Purifying PS-b-PXVP Block Copolymers by Lithium Salt Extraction
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Solution Overview
Problem
Conventional methods for manufacturing PS-b-PXVP result in high concentrations of impurities like lithium salts, which limit the purity of block copolymer compositions and affect the formation of nanoscale patterns in integrated circuitry and other devices, as these impurities can interfere with the self-assembly process and result in unwanted features on substrates.
Innovation Solution
A block copolymer-comprising composition with minimized lithium salt content, where the lithium salt is present at no greater than 1 ppm by weight, and a method involving the use of a carbon-containing solvent and subsequent precipitation steps to purify PS-b-PXVP, achieving a composition with PS-b-PXVP at 99.99998% by weight or higher, effectively reducing impurities and enhancing the purity of the block copolymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing methods are used for PS-b-PXVP, then production cost and ease of manufacture are improved, but lithium salt impurity content increases to 400-500 ppm
Solution Approach 1:
The patent applies extraction by dissolving the block copolymer in a carbon-containing solvent that selectively solubilizes lithium salt impurities, then removing the solvent to leave purified copolymer. This extracts the harmful lithium salt component (400-500 ppm initially) down to trace levels (≤1 ppm) while maintaining ease of manufacture through a straightforward dissolution-precipitation process.
Solution Approach 2:
The patent changes the physical-chemical parameters of the system by selecting a specific carbon-containing solvent (tetrahydrofuran, nitroethane, nitrobenzene, dimethylformamide, acetone, or methylethylketone) that alters the solubility characteristics. This parameter change enables selective dissolution of lithium salt impurities at room temperature, achieving purification without complex equipment or extreme conditions.
2Manufacturing precision
If lithium salt content is reduced to ≤1 ppm, then nanoscale pattern formation accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the inherent solubility characteristics of lithium salt in carbon-containing solvents. The purification process requires no external energy input, catalysts, or complex equipment—simply mixing the copolymer with the solvent allows spontaneous dissolution of lithium salt, followed by simple evaporation or filtration to achieve ≤1 ppm purity levels.
Solution Approach 2:
The patent employs a disposable solvent system where the carbon-containing solvent is used once for purification and then removed by evaporation or filtration. This single-use approach avoids the need for expensive, complex purification equipment while achieving the required precision, making the process economically viable despite the added step.
3Quantity of substance
If lithium salt impurities are present at 400-500 ppm, then manufacturing cost is reduced, but unwanted features appear on substrates during self-assembly
Solution Approach 1:
The patent converts the harmful effect of lithium salt impurities into a beneficial purification opportunity. By deliberately using a carbon-containing solvent that preferentially dissolves lithium salt, the process transforms the presence of impurities into a means of removing them. The lithium salt, initially harmful at 400-500 ppm, becomes the target of selective extraction, leaving ≤1 ppm in the final product and eliminating unwanted substrate features.
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 solution achieves significantly higher purity of PS-b-PXVP, reducing lithium salt concentrations to as low as 0.1 ppm, thereby improving the accuracy and reliability of nanoscale pattern formation by minimizing unwanted features and enhancing the precision of block copolymer self-assembly processes.
Implementation Method 1
dissolving the composition in a carbon-containing solvent
Implementation Method 2
removing the solvent
Data Source
AI summary
In one embodiment, a block copolymer-containing composition includes PS-b-PXVP and a lithium salt, where “X” is 2 or 4. All lithium salt is present in the composition at no greater than 1 ppm by weight. In one embodiment, a homogenous block copolymer-including comprising has PS-b-PXVP present in the composition at no less than 99.99998% by weight, where “X” is 2 or 4. Methods of forming such compositions are disclosed.