Mastrangelo Rosangela, Chelazzi David, Baglioni Piero
Department of Chemistry and CSGI, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, FI 50019, Italy.
Nanoscale Horiz. 2024 Mar 25;9(4):566-579. doi: 10.1039/d3nh00383c.
Nanomaterials have permeated numerous scientific and technological fields, and have gained growing importance over the past decades also in the preservation of Cultural Heritage. After a critical overview of the main nanomaterials adopted in art preservation, we provide new insights into some highly relevant gels, which constitute valuable tools to selectively remove dirt or other unwanted layers from the surface of works of art. In particular, the recent "twin-chain" gels, obtained by phase separation of two different PVAs and freeze-thawing, were considered as the most performing gel systems for the cleaning of Cultural Heritage. Three factors are crucial in determining the final gel properties, , pore size, pore connectivity, and surface roughness, which belong to the micro/nanodomain. The pore size is affected by the molecular weight of the phase-separating PVA polymer, while pore connectivity and tortuosity likely depend on interconnections formed during gelation. Tortuosity greatly impacts on cleaning capability, as the removal of matter at the gel-target interface increases with the uploaded fluid's residence time at the interface (higher tortuosity produces longer residence). The gels' surface roughness, adaptability and stickiness can also be controlled by modulating the porogen amount or adding different polymers to PVA. Finally, PVA can be partially replaced with different biopolymers yielding gels with enhanced sustainability and effective cleaning capability, where the selection of the biopolymer affects the gel porosity and effectiveness. These results shed new light on the effect of micro/nanoscale features on the cleaning performances of "twin-chain" and composite gels, opening new horizons for advanced and "green"/sustainable gel materials that can impact on fields even beyond art preservation, like drug-delivery, detergency, food industry, cosmetics and tissue engineering.
纳米材料已渗透到众多科技领域，在过去几十年里，其在文化遗产保护方面也日益重要。在对艺术保护中采用的主要纳米材料进行批判性综述之后，我们对一些高度相关的凝胶提供了新的见解，这些凝胶是从艺术品表面选择性去除污垢或其他不需要的层的宝贵工具。特别是，最近通过两种不同聚乙烯醇（PVA）的相分离和冻融获得的“双链”凝胶，被认为是用于文化遗产清洁的性能最佳的凝胶体系。在确定最终凝胶性能方面，有三个因素至关重要，即孔径、孔连通性和表面粗糙度，它们属于微/纳米域。孔径受相分离PVA聚合物分子量的影响，而孔连通性和曲折度可能取决于凝胶化过程中形成的互连。曲折度对清洁能力有很大影响，因为凝胶 - 目标界面处物质的去除随着上传流体在界面处的停留时间增加而增加（更高的曲折度产生更长的停留时间）。凝胶的表面粗糙度、适应性和粘性也可以通过调节致孔剂的量或向PVA中添加不同的聚合物来控制。最后，PVA可以部分被不同的生物聚合物替代，从而产生具有更高可持续性和有效清洁能力的凝胶，其中生物聚合物的选择会影响凝胶的孔隙率和有效性。这些结果为微/纳米尺度特征对“双链”和复合凝胶清洁性能的影响提供了新的思路，为先进的“绿色”/可持续凝胶材料开辟了新的前景，这些材料甚至可以影响艺术保护之外的领域，如药物递送、去污、食品工业、化妆品和组织工程。
