Tuning the Mechanical Behavior of Metal–Phenolic Networks through Building Block Composition

Abstract

Metalphenolic networks (MPNs) are an emerging class of functional metal-organic materials with a high degree of modularity in terms of the choice of metal ion, phenolic ligand, and assembly method. Although various applications, including drug delivery, imaging, and catalysis, have been studied with MPNs, in the form of films and capsules, the influence of metals and organic building blocks on their mechanical properties is poorly understood. Herein, we demonstrate that the 2 mechanical properties of MPNs can be tuned through choice of the metal ion and/or phenolic ligand. Specifically, the pH of the metal ion solution and/or size of phenolic ligand influence the Young's modulus (EY) of MPNs (higher pHs and smaller ligands lead to higher EY). This study systematically investigates the roles of both metal ions and ligands on the mechanical properties of metal-organic materials and lends new insight into engineering the mechanical properties of coordinated films.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

“…The versatility of metal coordinated networks arises from the vast number of possible combinations between organic ligands and coordination centers. 638 Pseudodendritic or polydentate ligands coordinated by multivalent metals are the most applied in materials development. They lead to a high coordination number, thus resulting in robust complexes and continuous networks by bridging the primary complexes across length scales.…”

“…(b) Phenolic compounds used to assemble metal phenolic networks, and (c) associated cohesion of the coordinated assembly. Adapted with permission from ref ( 638 ). Copyright 2019 American Chemical Society.…”

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

“…The versatility of metal coordinated networks arises from the vast number of possible combinations between organic ligands and coordination centers. 634 Pseudodendritic or polydentate ligands coordinated by multivalent metals are the most applied in materials development. They lead to a high coordination number, thus resulting in robust complexes and continuous networks by bridging the primary complexes across length scales.…”

“…The effect of the polyphenolic ligand size on the cohesion of the metal-phenolic networks has been studied. 634 Well-defined molecular structures, that is, TA, gallic acid (GA), pyrogallol (PG) and pyrocatechol (PC) (Figure 30b), were used to assess the mechanical cohesion of MPN complexes by AFM force measurements. Overall, the smaller phenolic molecules led to higher MPN mechanical performance (Figure 30c).…”

“…With smaller ligands, one can expect more uniform and long-range order coordinated structure, owing to their molecular geometry that enhances orientation and promote tighter packing. 634 The effect of the building block size remarkably affects the cohesion of protein assemblies. Silk proteins are classical examples of high-performing building blocks, recently used to synthesize materials with very precise control over their assembling structures and therefore over their proper-…”