Polymer networks containing transient bonds have received increasing attention over the past decade. Depending on the specific interaction (ionic, H-bonding, dynamic covalent), a certain amount of energy is required for the bonds to undergo an exchange process. We hypothesize and demonstrate that dynamic covalent bonds in polydimethylsiloxane (PDMS) networks can be used as an effective mechanism for shockwave energy dissipation (SWED). To test this, polymer networks were synthesized from boric acid and commercially available dimethylsiloxane diols of varying length. The density of dynamic boronic ester linkages can be controlled by varying the diol molecular weight while the network chemistry is invariant. Using a classical laser induced shockwave technique, we demonstrate superior energy dissipation in a PDMS boronic ester dynamic rubber (PDMS-B-DR) compared to the benchmark polyurea. The dynamic PDMS also outperforms covalent PDMS (cured via thiol-ene click chemistry) and shows a monotonic improvement in dissipation performance with increasing density of dynamic boronic ester bonds. For all boronic ester densities, the Tg is invariant (-125 °C) implying a minimal role of segmental dynamics on the variations in dissipation performance of these networks. Our results indicate that dynamic networks are a promising route to engineering improved SWED materials which are lightweight, flexible, and able to withstand repeated shocks. X-ray scattering and rheology have also been performed to relate dissipation performance to structure and relaxation timescales of the material.

Efficient shockwave energy dissipation in dynamic covalent PDMS rubber

256th National Meeting (2018)

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