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.