Consolidation of waterlogged archaeological woods by reversibly cross-linked polymers

Abstract

Reversibly cross-linked polymer-based conservation materials for waterlogged archaeological woods with excellent dimensional stability, environmental stability and reversible removability are firstly fabricated through the penetration of 2-formylphenylboric acid-terminated low-molecular-weight polydimethylsiloxane (PDMS-PBA), followed by in-situ reversibly cross-linking PDMS chains with N-coordinated boroxines (NCBs). In-situ formed reversibly cross-linked conservation materials (denoted as PDMS-NCB) can improve the dimensional stability of archaeological woods. The shrinkage rate of the PDMS-NCB-consolidated archaeological wood is ∼ 1.5 % and its anti-shrinkage efficiency is ∼ 95.7 %, which surpass those of conventional polyethylene glycol-consolidated wood. Meanwhile, the stable cross-linking network of PDMS-NCB endows the consolidated wood with excellent humidity stability and thermostability. Even at a relative humidity of 100 %, the water uptake of the consolidated wood is only ∼ 15.5 %, which is 2.4 times less than that of the un-consolidated wood. More importantly, owing to the reversibility of NCB cross-linkers in ethanol, the cross-linked PDMS-NCB conservation materials in consolidated archaeological woods can be depolymerized into linear and soluble PDMS-PBA during ethanol rinsing and removed from the archaeological woods.