Self assembled systems and gels for the conservation of cultural heritage

Piero Baglioni (University of Florence, Italy)

New perspectives have been opened by the application of colloids, and in particular of self-assembling systems and nanoparticles, to Conservation, generating a breakthrough in the development of innovative tools for the conservation and preservation of cultural heritage. This contribution is an overview of the most recent methodologies developed in the Conservation field, focusing on amphiphilic systems, and gels. I will report on two recently developed systems and on their application for the cleaning of works of art:

i) the characterization of two systems, EAPC and XYL, which have shown good to optimal performances in the removal of organic polymers from wall paintings. EAPC is a five-components fluid composed of water, sodium dodecylsulfate (SDS), 1-pentanol (PeOH), propylene carbonate (PC), and ethyl acetate (EA), while XYL is a “ classical ” o/w microemulsion where p-xylene droplets are stabilized in water by SDS and PeOH. Small-angle neutron scattering (SANS) with contrast variation is used to infer a detailed picture of the structure of these complex fluids. We found that the composition and the structure at the nanoscale determine the capability of removing a broad range of different polymer coatings from porous materials.

ii) an innovative hydrogel based on semi-interpenetrating poly(2-hydroxyethyl methacrylate)/polyvinylpyrrolidone networks with suitable hydrophilicity, water retention properties, and required mechanical strength to avoid residues after the cleaning the works of art. This family of gels is able to confine water or water based complex fluid, and has outstanding cleaning capacity for water-sensitive works of art, and in particular for watercolor paintings that are extremely difficult to clean with conventional methods.

References 1) Giorgi, R.; Baglioni, M.; Berti, D.; Baglioni, P. New Methodologies for the Conservation of Cultural Heritage: Micellar Solutions, Microemulsions, and Hydroxide Nanoparticles. Acc. Chem. Res. 2010, 43, 695– 704. 2) Baglioni, M.; Rengstl, D.; Berti, D.; Bonini, M.; Giorgi, R.; Baglioni, P. Removal of acrylic coatings from works of art by means of nanofluids: understanding the mechanism at the nanoscale. Nanoscale 2010, 2, 1723– 1732. 3) Baglioni, M.; Giorgi, R.; Berti, D.; Baglioni, P. Smart cleaning of cultural heritage: a new challenge for soft nanoscience. Nanoscale 2012, 4, 42– 53. 4) Baglioni, M.; Berti, D.; Teixeira, J.; Giorgi, R.; Baglioni, P. Nanostructured Surfactant-Based Systems for the Removal of Polymers from Wall Paintings: a SANS Study. Langmuir, 2012, 28, 15193– 15202. 5) Carretti, E.; Fratini, E.; Berti, D.; Dei, L.; Baglioni, P. Nanoscience for Art Conservation: Oil-in-Water Microemulsions Embedded in a Polymeric Network for the Cleaning of Works of Art. Angew. Chem. Int. Ed. 2009, 48, 8966?8969.

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