Tailoring Rate- and Temperature-Dependent Fracture of Polyether Networks with Organoaluminum Catalysts

Polyethers are ubiquitous in engineering and biomedical applications because their oxygen rich backbone allows them to interact with a variety of polar small molecules such as ions, gases, and pharmaceuticals. These materials are also able to sustain large reversible deformations when crosslinked at the molecular scale, leading to an interesting combination of functional and mechanical properties. We synthesized two families of polyether networks by organoaluminum catalyzed ring-opening copolymerization of ethyl glycidyl ether (EGE) monomer and 1,4-butanediol diglycidyl ether (BDGE) crosslinker, and explored the relationship between network architecture and fracture properties. The key result is that living copolymerizations, as enabled by a chelate of triethylaluminum with dimethylaminoethanol, afford access to a critical cross-link density, νx ≈ 3 x 1025 chains/m3, and loss tangent, tan() ≈ 0.09, at which fracture is dominated by chain scission rather than friction. Such control over the fracture resistance of polyether networks unveils the potential of living copolymerizations to design the functional and mechanical properties of soft materials.