Recently, photo-controlled reversible addition-fragmentation chain transfer (RAFT) polymerization has been successfully applied in digital light processing 3D printing. It provides a convenient way to tune the surface properties of the 3D printed object. However, so far, 3D micro-and nanostructures and reconfigurations based on photo-induced RAFT polymerization have not been presented. In this work, one macro-photoiniferter, synthesized by photocontrolled RAFT polymerization is applied, to 3D direct laser writing. Thanks to the exquisite spatial control of the photoreaction, 3D microstructures with feature sizes of around 500 nm are successfully obtained. Taking advantage of the presence of dormant polymeric RAFT agents, photo-induced postmodification of the printed microstructures is highlighted via the elaboration of multi-chemistry patterns including thermo-responsive ones. These results open new perspectives in multi-material and 4D micro-printing.

Novel sulfonium-based D-p-A photoacid generators (PAGs) with a benzene oligomer (from one to four) as a p-conjugated system that are highly photosensitive in the near-ultraviolet region (365 nm) were prepared.The maximum absorption and molar extinction coefficients of the PAGs redshifted and enhanced with the increasing length of the conjugated systems. The quantum yields of PAGs were high (three of them were over 0.6) and improved by adjusting the number of the phenyl rings. The quantum chemical calculation results proved that the molecular configuration and nature of the frontier orbitals are crucial factors which affect PAG performance. Photopolymerization kinetic results demonstrated that these sulfoniumbased PAGs were highly efficient cationic photoinitiators, and the i-line sensitivities were evaluated based on the photolithographic performance of the PAG-containing SU-8 resins. In addition, the two-photon absorption cross sections (d 700 nm > 400 GM) matched the requirements needed in the 3D fabrication of polymer microstructures. † Electronic supplementary information (ESI) available: Details of the organic synthesis and characterization, photodecomposition, photoacid generation, TGA curves, photopolymerization, photolithography and two-photon absorption. See

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An efficient strategy for comprehensive utilization of the conjugated sulfonium salt photoacid generator (PAG), namely, 3‐{4‐[4‐(4‐N,N′‐diphenylamino)‐styryl]phenyl}phenyl dimethyl sulfonium hexafluoroantimonate, was developed through photoinitiated cationic photopolymerization (CP) of epoxides and vinyl ether upon exposure to near‐UV and visible light‐emitting diodes (LEDs; e.g., 365, 385, 405, and 425 nm). Photochemical mechanisms were investigated by UV–vis spectra, molecular orbital calculations, fluorescence, cyclic voltammetry, and electron spin resonance spin‐trapping analyses. Compared with commercial PAGs, the prepared conjugated sulfonium salt generated H+, which can be used as photoinitiator. Moreover, the fluorescent byproducts from photodecomposition can be used as photosensitizer of commercial iodonium salt in the photoinitiating systems of CP. These novel D‐π‐A type sulfonium‐based photoinitiating systems are efficient (epoxide conversion = 85–90% and vinyl conversion >90%; LEDs upon exposure to 365–425 nm) even in low‐concentration initiators (1%, w/w) and low curing light intensities (10–40 mW cm−2). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2722–2730

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Novel thioxanthone (TX) derivatives are used as versatile photoinitiators upon visible light-emitting diode (LED; e.g., 405, 425, and 450 nm) exposure. The mechanisms for the photochemical generation of reactive species (i.e., cations and free radicals) produced from photoinitiating systems based on the photoinitiator and an iodonium salt, tris(trimethylsilyl)silane, or an amine, were studied by UV-vis spectroscopy, fluorescence, cyclic voltammetry, steady-state photolysis, and electron spin resonance spin-trapping techniques. The reactive species are particularly efficient for cationic, free radical, hybrid, and thiol-ene photopolymerizations upon LED exposure. The optimized photoinitiating systems exhibit higher efficiency than those of reference systems (i.e., isopropyl TXbased photoinitiating systems), especially in the visible range. According to their beneficial features, these photoinitiating systems have considerable potential in photocuring applications.

Three novel types of thiophene‐containing oxime sulfonates with a big π‐conjugated system were reported as non‐ionic photoacid generators. The irradiation of the newly synthesized photoacid generators using near UV–visible light‐emitting diodes (LEDs) (365–475 nm) results in the cleavage of two weak NO bonds in single molecules, which lead to the generation of different sulfonic acids in good quantum and chemical yields. The mechanism for the NO bond cleavage for acid generation was supported by the UV–visible spectra and real‐time 1H NMR spectra. They are developed as high‐performance photoinitiators without any additives for the cationic polymerization of epoxide and vinyl ether upon exposure to near‐UV and visible LEDs (365–475 nm) at low concentration. In the field of photopolymerization, especially visible light polymerization, it has great potential for application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 776–782