"Green" biocomposite Poly (vinyl alcohol)/starch cryogels as new advanced tools for the cleaning of artifacts

Gels made from synthetic polymers have improved the cleaning of artifacts, but there is the strong need to elaborate new systems through an all-green approach, developing materials with higher eco-compatibility while retaining optimal efficacy. Rice starch (RS) is a renewable biopolymer with high potential for formulating sustainable gels from composites with synthetic polymers, but its interaction with the latter in composite structures is poorly understood.

Poly (vinyl alcohol) (PVA) and RS were used to obtain biocomposite hydrogels through a robust and "green" freeze-thawing route. For the first time, extensive understanding of these composites was tackled by investigating their gel structure and rheological behavior. The cleaning effectiveness of the PVA/RS gels was assessed on soiled modern painting mock-ups, whose water-sensitiveness makes their cleaning too risky using traditional tools.

The composites behave as strong gels whose structure and viscoelastic response are controlled tuning the PVA/RS ratio. X-ray scattering and thermal analysis suggested the formation of hybrid PVA-RS links. Starch amylopectin likely acts as a porogen, while amylose forms hydrogen bonds with PVA. The gels adhere to rough paint layers and remove soil effectively without detectable residues. Overall, the PVA/RS composites are highly effective and provide a significant step forward in the formulation of eco-sustainable cleaning formulations.