Self-Healing Polymer Network with High Strength, Tunable Properties, and Biocompatibility

Abstract

Nature has designed and optimized materials to possess a range of properties and functions. Here, we introduced a molecular design strategy to impart customizable functionality and varying mechanical properties into gels; mimicking nature’s range of tunable materials. We demonstrate a gel that is not only tough but also exhibits self-healing, is easily controllable, and the final materials have a broad range of mechanical properties. To develop these materials, we first prepared a methacrylic acid (MAAc) and poly­(ethylene glycol) methyl ether methacrylate (OEGMA) random copolymer: poly­(MAAc-co-OEGMA). The network’s deliberate inter- and intramolecular hydrogen bondings were modified through some of the acid sites being postfunctionalized with benzaldehyde (BA) and cross-linked with diamine-terminated poly­(dimethylsiloxane) (PDMS) to form dynamic imine bonds. Due to the low glass transition temperature of the PDMS cross-linker, the chain mobility can be enhanced, enabling rapid self-healing (>98% within seconds), in addition to improving the stretchability (tensile strain) from a few % to almost 500%. The prepared polymers and gels were well characterized through various techniques including Fourier transform infrared spectroscopy (FTIR), 1H NMR, and size-exclusion chromatography (SEC) analysis. Mechanical testing and dynamic mechanical analysis (DMA) revealed interesting insights into the broad-range (Young’s modulus: 100 kPa to >300 MPa) and tunable mechanical properties, including the tensile strength (from 12 to 0.1 MPa) and strain (up to 500%) as well as the storage (0.1 to 60 MPa) and loss (1 to 40 MPa) moduli of the dynamic self-healing gel. Interestingly, the tensile strength decreasing with increasing cross-link density. Lastly, the biocompatibility of the gels was investigated, with an initial study of both human bone and skin cells indicating increased biocompatibility with gels that had been cross-linked with PDMS.

Polymer–solvent interactions as a tool to engineer material properties

“…The PDI was 2.5 however this is believed to be inaccurate due to aggregation caused by hydrogen bonding on the column. 18 and then post functionalized via esterification of anthracene methanol to yield the target system (Fig. 1).…”

“…16,17 By understanding the properties of these dynamic bonds, it is possible to tune the chemistry of a material to achieve a desired function and response to stimuli. 18–20…”

“…16,17 By understanding the properties of these dynamic bonds, it is possible to tune the chemistry of a material to achieve a desired function and response to stimuli. [18][19][20] As multiple functional groups are combined within a polymer network, the self-assembly behaviour and properties of the material become increasingly complex. Often these materials are designed using dynamic bonds with divergent properties for multi-stimuli responsiveness.…”

Healable, Recyclable, and High‐Stretchable Polydimethylsiloxane Elastomer Based on Synergistic Effects of Multiple Supramolecular Interactions

“…[13] Polydimethylsiloxane (PDMS) elastomer is an ideal substrate for flexible stretchable electronics DOI: 10.1002/mame.202200310 because of its excellent properties such as good hydrophobicity, high chain mobility, nontoxicity, and biocompatibility. [8,[14][15][16][17][18] Nowadays, it becomes the most common strategy to design PDMS elastomers with intrinsic self-healing capacity by embedding dynamic interaction into matrix, [8,[19][20][21][22][23] and various reversible noncovalent interactions (such as hydrogen bond, [8,24] 𝜋-𝜋 stacking interaction, [25,26] coordination bonds [12] ) or dynamic covalent bonds (such as dynamic boroxine bonds, [27] disulfide, [28] Diels-Alder reaction, [14,29] and dynamic imine linkage [30][31][32] ) have been employed to develop self-healing PDMS elastomers with high self-healing efficiency or lowtemperature-triggered self-healing.…”

“…[33,34] It has been proved that the synergetic combination of multiple dynamic interaction is an effective strategy to endow PDMS elastomers with desirable self-healing and mechanical performance. [8,32,20] Intend for high stretchability, Li et al [12] have reported a PDMS elastomer that exhibits high elongation at break of 1860% and high self-healing efficiency of 90% at room temperature by tuning the strength of metal-ligand interactions. Guo et al [19] developed a self-healing PDMS elastomer with excellent stretchability for both unnotched (14 000%) and notched (1300%) samples by synergistically incorporating multi-strength H-bonds and disulfide metathesis.…”