Competing interactions in hierarchical porphyrin self-assembly introduce robustness in pathway complexity

Mathijs F.J. Mabesoone, Albert J. Markvoort, Motonori Banno, Tomoko Yamaguchi, Floris Helmich, Yuki Naito, Eiji Yashima, Anja R.A. Palmans, E.W. Meijer

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Abstract

Pathway complexity in supramolecular polymerization has recently sparked interest as a method to generate complex material behavior. The response of these systems relies on the existence of a metastable, kinetically trapped state. In this work, we show that strong switch-like behavior in supramolecular polymers can also be achieved through the introduction of competing aggregation pathways. This behavior is illustrated with the supramolecular polymerization of a porphyrin-based monomer at various concentrations, solvent compositions, and temperatures. It is found that the monomers aggregate via an isodesmic mechanism in weakly coupled J-type aggregates at intermediate solvent quality and temperature, followed by nucleated H-aggregates at lower solvent qualities and temperatures. At further increased thermodynamic driving forces, such as high concentration and low temperature, the H-aggregates can form hierarchical superhelices. Our mathematical models show that, contrary to a single-pathway polymerization, the existence of the isodesmic aggregation pathway buffers the free monomer pool and renders the nucleation of the H-aggregates insensitive to concentration changes in the limit of high concentrations. We also show that, at a given temperature or solvent quality, the thermodynamically stable aggregate morphology can be selected by controlling the remaining free external parameter. As a result, the judicious application of pathway complexity allows us to synthesize a diverse set of materials from only a single monomer. We envision that the engineering of competing pathways can increase the robustness in a wide variety of supramolecular polymer materials and lead to increasingly versatile applications.

Original languageEnglish
Pages (from-to)7810-7819
Number of pages10
JournalJournal of the American Chemical Society
Volume140
Issue number25
DOIs
Publication statusPublished - 27 Jun 2018

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