Electrochromic Copolymers Without Acceptor Units
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Solution Overview
Problem
Existing electrochromic polymers (ECPs) with donor-acceptor (D-A) effects face challenges in achieving high transmissive states with minimal residual visible absorption, leading to unsatisfactory color tones, especially in oxidized states, due to steric interactions and charge carrier absorption in the near-infrared spectrum.
Innovation Solution
Development of copolymers without electron acceptor repeating units, utilizing only electron donor units and specific dioxythiophene derivatives like propylenedioxythiophene (ProDOT) and acyclic dioxythiophene (AcDOT), which are soluble in organic solvents, allowing for high stability and intense neutral state colors that transition effectively to highly transmissive states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If donor-acceptor (D-A) effects are used to generate desirable visible absorption and color in ECPs, then color intensity in neutral state is improved, but residual visible absorption in oxidized state increases causing blue tint
Solution Approach 1:
The patent removes electron acceptor units from the copolymer structure, extracting the source of charge carrier absorption that causes residual visible absorption and blue tint in oxidized states, while retaining electron donor units that provide intense neutral state colors
Solution Approach 2:
The patent changes the electronic parameters of the polymer by using only electron donor units with specific HOMO levels, altering the absorption characteristics to eliminate charge carrier absorption in the visible spectrum while maintaining intense neutral state colors
2Adaptability or versatility
If steric control is used to tune color in ECPs, then color tuning capability is improved, but transmissive oxidized state performance deteriorates
Solution Approach 1:
The patent applies local quality by using specific dioxythiophene units (ProDOT, AcDOT) with defined steric properties at specific positions in the copolymer, achieving color tuning through localized structural characteristics while maintaining overall transmissive performance
Solution Approach 2:
The patent creates composite copolymer structures combining different electron donor units (ProDOT, AcDOT, other heterocycles) to achieve both color tuning capability and high transmissive oxidized state performance through synergistic material composition
3Reliability
If highly electron rich alkylene dioxythiophenes are used to achieve highly transmissive oxidized states, then transmissive state performance is improved, but neutral state color intensity decreases
Solution Approach 1:
The patent optimizes the HOMO level parameters of the electron donor units to achieve the right balance, ensuring sufficiently high electron richness for transmissive oxidized states while maintaining adequate neutral state color intensity through controlled HOMO energy levels
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 copolymers exhibit high electrochromic contrast, rapid switching, and minimal residual absorption in oxidized states, enabling vibrant color transitions and stable charging/discharging capabilities, suitable for display and window devices, as well as supercapacitor applications.
Implementation Method 1
Electrochromic polymers (ECPs) display a broad array of colors that can switch from the colored states to highly transmissive states
Implementation Method 2
the low oxidation potentials required for long term redox switching
Data Source
AI summary
Copolymers including dioxythiophene repeating units and no acceptor units allow the formation of electrochromic polymers (ECPs) with vivid neutral state colors and very colorless oxidized states that can be switched rapidly. The dioxythiophene repeating units can included in sequences where all of one type of dioxythiophene is included exclusively as isolated dyads or triads within the copolymer, or the copolymer can be an alternating copolymer with propylenedioxythiophene units. Other non-acceptor units can be included in the copolymers. The copolymers are rendered organic solvent soluble by alkyl substituents on repeating units. The inclusion of sterically encumbered acyclic dioxythiophene (AcDOT) units promotes red color while unsubstituted ethylenedioxythiophene (EDOT) units promote blue colors, and their respective content can be manipulated to achieve a desired neutral state color. Soluble copolymers comprising at least 50% EDOT repeating units can be used in supercapacitor applications.