Tailoring network architecture and fracture properties of polyether networks using organo-aluminum catalysts

Polyethers are ubiquitous in engineering and biomedical applications with their oxygen rich backbone allowing them to interact with a variety of polar small molecules such as ions, gases, and pharmaceuticals. When crosslinked at the molecular scale, these materials can also sustain large reversible deformations, 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 monomer and 1,4-butanediol diglycidyl ether crosslinker, and explored the relationship between network architecture and fracture properties. The key result is that living copolymerizations (i.e. more controlled), as enabled by a chelate of triethylaluminum with dimethylaminoethanol, afford access to a critical cross-link density, ν_x ≈ 3 x 10²⁵ chains/m³, and loss tangent, tan(δ) ≈ 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.