PAA-modified PVA twin-chain polymer networks with reaction–transport coupling for pH-responsive confined cleaning of fragile archaeological ceramics

PAA-modified PVA TC-PNs enable confined cleaning of fragile celadon glaze surfaces. • pH-responsive network hydration modulates interfacial acid transport. • Freeze-derived pore morphology influences solute migration. • Open-pore transport and Ca retention help limit secondary CaSO₄ precipitation. • Mechanical adaptability enables conformal contact with irregular ceramic surfaces. Confining reactive agents at fragile solid–liquid interfaces while regulating mass transport remains a central challenge in surface cleaning. Marine-recovered archaeological ceramics exemplify this problem because calcareous bio-concretions mechanically interlock with microcracked glazes vulnerable to uncontrolled solvent penetration. Here, we developed pH-responsive poly(acrylic acid) (PAA)-modified poly(vinyl alcohol) (PVA) twin-chain polymer network (TC-PN) hydrogels that couple interfacial reaction with pore-mediated transport. Freeze–thaw processing generated formulation-dependent porous morphologies, and citric acid enabled localized carbonate dissolution. SEM and FTIR analyses of pH-conditioned gels and wet-state mass measurements revealed pH-dependent carboxyl-group ionization and hydration， while low-field NMR identified composition-dependent water-proton relaxation environments. Results suggest that local PAA deprotonation and increased network hydration facilitate acid transport during CaCO 3 dissolution, whereas carbonate removal allows acid accumulation, which may lower interfacial pH and favor PAA reprotonation, thereby attenuating transport. Dye-front and directional-freezing experiments showed that freeze-derived morphology influenced solute transport. Alizarin Red S visualization supported migration of dissolved Ca species from the interface into the hydrogel. Formulations with more open and reticulated morphologies showed less extensive CaSO 4 -rich accumulation within the corrosion pits than the less interconnected reference formulation. Rheological and application tests demonstrated an elastic behavior ( G ′ > G ′ ′ ), reversible deformation, and conformal contact with curved, heterogeneous surfaces. On archaeological celadon, the TC-PN hydrogels removed calcareous bio-concretions, with no evident glaze alteration detected by either Raman spectroscopy or SEM–EDS within the examined regions. Integrating pH-responsive acid transport with pore-mediated migration and retention of dissolved Ca species therefore enables spatially confined cleaning of fragile heritage surfaces. Download: Download high-res image (356KB) Download: Download full-size image