WO2007099889A1

WO2007099889A1 - Method of treating conductive polymer

Info

Publication number: WO2007099889A1
Application number: PCT/JP2007/053467
Authority: WO
Inventors: Hidenori Okuzaki
Original assignee: University Of Yamanashi
Priority date: 2006-02-28
Filing date: 2007-02-26
Publication date: 2007-09-07
Also published as: JPWO2007099889A1; JP5256454B2

Abstract

A method by which the conductivity characteristics and mechanical properties of a fibrous conductive polymer can be easily improved. The method for conductive-polymer treatment comprises immersing fibers of a conjugated conductive polymeric material having a dopant added thereto in a treating liquid comprising ethylene glycol and/or an aprotic solvent for a given time to improve the conductivity characteristics and mechanical properties of the fibers. Especially when the fibers are PEDOT/PSS fibers in which the conductive polymeric material is poly(3,4-ethylenedioxythiophene) (PEDOT) and the dopant is poly(4-styrenesulfonic acid) (PSS), a significant conductivity-improving effect is produced.

Description

Specification

Method for treating conductive polymer

Technical field

TECHNICAL FIELD [0001] The present invention relates to a conductive polymer immersion treatment method capable of simply improving the conductive properties and mechanical properties of a fibrous conductive polymer by immersing it in a treatment liquid.

Background art

[0002] In recent years, conjugated conductive polymers that have a conjugated double bond in the linear chain of the polymer and exhibit conductivity due to the ease of movement of electrons related to the π bond have attracted attention. Such a conjugated conductive polymer is generally used by injecting carriers by doping in order to increase carrier mobility. Japanese Patent Application Laid-Open Publication No. 2003-228707 discloses a method for producing a conductive polymer fiber.

[0003] Among conjugated conductive polymers, poly 3, 4 ethylene dioxythiophene (PED ΟΤ) has a relatively low band gap of 1.5 to 1.6 eV in the doped state. It is a conductive polymer that has excellent conductivity, transparency, and stability, and is attracting attention as a hole injection material for antistatic agents, electrification window, and organic electrescence luminescence (EL) devices.

[0004] Much of the previous work on PEDOT doped with poly-4 styrene sulfonic acid (PSS) is made of thin films made by casting or electrochemical techniques!ヽ It is done using a coating film or a thick film, and there is relatively little research on fiber production.

[0005] However, the production of conductive fibers is based on electromagnetic shield materials, conductive fabrics, artificial fabrics in the form of fibers that only have basic viewpoints to understand the electrical and mechanical properties of the material. It is also important in applications such as muscle fibers and high sensitivity sensors.

Patent Document 1: Japanese Patent Laid-Open No. 2005-330624

Disclosure of the invention

Problems to be solved by the invention [0006] Against the background described above, the present inventors have been conducting research on the production of conductive polymer fibers by a wet spinning method. By applying the wet spinning method to PEDOT doped with PSS, Strength We have successfully produced PEDOTZPSS microfibers on the order of S microns.

[0007] In the course of intensive research, the present inventors have found that the conductive properties and mechanical properties can be improved simply by immersing the conductive polymer fiber in a certain type of treatment liquid. The present invention has been completed.

[0008] That is, an object of the present invention is to provide a method capable of simply improving the conductive properties and mechanical properties of a fibrous conductive polymer.

Means for solving the problem

[0009] The present invention for solving the above-mentioned problems involves immersing a fiber of a conjugated conductive polymer material to which a dopant is added in a treatment liquid containing ethylene glycol and Z or an aprotic solvent for a predetermined time. Thus, there is provided a method for treating a conductive polymer characterized by improving the conductive properties and mechanical properties of the fibers.

[0010] In particular, when the conductive polymer material is poly 3, 4 ethylene dioxythiophene (PEDOT) and the dopant is poly 4 styrene sulfonic acid (PSS), the electrical conductivity is increased by the above treatment. The treatment method of the present invention is an epoch-making method that can improve the properties of the conductive polymer fiber very easily and inexpensively.

[0011] The above treatment liquid may be a pure solution of this active substance as long as it contains ethylene glycol and Z or one or more of aprotic solvents as the active substance. A solution obtained by diluting the active substance with a solvent such as water or alcohol may be used. The mechanical properties improved by the present invention include fiber Young's modulus, tensile cut strength, cut elongation, and the like. The reason why such an improvement effect can be obtained will be described in detail later.

[0012] In the above treatment method, the aprotic solvent is preferably dimethyl sulfoxide (DMSO) or dimethylformamide (DMF).

[0013] Further, the method of the present invention is characterized in that the fiber properties can be improved simultaneously with the formation of the fiber shape in the wet spinning process. That is, the fiber to be treated is an emulsion dispersion of a polymer material flowing out from a nozzle or a precursor solution thereof, and the treatment By using the treatment liquid as a coagulation bath, it is possible to simultaneously perform the fiber shape formation by the wet spinning method and the above-described property improvement treatment. As a result, the fiber characteristic can be improved in the wet spinning process, and simplification can be achieved.

[0014] As the treatment conditions for the immersion treatment in the present invention, when a treatment solution at room temperature is used, the immersion time of the fiber in the treatment solution may be 30 seconds or more. More preferably, the immersion time is 3 minutes or more.

[0015] The treatment method of the present invention involves immersing the polymer fiber in a solvent having the ability to dissolve the polymer, and therefore the solvent (treatment liquid component) remaining on the fiber after the immersion is used. There is a risk of degrading the fiber. In order to prevent this, in the present invention, the fiber treated by the above method is subjected to a heat treatment in which the fiber is maintained at a temperature of 0 to 50 ° C. for 1 minute or more under a reduced pressure of an absolute pressure of 1 Torr or less. Favored ,.

The invention's effect

[0016] According to the present invention, it has become possible to improve the conductive properties and mechanical properties of a conjugated conductive polymer fiber to which a dopant is added by simple and inexpensive means. In particular, the effect of improving the conductivity of PEDOT fibers doped with PSS is remarkable.

[0017] Further, by using the above-mentioned treatment liquid in the coagulation bath in the wet spinning process, it is possible to simultaneously form the shape of the fiber and improve its properties, and to conduct a conductive polymer with excellent properties by a simple method. It became possible to produce microfibers.

Brief Description of Drawings

[0018] Fig. I is a diagram showing the chemical structure of PEDOTPSPS.

FIG. 2 is a conceptual diagram showing a configuration of a wet spinning apparatus used in this example.

FIG. 3 is an explanatory diagram of conductivity measurement by a four-terminal method.

FIG. 4 is an explanatory diagram of a stress-strain curve.

FIG. 5 is a diagram showing the influence of the type of treatment liquid on the change in fiber conductivity in this example.

FIG. 6 is a graph showing the effect of immersion time on the change in fiber conductivity in this example.

FIG. 7 is a diagram showing an example of the measurement result of the fiber diameter in the present example. FIG. 8 is a diagram showing an example of a measurement result of temperature dependence of fiber conductivity in the present example.

[Fig. 9] The data of Fig. 8 is displayed with In σ and Τ_ ^1/2 on the vertical and horizontal axes.

FIG. 10 is a diagram showing a comparison of stress-strain curves of fibers before and after the dipping treatment in this example.

Explanation of symbols

[0019] 1: PEDOTZPSS solution

2: Cylinder

3: Injection needle

4: Coagulation tank (coagulation tank)

5: Syringe pump

6: Magnet

7: Piston

8: Controller

9: MicroFino Kuichi

10: Pin

11: Kelvin clip

12: Digital multimeter

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] The following is a description of preferred embodiments of the present invention based on examples. The embodiments of the present invention are not limited to these examples.

In this example, PED-doped PEDOT (hereinafter abbreviated as PEDOTZPSS) microfibers were prepared by a wet spinning method, the solidified fibers were immersed in a treatment solution for a predetermined time, and then adhered to the fibers by heat treatment. The test samples were prepared by completely evaporating and removing the solvent, and the changes in fiber diameter, conductivity, and mechanical properties before and after the immersion treatment were investigated. Hereinafter, the production method, test method, and measurement method of the specimen will be described in some detail.

[0021] <Production of microfiber> FIG. 1 shows the chemical structure of PEDOTZPSS used in this example. This PED OTZPSS was prepared by polymerizing 3,4 ethylenedioxythiophene, a monomer commercially available from Baytron P. Bayer Cotd in the presence of PSS, a dopant, in the form of an aqueous solution. . The ratio of repeat units from PEDOT to PSS was about 0.8, and the dope ratio was 0.33.

FIG. 2 is a conceptual diagram showing the configuration of the wet spinning apparatus used in this example. About 1 ml of PE DOTZPSS aqueous solution (emulsion dispersion) 1 is filled in a glass cylinder 2 (diameter 12 mm), and then injected into a coagulation tank 4 filled with acetone at room temperature from an injection needle 3 (inner diameter 180-410 / ζ πι). Spill into. At that time, the piston 7 is attached to the syringe pump 5 upright on the ground using a stand via the magnet 6, and the controller 8 controls the stroke of the syringe pump 5 so that the liquid from the injection needle 3 is discharged. The flow rate was adjusted. The fiber of PEDOT ZPSS that flowed out from the injection needle 3 was solidified in acetone for about 20 seconds, then pulled up from the coagulation tank 4 and dried over a wire wrap type IC socket previously wetted with acetone.

[0023] <Immersion treatment>

The microfiber produced by the above method is cut to an appropriate length and immersed in a glass vat (size: 145 x 80 x 10 mm) filled with the treatment solution for a predetermined time. It was hung on a wire wrap type IC socket that had been wet with water. Three types of treatment solutions were used: ethylene glycol (EG), dimethyl sulfoxide (DMS 2 O), or dimethylformamide (DMF). V and deviation were immersed in a pure solution to prepare test samples. The immersion time was changed in 5 steps of 30 seconds, 3 minutes, 10 minutes, 20 minutes and 30 minutes.

[0024] <Heat treatment>

An IC socket with microfibers was placed on a ceramic plate, covered with a windshield petri dish, placed in a vacuum oven, and heat-treated by heating for a predetermined time. The heat treatment condition was maintained at 160 ° C for 1 hour for the fiber prepared by PEDOTZPSS aqueous solution force.

[0025] <Measurement of diameter>

The diameter d of the microfiber produced by the above method is the image of a microscope (54590-F, Infinity Photo-Optical Company) equipped with a CCD color camera and an objective lens. A digital video camera (manufactured by Sony, HANDYCAM DCR-PC1000) was taken and measured on the computer using image measurement software (Image SXM, 175-2C).

[0026] <Conductivity measurement>

The conductivity of the microfiber was measured using the 4-terminal method shown in Fig. 3. Cross the microfiber 9 over the pin 10 and insert the tester probe into the two adjacent pins to confirm contact. Confirm that the pin that shows resistance is covered with microfiber on the four adjacent pins. After confirmation, insert the IC socket soldered with copper wire into the pin where the microfiber is firmly attached, and pinch the copper wire with the Kelvin clip 11. At this time, a plastic piece was sandwiched between the Kelvin clips as an insulator. In this state, resistance was measured using a digital multimeter 12 (Model 2000, Keithley). Also, using a reading microscope (manufactured by Shimadzu Corporation), the distance between the center two pins was measured and the distance between electrodes was 1 (cm). Using the fiber diameter d (cm) and resistance value R (Ω) measured by the above method, the electrical conductivity σ (S / cm) was calculated from the following equation.

σ = 1 / RX π (d / 2) ²

[0027] <Temperature dependence of conductivity>

For measurement, a digital multimeter (Model 2000, Keithley), a temperature controller (Model 9700, Scientific Instruments) cryostat (EYELA CA-112) attached (Daikin Kogyo Co., Ltd., cryokelvin (PS22)) It was used. The temperature controller was controlled by a computer and measured under the following conditions.

Temperature increase rate: lKZmin

Measurement temperature: 8K ~ 300K

Sampling: 6sec

[0028] The measurement procedure is as follows.

First, attach a wire wrap type socket with microfiber fixed to the sample holder. At this time, confirm that the resistance of the digital multimeter is shown. Attach two samples in one measurement. Next, the sample holder is closed, vacuum suction is performed, and cooling water for the compressor is poured to start measurement.

[0029] As soon as the compressor is turned on, the temperature control program on the computer make them run. After decreasing the temperature to 8K, it was increased to 300mm. Simultaneously with temperature control, the resistance value was measured by the 4-terminal method.

[0030] After the measurement, the sample in the holder was taken out, the diameter and the distance between the electrodes were measured, and the electrical conductivity was calculated. Using the calculated conductivity σ and temperature Τ, the following equation is used: force 匕 energy Τ, pre-excitation

0

The sponential factor σ was calculated.

0

σ = σ · exp — / Ύ)}

Ο 0

σ is the conductivity obtained by extrapolating the temperature to infinity, and Τ is the electric current between the regions as shown in the following equation.

0 0

It means the actual energy barrier of load carrier hopping.

T = 16 / k · (Ε)-L-L ²

O B F / /

Where N (E) is the density of states at the film level, k is the Boltzmann constant, and L is the high

F B // Local length in the direction parallel to the molecular chain, L means local length in the direction perpendicular to the polymer chain.

[0031] <Tensile test>

For the measurement, a tensile tester (TENSILON UTM-2 type) manufactured by Orientec Co., Ltd. was used. A load cell is attached to the upper part of the sample attachment of this device, which is connected to the combi-tor. As a result, a stress (STRESS) strain (STRAIN) curve as shown in FIG. 4 is obtained, and Young's modulus, cutting strength, and cutting elongation can be obtained. The measurement conditions are as follows.

Chuck interval: 2cm

Full scale: 50g

Sampling time: 0. Is

Head speed: 2mmZ min

Strain rate: 10% Zmin

Measurement temperature: 25 ° C

[0032] The sample was fixed to a cardboard made as a sample holder with a double-sided tape and a mending tape. As described above, the diameter of the sample was measured in advance using a microscope and PC software.

[0033] From the stress-strain curve obtained by measurement, Young's modulus, cutting strength, and cutting elongation are Calculated.

L = a + 15 (mm)

o

E = {(FXL) / (b XS)} X 9.807 X 10 " ⁵ (GPa)

o

St = (F / S) X (l + EL / 100) X 9.807X10— ⁵ (GPa)

EL = AL / L X100 (%)

o

Where L: Initial length of sample (mm)

o

AL: Elongation of sample (mm)

a, b: Numerical values shown in Fig. 4

F: Load when cutting (kg)

S: Sample cross-sectional area (cm ² )

E: Young's modulus (GPa)

St: Cutting strength (GPa)

EL: Cutting elongation (%)

It is.

Next, the effect of improving the conductive characteristics and mechanical characteristics by the treatment method of the present invention will be described.

Fig. 5 shows a comparison of the electrical conductivity of fibers treated by changing the type of treatment solution, pre-treatment fiber (Prestine) and fiber treated by immersion for 3 minutes in the following treatment solution at room temperature, and then heat treatment under the above conditions. The processing solutions used were pure solutions of EG, DMSO, DMF (all of the examples of the present invention) and ethanol (EtOH, comparative examples). As can be seen in the figure, the conductivity before treatment is 1-30 (average about 10) S / cm, whereas when treated with EG, 160-230 (average 200) S / cm DMSO and DMF are 160 to 230 and 120 to 170 S / cm, respectively, and it is known that the conductivity increases to nearly 20 times that before the treatment. On the other hand, when immersed in EtOH, the improvement effect was small at 20-50 S / cm.

[0035] FIG. 6 shows the results of examining the influence of the immersion time in the treatment liquid on the conductivity in the case of the treatment liquid power ¾G. As can be seen in the figure, the conductivity increases from 110 to 210 at an immersion time of 30 seconds, from 160 to 230 S / cm at an immersion time of 3 minutes, and then very large until 30 minutes. There is no change in degree. That is, it was known that the conductivity increased rapidly in 0.5 to 1 minute immediately after immersion and saturated in about 3 minutes. Therefore, in the present invention, the immersion time of the fiber in the treatment liquid is preferably 30 seconds or more, more preferably 3 minutes or more.

For reference, an example of the measurement result of the fiber diameter in this example is shown in FIG. It is known that the fiber diameter is about 5πι. In addition, the horizontal axis in this figure is the dipping time, and there are variations in measured values, but it cannot be said that a significant change in fiber diameter occurred due to the dipping treatment.

[0037] <Temperature dependence of conductivity>

Fig. 8 shows the measurement results of the temperature change of electrical conductivity σ between 8 and 300K of the fiber before dipping treatment (indicated as PEDOTZPSS in the figure) and the fiber (indicated as PEDOTZPSSZEG) that has been heat treated for 3 minutes after being immersed in ethylene glycol. Indicates. Figure 9 shows this data with 1ησ and __1 ^{/ 2} on the vertical and horizontal axes. In general, it has been reported that the temperature dependence of PEDOTZPSS follows a quasi-one-dimensional hopping model.From PEDOTZPSS microfibers, it is known from Fig. 9 that the characteristics are expressed by a quasi-one-dimensional hopping model at 100K and above. T can be obtained by extrapolating the straight line.

0

Table 1 shows a comparison of the values of σ, σ, and Τ obtained in this way.

300 0 0

[0038] [Table 1]

Fiber ^σ 300 'σ ₀ Τ ₀

, (S / cm (Start) (Κ)

PEDOT / PSS 5.3 9.1 85

PEDOT / PSS / EG 205 232 4.3

[0039] The activation energy によって 1S 85K force et al. 4. It decreased to 3K and 1Z20.

On the other hand, the value of conductivity has greatly increased from 5.3 S / cm to 205 S / cm. This is probably because EG entered the microfiber and reacted with PEDOTZPSS to reduce the active energy in carrier hopping. In other words, an increase in density of states and localization length at the Fermi level can be considered.

[0040] Further, the reason for the increase in conductivity is that the EGs wash away the excess insulating layer (PSS) surrounding the PEDOTZPSS particles, thereby facilitating the movement of carriers between the particles. You could think so. At the same time, since EG is a good solvent for PEDOTZPSS, it is thought that PEDOT is more uniformly distributed by extending the PSS chain and forming a three-dimensional network.

[0041] Even when DMSO or DMF is used as the treatment liquid, it is considered that the conductivity is increased by the same effect. The same applies when other aprotic solvents such as acetonitrile, dimethoxyethane, hexamethylphosphoric triamide, glycerin, etc. are used with a solvent of polyethylene glycol, sorbitol, etc. Expected to be effective.

[0042] <Improvement of mechanical properties>

Figure 10 shows a comparison of the stress-strain curves of the fiber before dipping (PEDOTZPSS) and the fiber (PEDOTZPSSZEG) that was dipped in ethylene glycol for 3 minutes and then heat-treated. In addition, Table 2 shows the values of Young's modulus, cutting strength, and cutting elongation obtained from this data by the method described above.

[0043] [Table 2]

Young's modulus Tensile strength

Fiber Elongation at break

(GPa) (Pa) (%)

PEDOT / PSS 2.47 ± 0.73 98.53 ± 34.42 12.28 ± 6.87

PEDOT / PSS / EG 3.66 + 0.64 125.07 ± 26.69 12.50 ± 8.15

[0044] The Young's modulus increases from 2.47 ± 0.73 GPa before treatment to 3.66 ± 0.64 GPa after treatment, and the cutting strength increases from 98.53 ± 34.42 MPa before treatment to 125.07 ± 26.69 MPa after treatment. The reason for this is that when the fiber before treatment is spun in acetone, stress concentration occurs in the structural defects caused by rapid dehydration, and it is easy to break. Therefore, compared to a cast film of the same material, Young's modulus, Both cutting strength is low. In contrast, soaking in EG causes rearrangement of molecular chains and reduces structural defects, which is thought to improve tensile properties.

[0045] The fiber used in the above example is manufactured by the wet spinning method of an acetone coagulation bath. However, the present invention does not have to limit the fiber to be processed in the present invention. It can also be applied to fibers produced by the method. In addition, By using the treatment liquid as a coagulation bath, an emulsion dispersion of a conjugated-diameter conductive polymer material or a precursor solution thereof is injected into the coagulation bath from a nozzle cover to form fibers by the wet spinning method as described above. It has also been confirmed that the characteristic improvement processing can be performed simultaneously.

This specification is based on Japanese Patent Application No. 2006-054131 filed on Feb. 28, 2006. All this content is included here.

Claims

The scope of the claims

[1] A fiber of a conjugated conductive polymer material to which a dopant is added is immersed in a treatment solution containing ethylene glycol and Z or an aprotic solvent for a predetermined time, and the conductive characteristics and mechanical properties of the fiber are immersed. A method for treating a conductive polymer, characterized by improving characteristics.

[2] The conductive polymer material according to claim 1, wherein the conductive polymer material is poly 3,4 ethylene dioxythiophene (PEDOT), and the dopant is poly 4 styrene sulfonic acid (PSS). Processing method.

[3] The aprotic solvent is dimethyl sulfoxide (DMSO) or dimethylformamide

The method for treating a conductive polymer according to claim 1 or 2, which is (DMF).

[4] The fiber is an emulsion dispersion or precursor solution of the conductive polymer material that has flowed out of the nozzle force, using the treatment liquid as a coagulation bath, forming fibers by wet spinning and 4. The method for treating a conductive polymer according to claim 1, wherein the property improvement treatment is performed simultaneously.

[5] The conductive polymer according to any one of claims 1 to 4, wherein the treatment liquid is room temperature, and the immersion time of the fibers in the treatment liquid is 30 seconds or more. Processing method.

[6] The method for treating a conductive polymer according to [5], wherein the immersion time is 3 minutes or more.

[7] A heat treatment is performed in which the fiber treated by the method according to any one of claims 1 to 6 is held at a temperature of 0 to 50 ° C for 1 minute or more under a reduced pressure of absolute pressure ΙΤο rr or less. A method for treating a conductive polymer characterized by the following.