Local and reversible self-folding of crosslinked polymers
Reversible switchable catalysts were developed that enable moldfree selffolding of crosslinked photopolymers.
Programme: COMET – Competence Centers forExcellent Technologies
Programme line: COMET-Module
Type of project: Project 1.02 - Fast repairable dynamic covalent polymer networks without creep for a circular economy of crosslinked polymer components, 2024-2027, multi-firm
LOCAL AND REVERSIBLE SELF-FOLDING OF CROSSLINKED POLYMERS
REVERSIBLE SWITCHABLE CATALYSTS WERE DEVELOPED THAT ENABLE MOLDFREE SELFFOLDING OF CROSSLINKED PHOTOPOLYMERS.
Thermosetting polymers, having a covalently crosslinked network structure, offer outstanding mechanical performance and chemical resistance. However, their robust nature poses critical challenges for the recycling, welding or reshaping of these materials. Dynamic polymer networks aim to bridge this gap between performance and sustainability by the introduction of dynamic covalent bonds capabl of reorganizing the network topology in response to an external stimulus. The resulting change in viscoelasticity imparts weldability, malleability and repairability in the crosslinked polymers. In the COMET module project Repairtecture, a merocyanine photoacid was synthetized in collaboration with University of New South Wales and University of Melbourne. The synthetized catalyst enables fast and reversible controll of viscoelastic properties in crosslinked polymers undergoing transesterification.
The work was published in the renowned Journal of the American Chemical Society, JACS. (https://doi.org/10.1021/jacs.5c13227).
© PCCL
Principle of reversible activation of the new catalyst (left) and reversible writing of patterns with mask lithography (right).
Impact and effects
When exposed to visible light, the photoacid's activated spiropyran form enables a macroscopic material flow through acid-catalyzed transesterification. Switching off the light yields the deactivated merocyanine form and a creep-resistant thermoset is obtained.
© PCCL
Local and reversible self-folding of photopolymer films.
Stress relaxation experiments clearly demonstrate a remarkable difference in mechanical properties resulting from the photoacid’s somerization state. Compared to previously studied catalysts, the merocyanine photoacid benefits from rapid isomerization kinetics and high fatigue resistance. The exceptionally high level of control achieved over the isomerization state of the photoacid is employed for the generation of micro-gradients of active catalyzing species. The resulting nonuniform profile of mechanical properties paves the way towards the gradient-driven, mold-free reshaping of free-standing polymer films. Moreover, bending radii are accurately predictable based on a newly established empirical model, designed to be easily transferable to other polymer systems exhibiting nonuniform stress relaxation properties.
In addition, the introduced catalytic concept itself can be applied to other acid-catalyzed dynamic polymer networks, rendering them reversibly switchable in terms of a light-controlled ON/OFF behavior.
Projektkoordination (Story)
Priv.-Doz. Dr. Sandra Schlögl
Division Manager
Polymer Competence Center Leoben GmbH
sandra.schloegl@pccl.at
PCCL GmbH
Sauraugasse 1
8700 Leoben
T +43 (0) 3842 42962-0
office@pccl.at
www.pccl.at
Project Partners
- Mitsui Chemicals Europe GmbH, Germany
- Eologix Sensor Technology GmbH; Austria
- Graz University of Technology, Austria
- Technical University of Leoben, Austria
- University of New South Wales, Australia
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Funding Body
Repairtecture is a COMET Module Project within the COMET – Competence Centers for Excellent Technologies Programme and funded by BMIMI, BMWET and the provinces Styria and Upper Austria. The COMET Programme is managed by FFG. Further information on COMET: www.ffg.at/comet
