Monomers Versus Prenucleation Clusters En Route toPolymorphism of Supramolecular Polymers

Abstract

Polymorphism in supramolecular polymers is strongly correlated with thepolymerization pathways underlying their formation. To effectively controlemerging polymorphs, a comprehensive understanding of nucleationpathways and mechanisms is essential. Herein, a coronene-dipeptideconjugate (Cr-o-FFOEt ) is introduced and its self-assembly into two differentstable 1D supramolecular polymorphs (Agg 1 and 2f ) is observed in the samesolvent composition (water/THF, 7:3 v/v) and same concentration at roomtemperature, following two competitive self-assembly pathways. Thedifference in the mode of solvent addition triggers the two self-assemblypathways. Furthermore, the isolated intermediate Agg 2i is found to transforminto Agg 1 or Agg 2f under controlled experimental conditions. Thesupramolecular aggregates of Cr-o-FFOEt are thoroughly examined with thehelp of optical, chiroptical, and morphological techniques to understand thesubtle difference in choosing the self-assembling pathways. The studiesreveal that the nanotube formation of Agg 1 follows a classicalnucleation-elongation supramolecular polymerization mechanism (involvingmonomers). In contrast, the helical fibers of Agg 2f are formed by theinvolvement of preorganized oligomers (nonclassical process). Theobservation highlights the underappreciated role of prenucleation clusters inpathway complexity and polymorphism of supramolecular 1D polymers.