Multibranched triarylamine end-capped oxime esters as visible-light absorbing type I photoinitiators for free radical photopolymerization

Abstract

A series of oxime esters (TPA-DP, TPA-CZ and TPA-PT) had been developed and synthesized, in which three electron-donating groups (diphenylamine, carbazole, or phenothiazine) are connected to the 4, 4’-positions of...

Recent advances on phenothiazine-based oxime esters as visible light photoinitiators of polymerization

“…These two-component systems were also used for promoting the CP of EPOX and a conversion of 83% could be obtained with the twocomponent PTZ2/Iod system (See Table 6). This value is greatly higher than that obtained with the previous triphenylamine derivatives since EPOX conversions of 54% and 47% were respectively obtained with the two-component TPA-CZ/Iod and TPA-PT/Iod systems upon irradiation at 405 nm for 800 s. [82] A conversion of only 69% was obtained with the PTZ3/Iod combination and this is directly related to the lower photochemical reactivity of PTZ3 in two component systems, slower photolysis rates being detected for this system compared to the PTZ2/Iod combination. Finally, by the possibility to initiate FRP and CP processes with the two-component systems, interpenetrated polymer networks could be generated by the concomitant polymerization of TA and EPOX.…”

“…TPA-PT was proposed as a visible light photoinitiator by Lalevée and coworkers. [82] Here again, in order to determine the real contribution of phenothiazine on the photoinitiating ability, analogues were prepared with carbazole and diphenylamine as the end-groups (See Figure 13). Absorption spectra of the different triphenylamine-based oxime esters were broad, extending between 300 and 435 nm.…”

“…These values are lower than that determined for TP-1M, TPA-CZ, TPA-PT, TP-1M, TPA-CZ and TPA-PT previously discussed. [82] Table 5. Maximal, onset polymerization temperatures and TA conversions obtained using PTZ1, PTZ2, and PTZ3 (1 wt%) as thermal initiators under nitrogen.…”

“…[53] In order to get a sufficient absorption in the visible range, chromophores different from those used in benchmark photoinitiators have to be used or structurally modified in order to improve their absorptions in the visible range. Thus, anthraquinone, [62] coumarins, [55,[63][64][65][66] carbazole, [67][68][69][70][71][72][73][74][75] carbazole-fused coumarins, [14,76,77] pyrene, [78] anthracene, [78] naphthalene, [79] triphenylamine, [80][81][82][83][84] thioxanthone, [85] phenylthioether thiophene, [86,87] bis-chalcones, [88] fluorophenyl derivatives, [89] stilbene derivatives, [90] thiophene derivatives, [91] naphthoquinones, [92] naphthalimides [93] and chalcones [94] have notably been examined as chromophores for the design of oxime esters. Among potential structures, phenothiazine has recently been used for the design of Type II and Type I photoinitiators.…”

“…Photopolymerization profiles of TA using TPA-1M, TPA-Cz and TPA-PT upon irradiation at 405 nm with a LED using PI/Iod (2%/1% w/w) or PI (2 wt%). Reproduced with permission of Ref [82].…”