UV Responsive, Bottlebrush Structured Silicone Elastomers: Synthesis, Healing, and Application

A series of bottlebrush silicone elastomers have been synthesized by using a solvent-free process based on hydrosilylation and thiol–ene reactions. The use of thiol-functionalized PDMS effectively suppresses the side reactions of Si–H bonds during the hydrosilylation process. The dynamic covalent C–S bonds in these materials can undergo reversible cleavage under UV illumination, imparting excellent forming and self-healing properties under UV. Remarkably, the elastomer not only retains a low elastic modulus but can heal within seconds, exhibiting toughness of up to 86% of its original value. The synthesis approach also allows small silane molecules to be efficiently grafted as spacers onto the polymer backbone, and the effects of both spacers with different steric hindrances and functional groups are reported. Spacers with different steric hindrances significantly altered the stiffness, while those with functional groups, such as fluorinated spacers, effectively modified the surface property. Potential applications are illustrated by using the material in 3D printing by digital light processing, healing under UV and recycling.