Controlled Polymerization of Norbornene Cycloparaphenylenes Expands Carbon Nanomaterials Design Space.

Ruth L Maust,Ramesh Jasti,Lev N Zakharov,Baihao Shao,Peiguan B Sun,Harrison W Reid,Penghao Li,Matthew R Golder,Sarah M Zeitler

doi:10.1021/acscentsci.1c00345

Ruth L Maust, Ramesh Jasti + Show 7 more

Open Access

https://doi.org/10.1021/acscentsci.1c00345

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Abstract

Carbon-based materials—such as graphene nanoribbons, fullerenes, and carbon nanotubes—elicit significant excitement due to their wide-ranging properties and many possible applications. However, the lack of methods for precise synthesis, functionalization, and assembly of complex carbon materials has hindered efforts to define structure–property relationships and develop new carbon materials with unique properties. To overcome this challenge, we employed a combination of bottom-up organic synthesis and controlled polymer synthesis. We designed norbornene-functionalized cycloparaphenylenes (CPPs), a family of macrocycles that map onto armchair carbon nanotubes of varying diameters. Through ring-opening metathesis polymerization, we accessed homopolymers as well as block and statistical copolymers constructed from “carbon nanohoops” with a high degree of structural control. These soluble, sp2-carbon-dense polymers exhibit tunable fluorescence emission and supramolecular responses based on composition and sequence. This work represents an important advance toward bridging the gap between small molecules and functional carbon-based materials.

Highlights

The versatility of carbon nanomaterials makes them extremely useful. From graphitic structures such as carbon nanotubes and fullerenes, which have become indispensable in electronics,1,2 to carbon quantum dots with tunable fluorescence,3 carbon materials have emerged as promising candidates for a wide range of applications
Significant progress has been made in synthesizing molecular nanocarbons with new geometries, functionalities, and properties,4−6 as well as employing polymer chemistry as a means to access useful carbon-based materials.7−11 Major challenges remain, ; the majority of syntheses of extended carbon structures rely on lengthy synthetic sequences often impeded by substrate insolubility, tedious purification steps, and low yields or uncontrolled, stepgrowth polymerization methods
Polymerization (ROMP) as a route that would not present unwanted modes of reactivity with CPPs, which can undergo strain-relieving reactions not seen in linear aromatic molecules

Summary

■ INTRODUCTION

The versatility of carbon nanomaterials makes them extremely useful. Significant progress has been made in synthesizing molecular nanocarbons with new geometries, functionalities, and properties,− as well as employing polymer chemistry as a means to access useful carbon-based materials.− Major challenges remain, ; the majority of syntheses of extended carbon structures rely on lengthy synthetic sequences often impeded by substrate insolubility, tedious purification steps, and low yields or uncontrolled, stepgrowth polymerization methods. Notwithstanding notable exceptions,− the connectivities and functionalities accessible via well-controlled methods remain limited. To address these challenges, we envisioned that a family of oligomeric nanocarbons cycloparaphenylenes could serve as the basis for constructing larger, structurally-defined carbon materials using controlled polymerization.

■ RESULTS AND DISCUSSION

■ CONCLUSIONS AND OUTLOOK

■ ACKNOWLEDGMENTS

■ REFERENCES