Shock Wave Energy Dissipation in Catalyst-Free Poly(dimethylsiloxane) Vitrimers

Abstract

Materials that absorb shock wave energy from blasts and high-speed impacts are critical for protection of structures, vehicles, and people. Incorporating dynamic bonds into polymers has enabled precise control over the time-dependent response and energydissipating modes, but this work has focused on much slower time scales and lower forces than those associated with shock waves. Here, we design polymers networks with dynamic covalent bonds, called vitrimers, where reversible exchange reactions provide a potential mechanism for shock wave energy dissipation. Increasing the density of dynamic bonds leads to a systematic increase in energy dissipation, measured by the drop in peak pressure of a laser-induced shock wave. An analogous permanent polymer network shows no dependence of dissipation on cross-link density. The vitrimers can absorb shock multiple times while maintaining performance, attributed to bond exchange and the intrinsic self-healing ability of the polymer. Our results are the first to demonstrate that vitrimers are an effective route to the design of energy-dissipating materials, particularly at the high frequencies and pressures associated with shock waves.

Effect of precise linker length, bond density, and broad temperature window on the rheological properties of ethylene vitrimers

“…45 Thus, there is still a need to understand under what conditions the mechanism of the exchange reaction will play a key role to the function or properties of dynamic networks. The rekindled interest in these networks in the last decade has led to numerous articles on vitrimers for shape memory polymers, [35][36][37] shockwave dissipation, 38 flame retardants, 39 and solid electrolytes. 40 While initial work was focused on stress relaxation times and self-healing as a function of bond chemistry and polymer backbone, recent work has moved to investigating the effects of crosslink density, 41,42 defects 43 and solvent concentration 44 on the rheological properties of vitrimers.…”

Ultra-thin self-healing vitrimer coatings for durable hydrophobicity

“…Twenty minutes after bubbles formed in the solution, indicating the release of H 2 O due to the reaction between the PDMS diol and boric acid taking place and the beginning of network formation, the temperature was decreased to room temperature to prevent full conversion. We showed a critical decrease in the -OH by analysis of the FITR spectrum 40 . The initial solution has 4 mL of IPA per 1 gram of PDMS, and the IPA is then reduced due to evaporation on heating.…”

“…The boric acid-diol complexation results in trigonal boron sites, where the B–O bonds can exchange in an associative, or conserved, manner (Fig. 1a ) 40 . Twenty minutes after bubbles formed in the solution, indicating the release of H 2 O due to the reaction between the PDMS diol and boric acid taking place and the beginning of network formation, the temperature was decreased to room temperature to prevent full conversion.…”

“…The PDMS concentration in IPA was 1 g·mL −1 and the viscosity was ~35 cSt. Bulk characterization of the dyn-PDMS networks showing the macroscopic modulus and stress relaxation time can be found elsewhere 40 .

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“…In addition to its demonstrated robustness, the dyn-PDMS film is also fluorine-free, which leads to greater environmental friendliness owing to lower bioaccumulation when compared to PFCs, which can take hundreds of years to degrade 11 . Silicone-based materials can be recycled and reused using organic solvents such as toluene 40 . From an application perspective, our developed PDMS vitrimer coating process is an important aspect to consider.…”