Polyacrylamide hydrogels for stone restoration: Effect of salt solutions on swelling/deswelling degree and dynamic correlation length

Hydrogels have prominent roles in many fields, being applied from the biomedical and pharmacological to engineering and chemical fields. Polyacrylamide (PAM) hydrogels with different crosslinking degree are synthesized and studied in this work by different analytical techniques. Swelling properties are characterized in water and in different aqueous salt solutions, and the results are correlated with the dynamic light scattering measurements of swollen hydrogels; it is demonstrated that gels are more swollen in salt solutions than in pure water. The dynamic correlation length in the swollen gel networks follows closely their mean linkage distance in accordance with De Gennes prescription. SEM observations show that the porous structure is associated with the variation of crosslinking agent amount. The cleaning process of artwork, in the cultural heritage field, can strongly benefit from the use of hydrogels. The desalting efficiency of the gel, when applied to salt contaminated stone surface for cleaning purpose, is tested and the ability of remove efflorescence is demonstrated.