3D-Printing of High-κ Thiol-Ene Resins with Spiro-Orthoesters as Anti-Shrinkage Additive

Tri(ethylene glycol) divinyl ether and the spiro-orthoester 2-((allyloxy)methy)-1,4,6-trioxospiro[4.4]nonane can be formulated in different ratios and crosslinked by thiol-ene reactions. The spiro-orthoester is used as anti-shrinkage additive, enabling shrinkage reduction of up to 39%. Addition of a radical photoinitiator for the thiol-ene reaction and a cationic photoinitiator for the double ring-opening of the spiro-orthoester enables dual-curing for application in 3D-printing. The formulation free of the spiro-orthoester shows gelation during the printing process and, correspondingly, low resolution. The formulations containing the spiro-orthoester exhibit higher resolutions in the range of 50 µm. The resins containing mixtures of tri(ethylene glycol) divinyl ether and the spiro-orthoester show permittivities as high as 10⁴. The dielectric loss factor of the resins is in the range of 0.5–7.6, and the conductivity in the range of 1.3⋅10⁻¹¹ to 2.0⋅10⁻¹¹ S cm⁻¹. These high-κ materials can be 3D-printed by digital light processing for the next generation of electronic materials.