Thermal-Induced Transformation of Polydopamine Structures: An Efficient Route for the Stabilization of the Polydopamine Surfaces

This work brings a new insight into the structural transformation and stabilization of polydopamine (PDA) surfaces induced by thermal treatment. Taking advantage of the isotopic enrichment, 15N CP/MAS NMR experiments produce significant signal enhancements for PDA, allowing detection of a range of nitrogen structural unitsthe reaction products of the conversion of NH3+ units of 15N-dopamine center dot HCl. In addition, 1H-15N cross-polarization polarization-inversion profiles measured for each of the detected 15N NMR signals and 1H-15N FSLG HETCOR NMR spectra allow revisions and extensions to be made in a structural elucidation of PDA. Combining the NMR data thermogravimetric analyses and an FTIR analysis, several competitive processes that occur during the thermal conversion of dopamine are identified.