Random Conjugated Copolymers for Black-to-Transmissive Electrochromism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current electrochromic polymers face challenges in achieving saturated neutral state colors, particularly black, with efficient and scalable processes, often lacking in optical contrast, switching speed, stability, and processability.
Innovation Solution
Development of random conjugated copolymers with a plurality of donor and acceptor repeating units, where A units are separated by only one D unit and adjacent to D units with solubilizing substituents, allowing for the design of polymers that are black or colored in the neutral state and highly transmissive in the oxidized state, using methods like Stille coupling for polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random oxidative polymerization of symmetric trimeric D-A-D species is used, then saturated black to transmissive electrochromic polymers can be achieved, but additional synthetic steps and costs are required
Solution Approach 1:
The polymer is segmented into alternating donor (D) and acceptor (A) units along the conjugated backbone. This segmentation allows independent optimization of each unit's electronic properties to achieve desired optical characteristics while simplifying the overall synthesis strategy through modular monomer design
Solution Approach 2:
Transition metal catalysts (e.g., Pd, Ni) serve as intermediaries to mediate the cross-coupling reactions between aryl diboronic esters and aryl dihalides. These catalysts enable the formation of alternating D-A copolymers through Suzuki polycondensation, avoiding complex oxidative polymerization steps while maintaining controlled microstructure
2Ease of manufacture
If strictly alternating polymers are formed via Suzuki polymerization, then soluble blue to transmissive polymers result, but saturated black to transmissive electrochromic polymers have limited success
Solution Approach 1:
Solubilizing side chains are locally attached to specific positions on the donor or acceptor units. This local modification provides sufficient solubility for processing while preserving the alternating D-A electronic structure needed for black-to-transmissive electrochromism. The side chains are positioned to minimize disruption to the conjugated backbone's electronic properties
Solution Approach 2:
The polymer combines the alternating D-A conjugated backbone (providing electrochromic function) with solubilizing side chains (providing processability). This composite structure integrates two functional requirements into a single material system, achieving both black-to-transmissive switching and solution processability
3Illumination intensity
If the optical band gap is lowered below 1.75 eV for green, blue, or black neutral state colors, then desired colors are achieved, but optical contrast and switching performance are compromised
Solution Approach 1:
The optical band gap and neutral state color are tuned by systematically varying the electronic properties of donor and acceptor units. By changing parameters such as the strength of electron donation/acceptance, aromatic ring substitution patterns, and side chain electronics, the band gap is optimized to achieve saturated colors while maintaining high optical contrast through appropriate HOMO-LUMO level alignment
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 random conjugated copolymers exhibit high optical contrasts and superior switching speeds and stability, enabling scalable and cost-effective production for reflective and transmissive electrochromic devices with improved electro-optic and mechanical properties.
Implementation Method 1
Polymeric electrochromics capable of a fast and reversible color change upon electrochemical oxidation and reduction
Implementation Method 2
Using common Suzuki polymerization conditions, an aryl diboronic ester and an aryl dihalide, are cross-coupled using palladium catalysis
Data Source
AI summary
Embodiments of the invention are directed to random conjugated copolymers comprising a plurality of one or more different donor (D) repeating units and a plurality of at least one acceptor (A) repeating unit. At least one of the D units has a solubilizing substituent, statistically a portion of the A repeating units are separated from each other by only one D units and a plurality of the A unit are adjacent to one the D units having the solubilizing substituents. The random conjugated copolymers are black or colored in the neutral state and highly transmissive in the oxidized state. The random conjugated copolymers have the structure -[(D)xA]n-, where x>1 and n(x+1)≧10 or the structure -[(DA))x-(D′A)y]n-, where D represents one substituted D unit and D′ represents another D units and where x≧1, y≧1 and 2n(x+y)≧10. Other embodiments of the invention are directed to forming the -[(D)xA]n- or -[(DA)x-(D′A)y]n- random conjugated copolymers by condensation polymerizations between monomers containing complementary reactive groups.