During the cleaning of certain objects, art conservators must remove selectively an organic solvent-soluble coating without disturbing a water-soluble layer below. Organogels can serve as a valuable tool for these types of cleaning procedures by controlling the placement of solvent (i.e. preventing seeping to deeper layers) while also minimizing the dissolution of water-soluble components. To this end, stable organogels have been formed from 40% hydrolyzed poly(vinyl acetate) (40PVAc) and benzene-1,4-diboronic acid (BDBA) without the addition of any water. The liquids gelled successfully by the system include dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, 2-ethoxyethanol, and methanol. Rheological measurements showed that these materials are soft gels. Reacting 40PVAc with phenylboronic acid, a molecule incapable of forming covalent crosslinks between two 40PVAc chains, did not lead to the formation of a gel, indicating that the gel network depends on the formation of boronate ester crosslinks from BDBA (Figure 1). Additional insights into the processes leading to the gels were obtained from <sup>1</sup>H NMR experiments, fluorescence measurements, and studies comparing properties of materials. To highlight the applicability of these types of materials, a 2-ethoxyethanol organogel was used to remove oxidized varnish from a statue coated with painted gold leaf.

Organogels from partially hydrolyzed poly(vinyl acetate) and benzene-1,4-diboronic acid for cleaning water-sensitive surfaces

254th National Meeting (2017)

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