The overall goal of this procedure is to offer a straightforward strategy for grafting multiwalled carbon nanotubes by polystyrene chains, which mediates a pro-molecular self-assembly and anisotropic patchiness. This method can help to modulate the surface properties of multiwalled carbon nanotubes, so as to establish improved processing conditions of the same in the field of thermoplastic polymers. The grafting strategy offers a straightforward alternative in processing protocols for carbon nanotubes in order to compatibilize them with industrially relevant, yet challenging polymers, such as polystyrene.
In general, the method starts with the traditional hydroxyl groups on the side walls of pristine carbon nanotubes followed by the coupling of silylated methacrylic moieties to the OH groups, and their sequential free radical polymerization with styrene on the inner atmosphere. To find the yield, nanotubes grafted with polystyrene chains. The main advantage of this technique is that it can be easily deployed to mole surface properties of carbon nanotubes.
And consequently, promote their anisotropic self assembly, which in turn may facilitate their inclusion in a polymer matrix. This technique opens promising alternatives to improve the supply chain of nanostructure carbon nanotropes in industrial processes, thus allowing for the creation of electrical percolation networks in polymer composites, which could find direct applications in electromagnetic shielding systems, mechanically reinforced parts, and electrically conducting materials under attractive cost-benefit conditions. Dry to 5 grams of pristine multi-walled carbon nanotubes, by introducing them into a vacuum oven at 80 Celsius degrees and 200 millimeters of mercury for 12 hours.
Pour the dried carbon nanotubes into a 100 milliliter round-bottom flask. Afterwards, transfer 50 milliliters of dichloromethane, 99 percent, into the flask, and set the mechanical stirring at 60 rpm. This will be the organic phase of a bi-faceted chotilitically mediated reaction.
In order to prepare the aqueous phase, dissolve 0.6 grams of tetroaropyl ammonium bromide in five milliliters of distilled water. Add five milliliters of acetic acid and five milliliters of an aqueous solution, containing potassium permanganate, 0.16 molar. Pour the latter solution into the round-bottom flask, already containing the organic phase and agitate vigorously, for example, about 80 rpm at room temperature for 24 hours.
After that time, transfer the reaction mixture into a separatory funnel. Then, agrigate around 0.25 milliliters of concentrated hydrochloric acid, 36 percent, and carefully agitate the system and purge. Then, discard the supernatant aqueous phase.
Once the aqueous phase was retired, the organic phase can be filtered using a vacuum filtration system as it is further described. Set this topper on base firmly into the neck of the filtered flask. With the small-tip forceps, center out 47 millimeter diameter membrane filter on the support surface.
Make sure to use a membrane with a pore size between 0.45 micrometers and 20 micrometers. Smaller pore sizes will easily block, while larger pore sizes will retain lower amounts of filtered nanotubes. Without disturbing the filter, center the flange of the holder on top of the assembly and lock the funnel and base together with a spring clamp.
Connect the filtering flask to the vacuum source, pour the sample into the funnel, and apply vacuum to filter the sample. Once the filter solid looks to be dried, wash with methanol 95 percent for at least five times the volume of the filtered solution. Afterward, transfer the solute into a petri dish and let it dry under vacuum for 24 hours at 80 Celsius degrees, at 200 millimeters of mercury.
In order to insert polymerizable methacrylic moieties into the hydroxilated carbon nanotube walls, disperse about 2.5 grams of the nanotubes and five grams of hydrochinoin 99 percent, using a 100 milliliters schlenk flask. Then, with the aid of a cannula, carefully add 50 milliliters of Toluene under nitrogen atmosphere, using a vacuum inner gas manifold. Later, put it under vigorous mechanical agitation.
Then, incorporate five milliliters of 3-thremethyl silane propel methacrylate 98 percent, and take it to reflux at 100 Celsius degrees for 12 hours. Once the reaction is complete, wash the obtained product with methanol in excess, using the vacuum filtration system and dry it overnight under vacuum at 80 Celsius degrees and 200 millimeters of mercury and store until needed. In order to graft the methacrylic modified nanotubes with acetoground polystyrene chains, disperse about 2.5 grams of the modified carbon nanotubes and 75 milligrams of AIBN in 50 milliliters of toluene.
Using a shlenk flask, improach the system with nitrogen atmosphere, using the vacuum inner gas manifold. Then, add freshly purified 7.5 milliliters of styrene monomer. AIBN will act as the initiator of the free-radical polymerization.
Subsequently, set the heating system at 70 Celsius degrees and stir it for 12 hours, under nitrogen atmosphere and reflux. Afterwards, filter the reaction mixture using the vacuum filtration system. Wash it with acetone, and finally wash it again with DHF 99 percent for at least five times to remove unbound polystyrene.
Dry the product under vacuum for 24 hours at 80 Celsius degrees and 200 millimeters of mercury. The solid will contain carbon nanotubes grafted with polystyrene chains. The polymer grafted carbon nanotubes were characterized by TM.Here are representative TM images for dropcast samples in which polystyrene wraps its carbon nanotubes appear as partially aligned and self-assembled by the side walls.
Such behavior is absent when pristine nanotubes are analyzed in a similar form. The values curve of thermogramemetric analysis for polymer-modified carbon nanotubes showed that the first weight loss, due to the loss of polystyrene chains starts at 270 Celsius degrees. Then, a second moderated step, which starts around 400 Celsius degrees, is caused by the loss of the siliyated methracrylic moieties, where as the final remark weight loss starting at around 600 Celsius degrees, corresponds to the carbon nanotubes.
Here we show our representative weight loss present-age curve of grafted carbon nanotubes with polyester range in comparison with pristine ones, which confirms that the most significant alteration in the samples weighed is comprised between 270 Celsius degrees and 775 Celsius degrees. From TGA, it is possible to affirm that after the hydroxilation step, carbon nanotube-side walls will typically contain hydroxyl moieties at two percent to five percent in weight. It is important to mention that after co-insulating material moieties to the OH groups, modified carbon nanotubes will typically contain between eight and ten percent weight for methracrylic in comparison with the nanotube content.
Once accomplished, the free radical polymerization with styrene, it is typically expected a grafting degree of about 30 to 40 percent relative to the nanotube weight. So, a selective modification of the surface properties of the nanotubes is obtained by successive chemical modification in steps to insert reactive functional robselectively to the side walls. We expect that this strategy can be reapplied to other acrylic or vinyl derivative polymer types and new hybrid materials and composites could arise in the future.
After watching this video, you should have a good understanding of the different steps needed to chemically modify carbon nanotubes with acetogram polyester range chains, which might play an important role in the surface properties of that kind of carbon nanotubes via super-molecular forces. This can result in the creation of self-assembly nanotubes through anisotropic nanoscale interactions, with potential applications in wide areas, such as material science and engineering, nanoscience and nanotechnology, or macromolecular chemistry. While attempting this procedure, it is important to be aware of the hazardous conditions of all reactants used in this technique, and ensure the use of suitable laboratory equipment.
