Thermoreversible Siloxane Networks: Soft Biomaterials with Widely Tunable Viscoelasticity

Polysiloxane elastomers represent a widely utilized soft material with excellent rubber-like elasticity, biocompatibility, and biodurability; however, there is a lack of an effective and straightforward approach to manipulate the material's viscoelastic response. A facile hydrosilylation reaction is employed to integrate ureidopyrimidinone hydrogen-bonding side-groups into linear and crosslinked siloxane polymers to achieve biocompatible soft materials with a highly tunable viscoelastic relaxation timescale. Stacking of H-bonded moieties is avoided in the designed macromolecular architectures with tight, side-groups substituents. The obtained siloxane network features the presence of both covalent crosslinks and truly thermoreversible crosslinks, and can be formulated across a broad material design space including elastic solids, recoverable viscoelastic solids, and viscous liquids. The elastomers exhibit unique temperature-dependent shape-memory capability and show good cytocompatibility. Importantly, a deformed material's shape-recovery occurs regardless of external triggering, and through manipulation of network formulations, the shape-recovery timescale can be easily tuned from seconds to days, opening new possibilities for biomedical, healthcare, and soft material applications.