How Shape Memory Effects can Contribute to Improved Self-Healing Properties in Polymer Materials

Macromolecules, vol. 54, pp. 2506–2517

Abstract

Realization of self-healing polymer materials cannot rely on the wealth of active repair tools found in living systems but must focus entirely on the structural composition of the material and the properties of its constituents. Current challenges of the search for such compositions include healing of large-scale defects as well as the need for a healing process that is generated by the scission itself. Herein, we describe ionomer–rubber blends from poly(ethylene- co -methacrylic acid) and peroxide cross-linked ethylene–propylene–diene monomer (EPDM) that combine three types of cross-links: covalent links of a network of EPDM, clusters of aggregated ionic groups, and crystalline domains of longer ethylene sequences in the ionomer. Above the melting point of the latter, the components mix homogeneously, indicated by the clarity of the samples and supported by small-angle X-ray scattering (SAXS) and NMR. At ambient conditions, the samples are hard like a thermoplastic material. Self-healing after mechanical damage is enabled by two types of structural memory related to a hierarchy of deformation- and defect-caused stresses and their relaxation paths. Because of the solid-like character of the materials, damage-caused stress is retained by the micro deformation and rupture of the aggregates on small scales and on large scale—by the macroscopic shape memory effect of the deformed covalent network. When the samples get annealed at an elevated temperature, the former enables mending of fracture-caused surfaces and the latter—shape recovery. Based on a careful evaluation of the structural relaxation effects on the blends and their constituents (differential scanning calorimetry, NMR, and wide-angle X-ray scattering/SAXS), we demonstrate the repair of defects in the range of millimeters to centimeters by the defect-caused stresses. It is intrinsic to our concept that it holds only to damages such as scratches, small cuts, and microcracks, whereby the object is not fully fragmented, and that it will require thermal activation.

Authors 7

1. Elizaveta V. Selezneva Aachen DWI - Leibniz Institute for Interactive Materials

   RWTH Aachen University · DWI – Leibniz Institute for Interactive Materials · Russian Academy of Sciences · Max Planck School Matter to Life · A. N. Nesmeyanov Institute of Organoelement Compounds · Institute of Synthetic Polymeric Materials

   Affiliation as printed

   A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Vavilova ul. 28, 119991 Moscow, Russia

   DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University, Forckenbeckstraße 50, D-52074 Aachen, Germany

   Enikolopov Institute of Synthetic Polymeric Materials Russian Academy of Sciences, Profsoyuznaya ul. 70, 117393 Moscow, Russia

   Max Planck School Matter to Live, Jahnstraße 29, D-69120 Heidelberg, Germany

2. Artem V. Bakirov

   Russian Academy of Sciences · Institute of Synthetic Polymeric Materials

   Affiliation as printed

   Enikolopov Institute of Synthetic Polymeric Materials Russian Academy of Sciences, Profsoyuznaya ul. 70, 117393 Moscow, Russia

3. Nikita G. Sedush

   Russian Academy of Sciences · Institute of Synthetic Polymeric Materials

   Affiliation as printed

   Enikolopov Institute of Synthetic Polymeric Materials Russian Academy of Sciences, Profsoyuznaya ul. 70, 117393 Moscow, Russia

4. Aleksandra V. Bystrova

   Russian Academy of Sciences · A. N. Nesmeyanov Institute of Organoelement Compounds · Institute of Synthetic Polymeric Materials

   Affiliation as printed

   A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Vavilova ul. 28, 119991 Moscow, Russia

   Enikolopov Institute of Synthetic Polymeric Materials Russian Academy of Sciences, Profsoyuznaya ul. 70, 117393 Moscow, Russia

5. С. Н. Чвалун

   Russian Academy of Sciences · A. N. Nesmeyanov Institute of Organoelement Compounds · Institute of Synthetic Polymeric Materials

   Affiliation as printed

   A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Vavilova ul. 28, 119991 Moscow, Russia

   Enikolopov Institute of Synthetic Polymeric Materials Russian Academy of Sciences, Profsoyuznaya ul. 70, 117393 Moscow, Russia

6. Dan E. Demco Aachen DWI - Leibniz Institute for Interactive Materials

   RWTH Aachen University · DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University, Forckenbeckstraße 50, D-52074 Aachen, Germany

7. Martin Möller corresponding Aachen DWI - Leibniz Institute for Interactive Materials

   RWTH Aachen University · DWI – Leibniz Institute for Interactive Materials · Russian Academy of Sciences · Max Planck School Matter to Life · A. N. Nesmeyanov Institute of Organoelement Compounds

   Affiliation as printed

   A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Vavilova ul. 28, 119991 Moscow, Russia

   DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University, Forckenbeckstraße 50, D-52074 Aachen, Germany

   Max Planck School Matter to Live, Jahnstraße 29, D-69120 Heidelberg, Germany