Enhancing the Biomimetic Mechanics of Bottlebrush Graft-Copolymers through Selective Solvent Annealing.

Self-assembled networks of bottlebrush copolymers are promising materials for biomedical applications due to a unique combination of ultra-softness and strain-adaptive stiffening, characteristic of soft biological tissues. Transitioning from ABA linear-brush-linear triblock copolymers to A-g-B bottlebrush graft copolymer architectures allows significant increasing the mechanical strength of thermoplastic elastomers. Using real-time synchrotron small-angle X-ray scattering, it is shown that annealing of A-g-B elastomers in a selective solvent for the linear A blocks allows for substantial network reconfiguration, resulting in an increase of both the A domain size and the distance between the domains. The corresponding increases in the aggregation number and extension of bottlebrush strands lead to a significant increase of the strain-stiffening parameter up to 0.7, approaching values characteristic of the brain and skin tissues. Network reconfiguration without disassembly is an efficient approach to adjusting the mechanical performance of tissue-mimetic materials to meet the needs of diverse biomedical applications.