Collaborative Research: Structure and Dynamics of Metal Soap Aggregates at the Pigment/Binder Interface. A Multinuclear Solid-State NMR Study

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With support from the Chemical Measurement and Imaging program in the Division of Chemistry, Dr. Silvia Centeno of the Metropolitan Museum of Art in New York City and Prof. Cecil Dybowski of the University of Delaware, will study the mechanism of aggregation of lead carboxylates (lead soaps) in oil paintings. Aggregation of lead carboxylates in oil paintings is known to lead to the formation of protrusions and paint loss in most cases, and to increased transparency of the paint films in others, resulting in damage to the integrity of the artworks. While widely observed, the phenomenon is not well understood. The collaborating investigators, their students and postdoctoral trainees will determine the structure, molecular dynamics, and phase behavior of lead carboxylates using solid state 13C,207Pb magic-angle-spinning (MAS) nuclear magnetic resonance (NMR), 1H-207Pb and 13C-207Pb dipolar re-coupling experiments, and deuterium NMR along with other analytical tools. They will elucidate the mechanism of aggregate formation/migration and based on the results, recommend procedures to arrest the deterioration process of oil paintings.The solid state NMR experiments have the potential to transform the field of cultural heritage science since they will provide molecular information, which is not currently available to the cultural heritage science community. The experiments are a gateway to the application of emerging minimally invasive NMR methods like micro-MAS NMR to study cultural heritage objects. Advancing the state of the art for 207Pb solid-state NMR also has broader implications for understanding the structure of lead-containing electronic and optoelectronic materials, high-Tc superconducting materials, and the speciation and reaction of lead in environmentally contaminated materials. The project will provide excellent training opportunities to students and postdoctoral researchers who wish to train in state of the art solid state NMR methods and cultural heritage science. Results of this study will be widely disseminated to the public through museum programs and publications.