Solvent-free, supersoft and superelastic bottlebrush melts and networks

Polymer gels are the only viable class of synthetic materials with a Young's modulus below 100 kPa conforming to biological applications(1-3), yet those gel properties require a solvent fraction(4-7). The presence of a solvent can lead to phase separation, evaporation and leakage on deformation, diminishing gel elasticity and eliciting inflammatory responses in any surrounding tissues. Here, we report solvent-free, supersoft and superelastic polymer melts and networks prepared from bottlebrush macromolecules. The brush-like architecture expands the diameter of the polymer chains, diluting their entanglements without markedly increasing stiffness. This adjustable interplay between chain diameter and stiffness makes it possible to tailor the network's elastic modulus and extensibility without the complications associated with a swollen gel. The bottlebrush melts and elastomers exhibit an unprecedented combination of low modulus (similar to 100 Pa), high strain at break (similar to 1,000%), and extraordinary elasticity, properties that are on par with those of designer gels(8,9).