Enhancing Toughness\nand Microstructural Memory by\nCoupling Crystallinity, Elasticity, and Plasticity in Layered Materials\nComposed of Liquid Crystalline Oligomers

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