“Click” coupling between alkyne‐decorated multiwalled carbon nanotubes and reactive PDMA‐PNIPAM micelles

Abstract

Covalent functionalization of alkyne-decorated multiwalled carbon nanotubes (MWNTs) with a well-defined, azide-derivatized, thermoresponsive diblock copolymer, poly(N,N-dimethylacrylamide)-poly(N-isopropylacrylamide) (PDMA-PNI-PAM) was accomplished by the Cu(I)-catalyzed [3 þ 2] Huisgen cycloaddition. It was found that this reaction could simultaneously increase the molecular size and bonding density of grafted polymers when PDMA-PNIPAM micelles were employed in the coupling system. On the other hand, attachment of molecularly dissolved unimers of high-molecular weight onto the nanotube resulted in low-graft density. The block copolymer bearing azide groups at the PDMA end was prepared by reversible addition-fragmentation transfer polymerization, which formed micelles with a diameter of $40 nm at temperatures above its critical micelle temperature. Scanning electron microscopy was utilized to demonstrate that the coupling reaction was successfully carried out between copolymer micelles and alkyne-bearing MWNTs. FTIR spectroscopy was utilized to follow the introduction and consumption of alkyne groups on the MWNTs. Thermogravimetric analysis indicated that the functionalized MWNTs consisted of about 45% polymer. Transmission electron microscopy was utilized to image polymer-functionalized MWNTs, showing relatively uniform polymer coatings present on the surface of nanotubes. V

Cycloaddition Reactions: A Controlled Approach for Carbon Nanotube Functionalization

“…The reaction was achieved in an efficient manner under a variety of favorable conditions, producing organo-soluble polymer nanotubes conjugates. [54] The micelle size and transition temperature can be controlled through the NIPAAm block length. Multiple kinds of polymers have been grafted onto CNTs using a grafting to and grafting from approach by means of the Cu I -catalyzed Huisgen cycloaddition reaction.…”

“…[53] Azide-moietycontaining diblock copolymer composed of hydrophilic N,Ndimethylacrylamide (DMA) and smart N-isopropylacrylamide (NIPAAm) blocks were coupled with alkyne-moietyfunctionalized MWNTs by means of click coupling. [54] The micelle size and transition temperature can be controlled through the NIPAAm block length. Shape-memory polyurethane (PU) block-copolymer-grafted-SWNTs were prepared by coupling of an azide-moiety-containing PU with alkyne-moiety-decorated SWNTs.…”

“Clickable” polymers via a combination of RAFT polymerization and isocyanate chemistry

“…“Click” reactions, defined as high‐yielding reactions under benign conditions,10 have recently been the subject of concerted scientific attention and typically fall into five categories: the azide‐alkyne cycloaddition,11 the thiol‐ene,12 thiol‐yne,13 thiol‐icocyanate,14 and the RAFT‐hetero‐Diels‐Alder reactions 15. There have been numerous reports of the use of RAFT in conjunction with click chemistry as a route towards surface modification16–24 and while the azide‐alkyne click reaction has been the most employed click reaction by far, several groups have recently been studying isocyanate‐bearing moieties as ideal candidates for click reactions due to their ability to react quantitatively with alcohols, thiols, and amines under mild reaction conditions 14, 25–30. In these reactions, the isocyanate functionality is incorporated into the polymeric backbone either by homopolymerizing an isocyanate‐bearing monomer, or by copolymerizing it along with another monomer 14, 25, 28–38.…”

Preparation and self‐assembly of poly(diglycidyl maleate‐co‐stearyl methacrylate)

“…π–π stacking interactions usually occur between two relatively nonpolar aromatic rings having overlapping π orbitals. Pyrene‐functional precursors have been successfully prepared23–25 and attached onto aromatic macromolecules such as carbon nanotubes,26–30 graphene oxide,31,32 fullerene, and so forth 33. The modification of graphene using π–π stacking should have advantages over previous attachment strategies as the conjugated structure of graphene will be retained after modification.…”