Ultra-Soft, Dry Polydimethylsiloxane Elastomers from Architecture-Driven Entanglement Free Design

Polydimethylsiloxane (PDMS) elastomers are the most widely used silicon-based organic polymeric materials. Conventional PDMS elastomers formed by crosslinking entangled linear polymers are intrinsically stiffer than an intrinsic limit, ~200 kPa, the value set by entanglements. Here we develop ultrasoft, solvent-free PDMS elastomers by crosslinking bottlebrush polymers rather than linear polymers. We design the chemistry to allow commercially available linear PDMS precursors to deterministically form bottlebrush polymers, which are simultaneously crosslinked, thus enabling a one-step, room temperature synthesis. The bottlebrush architecture prevents the formation of entanglements, resulting in elastomers with precisely controllable elastic moduli from ~1 to ~100 kPa, below the intrinsic lower limit of traditional elastomers. Moreover, the solvent-free nature of the soft PDMS elastomers enables a negligible contact adhesion compared to commercially available silicone products of similar stiffness. The exceptional combination of softness and negligible adhesiveness may greatly broaden the applications of PDMS elastomers in both industry and research.