Stretchable, robust and reprocessable poly(siloxane-urethanes) elastomers based on exchangeable aromatic disulfides

The rapid expansion of dynamic covalent chemistry world urges for materials not only possessing high mechanical properties and stretchability, but also including high reprocessability and reforming. Herein, aromatic disulfide-containing polysiloxanes elastomers with modified urea as chain-extender and crosslinker were first designed and fabricated. Dynamic crosslinks, including hydrogen bonding formed between urea and amide bonds, and aromatic disulfide are connected with polysiloxanes backbones through isocyanate (DTSA-HDI) reacted with systematically controlled aminopropyl groups in the side chains. Consequently, a series of ATPx-SS elastomers with polysiloxanes of different molecular weight and APPx-SS elastomers with different crosslinking densities are developed. The molar amount of DTSA-HDI has been proved to play a crucial role in adjusting the mechanical and thermal properties of the networks. Among all, ATP3-SS showed the best stretchability, of which the elongation at break was as high as 780%. APP1-SS achieved the highest tensile strength of 2.60 MPa. Besides, it has outstanding reprocessability and can be reprocessed and reformed without much decline of tensile strength after several cycles of hot-pressing. These remarkable properties demonstrate that the aromatic disulfide-containing elastomers are competitive to those un-filled polysiloxanes elastomers based on dynamic bonds ever reported. © 2021 Elsevier Ltd