Innovative Hydrogels Based
on Semi-Interpenetrating
p(HEMA)/PVP Networks for the Cleaning of Water-Sensitive Cultural
Heritage Artifacts
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Abstract
Water-based detergent systems offer several advantages,
over organic
solvents, for the cleaning of cultural heritage artifacts in terms
of selectivity and gentle removal of grime materials or aged varnish,
which are known to alter the readability of the painting. Unfortunately,
easel paintings present specific characteristics that make the usage
of water-based systems invasive. The interaction of water with wood
or canvas support favors mechanical stresses between the substrate
and the paint layers leading to the detachment of the pictorial layer.
In order to avoid painting loss and to ensure a fine control (layer
by layer) of grime removal, water-based cleaning systems have been
confined into innovative chemical hydrogels, specifically designed
for cleaning water-sensitive cultural heritage artifacts. The synthesized
hydrogels are based on semi-interpenetrating chemical poly(2-hydroxyethyl
methacrylate)/poly(vinylpyrrolidone) networks with suitable hydrophilicity,
water retention properties, and required mechanical strength to avoid
residues after the cleaning treatment. Three different compositions
were selected. Water retention and release properties have been studied
by quantifying the amount of free and bound water (from differential
scanning calorimetry); mesoporosity was obtained from scanning electron
microscopy; microstructure from small angle X-ray scattering. To demonstrate
both the efficiency and versatility of the selected hydrogels in confining
and modulating the properties of cleaning systems, a representative
case study is presented