PEDOT: A Revolutionary Conducting Polymer
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PEDOT |
Introduction
Poly(3,4-ethylenedioxythiophene), commonly known as PEDOT, is a fascinating
conducting polymer that has been a subject of extensive research over the past
few decades. With its unique properties, PEDOT holds tremendous potential for
applications across diverse fields ranging from electronic devices to biomedical
technologies.
Chemical Structure and Properties
PEDOT
is a thiophene-based polymer which in its oxidized state exists as
polythiophene cation with a positively charged backbone. It has a monomer unit
consisting of 3,4-ethylenedioxythiophene (EDOT) which provides solubility and
processability due to polar ethylene dioxy groups. The presence of these side
groups helps to overcome aggregation issues commonly seen in conducting
polymers.
The backbone of PEDOT can adopt planar and rigid conformations enabling high
carrier mobility. It has a low band gap of around 1.5 eV which makes it highly
conductive even at low doping levels. PEDOT displays good environmental,
thermal and electrochemical stability. It is less oxidatively and chemically
reactive compared to other conducting polymers like polypyrrole and
polyaniline.
PEDOT is usually processed from its oxidized form as PEDOT:PSS (polystyrene
sulfonate), which enhances its solubility and film forming ability. The
sulfonate anions in PSS act as counter ions to balance the positive charges on
PEDOT backbone imparting high conductivity. PEDOT:PSS has high transparency, is
solution processable and can be deposited easily on various substrates using
techniques like spin coating, inkjet printing etc.
Production Methods
PEDOT can be synthesized using chemical and electrochemical polymerization
techniques. However, the most common method employed commercially is chemical
oxidative polymerization. In this process, EDOT monomer is oxidatively
polymerized using chemical oxidizing agents like iron(III) salts in the
presence of a polymerization mediator like pyridine.
The oxidized form of polymer (PEDOT) is then treated with PSS to obtain
PEDOT:PSS dispersion. This dispersion has high thermal stability and remains
stable for months without any precipitation. PSS not only aids in solubility
but also prevents over-oxidation of PEDOT chains during processing.
Commercially available PEDOT:PSS dispersions have conductivity in the range of
0.1-1000 S/cm.
Applications of PEDOT
With its low cost, good stability and film forming ability, PEDOT:PSS has
become immensely popular for transparent electrode applications in recent
times. It is being widely used as a replacement for expensive materials like
indium tin oxide in touchscreen panels, OLED and LCD displays. PEDOT:PSS
electrodes offer advantages such as flexibility, light weight and anti-glare
properties.
PEDOT is also finding increasing use in bioelectronics and biomedical devices.
Its native electrical conductivity and biocompatibility make it attractive for
technologies like neural implants, biosensors, tissue engineering scaffolds.
PEDOT coatings have been shown to enhance cell adhesion and growth on neural
probes and enhances their performance. PEDOT coated neural probes cause minimal
tissue damage and show great potential for brain-machine interfaces.
PEDOT is also a promising material for energy storage applications such as
supercapacitors and batteries. PEDOT coated electrodes have high specific
capacitance and cycling stability. PEDOT allows fast ion transport and reduces
polarization effects improving electrochemical performance. Research is ongoing
on PEDOT-based cathodes for lithium and sodium ion batteries.
PEDOT is an emerging material for thermoelectric applications as well. Doped
and composite forms of PEDOT have demonstrated high Seebeck coefficients and
electrical conductivity making it suitable for waste heat recovery. PEDOT
nanostructures also show potential for efficient dye sensitized solar cells and
organic photovoltaics due to its ability to transport photogenerated charges
with minimum recombination losses.
PEDOT is a unique conducting polymer that has revolutionized fields ranging
from electronics and energy storage to biomedical engineering, due to its
excellent conductivity, environmental stability and film forming ability.
Continuous efforts are being made to functionalize PEDOT structure and fabricate
nanostructured forms to further enhance its properties. With rapid advancements
in science and processing techniques, PEDOT promises to significantly impact
technologies of the future.
For
more insights, Read- PEDOT
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