Water-Soluble Polythiophene Self-Doping Conductivity
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Solution Overview
Problem
Current water-soluble electrically conductive polymers, such as PEDOT-PSS, face challenges with low electrical conductivity, heat resistance, and water resistance due to excess sulfo groups, and have large polymer moieties that do not contribute to doping, making them unsuitable for high-performance applications like solid polymer electrolytes and printable electronics.
Innovation Solution
A polythiophene with specific structural units, including sulfo groups bonded by covalent bonds, is developed, which self-dopes and provides improved electrical conductivity, formability, and water solubility without the need for additional dopants, allowing for the creation of a water-soluble electrically conductive polymer aqueous solution with small particle size for enhanced infiltration and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EDOT is polymerized in the presence of water-soluble high molecular weight dopant such as PSS to obtain water-soluble electrically conductive polymer, then water solubility and formability are improved, but electrical conductivity becomes low due to large quantity of polymer moieties with low electrical conductivity that do not contribute to doping
Solution Approach 1:
The polymer chain is segmented into conductive segments (doped thiophene units) and water-soluble segments (sulfo groups with alkylene chains). This segmentation allows different parts of the polymer to fulfill different functions: electrical conductivity and water solubility, respectively.
Solution Approach 2:
The invention merges the doping function and water solubility function into a single polymer structure. The sulfo groups serve dual purposes: they provide water solubility through their ionic character and serve as dopants to provide electrical conductivity, eliminating the need for separate dopant molecules like PSS.
2Ease of manufacture
If EDOT is polymerized in the presence of water-soluble high molecular weight dopant such as PSS to obtain water-soluble electrically conductive polymer, then water solubility is improved, but heat resistance and water resistance become low due to sulfo groups in large excess
Solution Approach 1:
The invention changes the parameter of sulfo group concentration by controlling the polymerization conditions and monomer structure to achieve an optimal balance between water solubility and thermal stability. The sulfo group content is optimized rather than being in large excess.
3Ease of manufacture
If compound having substituents having both function to impart water solubility and doping function is polymerized to obtain water-soluble self-doping electrically conductive polymer, then formability is improved, but electrical conductivity becomes insufficient for high-performance applications due to excess sulfo groups
Solution Approach 1:
The polymer structure exhibits local quality differentiation where specific regions (thiophene units) provide electrical conductivity while other regions (sulfo groups with alkylene chains) provide water solubility. This local differentiation allows optimal performance in both functions without compromise.
4Ease of manufacture
If water-soluble electrically conductive polymer with large particle size is used for inkjet application, then formability is improved, but nozzle clogging occurs
Solution Approach 1:
The invention changes the particle size parameter by optimizing polymerization conditions and polymer structure to produce ultrafine particles with diameter of 10 nm or less. This parameter change eliminates nozzle clogging while maintaining formability for inkjet applications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The polythiophene achieves favorable electrical conductivity, formability, and water solubility, enabling improved performance in applications like solid electrolytes and printable electronics by self-doping and eliminating the need for external dopants, while maintaining a small particle size for better infiltration.
Implementation Method 1
a water-soluble self-doping electrically conductive polymer which is excellent in the formability
Implementation Method 2
a compound having substituents having both a function to impart water solubility and a doping function (for example, sulfo groups or sulfonate groups) introduced in a polymer molecular chain by covalent bonds
Implementation Method 3
a water-soluble electrically conductive polymer, which is soluble in water with a light environmental burden
Data Source
AI summary
To provide a water-soluble polythiophene used as an electrically conductive material, and its production method.A polythiophene comprising at least one type of structural units selected from the group consisting of structural units represented by the formula (1), structural units represented by the formula (2), structural units represented by the formula (3), structural units represented by the formula (4), structural units represented by the formula (5) and structural units represented by the formula (6). The polythiophene is obtained by polymerizing at least one thiophene compound selected from the group consisting of a thiophene compound represented by the formula (15), a thiophene compound represented by the formula (16) and a thiophene compound represented by the formula (17) in water or an alcohol solvent in the presence of an oxidizing agent.