Mechanistic Studies of Photoacid Generation from Substituted 4,6-Bis(trichloromethyl)-1,3,5-triazines

Abstract

The photochemistry and photophysics of 2-methyl-(1), 2-(2′-furylethylidene)-( 2), and 2-[(4′methoxy)styryl]-4,6-bis(trichloromethyl)-1,3,5-triazine (3), three compounds that find application as photoacid generators in photoresist formulations, have been investigated under conditions of direct excitation and using various phenothiazine derivatives as photosensitizers. C-Cl bond cleavage is confirmed by laser flash photolysis as the primary photochemical step in the direct photolysis of these compounds; the chlorine atoms formed in this reaction can be detected by complexation with chloride anions or benzene. In the case of 1, this photodissociation occurs with a lifetime of <20 ns. The quantum yield of bond breaking for 1 after direct excitation as determined by laser flash photolysis and steady-state irradiations was found to be 30-40 times greater than for 2 and 3. The mechanism under sensitized conditions involves electron transfer from the excited phenothiazines to the triazines as the primary photochemical step; the rate constants for excited-state quenching exceed 10 9 M -1 s -1 for the T 1 state and 10 10 M -1 s -1 for the S 1 state. The rate constants correlate with the free energy for electron transfer estimated from the excited-state energies and the oxidation potential of the sensitizers.

Triazine‐Based Type‐II Photoinitiating System for Free Radical Photopolymerization: Mechanism, Efficiency, and Modeling

“…This contention is confirmed by the apparition of a new band at 340 nm consecutively to the ITX triplet decay which has been previously assigned to ITX •+ . [27] An additional transient appears within the same time scale at 290 nm which is similar to that reported for a triazinyl radical (Tz -Cl • ) [22] and checked by ourselves by direct irradiation of TA at 355 nm ( Figure S1, Supporting Information). This new band can then be confidently attributed to the triazinyl radical of TS (TS -Cl In order to characterize the initiation mechanism of an acrylate photopolymerization reaction by triazinyl radicals, the reaction rate constant between triazinyl radicals and an acrylate (i.e., the initiation rate constant k i ) was measured by LFP.…”

“…Indeed, fundamental state of the PI is regenerated and can participate to a new cycle while the semi-reduced form of the triazine (Tz •− ) is expected to produce a triazinyl initiating radical (Tz -Cl • ) by dissociation of a CCl bond. [22] According to their electron acceptor nature, triazines would be able to react directly with an excited photoinitiator to generate triazinyl radicals. It has been reported that triazine A (TA) is not able to initiate acrylate photopolymerization when combined to several different dyes.…”

“…The TS •− dissociation rate constant has been reported equal to 1.0 × 10 5 s −1 . [22] As it was proved that ITX •+ can be quenched by hydrogen-donor species, [27] we also assume a similar reaction with impurities and stabilizers inherently present in the formulation. This reaction produces radicals reactive towards oxygen and other radical species, and the protonated form of ITX •+ , finally able to go back to 0 ITX after deprotonation (see the associated reactions in the Supporting Information).…”

Functionalized Cyclohexyl methacrylate based Copolymers for Negative Resist

“…In addition, in the figures of conversion (%) versus exposure time plot, rise up and conversion plateau % are higher in the order of OXE-02, TCT-A, TCT-B, and OXE-01. This is explained by the character of radicals generated from different initiators [21][22][23][24]. Methyl radical produced from OXE-02 has highest reactivity and mobility in the polymer matrix, and chlorine atom generated TCT-A and TCT-B, and phenyl radical from OXE-01 have similar ability in total.…”

Effect of Alkyl Group on the Photocrosslinking of Alkyl Methacrylate Based Copolymers

“…3 and 4 of conversion (%) versus exposure time plot, rise up and conversion plateau % are higher in the order of OXE-02, TCT-A=TCT-B, and OXE-01. This is explained by the character of radicals generated from different initiators [18][19][20][21]. Methyl radical produced from OXE-02 has highest reactivity and mobility in the polymer matrix, and chlorine atom generated TCT-A and TCT-B, and phenyl radical from OXE-01 have similar ability in total.…”