Description
3D-VAT printing is an excellent alternative to the traditional preparation of 3D objects from polymeric materials, reducing costs and increasing the resolution of objects. The use of cationic 3D-VAT printing unfortunately hits a number of limitations. One of these is the lack of suitable photoinitiators that absorb in the emission range of the light sources used in printers (around 405 nm).[1] Most of the commonly used iodonium salts are diaryl derivatives proposed by Crivello in the 1970s. They show only residual light absorption above 300 nm and require photosensitizers or special light sources to efficiently initiate polymerization.[2] It is therefore essential to develop advanced iodonium salts that absorb longer wavelength light and efficiently generate superacid (which is the actual initiator of cationic polymerization).
The new innovative design of chromophores makes it possible to obtain iodonium salts in a selective manner, which was previously impossible with more refined chromophores.[3,4] Furthermore, the design used has made it possible to obtain the first symmetric iodonium salts equipped with an extended chromophore with a double bond.[5] Such advances in the structure of iodonium salts have made it possible to obtain compounds with excellent absorption properties extending into the visible range. The new iodonium salts are able to efficiently photolyze the cationic polymerization under 365 nm and 405 nm LED irradiation and can photoinitiated the cationic polymerization of monomers such as epoxides and vinyl ethers.
This design leads to a significant improvement in photoinitiating properties, allowing the developed salts to be used in such advanced applications as cationic 3D-VAT printing allowing prints with a resolution superior to those obtained with commercial photoinitiating systems.
