Mapping the energy landscape of a supramolecular system via time-resolved asymmetric-flow field flow fractionation

Abstract

The optimisation of the design and preparation of supramolecular systems for targeted functions requires a comprehensive understanding of the self-assembly energy landscape, including the full spectrum of its pathway complexity. We propose here a general strategy to map this energy landscape, involving the monitoring of the formation and evolution of structures generated during self-assembly. As a demonstration of its utility, we applied this approach to a self-assembling cyclic peptide–polymer conjugate system, where assembly is governed by the interplay between β-sheet hydrogen bonding and secondary hydrophobic interactions. Using asymmetric flow field-flow fractionation (AF4), we gained key thermodynamic insights into this system, showing that equilibrium is reached through the formation of nanotubular assemblies stabilized by hydrogen bonding. Moreover, the complexity of the assembly pathways was found to be directly influenced by both the molecular design and the preparation protocol. These factors critically determine whether the system follows the thermodynamically favoured H-bonding route or is diverted into a competing kinetic pathway dominated by the hydrophobic effect. The latter leads to the formation of metastable disordered aggregates, which delay or obstruct the emergence of well-defined nanotube structures due to the inherently slow disassembly dynamics of the system. We show that clarifying this three-way relationship between pathway, molecular design, and preparation method is a pivotal step towards regulating pathway selection and achieving precise control over the final outcome of supramolecular self-assembly.