Highly Entangled Hydrogels by Photoiniferter-Mediated Polymerization
Gavin Irvine1, Konstantinos Myronidis2, Fulvio Pinto2
1Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Angewandte Chemie (International Ed. in English)
|February 12, 2025
Summary
We synthesized ultra-high molecular weight poly(N,N-dimethylacrylamide) hydrogels using reversible deactivation radical polymerization. These highly entangled polymer networks exhibit enhanced toughness and swelling resistance, even with minimal crosslinking.
Area of Science:
- Polymer Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Hydrogels are crucial in various applications, but achieving high toughness and swelling resistance often requires high crosslinking densities.
- Controlling polymer chain architecture and entanglement is key to designing advanced hydrogel properties.
- Reversible deactivation radical polymerization (RDRP) offers precise control over polymer chain growth and architecture.
Purpose of the Study:
- To synthesize ultra-high molecular weight (UHMW) poly(N,N-dimethylacrylamide) (PDMAm) hydrogels with extremely low crosslinking densities.
- To investigate the simultaneous control over crosslinking density and primary chain molecular weight.
- To explore the role of polymer chain entanglements in dictating hydrogel properties.
Main Methods:
- Utilized trithiocarbonate photoiniferter-mediated RDRP for controlled synthesis of PDMAm chains.
- Systematically varied the targeted degree of polymerization (DPtarget) while maintaining a fixed photoiniferter to crosslinker ratio.
- Characterized hydrogel properties, including storage modulus (G') and swelling behavior, in relation to polymer architecture.
Main Results:
- Achieved UHMW PDMAm hydrogels with vanishingly small crosslinking densities.
- Observed a transition to an entanglement-dominated regime for DPtarget > 5,000, indicated by a plateau in storage moduli.
- Demonstrated enhanced toughness and swelling resistance in highly entangled hydrogels, outperforming those reliant on covalent crosslinks.
Conclusions:
- Developed a facile method for synthesizing elastic and tough hydrogels with tunable contributions from entanglements and crosslinks.
- Showcased the potential of dense polymer chain entanglements to act as effective transient crosslinks, enhancing hydrogel stability.
- Established a structure-property relationship where high molecular weight chains and entanglements significantly improve hydrogel performance.
