Dielectric properties of shrinkage-free poly(2-oxazoline) networks from renewable resources

Fabio Blaschke, Philipp Marx, Stefan Hirner, Inge Mühlbacher, Karin Wewerka, Frank Wiesbrock

Research output: Contribution to journalArticleResearchpeer-review


In the course of this study, the dielectric and physicochemical properties of poly(2-oxazoline) (POx) networks from renewable resources were compared with those of fossil-based polyamide 12 (PA 12) networks. POx was synthesized by the energy-efficient, microwave-assisted copolymerization of 2-oxazoline monomers, which were derived from fatty acids of coconut and castor oil. For the preparation of composites, aluminum nitride nanoparticles n-AlN and microparticles μ-AlN as well as hexagonal boron nitride BN submicroparticles were used. Additionally, 0, 15, or 30 wt.% of a spiroorthoester (SOE) were added as an expanding monomer aiming to reduce the formation of shrinkage-related defects. For the crosslinking of the polymers and the SOE as well as the double ring-opening reaction of the SOE, a thermally triggered dual-cure system was developed. The fully-cured blends and composites containing SOEs exhibited lower densities than their fully-cured SOE-free analogues, which was indicative of a lower extent of shrinkage (or even volumetric expansion) during the curing reaction, which is referred to as relative expansion RE. The RE amounted to values in the range of 0.46 to 2.48 for PA 12-based samples and 1.39 to 7.50 vol.% for POx-based samples. At 40 Hz, the “green” POx networks show low loss factors, which are competitive to those of the fossil-based PA 12.
Original languageEnglish
Article number1263
Number of pages15
Issue number8
Publication statusPublished - 13 Apr 2021

Bibliographical note

Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.


  • Dual-cure mechanism
  • Nanodielectrics
  • Poly(2-oxazoline)
  • Polyamide 12
  • Renewable resources
  • Thermal conductivity
  • Volumetric expansion

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