Developing
methodologies that can efficiently decorate carbon nanotube
surfaces with various molecular structures while avoiding damage to
nanotube optoelectronic properties is an ongoing challenge. Here,
we outline a methodology to perform chemistry on the nanotube surface
without perturbing optoelectronic properties. Reactive, noncovalently
functionalized polymer–nanotube complexes were prepared using
polyfluorene with azide groups in its side chains. The azides enable
strain-promoted azide–alkyne cycloaddition to occur between
polymer–nanotube complexes and small molecules or polymers
derivatized with a strained cyclooctyne. This reaction was found to
occur efficiently at room temperature, without any catalyst or byproduct
removal required. The reaction was monitored by infrared spectroscopy
via the disappearance of the polymer azide stretch at ∼2090
cm–1, and this chemistry resulted in no damage to
the nanotube sidewall, as evidenced by Raman spectroscopy. The azide-containing
polyfluorene was used to prepare an enriched dispersion of semiconducting
carbon nanotubes in organic media, which could then be redispersed
in aqueous solution post-click with strained cyclooctyne-functionalized
poly(ethylene glycol). Taking advantage of the ability to preserve
optoelectronic properties, solvatochromism of an identical subset
of semiconducting carbon nanotubes was investigated using absorption,
fluorescence, and Raman spectroscopy. It was found that, in aqueous
media, fluorescence was nonuniformly quenched among the different
semiconducting species and that there was a significant red-shift
in the emission of all nanotubes in D2O relative to nonpolar
toluene.