Vinylidene Fluoride Copolymer Random Distribution via Supercritical Pressure
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Solution Overview
Problem
Vinylidene fluoride copolymers with hydrophilic (meth)acrylic monomers face challenges in achieving a random distribution of units, leading to impaired thermal stability and mechanical properties due to uncontrolled radical side reactions during polymerization, resulting in blocky structures and cross-linked materials.
Innovation Solution
A process involving polymerization in an aqueous medium with a radical initiator, where vinylidene fluoride and hydrophilic (meth)acrylic monomers are continuously fed, maintaining pressure above the critical pressure of vinylidene fluoride, to achieve a substantially random distribution of hydrophilic monomer units within the polymer backbone, resulting in a linear semi-crystalline copolymer with improved thermal stability and adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface functionalization of pre-formed PVDF is used to add hydrophilic properties, then adhesion towards metals and hydrophilic properties are improved, but uncontrolled radical side reactions occur leading to cross-linked materials with impaired mechanical properties
Solution Approach 1:
Instead of functionalizing pre-formed PVDF (adding hydrophilic groups to the fluorinated backbone), the invention inverts the approach by copolymerizing vinylidene fluoride with hydrophilic (meth)acrylic monomers from the beginning. This produces linear copolymers where hydrophilic units are incorporated into the polymer chain during polymerization, avoiding the need for post-polymerization modification and the associated radical side reactions that cause cross-linking and mechanical property degradation.
Solution Approach 2:
The invention changes the polymerization parameters and conditions to achieve controlled copolymerization. By using specific polymerization conditions and maintaining pressure above the critical pressure of vinylidene fluoride, the process achieves a substantially random distribution of hydrophilic monomer units (at least 40% fraction) while preventing uncontrolled radical reactions and cross-linking, thus maintaining both adhesion properties and mechanical integrity.
2Strength
If hydrophilic (meth)acrylic monomers are copolymerized with vinylidene fluoride, then adhesion and hydrophilic properties are improved, but blocky structures are obtained leading to impaired thermal stability
Solution Approach 1:
The invention changes the polymerization parameters, specifically maintaining pressure above the critical pressure of vinylidene fluoride and using controlled polymerization conditions. These parameter changes enable a substantially random distribution of hydrophilic monomer units (with a fraction of randomly distributed units of at least 40%) along the polymer chain, preventing blocky structures and preserving thermal stability while achieving improved adhesion properties.
Solution Approach 2:
The invention employs controlled polymerization processes with feedback mechanisms to monitor and adjust polymerization conditions. This ensures that hydrophilic (meth)acrylic monomers are incorporated in a substantially random distribution pattern rather than forming blocks, thereby maintaining thermal stability while achieving the desired adhesion improvement.
3Strength
If increasing level of acrylic acid is incorporated to improve adhesion, then adhesion is enhanced, but thermal stability is dramatically impacted
Solution Approach 1:
The invention changes the polymerization parameters to maintain pressure above the critical pressure of vinylidene fluoride and uses controlled polymerization conditions. This enables the incorporation of hydrophilic monomers at levels that improve adhesion (0.05 to 10% by moles) while maintaining a random distribution pattern that preserves thermal stability, avoiding the dramatic thermal degradation associated with blocky structures.
Solution Approach 2:
The invention applies local quality by ensuring that hydrophilic monomer units are randomly distributed throughout the polymer chain rather than concentrated in blocks. This local random distribution allows adhesion improvement through increased hydrophilic content while preventing the thermal instability that would result from localized clusters of hydrophilic units.
4Stability of the object's composition
If random distribution of hydrophilic monomer units is targeted, then thermal stability is improved, but uncontrolled radical side reactions occur during polymerization
Solution Approach 1:
The invention changes the polymerization parameters by maintaining pressure above the critical pressure of vinylidene fluoride and using controlled polymerization conditions. These parameter changes suppress uncontrolled radical side reactions while enabling the formation of a substantially random distribution of hydrophilic monomer units, thus achieving both thermal stability and polymerization control.
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 process ensures a random distribution of hydrophilic monomer units, enhancing the copolymer's thermal stability, adhesiveness, and mechanical properties without compromising the excellent properties of vinylidene fluoride polymers, even at low monomer levels, making them suitable for use in batteries and hydrophilic membranes.
Implementation Method 1
polymerization in an aqueous medium with a radical initiator, where vinylidene fluoride and hydrophilic (meth)acrylic monomers are continuously fed
Implementation Method 2
maintaining pressure above the critical pressure of vinylidene fluoride
Data Source
AI summary
The present invention pertains to a linear semi-crystalline copolymer [polymer (A)] comprising recurring units derived from vinylidene fluoride (VDF) monomer and at least one hydrophilic (meth)acrylic monomer (MA) of formula (I) wherein each of R1, R2, R3, equal or different from each other, is independently an hydrogen atom or a C1-C3 hydrocarbon group, and ROH is a hydrogen or a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group, said polymer (A) comprising from 0.05 to 10 % by moles of recurring units derived from said hydrophilic (meth)acrylic monomer (MA) and being characterized by a fraction of randomly distributed units (MA) of at least 40 %, having improved thermal stability, to a process for its manufacture, to a composition comprising the same, and to its use as binder in batteries or for the manufacture of hydrophilic membranes.