Tailoring the properties of castor oil polyurethanes organogels with green oligoesters

Castor oil (CO) can react with isocyanate to form polyurethane organogels, whose hydrophobicity can be regulated by functionalization with “green” oligoesters of bio-dicarboxylic acids. Here, we elucidated the gelation mechanism induced by the oligoesters to gain control of the gels’ mechanical properties and solvent confinement capacity. This can be useful in cleaning Cultural Heritage items, a socioeconomically important application, and other scientific/technological sectors. During gelation, the oligoesters react with isocyanate to form aggregates whose compatibility with CO is regulated by the oligoesters’ hydrophobicity. This allows fine control of gelation time and of the gels’ micro- and nanostructure structure, where the presence of oligoesters in solid-like regions regulates rheological behaviour and mechanical resistance. The gels’ solvent upload capacity also depends on the oligoesters’ hydrophobicity, which can favour chain relaxation over Fickian diffusion during swelling. Finally, the swollen organogels were used to remove organic varnishes/coatings from painted wood and glass, demonstrating potential as sustainable cleaning tools for works of art.