Tailoring Properties of Carbon Nanotube Dispersions and Nanocomposites Using Temperature-Responsive Copolymers of Pyrene-Modified Poly(N-cyclopropylacrylamide)

Abstract

Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Stimuli-responsive polymers show conformational changes with an applied external stimulus (pH, temperature, light, etc.). The dispersion of carbon nanotubes by thermoresponsive polymers is shown to enable the macroscopic properties of aqueous suspensions to be tailored as a function of temperature. This work presents the synthesis, characterization, and use of temperature-responsive poly(N-cyclopropylacrylamide) (PNCPA) polymers containing 1, 3, and 5 mol % pyrene-bearing repeat units to tailor the dispersion state of single-walled carbon nanotubes (SWNT) in water. Turbidity measurements show that the lower critical solution temperature (LCST) of PNCPA decreases with increasing pyrene content. Viscosity measurements on aqueous SWNT suspensions stabilized with pyrene-functionalized PNCPA show highly entangled and well-dispersed nanotube microstructure above and below the LCST of the polymer, respectively. UV-vis spectra also confirm that nanotube stabilization by these polymers is dependent upon the pyrene content. Drying of these suspensions produces composites whose microstructure and electrical conductivity vary with drying temperature and pyrene content of the stabilizing polymer. This temperature-dependent dispersion behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems.

Solid state self-assembly of the single-walled carbon nanotubes and poly(γ-benzyl-l -glutamate)s with different conformations

“…Noncovalent modification of CNTs by physical absorption of polymers or surfactants on the CNTs surface can enhance their dispersion while keeping the electrical and mechanical properties of CNTs intact. One of the common noncovalent modification methods is the use of pyrene moieties . Pyrenyl groups have demonstrated strong interaction with the CNTs surface via π–π stacking.…”

Synthesis and characterization of pyrene bearing amphiphilic miktoarm star polymer and its noncovalent interactions with multiwalled carbon nanotubes

“…One attractive method reported by Dai and coworkers7 to overcome this problem is the physical introduction of a functional group on the surface of nanotubes by means of strong “π–π” stacking interactions, thus not only improving the solubility but also preserving nearly all intrinsic properties of CNT's could be attained. Therefore, the noncovalent attachment of aromatic moieties to the nanotube surface has been widely investigated, using conjugated polymers49–55 as well as the polymers containing polynuclear aromatic moiety such as pyrene,56–70 napthalene,71 and porphyrin 72…”

A latent reactive handle for functionalising heparin-like and LMWH deca- and dodecasaccharides

“…Carboxylate 3 was utilised to evaluate model attachment of two fluorescent units, 4 19 and 5 , 20 which contained differing length C2 or C6, diaminoalkyl linker units, offering a divergent access to fluorescently tagged d -GlcN building blocks 6 and 7 ( Scheme 2 ). Coupling of 4 or 5 with 3 using standard amide bond forming reagents afforded the fluoro-tagged d -GlcN derivatives 6 and 7 , respectively.…”

“…Carboxylic acid 3 (69 mg, 0.13 mmol), N -(6-aminohexyl)-4-(pyren-4-yl)butanamide hydrochloride 5 20 (66 mg, 0.16 mmol), TBTU (41 mg, 0.13 mmol) and DIPEA (34 μL, 0.19 mmol) were dissolved in anhydrous DMF (4 mL) under nitrogen and the reaction stirred for 44 h whereupon it was shown to be complete by TLC analysis (EtOAc/Hex, 4 : 1). The reaction solution was diluted with diethyl ether (20 mL) and washed with water (7 × 20 mL).…”