Tuning the Sawtooth Tensile Response and Toughness of Multiblock Copolymer Diamond Networks

Abstract

Liquid crystalline elastomers of block copolymer chains end-linked into a diamond network have recently been shown to exhibit a sawtooth tensile response to uniaxial deformation [Macromolecules 2014, 47, 840−850], which can provide the basis to design supertough, highly stretchable materials. Molecular dynamics is used to study different chain designs that modulate the number of “teeth” and the strain-orientation dependence of the previously reported tensile response of ABA (25%–50%–25%) chains. Two chain designs with distinct tensile behaviors have been identified. First, ABA (15%–70%–15%) chains with lower backbone stiffness are found to exhibit a stress response independent of the extensional direction by virtue of morphological rearrangements occurring at low strains. Second, ABACA (20%–20%–20%–20%–20%) pentablock chains are found to exhibit a sawtooth response with twice as many “teeth” for a given strain and hence larger toughness. This architecture allows for more gradual chain unfolding events and...