Methacrylated gellan gum hydrogel: a smart tool to face complex problems in the cleaning of paper materials

One of the main challenges in the preservation of paper materials is the development of compatible and eco-friendly cleaning systems suitable for the wet removal of hydrophobic, aged compounds, such as greasy materials or synthetic adhesives, whose presence enhances paper degradation and worsens its optical features. To avoid the use of organic solvents that can be potentially harmful to operators, in this work we propose a new water-based gel obtained by chemical modification of gellan gum gel, a well-known paper cleaning hydrogel. With the aim of obtaining a cleaning system that is able to interact and adsorb not only hydrophilic cellulose degradation byproducts, but also greasy materials and synthetic adhesives, methacrylation has been applied on gellan gum. First, the chemical modification process of gellan gum has been monitored by means of NMR and ATR-FTIR spectroscopy. Then, the mechanical and physical-chemical properties of the resulting gel have been evaluated by using rheological, AFM, and wettability measurements. Finally, the compatibility and cleaning efficiency of the newly synthetized gel have been tested on paper with different age (from eighteenth and twentieth centuries) and composition by means of a multi-technique framework consisting of spectroscopic, chromatographic, SEM, colorimetric and pH measurements. This work shows a first interesting step towards the development of single component paper cleaning system, easy to use, for the removal of both cellulose hydrophilic degradation products and hydrophobic compounds from different paper typologies.