Amphiphilic functionalized nanocellulose coatings for the protection of water sensitive paintings

• Grant number: 23/10673-4
• Support Opportunities: Scholarships in Brazil - Support Program for Fixating Young Doctors
• Effective date (Start): August 01, 2023
• Effective date (End): June 30, 2025
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Acordo de Cooperação: CNPq
• Principal Investigator: Camila Alves de Rezende
• Grantee: Laura Caetano Escobar da Silva
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 23/01620-4 - Sustainable technologies for the artwork conservation based on cellulose and lignin nanomaterials, AP.R

Abstract

Paintings on canvas, documents, books and pictures are cellulose-based artifacts that might reach invaluable historical and cultural value. The conservation of cellulosic material is essential to ensure the preservation and public access to this material heritage. One of the main forms of preserving cultural artifacts is the application of varnishes, which create a superficial protective coating that prevents cellulose ageing and degradation due to humidity, light exposure, and other weather-related phenomena. Amongst the main requisites for paints and varnishes used in the preservation of historical objects, the transparency, the adhesion to cellulosic materials' surface and the moist resistance are the most relevant. In some cases, it is also important to guarantee that the protective coating is easily removable, either mechanically or by means of a solvent, to allow the relic restoration. Varnishes commonly used to this end are based on synthetic polymer resins, which require toxic solvents to their application and/or removal, imposing major health and fire hazard to the cultural heritage conservation units and their workers. To overcome this limitation, aqueous nanocellulose and nanolignin suspensions were previously developed on our research group and showed promising results as removable atoxic coatings for cellulosic substrates. Even though sustainable, these water-based varnishes find limited applications for water-sensitive relics such as gouache and watercolour paintings. Therefore, in this research proposal it is intended to investigate strategies to substitute water partially or totally for other atoxic solvents, such as isopropyl alcohol or tetrahydrofuran, without affecting the nanocellulose dispersibility or the protective capacity of the resulting cellulose nanocrystal or cellulose nanofibril coatings. In order to preserve the protective properties of the coating it is essential to ensure the retainment of the supramolecular structuring of the nanocellulose. To do so, two different strategies will be used, either alone or combined, and consist of the sequential solvent exchange and the surface modification of the cellulose nanomaterials through acetylation or silanization. The resulting suspensions will be characterized in terms of nanostructure and applied on paper prototypes for colorimetric analyses, ageing and protective capacity evaluation.