Imaging the Molecular Motions of Autonomous Repair in a Self‐Healing Polymer

• Published in: Advanced materials (Weinheim) Vol. 29; no. 26
• Main Authors: van der Kooij, Hanne M., Susa, Arijana, García, Santiago J., van der Zwaag, Sybrand, Sprakel, Joris
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-07-2017
• Subjects: Catastrophic failure analysis; Cohesion; Damage localization; Damage prevention; Design improvements; Imaging; Laser speckle Imaging; Materials science; Nonlinear mechanics; Polymer dynamics; Repair; Self healing materials; Self-healing; Service life; Structural damage; Thermoplastic elastomers; laser speckle Imaging; nonlinear mechanics; thermoplastic elastomers; polymer dynamics; self-healing
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201701017

Self‐healing polymers can significantly extend the service life of materials and structures by autonomously repairing damage. Intrinsic healing holds great promise as a design strategy to mitigate the risks of damage by delaying or preventing catastrophic failure. However, experimentally resolving the microscopic mechanisms of intrinsic repair has proven highly challenging. This work demonstrates how optical micromechanical mapping enables the quantitative imaging of these molecular‐scale dynamics with high spatiotemporal resolution. This approach allows disentangling delocalized viscoplastic relaxation and localized cohesion‐restoring rebonding processes that occur simultaneously upon damage to a self‐healing polymer. Moreover, frequency‐ and temperature‐dependent imaging provides a way to pinpoint the repair modes in the relaxation spectrum of the quiescent material. These results give rise to a complete picture of autonomous repair that will guide the rational design of improved self‐healing materials.
A new multiple‐scattering‐based optical technique illuminates the molecular motions via which self‐healing polymers can spontaneously and autonomously restore damage. This method allows the construction of 4D micromechanical maps of repair, in situ and spanning five decades of frequency. The complex interplay of diverse dynamics at the origin of self‐healing can thus be quantitatively unraveled.