Syndiotactic Polyvinyl Alcohol Copolymer Water Solubility
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Solution Overview
Problem
Syndiotactic polyvinyl alcohol (PVOH) exhibits low water solubility, leading to harsh operating conditions and difficulties in processing and converting it into end products, especially when forming polarizing films, due to strong intramolecular hydrogen bonds and iodine desorption under hot and humid conditions.
Innovation Solution
A water-soluble polyvinyl alcohol copolymer with a diad syndiotacticity of 60-70% is achieved by copolymerizing vinyl esters with solubilizing comonomers, allowing for high water solubility at temperatures below 100°C, enabling the formation of polarizing films with improved iodine complexation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If syndiotactic PVOH is used to reduce iodine desorption, then polarizing film stability is improved, but water solubility deteriorates due to strong intramolecular hydrogen bonds
Solution Approach 1:
The patent applies parameter changes by controlling the syndiotacticity of PVOH to a specific range (55-65%, particularly 58-62%) rather than using high syndiotacticity (>70%). This optimized parameter range reduces intramolecular hydrogen bonding while maintaining sufficient iodine complex stability, achieving both water solubility and film stability. The patent also controls molecular weight (10,000-100,000) and uses specific processing conditions to balance these properties.
2Reliability
If high syndiotacticity PVOH (>70%) is used, then iodine desorption is reduced, but processing difficulty increases due to poor solubility requiring harsh conditions
Solution Approach 1:
The patent changes the syndiotacticity parameter from conventional high values (>70%) to an optimized range (55-65%). This parameter modification reduces the strength of intramolecular hydrogen bonds, improving water solubility and processing ease while maintaining adequate iodine complex stability for polarizing film applications. The patent demonstrates that this intermediate syndiotacticity range optimizes the balance between processability and performance.
3Ease of operation
If atactic PVOH (diad syndiotacticity <53%) is used, then water solubility is improved, but iodine desorption increases under hot and humid conditions
Solution Approach 1:
The patent optimizes the syndiotacticity parameter to a specific range (55-65%, particularly 58-62%) that lies between atactic and highly syndiotactic PVOH. This intermediate value provides sufficient chain regularity to maintain iodine complex stability and reduce desorption, while avoiding excessive intramolecular hydrogen bonding that would reduce water solubility. This precise parameter control resolves the contradiction between solubility and stability.
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 high syndiotactic polyvinyl alcohol copolymers demonstrate excellent water solubility, ease of processing, and high polarizing efficiency with reduced iodine desorption, even under high heat and humidity, facilitating the production of durable and efficient polarizing films.
Implementation Method 1
PVOH may form a complex with iodine as the polyiodide ions interrupt the intermolecular hydrogen bonds
Implementation Method 2
syndiotactic PVOH exhibit a strong intramolecular hydrogen bond
Data Source
AI summary
A water soluble polyvinyl alcohol copolymer having a diad syndiotacticity of greater than about 60% and less than about 70%. In some embodiments, the water soluble polyvinyl alcohol copolymer is soluble in water at a concentration of at least 1 wt % at a temperature of less than 100° C. In other embodiments, the composition is soluble in water at a concentration of at least 5 wt % at a temperature in the range from about 90° C. to less than 100° C. The high solubility of the high syndiotactic poly vinyl alcohols disclosed herein may provide various advantages as described herein, including ease of processing and decreased use of harmful solvents.