CN109535357B - Chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material and preparation method and application thereof - Google Patents

Chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material and preparation method and application thereof Download PDF

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CN109535357B
CN109535357B CN201811436412.4A CN201811436412A CN109535357B CN 109535357 B CN109535357 B CN 109535357B CN 201811436412 A CN201811436412 A CN 201811436412A CN 109535357 B CN109535357 B CN 109535357B
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罗延龄
张瑞乾
徐峰
陈亚芍
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Abstract

The invention discloses a chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material and a preparation method and application thereof. The composite material is prepared by coating a hydroxyl polybutadiene-polystyrene segmented copolymer at the end of a chain expansion on the surface of a multi-wall carbon nano tube; the segmented copolymer is obtained by firstly carrying out chain extension through polyaddition reaction of hexamethylene diisocyanate and hydroxyl-terminated polybutadiene, then preparing a polymer after chain extension into a macromolecular initiator through acylation reaction, and finally initiating polymerization of styrene through in-situ atom transfer radical polymerization in the presence of a multi-walled carbon nanotube. The conductive composite material has good dispersion stability and film forming property, and the gas-sensitive sensing film assembled by the conductive composite material has high selectivity, response sensitivity, stability and repeatability on methylene dichloride organic solvent steam.

Description

Chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of conductive polymer composite materials and functional materials, and particularly relates to a chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material, a preparation method of the conductive composite material and gas-sensitive sensing application.
Background
As more and more volatile organic gases are emerging in the human living environment, there is an urgent need for a mini monitor to assess the impact of organic vapors on the environment. Due to their unique physicochemical properties, polymer conductive composites (CPCs) have attracted much attention in the field of environmental gas monitoring. The polymer conductive composite material is generally prepared by dispersing conductive fillers such as Carbon Black (CB), Carbon Nanotubes (CNTs), graphene, metal powder and the like in an insulating polymer matrix to form a conductive network. In particular, since the carbon nanoparticle-filled polymer conductive composite material has good responsiveness to different organic vapors, such polymer conductive composite material is very suitable for monitoring volatile organic gases.
Carbon nanotubes possess a one-dimensional nanostructure and present excellent physical and chemical properties: good heat resistance, large surface area, high conductivity and network connectivity. In particular, one of the most prominent characteristics of carbon nanotubes is the ability to construct low permeability threshold conducting networks for smart sensor materials. However, the original carbon nanotubes are not selective to organic vapors, and organic molecules are only adsorbed on the sidewalls of the carbon nanotubes and do not transfer electrons with the carbon nanotubes. Meanwhile, strong van der waals force exists among the carbon nanotubes, so that the carbon nanotubes are easy to agglomerate, and thus poor dispersibility of the carbon nanotubes is caused, and the application of the carbon nanotubes is limited. Covalent bonding or physical coating of carbon nanotubes with polymers can ameliorate this disadvantage of the original carbon nanotubes. The polymer/carbon nanotube composite conductive gas-sensitive sensing material may generate a negative vapor coefficient phenomenon, which affects the recurrence stability of the gas-sensitive element; there are also problems of long response recovery time, lack of selectivity, etc. How to improve the distribution behavior and the gas sensitivity responsiveness of the conductive particles becomes a key technology for preparing the polymer/conductive particle composite sensing material. For this reason, many studies have been carried out to improve various properties of the gas sensor.
Kun Dai et al (Y L Li, H Liu, G Q Zhen, C T Liu, J B Chen, C Y Shen. tuning of vacuum sensing copolymers using ingredients with emulsion polymerization and additives B: Chemical,2015,221: 1279-. The European university of Bronstatten J F Feller et al (J Lu, J F Feller, B Kumar, M Castro, Y S Kim, Y T Park, J C Grunlan. Chemo-sensitivity of latex-based films conditioning networks of carbon nanotubes. Sensors and Actuators B: Chemical,2011,155:28-36) form an isolated conductive network with latex nanoparticles and carbon nanotubes and self-assembleThe nano composite material is assembled into a 3D structure, and has higher selectivity and responsiveness to water vapor. Faban Sch ü tt et al, Kill university of Germany (F Sch tt, V Postica, R Adelung, O Lupan. Single and network ZnO-CNT Hybrid for Selective Room-Temperature High-Performance Ammonia Sensors. ACS Applied Materials&Interfaces,2017,9(27):23107-23118) use carbon nanotubes and tetragonal ZnO to construct 3D networks to enhance NH response at room temperature3The responsiveness of (c). However, these studies are not sufficiently concerned about the dispersibility, film-forming property of the conductive particles and their influence on the gas sensitivity responsiveness.
Disclosure of Invention
The invention aims to overcome the defects that a polystyrene (copolymer) -based conductive polymer composite material is difficult to form a film, so that the conductive performance is unstable, the sensing response performance is poor and the like, and provides a chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material with good conductive performance and response characteristics and a preparation method thereof, and the composite material is used for detecting dichloromethane vapor of a volatile organic compound.
Aiming at the purposes, the conductive composite material adopted by the invention is prepared by coating the surface of a multi-wall carbon nano tube with an expanded chain end hydroxyl polybutadiene-polystyrene segmented copolymer with the following structural formula;
Figure BDA0001883895790000021
wherein x is an integer of 1 to 6, and y is an integer of 20 to 125; preferably, x is 4 and y is an integer of 46 to 91.
In the conductive composite material, the mass percentage content of the multi-wall carbon nano tube is 10-30%.
The preparation method of the chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nano tube conductive composite material comprises the following steps:
Figure BDA0001883895790000031
1. preparation of extended chain end hydroxyl polybutadiene macroinitiator
Taking methylbenzene as a solvent and dibutyltin dilaurate (DBTDL) as a catalyst, and reacting hydroxyl-terminated polybutadiene (HTPB) shown in a formula I with Hexamethylene Diisocyanate (HDI) at the temperature of 60-80 ℃ for 2-4 hours to obtain chain-extended hydroxyl polybutadiene shown in a formula II; and (3) reacting the chain-extended hydroxyl-terminated polybutadiene, Triethylamine (TEA) and 2-bromoisobutyryl bromide (BIB) at room temperature for 20-24 hours to obtain the chain-extended hydroxyl-terminated polybutadiene macromolecular initiator shown in the formula III.
2. Preparation of chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nano tube conductive composite material
The method comprises the steps of taking cyclohexanone as a solvent, cuprous chloride as a catalyst, and N, N, N' -pentamethyl diethylene Triamine (TEA) as a ligand, and carrying out atom transfer radical polymerization reaction on a multiwall carbon nanotube (MWCNTs), a hydroxyl-terminated polybutadiene macroinitiator shown in a formula III and styrene at 110-120 ℃ to obtain a conductive composite material of the multiwall carbon nanotube surface in-situ coated type IV-shown chain-extended hydroxyl polybutadiene-polystyrene segmented copolymer, namely the chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material.
In the step 1, the molar ratio of the hydroxyl content in the hydroxyl-terminated polybutadiene to the isocyanate group and dibutyltin dilaurate in hexamethylene diisocyanate is preferably 1.5-5: 1: 0.015-0.020, and the molar ratio of the chain-extended hydroxyl-terminated polybutadiene to the 2-bromoisobutyryl bromide and the triethylamine is preferably 1: 2-3.
In the step 2, the molar ratio of the chain-extended hydroxyl-terminated polybutadiene macroinitiator to styrene, cuprous chloride, N, N, N' -pentamethyldiethylenetriamine is preferably 1:150 to 250:1 to 2:1 to 1.5.
In the step 2, the addition amount of the multi-walled carbon nano-tube is 5-12.5% of the total mass of the chain-extending hydroxyl-terminated polybutadiene macromolecular initiator, the styrene and the multi-walled carbon nano-tube.
The invention discloses application of a chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nano tube conductive composite material in detecting dichloromethane vapor, which comprises the following specific application methods: adding the extended chain end hydroxyl polybutadiene-polystyrene segmented copolymer/carbon nano tube conductive composite material into cyclohexanone, and uniformly dispersing by ultrasonic; and preparing the obtained dispersion into a gas-sensitive sensing film by a spin coating method, wherein the gas-sensitive sensing film is used for detecting dichloromethane vapor.
The invention firstly carries out chain extension on hydroxyl polybutadiene at the end and prepares a macromolecular initiator, and styrene is polymerized in situ by an atom transfer radical polymerization method and is coated on the surface of the multi-walled carbon nano tube at the same time, thus preparing the conductive composite material of the multi-walled carbon nano tube in situ coated hydroxyl polybutadiene-polystyrene segmented copolymer at the end of chain extension.
The conductive composite material has good dispersion stability and film forming property, can be used for assembling a gas-sensitive sensing film so as to effectively detect dichloromethane vapor, and has the characteristics of high response sensitivity, good stability, quick response and the like.
Drawings
FIG. 1 is a block diagram of a chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer of example 11H NMR spectrum.
FIG. 2 is a dynamic light scattering gel chromatogram of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer prepared in examples 1 to 3.
FIG. 3 is a TEM image of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite prepared in example 1.
FIG. 4 is a scanning electron micrograph of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite prepared in example 1.
FIG. 5 is a photograph showing the variation of transmittance with time of centrifugation and digital images of multi-walled carbon nanotubes and the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite prepared in example 1.
FIG. 6 is a bar graph showing the response of the gas-sensitive sensing film prepared from the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material of example 1 to different organic saturated vapors.
FIG. 7 is a response curve of a gas-sensitive sensing film prepared by using the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material of examples 1-3, exposed to 4000ppm of dichloromethane.
FIG. 8 is a graph of the responsiveness of gas sensing films prepared from the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composites of examples 1, 4, and 5 to exposure to 4000ppm methylene chloride.
FIG. 9 is a graph of the response behavior of a gas sensing film made of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite of example 1 as a function of methylene chloride vapor concentration (the inset shows a linear dependence).
FIG. 10 is a graph of the repeated stability of a gas sensing film prepared from the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite of example 1 exposed to 4000ppm (solid line) and 500ppm (dashed line) methylene chloride vapor.
Detailed Description
The invention is described in more detail below with reference to the figures and examples, but the scope of protection of the invention is not limited to these examples only.
Purity of multiwall carbon nanotubes in the following examples>95%, an outer diameter of 20-30 nm, a length of 10-30 μm, provided by the institute of organic chemistry of Chinese academy of sciences; purity of styrene>98% by Tianjin's Nikko Chemicals Co., Ltd; hydroxyl-terminated polybutadiene having an average molecular weight of 2300 and a hydroxyl group content of 1.1mmol g-1Provided by Zibo Qilong chemical Co., Ltd; purity of dibutyltin dilaurate>98% of the total amount of the chemical reagent provided by Fuchen chemical reagent company Limited in Tianjin; 2-Bromoisobutyroyl bromide>98% by alatin reagent, inc; purity of triethylamine>99% by chemical agents of the national drug group; purity of cuprous chloride>98% by sigma aldrich trade, ltd; purity of N, N, N' -pentamethyldiethylenetriamine>99% by the company Aladdin reagent.
Example 1
Figure BDA0001883895790000061
1. Preparation of extended chain end hydroxyl polybutadiene macroinitiator
2g (hydroxyl content: 2.20mmol) of hydroxyl-terminated polybutadiene (HTPB) represented by the formula I was dissolved in 12mL of dry toluene and charged into a round-bottomed flask, followed by addition of 0.0925g (0.55mmol) of hexamethylene diisocyanate (HDI, isocyanate group content: 1.10mmol) and 12mg (0.019mmol) of dibutyltin dilaurate (DBTDL), reaction at 60 ℃ for 2 hours under a nitrogen atmosphere, and vacuum drying of the resultant at 40 ℃ for 12 hours to obtain chain-extended hydroxyl-terminated polybutadiene (HTPB) represented by the formula II-1 (HTPB-1)5Molecular weight 11880).
23.76g (2mmol) of chain-extended hydroxyl-terminated polybutadiene and 0.5252g (5.2mmol) of Triethylamine (TEA) were dissolved in 30mL of dry toluene and added to a round-bottomed flask, the temperature was reduced to 0 ℃, 1.195g (5.2mmol) of dibromoisobutyryl bromide (BIB) dissolved in 10mL of dry toluene was added dropwise under a nitrogen atmosphere, after stirring for 2 hours under ice bath, the temperature was raised to room temperature and reacted for 24 hours, filtration was performed, the filtrate was freed from most of the solvent by rotary evaporation and precipitated in methanol 3 times, and the product was dried under vacuum at room temperature for 24 hours to give a chain-extended hydroxyl-terminated polybutadiene macroinitiator (Br-HTPB) represented by formula III-1 (I-B)5-Br)。
2. Preparation of chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nano tube conductive composite material
Ultrasonically dispersing 0.5015g of multi-walled carbon nanotube (MWCNT) in 10mL of cyclohexanone, adding the mixture into a 50mL dry Schlenk bottle, adding 3.162mL (27.6mmol) of styrene and 1.6394g (0.138mmol) of chain-extended hydroxyl-terminated polybutadiene macroinitiator into the Schlenk bottle, freezing the reaction liquid by using liquid nitrogen, vacuumizing the reaction bottle by using a vacuum pump, filling nitrogen into the reaction bottle for thawing (freezing and pumping for short), adding 20 mu L (0.137mmol) of Pentamethyldiethylenetriamine (PMDETA) in the nitrogen atmosphere, quickly adding 0.0136g (0.137mmol) of CuCl in the nitrogen atmosphere after freezing and pumping again, reacting at 110 ℃ for 24 hours after the reaction is finished, precipitating the obtained product 4 times by using methanol at 40 DEG CVacuum drying for 12 hours to obtain the multi-walled carbon nanotube in-situ coated conductive composite material of the chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer shown in the formula IV-1, namely the chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material (MWCNTs @ PS)74-b-HTPB5-b-PS74). The structural characterization result of the chain-extended hydroxyl polybutadiene-polystyrene block copolymer is shown in figures 1 and 2, and the molecular weight is 27290. As can be seen from fig. 3 and 4, the surface of the multi-walled carbon nanotube is coated with a layer of polymer.
The multi-walled carbon nanotube and the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material were ultrasonically dispersed in toluene, and the dispersion behavior of the obtained dispersion was tested, with the results shown in fig. 5. As can be seen in fig. 5, the multi-walled carbon nanotube dispersion settles quickly and the light transmittance increases with increasing room temperature standing time. After physically coating the hydroxyl polybutadiene-polystyrene segmented copolymer at the chain-extended end, the dispersibility of the obtained conductive composite material dispersion system is good, and the light transmittance is still basically 0 along with the extension of the standing time at room temperature, which shows that the obtained conductive composite material does not settle in toluene and has good stability. Further, it was found that the dispersion did not cause sedimentation of the suspension even when the obtained conductive composite dispersion was centrifuged at 4000 rpm for 30 minutes.
Example 2
In step 2 of this example, the amount of the multi-walled carbon nanotube was 0.2376g, and the other steps were the same as in example 1, to obtain a chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite (MWCNTs @ PS)74-b-HTPB5-b-PS74)。
Example 3
In step 2 of this example, the amount of the multi-walled carbon nanotubes was 0.6449g, and the other steps were the same as in example 1, to obtain a chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material (MWCNTs @ PS)74-b-HTPB5-b-PS74)。
Example 4
In step 2 of this example, the amount of the multi-walled carbon nanotube was 0.4214g, the amount of the styrene was 2.1528g, and the other steps were the same as those of example 1, to obtain a conductive composite material in which the multi-walled carbon nanotube was coated in situ with the chain-extended hydroxyl polybutadiene-polystyrene block copolymer shown in formula IV-2, that is, a chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material (MWCNTs @ PS)46-b-HTPB5-b-PS46Molecular weight 21460).
Figure BDA0001883895790000081
Example 5
In step 2 of this example, the amount of carbon nanotubes used was 0.5808g, the amount of styrene used was 3.5880g, and the other steps were the same as in example 1, to obtain a multi-walled carbon nanotube in-situ coated chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer conductive composite material shown in formula IV-3, that is, a chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/multi-walled carbon nanotube conductive composite material (MWCNTs @ PS)91-b-HTPB5-b-PS91Molecular weight 30840).
Figure BDA0001883895790000082
Comparative example 1
1. Macroinitiator for preparing hydroxyl-terminated polybutadiene
1.818g (2mmol) of hydroxyl-terminated polybutadiene and 0.5252g (5.2mmol) of Triethylamine (TEA) were dissolved in 30mL of dry toluene and added to a round-bottomed flask, the temperature was reduced to 0 ℃, 1.195g (5.2mmol) of dibromoisobutyryl bromide (BIB) dissolved in 10mL of dry toluene was added dropwise under a nitrogen atmosphere, after stirring for 2 hours under ice bath, the temperature was raised to room temperature and reacted for 24 hours, filtration was carried out, the filtrate was freed of most of the solvent by rotary evaporation and precipitated in methanol 3 times, and the product was dried under vacuum at room temperature for 24 hours to give a hydroxyl-terminated polybutadiene macroinitiator (Br-HTPB-Br) represented by formula III-2.
Figure BDA0001883895790000091
2. Preparation of hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material
0.3066g of multi-walled carbon nanotube (MWCNT) is ultrasonically dispersed in 10mL of cyclohexanone and added into a 50mL dry Schlenk bottle, 2.488mL (21.74mmol) of styrene and 0.5g (0.2174mmol) of hydroxyl-terminated polybutadiene macroinitiator are added into the Schlenk bottle, after one freezing and one pumping, 45.1 muL (0.2161mmol) of Pentamethyldiethylenetriamine (PMDETA) is added under the nitrogen atmosphere, after one freezing and one pumping again, 0.0214g (0.2161mmol) of CuCl is rapidly added under the nitrogen atmosphere, after the last freezing and one pumping, the mixture is reacted for 24 hours at 110 ℃, after the reaction is finished, methanol is used for precipitation for 4 times, and the obtained product is dried under vacuum at 40 ℃ for 12 hours to obtain the conductive nanocomposite (MWCNTs PS-b-HTPB-b-PS) of the multi-walled carbon nanotube in-situ coated hydroxyl-terminated polybutadiene-polystyrene block copolymer.
Comparative example 2
In step 2 of comparative example 1, the amount of the multi-walled carbon nanotube was 0.1811g, the amount of the styrene was 1.1304g, and the other steps were the same as in comparative example 1, to obtain a conductive composite material in which the multi-walled carbon nanotube was coated with the hydroxyl-terminated polybutadiene-polystyrene block copolymer in situ.
Comparative example 3
In step 2 of comparative example 1, the amount of the multi-walled carbon nanotube was 0.0858g, the amount of the styrene was 1.1304g, and the other steps were the same as in comparative example 1, to obtain a conductive composite material in which the multi-walled carbon nanotube was coated with the hydroxyl-terminated polybutadiene-polystyrene block copolymer in situ.
Comparative example 4
In step 2 of comparative example 1, the amount of the multi-walled carbon nanotube was 0.3066g, the amount of the styrene was 2.2608g, and the other steps were the same as in comparative example 1, to obtain a conductive composite material in which the multi-walled carbon nanotube was coated with the hydroxyl-terminated polybutadiene-polystyrene block copolymer in situ.
The inventor respectively adds the composite materials prepared in the embodiments 1-5 into cyclohexanone, ultrasonically disperses the cyclohexanone for 10 minutes by using ultrasonic cleaning machines with the frequency of 250W and 45kHz, adopts a spin coating method to prepare the gas-sensitive sensing film, observes the film forming property of the gas-sensitive sensing film, and compares the film forming property with the composite materials of the comparative examples 1-4, and finds that when the solvent is completely evaporated, the film coated by the materials prepared in the comparative examples 1-4 has a cracking phenomenon, i.e., the film forming property is poor, while the film forming property of the composite materials obtained in the embodiments 1-5 is very good even if more styrene is added in the formula after the chain extension of the macroinitiator is carried out in the embodiments 1-5.
In order to prove the beneficial effects of the invention, the inventor uses a WS-30A type gas-sensitive sensing tester produced by Zhengzhou Weisheng electronic technology Limited company to perform gas-sensitive responsiveness tests on the gas-sensitive sensing film prepared by the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/multi-walled carbon nanotube conductive composite materials prepared in the examples 1-5 and the hydroxyl-terminated polybutadiene-polystyrene block copolymer/multi-walled carbon nanotube conductive composite materials prepared in the comparative examples 1-4, and the results are shown in FIGS. 6-10 and Table 1.
As can be seen from fig. 6, the gas-sensitive sensing film prepared from the composite material of example 1 has higher response intensity to dichloromethane than other gases, and can be used for monitoring dichloromethane vapor.
TABLE 1 influence of different feeding proportions of the sensitive film sensor of the present invention on the response
Figure BDA0001883895790000101
As can be seen from the experimental results of examples 1-5 in Table 1 and FIGS. 7 and 8, the response or response intensity RI (RI is defined as (R) for dichloromethane (4000ppm) when the carbon nanotube content in the composite material is increased from 5% to 10% without changing the ratio of the macroinitiator to the monomerg-R0)/R0Wherein R isgThe maximum resistance of the film in the solvent vapor, R0As an average of 6 sets of resistance data measured in air), the RI value decreased significantly as the carbon nanotubes increased from 10% to 15%. When the content of the carbon nanotube is not changedIn this case, the RI increases with the increase of the polystyrene segment, and the RI decreases with the continued increase of the polystyrene segment. Finally, when the content of the carbon nano tube is determined to be 10% and the molar ratio of the macroinitiator to the styrene is 1:200, the gas-sensitive sensing film prepared from the composite material has the maximum response strength to the dichloromethane.
As can be seen from FIGS. 9 and 10, the gas-sensitive sensing film prepared from the composite material of example 1 has very good responsiveness to methylene chloride vapor, and the responsiveness is in a linear relationship with the concentration of the measured object, R2And if the temperature is more than 0.99, the linear regression result has good reliability, the gas-sensitive sensing film shows good repeated use stability, and the response intensity, the response time and the recovery time are basically kept unchanged after the gas-sensitive sensing film is repeatedly used for many times. In conclusion, the conductive composite material of the multiwalled carbon nanotube in-situ coated extended chain end hydroxyl polybutadiene-polystyrene segmented copolymer can be used as a nano gas sensor for effectively monitoring dichloromethane vapor.

Claims (8)

1. A chain-extended hydroxyl-terminated polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material is characterized in that: the composite material is prepared by coating a hydroxyl polybutadiene-polystyrene segmented copolymer with an expanded chain end with the following structural formula on the surface of a multi-wall carbon nano tube;
Figure DEST_PATH_IMAGE001
in the formulaxAn integer of not less than 1 but not more than 6,yan integer of 20 to 125; the mass percentage of the multi-wall carbon nano tube in the composite material is 10-30%.
2. The chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material as claimed in claim 1, wherein: the above-mentionedx= 4，yAnd (c) = integers of 46 to 91.
3. A method for preparing the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material according to claim 1, which is characterized by comprising the following steps:
Figure 267422DEST_PATH_IMAGE002
Figure DEST_PATH_IMAGE003
(1) preparation of extended chain end hydroxyl polybutadiene macroinitiator
Taking methylbenzene as a solvent and dibutyltin dilaurate as a catalyst, and reacting hydroxyl-terminated polybutadiene shown in a formula I with hexamethylene diisocyanate at the temperature of 60-80 ℃ for 2-4 hours to obtain chain-extended hydroxyl polybutadiene shown in a formula II; reacting the chain-extended hydroxyl-terminated polybutadiene, triethylamine and 2-bromoisobutyryl bromide at room temperature for 20-24 hours to obtain a chain-extended hydroxyl-terminated polybutadiene macromolecular initiator shown in a formula III;
(2) preparation of chain-extended hydroxyl polybutadiene-polystyrene block copolymer/carbon nano tube conductive composite material
The preparation method comprises the steps of taking cyclohexanone as a solvent, cuprous chloride as a catalyst, and N, N, N ', N ' ', N ' ' -pentamethyldiethylenetriamine as a ligand, and carrying out atom transfer radical polymerization reaction on a multiwall carbon nanotube, a chain-extended hydroxyl polybutadiene macromolecular initiator shown in a formula III and styrene at 110-120 ℃ to obtain a conductive composite material of which the surface of the multiwall carbon nanotube is coated with a chain-extended hydroxyl polybutadiene-polystyrene segmented copolymer shown in a formula IV in an in-situ manner, namely the chain-extended hydroxyl polybutadiene-polystyrene segmented copolymer/carbon nanotube conductive composite material.
4. The preparation method of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material according to claim 3, wherein the preparation method comprises the following steps: in the step (1), the molar ratio of the hydroxyl content in the hydroxyl-terminated polybutadiene to the isocyanate group and dibutyltin dilaurate in hexamethylene diisocyanate is 1.5-5: 1: 0.015-0.020.
5. The preparation method of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material according to claim 3, wherein the preparation method comprises the following steps: in the step (1), the molar ratio of the chain-extended hydroxyl polybutadiene to the 2-bromoisobutyryl bromide to the triethylamine is 1: 2-3.
6. The preparation method of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material according to claim 3, wherein the preparation method comprises the following steps: in the step (2), the molar ratio of the chain-extended hydroxyl-terminated polybutadiene macroinitiator to styrene, cuprous chloride, N, N, N ', N ' ', N ' ' -pentamethyldiethylenetriamine is 1:150 to 250:1 to 2:1 to 1.5.
7. The preparation method of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite material according to claim 6, wherein the preparation method comprises the following steps: in the step (2), the addition amount of the multi-wall carbon nano tube is 5-12.5% of the total mass of the chain-extending hydroxyl-terminated polybutadiene macromolecular initiator, the styrene and the multi-wall carbon nano tube.
8. Use of the chain-extended hydroxyl-terminated polybutadiene-polystyrene block copolymer/carbon nanotube conductive composite of claim 1 in the detection of methylene chloride vapor.
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