Design of photoinitiating systems based on the chalcone-anthracene scaffold for LED cationic photopolymerization and application in 3D printing

Abstract

In this study, light-emitting diodes (LEDs) used as secure, low-cost and possessing long emission wavelengths irradiation sources were applied in photopolymerization. Seven novel anthracene derivatives (noted A1-A7) were proposed and evaluated in photosensitive systems. Three of them were never synthesized before (A1, A2 and A7) and the other derivatives were evaluated in other fields. Due to the in-silico design of molecular structure by molecular modeling, the proposed chalcone-anthracenes showed a broad absorption band in the visible region with favorable molar extinction coefficients. Photoinitiation abilities of the different photoinitiating systems were examined by the Real-Time Fourier Transformed Infrared Spectroscopy. The free radical polymerization of acrylates under LED@405 nm irradiation in laminate was evaluated and high final function conversions (FCs) were obtained in the presence of three-component photoinitiating systems based on chalcone-anthracenes/iodonium salt/amine. Meanwhile, the chalcone-anthracene derivatives exhibited high photoinitiation abilities in cationic photopolymerization of epoxides in combination with an iodonium salt under LED@405 nm irradiation. The final function conversions of epoxy using some anthracene/iodonium salt systems were even higher than the well-established dibutoxyanthracene (DBA)/iodonium salt benchmark system. In addition, due to the good light absorption properties, the cationic photopolymerization also was carried out in the presence of the chalcone-anthracene/iodonium salt systems under LED@470 nm or laser diode@447 nm irradiation (not possible to do with the reference DBA systems). Markedly, these derivatives were also able to sensitize sulfonium salts. The photochemical reactivity of anthracene derivatives was investigated through the steady state photolysis and fluorescence quenching experiments. Furthermore, the proposed interaction mechanisms of chalcone-anthracene derivatives and additives (iodonium salt and amine) were discussed using the free energy changes of electron transfer reactions. Interestingly, the cationic photopolymerization of A5/iodonium salt system was applied in 3D printing and the 3D patterns showed a good spatial resolution.