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

Abstract

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.

Recent Trends in Applying Ortho-Nitrobenzyl Esters for the Design of Photo-Responsive Polymer Networks

“…In addition, thiol-click reactions do not suffer from oxygen or water inhibition [111][112][113][114]. The step-growth polymerization mechanism further leads to homogeneous polymer matrix with low shrinkage stresses and narrow glass transition regions [111][112][113][114][115][116].…”

Photochemical Study of a New Bimolecular Photoinitiating System for Vat Photopolymerization 3D Printing Techniques under Visible Light

“…Due to the unique features of thiol-ene photopolymerization, such as low shrinkage stress and the yielding of homogeneous networks, this type of reaction is very promising for 3D-printing [37,38]. Therefore, thiol-ene resin has been applied to the fabrication of devices via 3D printing [39,40]. For this reason, it was decided to study the suitability of the developed bimolecular photoinitiating systems consisting of 2-amino-4,6-diphenyl-pyridine-3-carbonitrile derivatives and iodonium salt during thiol-ene photopolymerization of methacrylate monomer trimethylopropane trimethacrylate (TMPTA) and trimethylolpropane tris(3-mercaptopropionate) (MERCAPTO) upon exposure to near-UV light at It is worth mentioning that the diphenyliodonium salt alone does not initiate the free-radical photopolymerization of acrylates, indicating the role of 2-amino-4,6-diphenyl-pyridine-3-carbonitrile derivatives as photosensitizers of iodonium salt through the mechanism of photo-oxidizable sensitization of this salt under near-UV light.…”

Enhancement of 3D-Printable Materials by Dual-Curing Procedures

“…Mechanism of the cationic double ring-opening and the thiol-ene reaction of the spiroorthoester (SOE). Reproduced from [55] with permission from Wiley. 3D-printable hybrid materials have also been studied with the purpose of producing shape-memory materials.…”

“…Polymerization of bicyclic spiranic structures based on spiroorthoester (SOE) or other monomers is known to proceed with very little or no shrinkage at all [ 54 ]. Following this distinct approach, Marx et al [ 55 ] combined radical thiol-ene with cationic ring-opening of an SOE to produce low-shrinkage materials with good material permittivity. An SOE-modified ene monomer was synthesized and incorporated into a thiol-ene formulation (see scheme in Figure 6 ), leading to a relevant decrease in curing shrinkage by the cationic tandem ring-opening of the SOE.…”

“… Mechanism of the cationic double ring-opening and the thiol-ene reaction of the spiroorthoester (SOE). Reproduced from [ 55 ] with permission from Wiley. …”