Revealing Deformation Mechanisms in Polymer-Grafted Thermoplastic Elastomers via In Situ Small-Angle X-ray Scattering

The tunable properties of thermoplastic elastomers (TPEs), through polymer chemistry manipulations, enable these technologically critical materials to be employed in a broad range of applications. The need to “dial-in” the mechanical properties and responses of TPEs generally requires the design and synthesis of new macromolecules. In these designs, TPEs with nonlinear macromolecular architectures outperform the mechanical properties of their linear copolymer counterparts, but the differences in the deformation mechanism providing enhanced performance are unknown. Here, in situ small-angle X-ray scattering (SAXS) measurements during uniaxial extension reveal distinct deformation mechanisms between a commercially available linear poly(styrene)-poly(butadiene)-poly(styrene) (SBS) triblock copolymer and the grafted SBS version containing grafted poly(styrene) (PS) chains from the poly(butadiene) (PBD) midblock. The neat SBS (φSBS = 100%) sample deforms congruently with the macroscopic dimensions, with the domain spacing between spheres increasing and decreasing along and transverse to the stretch direction, respectively. At high extensions, end segment pullout from the PS-rich domains is detected, which is indicated by a disordering of SBS. Conversely, the PS-grafted SBS that is 30 vol % SBS and 70% styrene (φSBS = 30%) exhibits a lamellar morphology, and in situ SAXS measurements reveal an unexpected deformation mechanism. During deformation, there are two simultaneous processes: significant lamellar domain rearrangement to preferentially orient the lamellae planes parallel to the stretch direction and crazing. The samples whiten at high strains as expected for crazing, which corresponds with the emergence of features in the 2D SAXS pattern during stretching consistent with fibril-like structures that bridge the voids in crazes. The significant domain rearrangement in the grafted copolymers is attributed to the new junctions formed across multiple PS domains by the grafting of a single chain. The in situ SAXS measurements provide insights into the enhanced mechanical properties of grafted copolymers that arise through improved physical cross-linking that leads to nanostructure domain reorientation for self-reinforcement and craze formation where fibrils help to strengthen the polymer.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Appl. Mater. Interfaces, copyright © 2023 American Chemical Society after peer review and technical editing by the publisher.

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Work Title Revealing Deformation Mechanisms in Polymer-Grafted Thermoplastic Elastomers via In Situ Small-Angle X-ray Scattering
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Open Access
Creators
  1. Vincent M. Torres
  2. Erik Furton
  3. Jensen N. Sevening
  4. Elisabeth C. Lloyd
  5. Masafumi Fukuto
  6. Ruipeng Li
  7. Darren C. Pagan
  8. Allison M. Beese
  9. Bryan D. Vogt
  10. Robert J. Hickey
Keyword
  1. Block polymers
  2. Nanostructure
  3. In situ measurement
  4. Toughness
  5. Grafted polymers
  6. Tensile properties
  7. Crazing
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. ACS Applied Materials & Interfaces
Publication Date October 10, 2023
Publisher Identifier (DOI)
  1. https://doi.org/10.1021/acsami.3c09445
Deposited May 06, 2024

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Version 1
published

  • Created
  • Added In_Situ_SAXS_Revised_Final-1.pdf
  • Added Creator Vincent M. Torres
  • Added Creator Erik Furton
  • Added Creator Jensen N. Sevening
  • Added Creator Elisabeth C. Lloyd
  • Added Creator Masafumi Fukuto
  • Added Creator Ruipeng Li
  • Added Creator Darren C. Pagan
  • Added Creator Allison M. Beese
  • Added Creator Bryan Vogt
  • Added Creator Robert Hickey
  • Published
  • Updated
  • Updated Keyword, Publisher Show Changes
    Keyword
    • Block polymers, Nanostructure, In situ measurement, Toughness, Grafted polymers, Tensile properties, Crazing
    Publisher
    • ACS applied materials & interfaces
    • ACS Applied Materials & Interfaces
  • Renamed Creator Bryan D. Vogt Show Changes
    • Bryan Vogt
    • Bryan D. Vogt
  • Renamed Creator Robert J. Hickey Show Changes
    • Robert Hickey
    • Robert J. Hickey