Conductive polymers having highly enhanced solubility in organic solvent and electrical conductivity and synthesizing process thereof

Abstract

The present invention relates to a new process of synthesizing conductive polymers from monomers substituted with amine group. The process provides simple synthesizing steps for the conductive polymers without using other additives such as stabilizers or emulsifiers. The conductive polymers synthesized according to the present invention have highly enhanced solubility in common organic solvents and electrical conductivity compared to conventional conductive polymers. Therefore, the conductive polymers synthesized according to the present process can be utilized in applications that require high electrical conductivity, for example an electromagnetic interference shield or a transparent electrode of thin film, as well as in specific applications such as various conductive films, fibers, polymer blends, battery electrodes or conductive etch mask layers.

Description

[0001] This application claims the benefits of Korean Patent Application No. 2004-33168, filed on May 11, 2004 in Korea and Korean Patent Application No. 2005-0032461, filed on Apr. 19, 2005, which are herein incorporated by reference for all purposes as if fully set forth herein. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to conductive polymers, and more particularly to conductive polymers which have highly enhanced solubility in organic solvents and electrical conductivity, and synthesizing process thereof. [0004] 2. Discussion of the Related Art [0005] Conductive polymers have conjugated structures along double bonds present in the backbone thereof and has much enhanced electrical conductive properties compared to other organic materials because the conductive polymers form partial electrical charges along the conjugate structures and thereby having unlocalized electrons when the polymers are doped with dopants such as a prot...

AI Technical Summary

Benefits of technology

[0037] The present invention is based on a new concept of self-stabilized dispersion polymerization (referred to as “SSDP”). The use of the term “self-stabilized” herein includes, but is not limited to, the dispersion in the absence of any stabilizers. For example, in contrast with conventional homogeneous or dispersion polymerization using an aqueous medium containing aniline, pyrrole, acid, and oxidant, this new polymerization process is performed in a heterogeneous biphasic system of organic and aqueous medium without any stabilizing additives. Here, the monomers and growing polymer chains act as a stabilizer, resulting in excellent dispersion of the organic phase inside of the aqueous reaction medium.

[0038] It is an objective of the present invention is to provide a synthesizing process of conductive polymers without using other additives such as emulsifier and antifreeze thereby reducing polymerization reaction time. Accordingly, the conductive polymers of the present invention have much highly improved physical property, for example electrical conductivity and solubility to common solvents.

[0039] It is another objective of the present invention is to provide a conductive polymer that has highly improved micro-chemical structure with little structural defects.

[0063] The conductive polymer synthesized according to the present invention has highly linear configuration, fewer side chains, and therefore highly improved electrical conductivity compared to polyaniline synthesized according to conventional process. Accordingly, polyaniline of the present invention may be used as various conductive films, fibers, coatings, blends with other polymers, battery electrodes, or material for organic semiconductors or organic device. Especially, polyaniline synthesized according to the present invention may be utilized as transparent electrodes, solar cells, conductive etch mask layer or for anti-corrosion, absorbency of near infrared light since composites or composition comprising polyaniline of the present invention has highly improved electrical conductivity even though low contents of polyaniline.

Problems solved by technology

However, the conductive polymers synthesized through the conventional processes, especially the polyaniline as the completely reduced from, leucoemeraldine, the intermediated oxidized from, emeraldine salt, and the fully oxidized form, pernigraniline, have disadvantages that they cannot be made from melting process owing to their high boiling point and that they must experience complex processing steps since they have low solubility in solvents with high-boiling point or universal or compatible solvents such as meta-cresol.

However, those composites have lower electrical conductivity compared to the conductive polymers before reforming.

Especially, the polyaniline synthesized according to the MacDiarmid process has low molecular weight, broad molecular weight distribution, and inferior solubility to solvents or electrical conductivity resulted from side chain reactions to the backbone.

However, since Cao et al. uses functionalized protonic acids as emulsifier, it is difficult to control doping the emulsifier and the process requires commonly expensive material.

Further, since the functionalized organic acid is hardly separated from polyaniline after polymerizing reaction, the conductive polymers may have only very limited uses and highly inferior electrical properties.

However, it is difficult to synthesize polyaniline because the radical initiator in the aqueous layer is separated from the monomer in the organic layer and polyaniline synthesized according to Kinlen process has low electrical conductivity owing to difficulty of control doping process.

However, since pyruvic acid has lower acidity it is difficult to dope polyaniline by pyruvic acid.

However, since it is not easy to separate the non-aqueous layer from an aqueous layer, it is expected that polyaniline synthesized according to Ho process may not have high electrical conductivity.

However, polyaniline film prepared from Palaniappan process has very low electrical conductivity, for example about 0.1 S / cm, and may be only used in much limited applications since it is impossible to raise molecular weight of polyaniline.

However, the synthesized polyaniline has a particle size of about 60˜300 nm, which is affected by the stabilizer, and has low electrical conductivity, which defines its application.

However, since it needs very long polymerization reaction time in Geng process, a probability of side reaction is raised.

However, mixing those metallic salts with the solution system causes the reaction to being slow, that is to say, at least 48 hours to complete the polymerizing reaction, and therefore, it is difficult to control the polymerization reaction.

Besides, since the monomers are added into the polyaniline on the ortho-positions as much as the para-positions of the benzene ring in the polyaniline backbone in case of emulsion polymerization or interfacial polymerization, such synthesized polyaniline has much side chains, which cause the polyaniline to have lower electrical conductivity and solubility.

Such polymers synthesized by ortho-coupling has lower hydraulic dimensions, which results in decreased intrinsic viscosity, compared to polymers synthesized by para-coupling, i.e. polymers without side chains.

Accordingly, the polymers synthesized by ortho-coupling has inferior processability without improving the electrical conductivity.

However, the polyaniline producing processes disclosed to date make use of introducing substituents into monomers or mixing the monomers with immense amount of additives such as stabilizer or emulsifier, and therefore, it is difficult to obtain pure polyaniline.

Also, because polyaniline according to conventional processes has synthesized by ortho-coupling as much as para-coupling and frequently forms side chains by side reactions, such polyaniline does not have high electrical conductivity, which limits its applications.

However, when polypyrrole is synthesized according to the chemical process, side reactions such as inter-chain crosslink or side chain addition to the backbone of polypyrrole frequently happened, which causes synthesized polypyrrole to not dissolving in common solvents and therefore deteriorates processability.

However, polypyrrole film sample synthesized by Lee et al. has very low electrical conductivity of about 5 S / cm.

However, such synthesized polypyrrole did not have electrical conductivity at all.

However, since polypyrrole powders are surrounded by a lot of stabilizers, like polyaniline, and therefore polypyrrole has a very low electrical conductivity.

As mentioned above, pyrrole may be soluble in much solvents compared to aniline, however, it is very difficult to dissolve oxidizing agent and pyrrole monomer in the same solvent.

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