Interactions Between Polyethyleneimine Xerogels and Acetic Acid Vapor from Degraded Cellulose Acetate. A Novel Therapy for Motion Picture Films Affected by the “Vinegar Syndrome”

Motion picture films made of cellulose acetate (CA) are subjected to degradation mainly due to the "vinegar syndrome". The goal of this study is to investigate the absorption of acetic acid vapor by some polyethyleneimine (PEI) xerogels, aim at developing innovative, inexpensive, reusable, and easy-to-produce and handle chemical inhibitors for the "vinegar syndrome". PEI-based xerogels (SPEI) are obtained through cryo-polymerization via epoxy-amine reaction between PEI and 1,4-Butanediol di-glycidyl ether (BDDE). The intent is to enhance the absorption of the acetic acid vapor by the porous and high-specific surface area network of the obtained PEI xerogel, allowing its neutralization through the free amino groups present in the gel. A chemical-physical, morphological, and rheological characterization of the SPEIs is performed and their behavior in the absorption and desorption of acetic acid is also studied. The efficacy of the SPEI in inhibiting the "vinegar syndrome" is evaluated on both CA-based real motion picture films, on which the deacetylation process is artificially and naturally induced. The characterization of degraded CA films stored with and without the inhibitor is evaluated using an already validated multi-analytical protocol. The excellent results achieved open interesting perspectives for the conservation of these 20th-century cultural heritage objects.