Multi-analytical and computational approaches to the study of hydrogen bonding interactions in N-methoxymethyl Nylon 6,6

This research explores the change in hydrogen bonding interactions between Nylon 6,6 and soluble Nylon 6,6 (N-methoxymethyl Nylon 6,6) polymer materials that were originally synthesized in the early 1940s. This substitution resulted in increased solubility in strong acids (for Nylon 6,6), to solubility in aliphatic alcohols (N-methoxymethyl Nylon 6,6). Soluble nylon (N-methoxymethyl Nylon 6,6) was most commonly used in the art conservation field as a consolidant for artwork but is no longer used due to photooxidation back to insoluble Nylon 6,6. This work encompasses synthesizing the N-methoxymethyl Nylon 6,6, and studying various changes via FTIR, Raman, DSC, and TGA-IR analyses. The changes in the FTIR and Raman spectra were computationally modeled using the Gaussian program (Gaussian 16). IR and Raman spectra were computed with varying N-alkoxymethyl substitution using computationally optimized structures to visualize IR and Raman active vibrations. Donated N-methoxymethyl Nylon 6,6 (referred to as Calaton CB) from the Department of Conservation, Winterthur Museum, Garden and Library (dated 1970) and commercial Nylon 6,6 were used as the two comparisons in this study with the Nylon 6,6 being the starting material and the donated Calaton CB being the desired N-methoxymethyl Nylon 6,6 product. Changes in thermal transition temperatures and enthalpies of nylon 6,6, Calaton CB, and synthesized soluble nylon materials were found using DSC. Decomposition products were analyzed via TGA with FTIR for evolved gas analysis to confirm N-methoxymethyl substitution in synthesized materials. To further study changes in hydrogen bonding interactions, via temperature dependent Raman analysis (TDRA), a thermal cell was used to heat the material close to the melting temperature. This would result in reduction or even disappearance of peaks in the Raman spectra where hydrogen bonding interactions would be observed. Samples donated from the Department of Conservation, Philadelphia Museum of Art of soluble nylon coating from a Japanese painted cedarwood door (Sugito), dated to the 16th-17th Century, were analyzed with FTIR (FPA and ATR) to compare against Nylon 6,6, Calaton CB, and synthesized soluble nylon 6,6. This study shows the change in hydrogen bonding interactions when N-methoxymethyl substitution is present in these polymer materials.M.S.Includes bibliographical reference