Decoupling Softness and Damping in Brush Elastomers for Tissue-Mimetic Mechanics

Biological tissues uniquely combine softness with firmness and elasticity with damping—traits rarely achieved in synthetic materials. Conventional approaches to tune viscoelasticity rely on chemical modification or additives, often compromising stability and biocompatibility. Here, we introduce brush elastomers as solvent- and additive-free networks that enable independent control of modulus and damping through molecular architecture. Densely grafted side chains dilute backbone entanglements to promote softness while extending network strands to maintain firmness. To reproduce tissue-like viscoelasticity across frequencies, we employ two complementary strategies: (i) systematic variation of network parameters (side-chain length, grafting density, and crosslink density) and (ii) incorporation of a controlled fraction of dangling strands. This framework allows modulation of the Rouse time independently of the plateau modulus, decoupling elastic and dissipative responses. Our results establish structure–property relationships for brush-like polymer networks that mimic the frequency-dependent mechanical behavior of biological tissues and expand the design space for next-generation biomedical devices.