Enhancing Toughness and Microstructural Memory by Coupling Crystallinity, Elasticity, and Plasticity in Layered Materials Composed of Liquid Crystalline Oligomers

Molecular dynamics simulations are used to show that triblock oligomers, which are first preassembled into a lamellar phase and then cross-linked, exhibit high extensibility and toughness in response to uniaxial tensile deformation parallel to the layer stacking. A coarse-grained model is adopted based on a coil–rod–coil oligomer capped with cross-linkable units. Upon uniaxial strain, a buckling instability ensues in the uncross-linked systems, which eventually leads to defective lamellar “islands” as the stress drops off. In contrast, a toughening behavior, manifested as a “sawtooth” stress–strain profile, is observed in the cross-linked systems, which is associated with “recrystallization” of the rod domains mediated by the interlayer bonds formed upon cross-linking. It is also shown that this toughening mechanism can be encoded in longer multilayer-spanning oligomer designs that forsake the cross-linking step. These structures, which integrate rigidity, elasticity, and plasticity, could be leveraged to experimentally realize novel materials with shape-memory and self-healing properties.