Activation of Self-healing Processes in Ionomeric Elastomers by Local Heating
Final Report Abstract
The overall objective of this project is the development, optimization and application of tailor‐made, self‐healing elastomeric materials activated by local heating. Ionomeric polymers that are exclusively crosslinked by dynamic bonds are shown to be of potential for autonomous or on‐demand self‐healing of flexible polymeric materials. By developing a model system and by investigating the underlying structure‐property correlations with respect to the dynamic mechanical properties, we gain valuable information concerning the bond dynamics and the optimization of the ionomer architecture and composition with respect to its thermally triggered self‐healing behavior. We achieved a profound understanding of the impact of the internal cluster structure and dynamics on the rheological behavior, the tensile performance, and the self‐healing efficiency as found in tensile and scratch tests, and showed that the effective modulus and the longest relaxation time can independently be tailored by proper choice of the ion content and the counter ion, and that the latter is a prerequisite for effective healing under moderate conditions. An elegant way to restore the materials structural integrity proceeds by the selective heating of damaged areas to accelerate local healing processes proceeding by enhanced interdiffusion and (re)formation of dynamic bonds. The incorporation of dipolar particles like metal/magnetic nanoparticles into the polymeric matrix leads to a transformation of electromagnetic energy to heat by selective treatment in an oscillating electromagnetic field (OEMF). We obtained valuable insight in the preparation and characterization of ionomeric elastomer‐based nanocomposites designed for local heating in OEM fields. The latter is possible by the incorporation of inorganic nanoparticles that serve as antennas for the transformation of electromagnetic energy into dissipating heat. By remote‐controlled operation in OEMF, a local heat development occurs in selective zones of the ionomers, keeping the surrounding regions close to room temperature. This disparity in the temperature creates a property gradient within the elastomer ranging from an elastic network to a highly viscous yet mobile fluid in the softened region. The model system‐based approach to elucidate the structure‐property correlations in elastomeric ionomers clearly illustrates their principal potential for self‐healing materials, and that an optimization of the effect with respect to the counter‐ion nature and the ion fraction is possible. For a local heal‐on‐demand option, a low volume fraction of magnetic particles is sufficient to result in a fast property recovery under influence of an oscillating electromagnetic field. The results are transferable to other ionomer‐based systems.
Publications
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"Self‐Healing in Plants as a Model for Self‐Repairing Elastomer Materials", Intern. Polym. Sci. Technol., 38(9), 1‐4 (2011)
A. Nellesen, M. v. Tapavicza, J. Bertling, A. M. Schmidt, G. Bauer, T. Speck
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"Bio‐Inspired Self‐Healing Materials", in: Materials design inspired by Nature: Function through inner Architecture, P. Fratzl, J. W. C. Dunlop, R. Weinkammer (eds.), RSC Publishing 2013, ISBN: 978‐1‐84973‐553‐7
T. Speck, M. von Tapavicza, A. Nellesen, A. M. Schmidt, R. Mülhaupt, at al.
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"Self‐Healing Ionomers", in: Self‐Healing Polymers: from Principles to Applications, W. H. Binder (ed.), Wiley‐VCH 2013, ISBN‐10: 3527334394
N. Hohlbein, M. von Tapavicza, A. Nellesen, A. M. Schmidt
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"Connecting supramolecular bond lifetime and network mobility for scratch healing in poly(butyl acrylate) ionomers containing sodium, zinc and cobalt", Phys. Chem. Chem. Phys., 17, 1697‐1704 (2015)
R. K. Bose, N. Hohlbein, S. J. Garcia, A. M. Schmidt and S. van der Zwaag
