glycosylic ketone was synthesized by condensation of pentan-2,4-dione with unprotected sugars in water. Then the ketone was acetylated with acetic anhydride. After that, we tried different methods to get the reductive amination product of the acetylated ketone. At the same time, we also started from the acetylated glucose, and got the fluorinated compound.
A second family is PFE hydroxylated oligoamides. Polyamides obtained from natural raw material will be used to obtain perfluoropolyether di- (PFD) or tri-amides (PFT) with different chemical-physical characteristics according to the choice of monomers. Stability and longterm performance durability of PFD-PFT treatments will be studied, by means of chemical, thermal and photo-oxidative ageing tests and field exposure tests.
Intérêts sociétaux et valorisation
Firsly, the protective performance of the new perfluoropolyether amides (PFD, PFT) will be determined performing a series of standard tests on some stone specimens with different chemical and mineralogical composition and physical properties. In particular, water repellence, vapor permeability, cohesive properties, penetration depth and chromatic features of coated stone will be tested and the results compared with those obtained when a commercial fluoroelastomer is applied as a reference material.
Stability and longterm performance durability of PFD-PFT treatments will be studied, by means of chemical, thermal and photo-oxidative ageing tests and field exposure tests. In our previous work, new adapted treatments based on the application of perfluropolyether diamides on damaged surfaces were proposed. Analyses were achieved by spectrocolorimetry and X-ray microtomography to monitor color changes and the treatment impact on micropores. It was tested on mock-ups samples and then real ancient paintings.