Sulfonium salt based charge transfer complexes as dual thermal and photochemical polymerization initiators for composites and 3D printing

Charge transfer complexes (CTCs) exhibit excellent initiating abilities as safe photo, thermal, or photo/thermal dual initiators, which cannot be achieved by classical initiators. New dual initiators based on a phenacyl sulfonium salt (ITXPhenS) acceptor and selected donors capable of initiating both thermal and photochemical polymerizations are investigated. Excellent dual initiating ability and long storage stability were examined by RT-FTIR and DSC experiments. The formations of the CTCs were confirmed by UV-vis spectroscopic investigations and MOC (Molecular Orbital Calculations). The application of the newly developed initiating system in laser writing experiments at 405 nm shows excellent spatial resolution performance. High-tech composites with tack free surfaces can be easily fabricated by employing these kinds of CTCs via fast photochemical curing of the surface associated with a thermal curing in depth. Both carbon fibers and glass fiber composites were prepared.