Pillar[5]arene-based self-assembled linear supramolecular polymer driven by guest halogen-halogen interactions in solid and solution states

A pillar[5]arene-based linear supramolecular polymer mediated by guest halogen-halogen interactions (C-Br⋯Br-C) was studied in both the solution and solid states. The structure of the solid-state supramolecular assembly was determined by single crystal X-ray analysis. The binding affinity was investigated by ¹H NMR titration and isothermal titration calorimetry (ITC). The formation of the halogen-bonded linear supramolecular polymer in solution was demonstrated by ¹H NMR spectroscopy, diffusion ordered spectroscopy (DOSY), ITC, and dynamic light scattering measurements. From the ITC dilution experiments, we found that the supramolecular polymer dissociation process is mainly entropically driven (TΔS = 27.12 kJ mol^-1) and enthalpically disfavored (ΔH = 9.99 kJ mol^-1). The morphology of the linear polymer-like structures was characterized by atomic force microscopy, scanning electron microscopy, and transmission electron microscopy measurements.