Soft elastic materials enable the creation of implants, substrates, and haptic robotic digits with mechanical properties matching those of biological tissues. Currently, polymer gels are the only viable class of synthetic materials with a Young’s modulus below 100 kPa. However, the liquid fraction in the gels may cause phase separation and solvent leakage on deformation. Herein, we have created bottlebrush and comb-like networks that are superelastic and supersoft, even in the absence of solvent [1]. The attachment of side chains results in an increase of the diameter of individual macromolecules, but unlike typical filaments, molecular bottlebrushes remain flexible [2,3]. This enables a significant decrease in the entanglement density, which reduces the limit of stiffness in dry polymer materials by 1000 times and has opened up new applications not available to stiffer materials or materials with liquid fractions [4]. The comb-like architecture offers three independently controlled parameters – side-chain length, grafting density, and crosslink density - that allow for combinatorial variations of elastomer mechanical properties impossible for conventional linear chain elastomers, e.g. simultaneously increasing rigidity and elasticity. In contrast to linear chain elastomers, brush-like architecture allows independent variation of modulus and elongation at break in broad ranges. Based on this materials design platform, we have prepared elastomers that closely match the mechanical behaviour of biological tissue and may be moldable through physical crosslinking [5]. Furthermore, this architecture affords many chain-ends that are amendable for chemical modifications and enhance molecular mobility, which directly affects vital physical properties ranging from glass transition and crystallization temperatures to adhesion and permeability.<br/>

Architectural programming mechanical properties of polymeric elastomers

254th National Meeting (2017)

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