Controlled Polymerization of Norbornene Cycloparaphenylenes Expands Carbon Nanomaterials Design Space

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.