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Molecular dynamics simulations are used to show that triblock oligomers which are first preassembled into a lamellar phase and then crosslinked, 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 crosslinkable units. Upon uniaxial strain, a buckling instability ensues in the uncrosslinked systems, which eventually leads to defective lamellar ‘islands’ as the stress drops off. In contrast, a toughening behavior, manifested as a ‘saw-tooth’ stress-strain profile, is observed in the crosslinked systems, which is associated with ‘recrystallization’ of the rod domains mediated by the inter-layer bonds formed upon crosslinking. It is also shown that this toughening mechanism can be encoded in longer multilayer-spanning oligomer designs that forsake the crosslinking step. These structures, which integrate rigidity, elasticity, and plasticity, could be leveraged to experimentally realize novel materials with shape-memory and self-healing properties.