Doubly-crosslinked hydrogels via metal coordination
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Solution Overview
Problem
Hydrogel polyHIPEs (HG-PHs) have relatively low mechanical properties, limiting their applications, and existing methods to enhance mechanical properties, such as dynamic interactions and ionic interactions, have not successfully produced robust doubly-crosslinked hydrogels with high modulus and reversible interactions.
Innovation Solution
The creation of doubly-crosslinked polyHIPEs (DC-PHs) through metal coordination crosslinking in hydrogel polyHIPEs, specifically using FeCl3 to form metal coordination bonds with -COO- groups in copolymers of acrylamide and sodium acrylate, resulting in enhanced mechanical behavior and shape memory effects while preserving macroporous structures and rapid water absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dynamic interactions or ionic interactions are used to enhance mechanical properties, then the hydrogel's modulus is improved, but the strength and robustness remain relatively low
Solution Approach 1:
The patent combines two different crosslinking mechanisms: covalent crosslinking (permanent) and metal coordination crosslinking (reversible/dynamic). This merging creates a doubly-crosslinked hydrogel network that integrates the stability of covalent bonds with the adaptability of metal-ligand interactions, achieving both high strength and robustness simultaneously.
Solution Approach 2:
The invention creates a composite crosslinking system within the hydrogel by incorporating both covalent crosslinks and metal coordination crosslinks. This composite approach allows the material to exhibit enhanced mechanical properties while maintaining reversibility, as the metal coordination bonds can dynamically adjust to mechanical stress.
2Strength
If metal coordination crosslinking is introduced to enhance mechanical properties, then the modulus is significantly improved, but the complexity of the crosslinking system increases
Solution Approach 1:
Metal ions (such as Fe3+, Cu2+, Zn2+) serve as intermediary crosslinking agents that coordinate with ligand groups on polymer chains. These metal ions act as mediators that simplify the crosslinking process compared to direct covalent bonding, while still providing strong crosslinking interactions. The metal ions can be easily introduced and removed, managing system complexity.
Solution Approach 2:
The metal coordination crosslinks are dynamic and reversible, allowing the crosslinking system to adapt to changing conditions. This dynamic nature simplifies the overall system behavior compared to permanent covalent crosslinks, as the metal-ligand bonds can form and break in response to environmental changes, maintaining robustness without excessive complexity.
3Strength
If the degree of crosslinking is enhanced to improve mechanical properties, then the modulus is increased, but the hydrogel's ability to absorb water and maintain porosity is reduced
Solution Approach 1:
The patent segments the crosslinking into two distinct networks: a covalent crosslinking network that provides structural stability and porosity, and a metal coordination crosslinking network that enhances mechanical strength. This segmentation allows each network to optimize its function independently, with the covalent network maintaining water absorption and the metal coordination network providing strength.
Solution Approach 2:
Different regions of the hydrogel network have different crosslinking densities and types. The covalent crosslinks provide a stable framework with pores for water absorption, while the metal coordination crosslinks are distributed to enhance local mechanical strength. This local differentiation allows the hydrogel to simultaneously achieve high modulus and maintained porosity.
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 doubly-crosslinked hydrogels exhibit significantly improved mechanical properties, including higher compressive moduli and shape memory behavior, with the metal coordination crosslinking being reversible and easily removable, allowing for multiple cycle shape memory behavior.
Implementation Method 1
The demonstrative exemplary DC-PHs were fabricated by adding FeCl3 to HG-PHs containing —COO− groups, thus forming a second crosslinking network via metal coordination with Fe3+ cations
Implementation Method 2
The demonstrative exemplary DC-PHs exhibited enhanced mechanical behavior and shape memory effects, while preserving the interconnected macroporous structures and rapid water absorption
Data Source
AI summary
Doubly-crosslinked hydrogel polyHIPEs (DC-PHs), which exhibit rapid water absorption, enhanced mechanical properties, and shape memory behavior, are provided herein, as well as processes of producing the same and uses thereof. DC-PHs comprise a continuous HIPE-templated doubly-crosslinked hydrogel, formed from hydrogel-forming monomers, ligand-bearing monomers, and crosslinking monomers.