Breaking Composition Constraints: Viscoelasticity-Driven Phase Inversion for Mechanically Robust Block Copolymer Networks

Overcoming the thermodynamic constraints of minority composition for achieving continuous networks in block copolymers remains a fundamental challenge to realize lightweight structural nanomaterials. To resolve this challenge, we develop multiscale modeling to establish dynamic asymmetry as an engineering strategy for achieving metastable nanostructures and enhanced mechanical properties through unusual viscoelastic microphase separation. The simulations of dynamic self-consistent field theory reveal that the dynamic asymmetry arising from bulk modulus differences has the capability to reprogram the kinetic pathways of microphase separation of block copolymers, triggering composition-independent phase inversion. Particularly, this inversion phenomenon can yield the continuous percolating networks of high-bulk-modulus blocks in spite of their minority composition, a thermodynamically forbidden configuration at equilibrium. Furthermore, we employ a dynamic lattice spring model to demonstrate that nanostructured materials with quenched metastable networks have exceptional mechanical enhancement, surpassing both cases of homogeneous melts and stable morphologies. Overall, the viscoelastic microphase separation induced by the dynamic asymmetry presents a robust alternative to accessing lightweight, high-strength nanomaterials beyond thermodynamic design rules.