CN101798386A - Method for preparing water-soluble conductive polyaniline - Google Patents

Abstract

The invention relates to a water-soluble conductive polyaniline and a preparation method thereof. The present invention adopts the microemulsion polymerization method, in an ice-water bath, with aniline as a monomer, ammonium persulfate as an initiator, dodecylbenzenesulfonic acid as a dopant and emulsifier, and ethanol as a co-emulsifier to synthesize a water-soluble Conductive emeraldine polyaniline. The preparation method is: add aniline to the aqueous solution of dodecylbenzenesulfonic acid (the molar ratio of aniline and dodecylbenzenesulfonic acid is 1:1~1:2) under the condition of ice-water bath and stirring, add ethanol (volume ratio of ethanol to deionized water is 1:4~4:1), stirred for 30min, the concentration of aniline in the system is 0.15~0.3mol/L, add 1mol/L ammonium persulfate aqueous solution (ammonium persulfate and The molar ratio of aniline is 1:1～1:1.25), stirring for 60min. Put the reaction system into a container at 0-5°C and react for 48 hours. Filter with suction, wash with ethanol/water to obtain a filter cake, and dry in vacuo to obtain a dark green powder.

Description

Preparation method of water-soluble conductive polyaniline

technical field

The invention belongs to the field of optoelectronic polymer materials, and relates to a preparation method of large molecular weight water-soluble high-conductivity polyaniline.

Background technique

Polyaniline (PANI) has excellent electrical, optical and electrochemical properties and excellent environmental stability, and the monomer aniline (AN) for preparing polyaniline is cheap and easy to obtain, and the synthesis process is simple, so it is considered to be very likely to be commercialized. One of the optoelectronic polymer materials. But its application in the field of optoelectronics largely depends on its formability. Due to the presence of benzene rings on polyaniline chains, interchain hydrogen bond interactions, and charge delocalization effects, the polymer is insoluble and infusible, which seriously hinders its large-scale application in the field of optoelectronics. Polyaniline is a high polymer with delocalized electronic conjugated system, which can be made to have metal or semiconductor properties by doping or changing the structure.

At present, there are many synthetic methods for preparing water-soluble conductive polyaniline, such as chemical oxidative polymerization, electrochemical polymerization, condensation polymerization, on-site adsorption polymerization, emulsion polymerization and precipitation polymerization, etc., but due to harsh process conditions or expensive auxiliary raw materials, it has not been possible. be widely used. The invention adopts a novel emulsion polymerization method with low price, simple equipment and convenient operation to prepare highly conductive polyaniline with good solubility and large molecular weight. Compared with previous synthesis methods of polyaniline, this method uses low-cost ethanol instead of long-chain alcohols or alkanes as cosolvents, does not involve highly corrosive and toxic reagents in the preparation process, and the product has low viscosity, easy washing, and good solubility. Good electrical conductivity and large molecular weight.

Contents of the invention

The purpose of the present invention is to provide a method for preparing water-soluble conductive polyaniline with simple process and low cost.

The purpose of the present invention is achieved by adopting the following technical solutions.

Using microemulsion polymerization, in an ice-water bath, using aniline as a monomer, ammonium persulfate as an initiator, dodecylbenzenesulfonic acid as a dopant and emulsifier, and ethanol as a co-emulsifier, synthesized a highly conductive , emeraldine polyaniline with good solubility and molecular weight above 10 ⁵ . The preparation method of above-mentioned high molecular weight water-soluble conductive polyaniline, its specific implementation method is the following steps:

1) Aniline is distilled under reduced pressure at 90-110°C, and steamed 1-2 times.

2) Under the conditions of ice-water bath and mechanical stirring, add the aniline monomer to the dodecylbenzenesulfonic acid (the molar ratio of aniline and dodecylbenzenesulfonic acid is 1:1~1:2) Add an appropriate amount of ethanol (the volume ratio of ethanol to deionized water is 1:4 to 4:1) in deionized water, stir for 30 to 60 minutes, and the reaction system is a colorless transparent liquid (the concentration of aniline in the final system is 0.15mol/L ~0.3mol/L).

3) At 0-5°C, slowly add 1mol/L ammonium persulfate aqueous solution (the molar ratio of ammonium persulfate to aniline is 1:1-1:1.25), stir for 30-60min, and the reaction system changes from colorless to slowly It turns white, quickly turns blue, and finally dark green.

4) Put the reaction system into a container at 0-5°C and fully react for 36-48 hours.

5) Suction filtration, washing with ethanol/water to obtain a dark green filter cake, and vacuum drying at 40-60° C. to obtain a dark green powder.

The polyaniline prepared by the above method is characterized by gel permeation chromatography (GPC), and the number average molecular weight is above 10 ⁵ , and the molecular weight distribution is about 1.1; the water solubility is good, and the solution is dark green; the conductivity reaches 30 S/cm.

In the present invention, dodecylbenzenesulfonic acid is used as dopant and emulsifier, ammonium persulfate is used as oxidant, water is used as solvent, aniline is used as monomer, and cheap and non-toxic conventional solvent ethanol is used to replace n-butylene used in emulsion polymerization. Alcohol, pentanediol and other highly equivalent organic solvents are used as co-emulsifiers to synthesize polyaniline. By controlling the amount of ethanol, polyaniline with good solubility and large molecular weight was synthesized. The microemulsion polymerization system is composed of water, aniline, emulsifier and co-emulsifier. In the past, co-emulsifiers are generally long-chain alcohols or alkanes, but in the present invention, conventional ethanol is used to obtain a microemulsion system, and the product has a large molecular weight while ensuring solubility. The method that the present invention adopts has cost low (used raw material has only used cheap water and ethanol as solvent and auxiliary emulsifier respectively, rather than the long-chain Alkanes are equivalent to highly toxic organic solvents), which is expected to save costs by 8% to 10%, while avoiding the harm of toxic solvents such as toluene and n-hexane to the human body; in addition, the preparation process does not require the protection of inert gases such as nitrogen and argon. The operating conditions are easy to control (under mild temperature and stirring conditions), which is convenient for large-scale production; it does not need to add acetone and other demulsifiers during post-treatment, and can be directly filtered, reducing the use of solvents and reducing costs.

The present invention has the following advantages:

The invention has the advantages of easy control of reaction conditions, simple reaction equipment, low price of raw materials, and no pollution, and can better meet the needs of today's green economy.

In the past, co-emulsifiers were generally long-chain alcohols or alkanes. In the present invention, common ethanol is used to obtain a microemulsion system, which is cheap, non-toxic and harmless, has little impact on the environment, and has good effects.

In the microemulsion method adopted by the present invention, the concentration of emulsifier and co-emulsifier in the system is very high, and the concentration of monomer is very low. The monomer is mainly dispersed in water in the form of microbead droplets, wherein the organic acid plays the role of emulsifier , while providing the pH and counterions required for doping. The sulfonate group of the emulsifier dodecylbenzenesulfonic acid forms an ion pair with the nitrogen cation on the main chain of polyaniline, and the dodecylbenzenesulfonic acid has a good doping effect on PANI, so that the prepared polyaniline has a good High molecular weight and good solubility.

Detailed ways

Example 1

1) Aniline was distilled under reduced pressure at 95°C, and distilled twice.

2) Under the conditions of ice-water bath and mechanical stirring, add 1 mL of aniline monomer to 25 mL of deionized water dissolved with 2.63 g of dodecylbenzenesulfonic acid, add 25 mL of ethanol, and stir for 30 min. The reaction system changes from white emulsion to no Color transparent liquid.

3) Slowly add ammonium persulfate (2.49g dissolved in 10mL water) solution dropwise at 0-5°C, stir for 1 hour, the reaction system turns from colorless to white slowly, then blue soon, and finally dark green .

4) Put the reaction system into a container at 5°C and fully react for 48 hours.

5) Suction filtration, washing with ethanol/water to obtain a dark green filter cake, and vacuum drying at 40° C. to obtain a dark green powder.

The polyaniline prepared in this example was characterized by gel permeation chromatography (GPC), and the number average molecular weight was 1.3×10 ⁵ , and the molecular weight distribution was 1.10. The water solubility is good, and the solution is dark green. The conductivity is 24S/cm.

Example 2

1) Aniline was distilled under reduced pressure at 95°C, and distilled twice.

2) Under the conditions of ice-water bath and mechanical stirring, add 1 mL of aniline monomer to 30 mL of deionized water dissolved with 2.63 g of dodecylbenzenesulfonic acid, add 20 mL of ethanol, and stir for 30 min. The reaction system changes from white emulsion to no Color transparent liquid.

3) Slowly add ammonium persulfate (2.49g dissolved in 10mL water) solution dropwise at 0-5°C, stir for 1 hour, the reaction system changes from colorless to white slowly, then blue soon, and finally dark green .

4) Put the reaction system into a container at 5°C and fully react for 48 hours.

5) Suction filtration, washing with ethanol/water to obtain a dark green filter cake, and vacuum drying at 40° C. to obtain a dark green powder.

The polyaniline prepared in this example was characterized by gel permeation chromatography (GPC), and the number average molecular weight was 9×10 ⁴ , and the molecular weight distribution was 1.08. The water solubility is good, and the solution is dark green. The conductivity is 26S/cm.

Example 3

1) Aniline was distilled under reduced pressure at 95°C, and distilled twice.

2) Under the conditions of ice-water bath and mechanical stirring, add 1 mL of aniline monomer to 10 mL of deionized water dissolved with 2.63 g of dodecylbenzenesulfonic acid, add 40 mL of ethanol, and stir for 30 min. The reaction system changes from white emulsion to no Color transparent liquid.

3) Slowly add ammonium persulfate (2.49g dissolved in 10mL water) solution dropwise at 0-5°C, stir for 1 hour, the reaction system changes from colorless to white slowly, then blue soon, and finally dark green .

4) Put the reaction system into a container at 5°C and fully react for 48 hours.

5) Suction filtration, washing with ethanol/water to obtain a dark green filter cake, and vacuum drying at 40° C. to obtain a dark green powder.

The polyaniline prepared in this example was characterized by gel permeation chromatography (GPC), and the number average molecular weight was 6×10 ⁴ , and the molecular weight distribution was 1.04. The water solubility is good, and the solution is dark green. The conductivity is 40S/cm.

Claims (1)

1. the preparation method of a water-soluble conducting polyaniline is characterized in that the concrete steps of this method are as follows:

A. aniline steams 1～2 time 90～110 ℃ of underpressure distillation;

B. under ice-water bath, mechanical stirring condition, aniline monomer is joined in the deionized water that is dissolved with Witco 1298 Soft Acid, the mol ratio of aniline and Witco 1298 Soft Acid is 1: 1～1: 2, add an amount of ethanol, the volume ratio of ethanol and deionized water is 1: 4～4: 1, stir 30～60min, reaction system is a water white transparency shape liquid, and the concentration of aniline is 0.15～0.3mol/L in the final system;

C. under 0～5 ℃, slowly drip the ammonium persulfate aqueous solution of 1mol/L, the mol ratio of ammonium persulphate and aniline is 1: 1～1: 1.25, stirs 30～60min afterreaction system and becomes blackish green;

D. reaction system is put into 0～5 ℃ container, fully reacted 36～48h;

E. suction filtration with the ethanol/water washing, obtains blackish green filter cake, and 40～60 ℃ of vacuum-dryings obtain blackish green powder.