Zwitterionic Block Copolymer Gelation Under Mild pH Conditions
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Solution Overview
Problem
Current block copolymers are unable to gel in aqueous solutions under mild conditions, such as neutral pH or body temperature, which limits their applications in drug delivery and other biologically relevant environments.
Innovation Solution
Development of a block copolymer composition with a hydrophilic core block and at least two terminal blocks, each formed from ethylenically unsaturated monomers, where the core block comprises zwitterionic pendant groups and has a degree of polymerization of at least 100, allowing for reversible gelation in response to stimuli like pH changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional block copolymers are used, then they can be formed with controlled molecular weight, but they are unable to gel in aqueous solutions under mild conditions
Solution Approach 1:
The patent applies local quality by introducing zwitterionic pendant groups specifically in the core block of the block copolymer, while keeping the terminal blocks as stimulus-responsive blocks. This localized modification of the core block's chemical structure enables gelation under mild conditions without affecting the overall block copolymer architecture. The zwitterionic groups provide hydrophilicity and specific interactions that facilitate gel formation at neutral pH and body temperature.
Solution Approach 2:
The patent creates a composite block copolymer structure combining zwitterionic core blocks with stimulus-responsive terminal blocks. This composite architecture integrates the gelation capability of zwitterionic polymers with the stimulus responsiveness of other functional blocks, achieving both gelation under mild conditions and responsiveness to environmental changes for controlled drug delivery.
2Adaptability or versatility
If block copolymers are designed with stimulus-responsive terminal blocks, then they can respond to environmental changes, but they cannot form gels under physiologically relevant conditions
Solution Approach 1:
The patent applies local quality by introducing zwitterionic pendant groups specifically in the core block of the block copolymer, while keeping the terminal blocks as stimulus-responsive blocks. This localized modification of the core block's chemical structure enables gelation under mild conditions without affecting the overall block copolymer architecture. The zwitterionic groups provide hydrophilicity and specific interactions that facilitate gel formation at neutral pH and body temperature.
Solution Approach 2:
The patent changes the chemical parameters of the core block by incorporating zwitterionic pendant groups, which fundamentally alter the solubility and interaction properties of the polymer in aqueous environments. This parameter change enables the polymer to maintain solubility and gelation capability at physiological temperatures and pH levels, unlike conventional block copolymers that require extreme conditions.
3Ease of manufacture
If conventional block copolymers are used, then they can be synthesized by sequential monomer addition, but they lack biocompatibility for drug delivery applications
Solution Approach 1:
The patent applies local quality by introducing zwitterionic pendant groups specifically in the core block of the block copolymer, while keeping the terminal blocks as stimulus-responsive blocks. This localized modification of the core block's chemical structure enables gelation under mild conditions without affecting the overall block copolymer architecture. The zwitterionic groups provide hydrophilicity and specific interactions that facilitate gel formation at neutral pH and body temperature.
Solution Approach 2:
The patent creates a composite block copolymer structure combining zwitterionic core blocks with stimulus-responsive terminal blocks. This composite architecture integrates the gelation capability of zwitterionic polymers with the stimulus responsiveness of other functional blocks, achieving both gelation under mild conditions and responsiveness to environmental changes for controlled drug delivery.
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 block copolymers can form gels under mild conditions, enabling controlled drug delivery and other biologically relevant applications by changing their molecular form in response to external stimuli, such as pH changes, while maintaining biocompatibility.
Implementation Method 1
aqueous solutions of the block copolymers may be gelled by changing the pH of the environment
Implementation Method 2
changing their molecular form in response to external stimuli, such as pH changes
Data Source
AI summary
Block copolymers comprise a core block formed of hydrophilic monomers and have pendant zwitterionic groups, and at least two terminal blocks, comprising stimulus-responsive groups. The core block has a degree of polymerisation of at least 100, whilst the terminal blocks have an average degree of polymerisation of at least 20. A solution of polymer in a liquid may be caused to change its characteristics, for instance rheology, upon being subjected to a stimulus such as a change in temperature or pH. Examples comprise core blocks formed of 2-methacryloyloxyethyl-2′-trimethylammonium ethylphosphate inner salt (MPC) and terminal blocks formed of 2-(diisopropylamino)ethyl methacrylate. Upon changing the pH from around 2 to around 8, an aqueous solution of the block copolymer gels, the solution becoming mobile again upon lowering the pH. The effect is due to deprotonation of a quaternary ammonium pendant ion to form a non-ionised group and subsequent protonation to form an ionised group. This changes the hydrophilicity of the terminal blocks and allowing formation of a network of micellar structures when the pendant groups are not ionised and relatively hydrophobic and associated in micelles.