Control of hierarchical polymer mechanics with bioinspired metal-coordination dynamics

Abstract

In conventional polymer materials, mechanical performance is traditionally engineered via material structure, using motifs such as polymer molecular weight, polymer branching, or copolymer-block design1. Here, by means of a model system of 4-arm poly(ethylene glycol) hydrogels crosslinked with multiple, kinetically distinct dynamic metal-ligand coordinate complexes, we show that polymer materials with decoupled spatial structure and mechanical performance can be designed. By tuning the relative concentration of two types of metal-ligand crosslinks, we demonstrate control over the material’s mechanical hierarchy of energy-dissipating modes under dynamic mechanical loading, and therefore the ability to engineer a priori the viscoelastic properties of these materials by controlling the types of crosslinks rather than by modifying the polymer itself. This strategy to decouple material mechanics from structure may inform the design of soft materials for use in complex mechanical environments.

Hydrogen bonding and thermoplastic elastomers – a nice couple with temperature-adjustable mechanical properties

“…3,4 Especially the variety of available non-covalent bonds which can be used to form transient connections and therefore supramolecular polymers and networks is nowadays large. This broad variety of different interactions includes p-p stacking, 5,6 metal-ligand interactions, [7][8][9][10] hydrophobic forces, 11,12 electrostatic effects, 13,14 and hydrogen bonding. 4,[15][16][17][18][19][20] Not only the functionalization of the precursor building blocks (telechelic units) for the polymer chains and networks is today synthetically quite feasible, 21,22 but also the post modification of a polymer along the chain.…”

The effects of counter anions on the dynamic mechanical response in polymer networks crosslinked by metal–ligand coordination

“…[1][2][3][4][5][6][7] One important subset of dynamic mechanical properties is the self-healing ability after mechanical damages. [8][9][10][11][12][13][14][15][16] The combination of mechanophore with luminescence can further endow materials with selfreporting damage detection property [17][18][19] and novel bio-mimic electronics with multifunctionalities. 20,21 The macroscopic dynamic mechanical properties of materials rely on the incorporated dynamic bonding at molecular levels.…”

Significant Performance Enhancement of Polymer Resins by Bioinspired Dynamic Bonding

“…The elastic modulus, E > 3.5 GPa, of the bioinspired composites we present here is substantially (up to a million fold) stiffer than those tough elastomers found in literature. [46,47] This study thus demonstrates the utility of mussel-inspired dynamic bonding for processing a wide range of practical polymeric interfaces, including structural, load-bearing materials.…”

“…[43] However, in man-made systems these toughening phenomena have been shown only in relatively soft materials to date. For example, although it has been recently reported that sample toughness increases can be achieved with the addition of catechol-mediated dynamic bonds [46] and double networks, [47] these studies have been limited to hydrogels and elastomers, where the elastic modulus E is less than 300 kPa. [48] In this study, we present significant toughness enhancement of a highly rigid synthetic polymer resin composite by a biologically inspired adhesive primer, providing strong and dynamic binding.…”