Covalent Attachment and Detachment by Reactive DESI of Sequence-Coded Polymer Taggants

The use of sequence-defined polymers is an interesting emerging solution for materials identification and traceability. Indeed, a very large amount of identification sequences can be created using a limited alphabet of coded monomers. However, in all reported studies, sequence-defined taggants are usually included in a host material by noncovalent adsorption or entrapment, which may lead to leakage, aggregation, or degradation. To avoid these problems, sequence-defined polymers are covalently attached in the present work to the mesh of model materials, namely acrylamide hydrogels. To do so, sequence-coded polyurethanes containing a disulfide linker and a terminal methacrylamide moiety are synthesized by stepwise solid-phase synthesis. These methacrylamide macromonomers are afterward copolymerized with acrylamide and bisacrylamide in order to achieve cross-linked hydrogels containing covalently-bound polyurethane taggants. It is shown herein that these taggants can be selectively detached from the hydrogel mesh by reactive desorption electrospray ionization. Using dithiothreitol the disulfide linker that links the taggant to the gel can be selectively cleaved. Ultimately, the released taggants can be decoded by tandem mass spectrometry.