Colorless, transparent, and healable silicone elastomers by introducing Zn(II)-carboxylate interactions via aza-Michael reaction

It is a challenge to fabricate smart materials with excellent optical, mechanical, and healable properties simultaneously. Herein, colorless, transparent, and healable polydimethylsiloxane (PDMS) elastomers were successfully prepared by introducing Zn(II)-carboxylate interactions via aza-Michael reaction of amino polysiloxane and zinc acrylate. The mechanical properties of these polymers can be easily tuned in a wide range between stretchability and rigidity by tailoring the ion content simply. The sample with medium ion content has the best integrated mechanical properties (breaking strain: similar to 1000%; breaking stress: similar to 3 MPa), which can also be recovered with high efficiency (similar to 90%) after healed or reprocessed at mild temperature (80-100 degrees C). Furthermore, based on the results of stress relaxation and scanning electron microscopy, the excellent mechanical properties are considered to be due to the gradient ionic aggregates, as the small and weak ionic aggregates can preferentially sacrifice to dissipate energy under external loading, while the large and stiff aggregates impart the elastomers with high strength and elasticity. Finally, due to the colorless appearance, good transparency, healing ability, and adhesive strength for glass substrates, these ionic PDMS elastomers can also be applied as reusable adhesives in optical devices.