Noncovalent Functionalization of SWNTs with Azobenzene-Containing Polymers: Solubility, Stability, and Enhancement of Photoresponsive Properties

Abstract

Azobenzene-derived photoactive polymers (P1-P3) containing pyrene pendants were designed and synthesized (M w ∼ 30 000) for the noncovalent functionalization of single-walled carbon nanotubes (SWNTs). P1-P3 were found to be highly effective for the solubilization of SWNTs in common organic solvents, resulting in hybrid materials with enhanced thermal stability. The solubilization process was mostly driven by the π-π stacking interactions of pyrene with SWNTs. It also brings the azobenzene chromophores to the vicinity of nanotube surface, thereby allowing the electronic interactions between them. In addition to that, stacking of the pyrene and subsequent wrapping of the polymer around CNT surface provides more volume for the photoisomerization of azobenzene. These effects eventually accelerate the kinetics of photoisomerization of azobenzene in the polymer-SWNT composite. The photoalignment property of the composite was also increased when compared to that of the parent polymer which was studied by means of photoinduced birefringence.

Catalysis with Gold Complexes Immobilised on Carbon Nanotubes by π–π Stacking Interactions: Heterogeneous Catalysis versus the Boomerang Effect

“…The non‐covalent modification of carbon nanotubes is of growing interest and different types of molecular structures can be immobilised onto CNTs, such as aromatic small molecules (pyrene, porphyrin and their derivatives), biomacromolecules (proteins, enzymes, DNA, (poly)saccharides, etc) and polymers. This strategy has been applied to various areas of interest, such as nanoelectronics, nanomaterials science, drug delivery and catalysis 12–15. We have chosen carbon nanotubes as a support for homogeneous catalysts for their potential to interact strongly with polyaromatics through non‐covalent π–π interactions.…”

Photobleaching effect in azo-dye containing epoxy resin films: the potentiality of carbon nanotubes as azo-dye dispensers

“…This suggests that the process to photoinduce birefringence is affected by the addition of MWCNTs. In particular, the change in the rate at which birefringence is photoinduced could be due to an increment in the steric hindrance introduced by the addition of MWCNTs [3]. The maximum levels of birefringence for all the measured cycles are plotted in Figure 3 for both kinds of films: DO3 films and DO3-MWCNTs films.…”

“…Particularly, the electronic structure of carbon nanotubes and azo-dye chromophores allows them to weakly interact via a non-covalent binding [1,2]. Among the many possible ways of working with carbon nanotubes and azo-dye chromophores, one alternative turns out from the addition of both carbon nanotubes and azo-dye molecules into a polymeric matrix [3,4]. As a result, this nanocomposite material can exhibit new properties given by the presence of the dye and the nanotubes.…”

Stabilization and functionalization of single‐walled carbon nanotubes with polyvinylpyrrolidone copolymers for applications in aqueous media

“…To address the issues of functionalization and solubility, we wanted to develop a robust polymer wrapping that would impart stability in aqueous environments, retain robust opto‐electric properties including IR fluorescence, and allow covalent surface functionalization with useful molecules. A variety of biopolymers and synthetic polymers have been used to solubilize SWNTs; of these we decided to explore polyvinylpyrrolidone (PVP) as a substitute for SDBS . PVP has excellent amphiphilic properties, is nontoxic, and is stable for long periods in aqueous environments.…”