Year: 2024
Type: article
Abstract: Polarity-reversal catalysts (PRCs) for hydrogen-atom transfer reactions have been known in radical chemistry for more than 60 years but are rarely described and utilized in the field of photopolymerization up to now. Herein, we present the use of thiols in a unique dual function as thiol-ene click reagents and as polarity-reversal catalyst (PRC) for the radical-mediated redox rearrangements of benzylidene acetals. During the rearrangement reaction, cyclic benzylidene acetals are transformed into benzoate esters leading to a significant volumetric expansion to reduce thermoset shrinkage. We were able to show that this expansion on a molecular level reduces shrinkage and polymerization stress but does not significantly affect the (thermo-)mechanical properties of the cross-linked networks. One of the key advantages of this process lies in its simplicity. No additives like sensitizers or combinations of different initiators (radical and cationic) are needed. Furthermore, the same light source can be used for both the polymerization reaction and expansion through rearrangement. Additionally, the applied photoinitiator enables spatial and temporal control of the polymerization; thus, the developed system can be an excellent platform for additive manufacturing processes.
Authors: Alexander Ricke, Oskar Berk, Thomas Koch, Robert Liska, Stefan Baudis
Institutions: TU Wien, Austrian Cluster for Tissue Regeneration
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $5,510
Funders: Österreichische Nationalstiftung für Forschung, Technologie und Entwicklung, European Commission, Technische Universität Wien, Christian Doppler Forschungsgesellschaft, Bundesministerium für Digitalisierung und Wirtschaftsstandort, Technische Universität Wien Bibliothek, H2020 Marie Skłodowska-Curie Actions
OpenAlex ID: W4402401990