Two-photon lithography in visible and NIR ranges using multibranched-based sensitizers for efficient acid generation

Abstract

We investigated methodically the one- and two-photon absorption properties of a series of multibranched triphenylamine-based chromophores incorporating 4-(methylthio)styryl fragments as external substituents. Some relevant structure–property relationships relative to these highly fluorescent compounds have been derived based on emission anisotropy measurements, quantum chemical calculations and the use of the exciton coupling theory. Even though branching effects lead to a cooperative enhancement of the two-photon absorption (2PA), all compounds exhibit relatively low-to-moderate 2PA cross-sections (δ ≤ 100 GM) in the NIR region. However, the ‘so-called’ one-photon resonance enhancement effect leads to a remarkable increase of δ by more than one order of magnitude in the visible range. This strong 2PA ability has been associated with an efficient photosensitization of iodonium salt to elaborate a new bicomponent photoacid generator, which is readily two-photon activable at 532 nm. In the visible range, the strong enhancement of the efficiency of the two-photon induced polymerization is clearly demonstrated as compared with that observed in the NIR region

One/two-photon cationic polymerization in visible and near infrared ranges using two-branched sulfonium salts as efficient photoacid generators

“…1). These results suggest that the presence of multiple S 0 /S n electronic transitions and the calculated energies of the electronic transitions of PAGs and their corresponding oscillator strengths support the conclusion (f (S0/S2) ¼ 0.49e1.06, Table 2) and the LUMOþ1 orbital was also involved in the frontier orbitals in these two-branched molecular structures [41]. Saeva [42e44] proved that for arylsulfonium salts, the photoreaction can occur either by direct excitation of a pes* (sulfurecarbon bond) transition or by excitation of a pep* transition, which was followed by intramolecular electron transfer to the s* on sulfurecarbon bond.…”

Dual roles for promoting monomers to polymers: A conjugated sulfonium salt photoacid generator as photoinitiator and photosensitizer in cationic photopolymerization

“…The spectrum of PI‐PAG presents a slight redshift but a lower ε value compared with its precursor (Precursor). The excellent absorption properties of the compounds are associated with the large delocalization of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), which are involved in the lowest energy transition …”

Mechanosynthesis of a Copper complex for redox initiating systems with a unique near infrared light activation

“…Nevertheless, the photochemical bleaching remains an obstacle to its widespread use. Most of the known PISs under NIR irradiation results in highly colored polymers as for example the cyanine‐based dyes, Bacteriochlorophyll a or other multi‐branched NIR photosensitizers . A complete bleaching of the produced polymer upon NIR irradiation is – to the authors ' knowledge – not possible with such current NIR PISs.…”