Folding versus Self‐Assembling

TLDR

The authors synthesized foldable polymers containing rigid hydrophobic chromophores and flexible hydrophilic tetra(ethylene glycol) segments to study molecular folding and self‑assembly, hypothesizing that inter‑unit interactions governed by the distance R drive these processes. Each polymer unit generates a force field that increases interaction probability when another unit enters it, with an estimated force‑field radius of 90–120 Å for the perylene tetracarboxylic diimide chromophore. In the 1 µM–0.1 M concentration range, intramolecular folding dominates over self‑assembly, yielding polymeric nanostructures with distinct absorption and fluorescence properties that arise when the force‑field conditions are met.

Abstract

Abstract Model foldable polymers with sequences of rigid hydrophobic chromophores and flexible hydrophilic tetra(ethylene glycol) were synthesized and used as a paradigm for studying molecular‐folding and self‐assembly phenomena. Our results demonstrate that intramolecular association or folding prevails over intermolecular interaction or self‐assembling in the concentration region from 1 μ M to 0.1 M . Importantly, folded polymeric nanostructures have absorption and fluorescence properties that are distinct from those of unfolded polymers or free monomers. We hypothesize that the origins of folding and self‐assembly come from interactions between molecular units, and that the key parameter that regulates the on‐and‐off of such interactions is the distance R separating the two molecular units. Each molecular unit produces a characteristic force field, and when another molecular unit enters this field, the probability that the two units will interact increases significantly. A preliminary estimate of the radius of such a force field for the perylene tetracarboxylic diimide chromophore is about 90–120 Å. As a result, phenomena associated with folding or self‐assembly of molecular species are observed when these conditions are met in solution.