Preparation of poly(oxanorbornene) based single and double-folding polymers via nucleophilic aromatic substitution reaction

A facile approach is introduced to prepare single-chain nanoparticles (SCNPs) utilizing intramolecular crosslinking based on nucleophilic aromatic substitution reaction. The linear polymeric precursor comprising dichlorotriazine (DCT) moiety as a reactive pendant group is synthesized via ring-opening metathesis polymerization (ROMP). The reactive chlorine atoms on DCT motifs are substituted with a dithiol nucleophile in varying degrees to yield individually intramolecularly crosslinked polymer nanoparticles. In addition, double-collapse and modification reactions are exploited through the substitution reaction from the remaining unreacted chlorine atoms. A significant reduction in hydrodynamic volumes of the corresponding SCNPs is observed compared to their linear analogues. The obtained nanoparticles are characterized by size exclusion chromatography (SEC), proton nuclear magnetic resonance spectroscopy (¹H NMR), diffusion-ordered spectroscopy (DOSY), dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques.