Electrochemical Preparation of Electro-active Polymers having Nitrogen Atom
Authors: Eguchi Naoto , Goto Hiromasa 
Published: February 2020

New functions of polymer film can be developed by using template. We synthesized polypyrrole (PPy) as a conducting polymer in liquid crystal electrolyte solution. The liquid crystal electrolyte solution for the electrochemical polymerization contains monomer, electrolyte, and matrix liquid crystal. The electrochemical polymerization in liquid crystal was simply performed by using sandwich cell electrochemical polymerization method, which we have originally developed. Application of constant voltage between the two electrodes produces a solid polymer film at anode side through electrochemical oxidation polymerization process. Polarizing optical microscopy observation revealed that the polymer film thus obtained show beautiful optical texture like liquid crystal. The surface texture was derived from molecular structure transcription from the liquid crystal electrolyte solution. The transcription is occurred from molecular level to macroscopic level. Infrared absorption spectroscopy measurements, UV-Vis absorption measurements confirm that the polymer film is exactly pi-conjugated film, although the optical structure is very similar to that of liquid crystal. Furthermore, the polymer film can be tuned its color via electrochemical redox reaction (doping-dedoping). Therefore, the polymer has both liquid crystal order and electro-active property.

Lyotropic liquid crystals have good affinity with water, and form crystal like aggregation structure via a self-assembly. Lyotropic liquid crystal shows variety in liquid crystal type, such as columnar phase, smectic phase, nematic phase, and cholesteric phase.  In this research, we employed lyotropic liquid crystals for electrolyte solution.

Columnar liquid crystals have paid attention as an electrical conduction materials having good carrier mobility. Therefore, the polymer thus prepared can be expected to show structure based unique electrical conduction function through columnar form produced by the transcription from the liquid crystal electrolyte solution in the electrochemical polymerization.

Cholesteric liquid crystals show chiral aggregation form. The polymer prepared in cholesteric liquid crystal shows fingerprint texture under the observation of polarizing optical microscope, and optical rotation and circular dichroism. The optical rotation angle can be controlled with electrochemical redox reaction.

In this presentation, we report,

1) Preparation of liquid crystal electrolyte solution and characterization

2) Electrochemical polymerization

3) Spectroelectrochemistry.

     This research can be involved molecularly imprinting (MIP) [3,4]. We discuss the method of electrochemical polymerization, functions, and future prospective of the polymer films prepared in liquid crystals based on electrochemistry.

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