Visible light-induced cationic photopolymerization by diphenyliodonium hexafluorophosphate and benzothiadiazole dyes

Abstract

New benzothiadiazole-based long-wavelength organic dyes (Y-1 and Y-2) were prepared for effectively sensitizing diphenyliodonium hexafluorophosphate (IOPF) to initiate the fast curing of bisphenol-A epoxy resin (E51) under visible light, avoiding traditional UV light sources that have high energy and high radiation. Y-1 and Y-2 have absorption spectra extended to more than 550 nm. By using Y-1 and Y-2 as photosensitizers for IOPF, E51 reach high epoxy conversions of 95% under light wavelength of 470-nm irradiation. IOPF and benzothiadiazole dyes present at the same time show good visible-light initiating activity. The high curing conversions are attributed to the photoelectron transfer reaction between diphenyliodonium hexafluorophosphate and benzothiadiazole dyes, based on our photochemical and electrochemical experiments. In addition, the terminated groups or of Y-1 (-F) and Y-2 (-OCH 3) have a great influence on the photopolymerization rate of the curing systems and thermal properties of E51 after cured. In addition, E51 was even polymerized about 70% in the presence of 510-nm light filter.

Green enzymatic synthesis and processing of poly (cis-9,10-epoxy-18-hydroxyoctadecanoic acid) in supercritical carbon dioxide (scCO2)

“…Therefore, for the same material a higher Tg could be indicative of higher degree of crosslinking 62 . These results show that postcuring effects were present during the second curing phase, hinting that the first curing step did not achieve full conversion of all the epoxy groups even if, as shown in the FTIR, the curing agent appeared to be fully consumed 63 (Figure 4 -red circle). Our hypothesis is that the uncompleted crosslinking may give rise to the broad feature because of an uneven distribution of the network formed and due to the complexity of the system broad range of crosslinked structures can be formed.…”

A review on self-initiated and photoinitiator-free system for photopolymerization

“…These photopolymerization reactions are majorly classified based on their reaction mechanism into three categories-free-radical photopolymerization [12,13,42], cationic photopolymerization [39,[43][44][45] and anionic photopolymerization [6,31]. The most extensively used method from an industrial point of view is free-radical photopolymerization.…”