Tuning the Sawtooth Tensile Response and Toughness of Multiblock Copolymer Diamond Networks
C Nowak and FA Escobedo, MACROMOLECULES, 49, 6711-6721 (2016).
Liquid crystalline elastomers of block copolymer chains end-linked into a diamond network have recently; been shown to exhibit a sawtooth tensile response-tor 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%-1.5%) 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 addititional "tooth-triggering" block segregation events.
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