One-shot preparation of topologically chimeric nanofibers via a gradient supramolecular copolymerization

Yuichi Kitamoto,Tomonori Ohba,Nobutaka Shimizu,Deepak D Prabhu,Rie Haruki,Shiki Yagai,Atsushi Isobe,Shin-Ichi Adachi,Hideaki Takagi,Ziyan Pan

doi:10.1038/s41467-019-12654-z

Yuichi Kitamoto, Tomonori Ohba + Show 8 more

Open Access

https://doi.org/10.1038/s41467-019-12654-z

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Abstract

Supramolecular polymers have emerged in the last decade as highly accessible polymeric nanomaterials. An important step toward finely designed nanomaterials with versatile functions, such as those of natural proteins, is intricate topological control over their main chains. Herein, we report the facile one-shot preparation of supramolecular copolymers involving segregated secondary structures. By cooling non-polar solutions containing two monomers that individually afford helically folded and linearly extended secondary structures, we obtain unique nanofibers with coexisting distinct secondary structures. A spectroscopic analysis of the formation process of such topologically chimeric fibers reveals that the monomer composition varies gradually during the polymerization due to the formation of heteromeric hydrogen-bonded intermediates. We further demonstrate the folding of these chimeric fibers by light-induced deformation of the linearly extended segments.

Highlights

Supramolecular polymers have emerged in the last decade as highly accessible polymeric nanomaterials
We find that the interplay of these two supramolecular recognition events can be controlled kinetically, leading to a gradient supramolecular copolymerization, where the monomer composition varies gradually along the main chain
The helical folding is due to the specific π–π stacking arrangement of the sixmembered hydrogen-bonded rosettes[38,39,40] with rotational and translational offsets, which generates an intrinsic curvature in the main chain with a curvature radius of ca. 13 nm (Fig. 2c)[41,42,43]

Summary

Introduction

Supramolecular polymers have emerged in the last decade as highly accessible polymeric nanomaterials. We report the one-shot synthesis of topologically chimeric supramolecular copolymers that are comprised of distinct secondary-structure segments (Fig. 1b) This unique polymeric material is developed by the temperature-controlled supramolecular copolymerization of two different aromatic (naphthalene and anthracene) monomers, which individually afford supramolecular polymers with entirely different secondary structures, i.e., helically folded and linearly extended arrangements, despite their similar molecular structures. These monomers carry the same hydrogen-bonding heterocycle (barbiturate), which allows them to assemble into supermacrocycles (rosettes) that are capable of polymerizing primarily via π–π stacking interactions (Fig. 1c). We report the temperature-induced preparation of nanofiber topologies that comprise helically folded and linearly extended segments

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Results

Conclusion