Unraveling the forming mechanism of hierarchical helices via self-assembly of an achiral supramolecular polymer brush

Abstract

Developing supramolecular helical assemblies with a controlled helix sense and revealing the forming mechanism of hierarchical helices for mimicking biological self-organization and physiological processes remain major challenges. In this work, a bottlebrush-like supramolecular polymer is prepared through the formation of a hydrogen bond between the keto group of polyvinylpyrrolidone (PVP) and the phenolic hydroxyl group of p-dodecylphenol (PDP), characterized by ¹H NMR and FT-IR spectroscopy. CD spectra show an unsplit Cotton effect, suggesting the emergence of a helical structure in this supramolecular polymer brush (PVP–PDP). In particular, straightforward experimental evidence for the formation of hierarchical helices is obtained via TEM and AFM methods. We propose a detailed structural transition of the hierarchical helix or superhelix of PVP–PDP from primary to secondary, tertiary and even quaternary structures, resulting from the incorporation of bulky pendant PDP into the PVP backbone and the binding site of the hydrogen bond at ortho-position.