CN1257945C - Polymer thin layer coated carbon nanometer tube and its preparation method - Google Patents

Abstract

The present invention provides a carbon nanometer tube coated by a polymer thin layer and a preparation method thereof. The preparation method comprises: step (a), the carbon nanometer tube and a dense strong oxidation acid are co-boiled to prepare an amphipathic carbon nanometer tube with a modified surface; steps (b), after mixed with a polymer with the corresponding proportion, the amphipathic carbon nanometer tube in the step (a) is dispersed into one solvent; steps (c), the other immiscible solvent is added, and is stood after treated by ultrasonic waves, and carbon nanometer tube samples on an interface are collected so as to obtain the carbon nanometer tube coated by a polymer thin layer. The preparation method has the advantages of simplicity, practicality and high coating efficiency. On the basis of maintaining the original intensity and the mechanical property of the carbon nanometer tube, the surface property is changed. One layer of polymers with nanometers of thicknesses are uniformly coated on the surface of the obtained carbon nanometer tube. The carbon nanometer tube coated by a polymer thin layer can be used as a super capacitor or nanometer devices, such as nanometer cables, etc., and has wide application prospects.

Description

A kind of polymer thin layer coated carbon nanotube and preparation method thereof

Technical field: The present invention relates to a method for preparing a carbon nanotube device, in particular to a carbon nanotube coated with a polymer thin layer and a method for preparing the same.

Background technology: Carbon nanotube (Cabon Nanotube, referred to as CNT) is a new type of carbon structure discovered in 1991. It is a tube formed by graphene sheets formed by carbon atoms. Carbon nanotubes are divided into single-wall nanotubes (Single-wall Nanotube, SWNT) and multi-wall carbon nanotubes (Multi-wall Nanotube, MWNT). Its preparation methods mainly include catalytic pyrolysis, arc discharge, template method and laser evaporation.

Due to their small diameter and large aspect ratio, carbon nanotubes are regarded as quasi-one-dimensional nanomaterials. Now it has been confirmed that carbon nanotubes have peculiar electrical properties, super strong mechanical properties, and good adsorption properties, so they have attracted great attention in the field of materials. There are already transistors and displays made of carbon nanotubes.

With the development of nanoscience and technology, various carbon nanotubes with specific properties have gradually attracted people's interest. Richard E.Smalley and others carefully studied the acid treatment of carbon nanotubes in 1998, and obtained the distribution of products under different treatment conditions, which laid a good foundation for further research in the future (Science, 1998, 280 (22 ): 1253-1255). Afterwards, various modified carbon nanotubes and their composite structures were prepared. For example, carbon nanotubes with solvent solubility, carbon nanotube devices with molecular detection functions, and so on.

Carbon nanotube/polymer nanocomposites have been developed due to their excellent properties. The preparation of carbon nanotubes/polymer nanocomposites is generally divided into two ways, one is to mechanically disperse carbon nanotubes into polymers, which is called "blending"; the other is to mix carbon nanotubes After surface treatment and connection of functional groups, in-situ polymerization is carried out to obtain a carbon nanotube/polymer nanocomposite material connected by covalent bonds.

The above composite methods only focus on the use of carbon nanotubes as polymer reinforcement materials, and do not pay attention to the direction of polymer thin-layer composite carbon nanotubes as nano-devices, and the preparation process is relatively complicated. However, carbon nanotubes coated with polymer thin layers have properties different from those of carbon nanotubes, and thus have different application ranges.

Invention content:

The invention relates to a carbon nanotube device, in particular to a carbon nanotube device coated with a polymer thin layer.

Through molecular design, the surface of carbon nanotubes is treated to make them have amphiphilic properties, so that they can have affinity for both polar and non-polar substances; when carbon nanotubes are added to the polymer solution, due to carbon nanotubes The tube itself has a very strong adsorption capacity, and a layer of polymer molecules is adsorbed on the carbon nanotubes, but this process is reversible. After the carbon nanotubes are taken out of the polymer solution, there is no uniform polymer thin layer coated to the polymerization. When another incompatible solvent is added to the surface of the object, the amphiphilic carbon nanotubes will gather at the two-phase interface after mechanical vibration, and the polymer molecules can only be wound on the carbon nanotubes to form a polymer Carbon nanotubes coated with thin layers.

Technical scheme of the present invention is as follows:

The present invention firstly prepares amphiphilic carbon nanotubes, then selects two kinds of solvents that are not compatible with each other, dissolves or disperses the carbon nanotubes and the polymer in one of the phases, and after they are basically stable, adds another solvent to obtain an interface , after the carbon nanotubes gather at the interface, collect them to obtain the product.

The preparation method of hyperbranched coated carbon nanotubes of the present invention is specifically as follows:

Step (a): 1 weight part (mass, the same below) of dry carbon nanotube raw material and 0.1 to 100 weight parts of strong oxidizing acid, ultrasonic treatment at 0 to 100 kHz for 0.1 to 100 hours, then heating to 20 to 200 ° C, and reacting for 0.5 ~100hr, filter with filter membrane, wash repeatedly until neutral, vacuum dry at 0~180℃ for 10~30hr to obtain amphiphilic carbon nanotubes;

Step (b): After mixing 1 weight part of amphiphilic carbon nanotubes obtained in step (a) with 0.1-100 weight parts of a polymer, disperse them in a solvent in which the polymer can be well dissolved;

Step (c): adding another solvent immiscible with the solvent used in step (b) to the system obtained in step (b), ultrasonic treatment for 0.1 to 100 hr, and then standing for stratification, collecting carbon nanotube samples on the interface, After washing with a polymer-soluble solvent, drying is performed to obtain polymer-coated carbon nanotubes.

The carbon nanotubes used in step (a) of the method of the present invention are single-wall or multi-wall carbon nanotubes prepared by catalytic pyrolysis, arc discharge, template method and laser evaporation method.

The strong oxidizing acid used in the method step (a) of the present invention comprises 0.1～70% acid concentration nitric acid by weight, 0.1～100% acid concentration sulfuric acid by weight, 1/100～100/1 molar ratio nitric acid and sulfuric acid mixed solution, 1/100 ～100/1 molar ratio potassium permanganate and sulfuric acid mixed solution, 1/100～100/1 molar ratio potassium permanganate and hydrochloric acid mixed solution, 1/100～100/1 molar ratio potassium permanganate and nitric acid mixed solution , 1/100～100/1 molar ratio H ₂ O ₂ and sulfuric acid mixed solution, 1/100～100/1 molar ratio H ₂ O ₂ and hydrochloric acid mixed solution, 1/100～100/1 molar ratio H ₂ O ₂ mixed solution with nitric acid.

Polymers used in step (b) of the process of the present invention include polyolefins, polyacrylics, polystyrenes and polyamides, especially polyethylene, polypropylene, polybutylene, polystyrene, polysulfonated benzene Vinyl, polyvinyl chloride, polymethyl methacrylate, polymethyl acrylate, polybutadiene, polyethyl acrylate, polyacrylamide and mixtures thereof.

The solvent used in the method steps (b) and (c) of the present invention is water, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2- Pyrrolidone, chloroform, dichloromethane, dichloroethane, tetrahydrofuran, ethyl acetate, acetone, methyl ethyl ketone, acetonitrile, propanol, ethanol, methanol or mixtures containing these solvents.

The coating amount of polymer thin layer coated carbon nanotubes was determined by thermogravimetric analysis. The morphology of carbon nanotubes coated with polymer thin layer was confirmed by digital photos and transmission electron microscope, and the results are shown in the accompanying drawings.

The polymer thin-layer-coated carbon nanotube prepared according to the method of the invention has a simple preparation process and uniform polymer coating of the obtained product, and is suitable as a special nanometer device such as a supercapacitor, and has broad application prospects in the fields of electronics and the like.

Description of drawings:

Figure 1: Photos of amphiphilic carbon nanotubes aggregated at the two-phase interface

Figure 2: Transmission electron micrograph of carbon nanotubes coated with polymethyl methacrylate (PMMA)

Specific embodiments: the following examples are further descriptions of the present invention, rather than limiting the scope of the present invention.

Example 1: The multi-walled carbon nanotubes prepared by catalytic pyrolysis are used as the initial raw material, and the azeotropic treatment is carried out with concentrated nitric acid to make the surface have hydrophilic functional groups. Due to the lipophilicity of the carbon nanotube body, such carbon Nanotubes are amphiphilic and can be dispersed in different solvents. Then make polymethyl methacrylate into chloroform solution, add a small amount of amphiphilic carbon nanotubes, stir for a period of time, then add a certain volume of deionized water, shake vigorously, make the two phases contact as much as possible, and then let it stand , layered, and when the carbon nanotubes are gathered at the two-phase interface, the product is collected, washed with methanol and dried to obtain polymethyl methacrylate-coated carbon nanotubes.

Step (a): In a 100mL single-neck round bottom flask equipped with a magnetic stirring rotor, add 2g of dry carbon nanotube raw material and 20mL of 60% nitric acid, heat to 120°C after 40kHz ultrasonic treatment for 30min, stir and reflux React for 24 hours, filter with a φ0.22 μm polytetrafluoroethylene microporous membrane, wash repeatedly with deionized water until neutral, and vacuum dry at 80°C for 24 hours to obtain 1.5 g of amphiphilic carbon nanotubes;

Step (b): Weigh 1g of polymethyl methacrylate (PMMA, M _n = 10,000, M _w /M _n = 1.45) into a large test tube, add 20 mL of chloroform, and add amphiphilic carbon nanotubes after dissolution 0.05g, shake vigorously, keep stirring for 2hr;

Step (c): add 20 mL of deionized water, vibrate vigorously and sonicate for 10 minutes, then stand to separate and separate, collect carbon nanotube samples on the interface, wash with methanol, and dry to obtain polymer-coated carbon nanotubes.

The results were analyzed by TGA and TEM. TGA results are shown in Table 1.

Table 1 sample Weightlessness Weight loss at 300～400℃ raw carbon nanotubes No weight loss up to 650℃ 0 amphiphilic carbon nanotubes There is a small amount of weight loss at 650°C 3% PMMA coated carbon nanotubes Obvious weight loss at 330～400℃ 20%

Example 2: Multi-walled carbon nanotubes prepared by catalytic pyrolysis were used as raw materials to coat polystyrene.

Except that the polymer was changed to polystyrene (PS, M _n =13,000, M _w /M _n =1.50), polystyrene-coated carbon nanotubes were prepared according to the above-mentioned preparation steps. The results of TGA analysis are shown in Table 2.

Table 2 sample Weightlessness Weight loss at 350～450℃ raw carbon nanotubes No weight loss up to 650℃ 0 amphiphilic carbon nanotubes There is a small amount of weight loss at 650°C 3% PS coated carbon nanotubes Obvious weight loss at 350～450℃ twenty four%

Claims (3)

1. the preparation method of polymer foil enveloped carbon nanometer tube is characterized in that the preparation method is as follows:

Step (a): 1 weight part exsiccant carbon nanotube and 0.1～100 weight part acid with strong oxidizing property, with 0.1～100kHz ultrasonication, 0.1～100hr post-heating to 20～200 ℃, reaction 0.5～100hr, use the filter membrane suction filtration, repetitive scrubbing repeatedly to neutral, obtains amphiphilic carbon nano tubes behind 0～180 ℃ of vacuum-drying 10～30hr; Wherein acid with strong oxidizing property is selected from 0.1～70wt% nitric acid, 0.1～100wt% sulfuric acid, 1/100～100/1 mol ratio nitric acid and sulfuric acid mixed solution, 1/100～100/1 mol ratio potassium permanganate and sulfuric acid mixed solution, 1/100～100/1 mol ratio potassium permanganate and hydrochloric acid mixed solution, 1/100～100/1 mol ratio potassium permanganate and nitric acid mixing solutions, 1/100～100/1 mol ratio hydrogen peroxide and sulfuric acid mixed solution, 1/100～100/1 mol ratio hydrogen peroxide and hydrochloric acid mixed solution or 1/100～100/1 mol ratio hydrogen peroxide and nitric acid mixing solutions;

Step (b): 1 weight part step (a) gained amphiphilic carbon nano tubes with after 0.1～100 parts by weight polymer is mixed, is distributed in a kind of solvent, and polymkeric substance can well dissolving in this solvent; Wherein polymkeric substance is selected from polyethylene, polypropylene, polybutene, polystyrene, poly-sulfonated phenylethylene, polyvinyl chloride, polymethylmethacrylate, polymethyl acrylate, polyhutadiene, polyethyl acrylate, polyacrylamide or its mixture; Solvent is selected from water, dimethyl sulfoxide (DMSO), N, dinethylformamide, N,N-dimethylacetamide, N-N-methyl-2-2-pyrrolidone N-, chloroform, methylene dichloride, ethylene dichloride, tetrahydrofuran (THF), ethyl acetate, acetone, butanone, acetonitrile, propyl alcohol, ethanol, methyl alcohol or its mixed solvent;

Step (c): the immiscible solvent of solvent for use in another kind and the step (b) is joined step (b) gained system, standing demix behind ultrasonication 0.1～100hr, collect the carbon nanotube sample on the interface, after the solvent cleaning with the soluble polymeric thing, drying obtains the carbon nanotube of polymer overmold; Wherein solvent is selected from water, dimethyl sulfoxide (DMSO), N, dinethylformamide, N,N-dimethylacetamide, N-N-methyl-2-2-pyrrolidone N-, chloroform, methylene dichloride, ethylene dichloride, tetrahydrofuran (THF), ethyl acetate, acetone, butanone, acetonitrile, propyl alcohol, ethanol, methyl alcohol or its mixed solvent.

2. the preparation method of polymer foil enveloped carbon nanometer tube according to claim 1 is characterized in that used carbon nanotube is selected from single wall or the multi-walled carbon nano-tubes that catalyse pyrolysis, arc-over, template or laser evaporation method prepare in the step (a).

3. the polymer foil coated carbon nanotube is characterized in that the polymer foil coated carbon nanotube that adopts each described preparation method of claim 1-2 to obtain.