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.

Decorating hydrophobic carbon nanotube surfaces efficiently in aqueous solution without adversely affecting nanotube optoelectronic properties remains a challenge. In this work, we designed a water-soluble polyfluorene derivative that contains azide groups and polyethylene glycol grafts in the side chains. This polyfluorene derivative was used to coat carbon nanotube surfaces, producing a latently reactive and aqueous-dispersible polymer−nanotube complex. Reaction progress of the aqueous polymer−nanotube dispersion with various polar and nonpolar alkyne derivatives was followed using infrared spectroscopy. Decoration of the polymer−nanotube complex with various small molecules or polymers was found to modulate the surface properties of the resulting nanohybrid thin films. Additionally, we developed a vanillin-derived indolinooxazolidine switch that is functionalized with a terminal alkyne and appended it to the polymer−nanotube complex. This switch possesses two long-lived states that are interchangeable via exposure to acidic or basic conditions. We studied the fluorescence emission response of the polymer−nanotube complex using UV−vis−NIR and fluorescence spectroscopy. The acidochromic switch linked to the polymer−nanotube complex enables control over nanotube emission, while the free switch in solution does not. Photoluminescence mapping reveals a nanotube species-dependent fluorescence quenching response to charge buildup at the nanotube surface.

Previous approaches used to decorate latently reactive conjugated polymer-coated carbon nanotube complexes have utilized "grafting-to" strategies. Here, we coat the carbon nanotube surface with a conjugated polymer whose side chains contain the radical initiator, α-bromoisobutyrate, which enables atom transfer radical polymerization (ATRP) from the polymernanotube surface. Using light to generate Cu(I) in situ, ATRP is used to grow narrow dispersity polymer chains from the polymer-nanotube surface. We confirm the successful polymerization of (meth)acrylates from the polymer-nanotube surface using a combination of gel permeation chromatography and infrared spectroscopy. Strikingly, we demonstrate that nanotube optoelectronic properties are preserved after radical-mediated polymer grafting using Raman spectroscopy and photoluminescence mapping. Overall, this work elucidates a method to grow narrow dispersity polymer chains from the polymernanotube surface using light-driven radical chemistry, with concurrent preservation of nanotube optoelectronic properties.We first explored conditions for light-driven ATRP using methyl methacrylate (MMA). While there are several options available to generate Cu(I) in situ to improve oxygen tolerance Additional supporting information may be found in the online version of this article.