Photoinduced acid generator

Figure 4.28. Molecular structures and photoinduced reactions of common photoresists. Shown (top) is the positive tone resist containing the active diazonapthoquinone (DNQ) chromophore group. Chemical amplification (CAM) reactions are illustrated in (i)-(iii). Reaction (i) represents photoinduced acid generation step (ii) is an acid-catalyzed deprotection mechanism (positive tone resist) and step (iii) is an acid-catalyzed crosslinking mechanism (negative tone resist).

Figure 3.79. Protonation of 43e2 caused by irradiation of triarylsulfonium hexafluor-oantimonate as photoinduced acid generator [118].

Figure 3.80. Two-photon induced dual-channel fluorescence image formation within a photosensitive polymer film containing 43e2 and triarylsulfonium hexafluoroantimonate as photoinduced acid generator. (From Ref. [118] with permission of the American Chemical Society.)...

The deprotection kinetics of alicyclic polymer resist systems designed for 193 nm lithography was examined using JR and fluorescence spectroscopic techniques. A kinetic model was developed that simulates the deprotection of the resists fairly well. A new, simple, and reliable method for monitoring photoinduced acid generation in polymer films and in solutions of the kind used in 193 nm and deep-UV lithography was developed. This technique could find application in the study of diffusional processes in thin polymer films. 

Novel Anafytic Method of Photoinduced Acid Generation and Evidence of Photosensitization via Matrix Resin... 

Figure 6. Time profiles of photoinduced acid generation of TBI with and without PHS matrix...

There was no HBr production from the PMMA film containing TBI and HMM. HMM did not hinder the photoinduced acid generation. 

In order to learn about the true quantum efficiency of photogeneration one therefore has to study the photoinduced charge generation mechanism at faster time scales. Pump probe spectroscopy utilising a few optical-cycle laser pulses (5-6 fs) in the visible spectral range with broadband frequency conversion techniques [89] now makes it possible to study extremely fast optically-initiated events with unprecedented time resolution. Such a setup was used to time-resolve the kinetics of the charge transfer process from a polymer chain to a fullerene moiety in thin films of poly[2-methoxy, 5-(3, 7 -dimethyl-octyloxy)]-p-phenylene vinylene (MDMO-PPV) and [6,6]-phenyl C6i butyric acid methyl ester (PCBM). Solutions prepared from 1 wt% solutions of toluene on thin quartz substrates were studied. 

Ren, Y, Jager, W.F., Neckers, D.C., 1996. Simultaneous photoinduced color formation and polymerization the formation of highly colored thin films from colorless precursors due to formation of triaryknethane cations by acid generating decomposition of iodonium saltsl. Macromolecules 29, 3751-3757. 

Figure 7 shows the effect of acid generating unit fraction on the polysiloxane formation rate. The polysiloxane formation rate decreased in the order 2c > 2b > 2a, if the photolysis degrees of the NIS units in the polymers were same (4.5 mol%). The higher the concentration of the photoinduced acids at the surface, the larger the polysiloxane formation rate. 

Polymer films containing the photoacid generator FITS were irradiated at 254 nm and insoluble fraction in THF was studied. FITS was photolyzed to generate p-toluenesulfonic acid. The photoinduced-acid initiated cationic polymerization of epoxy units in the side chain to generate networks (Figure 4). Insoluble fractions for the polymers were 60-90%, except for... 

We have synthesized a novel methacrylate monomer (MOBH) which has an epoxy moiety and a tertiary ester linkage in a molecule. Homopolymer of MOBH and copolymers of MOBH with tert-butyl methacrylate, tert-butoxystyrene, cyclohexyl styrenesulfonate, neopentyl styrenesulfonste or phenyl styrenesulfonate were obtained by the conventional radical photopolymerization. Polymer films containing photoacid generators (PAG) became insoluble in tetrahydrofuran on UV irradiation because of the photoinduced-acid catalyzed crosslinking reaction of epoxy units. 

The photoreduction of aromatic nitro compounds to the amino compounds can be carried out on the surface of semiconductor particles such as titanium oxide1 with H-atom donors (equation 1). At a shorter duration of the photoinduced reduction of p-nitroacetophenone, the hydroxylamine intermediate can be obtained in about 30% yield. The reaction mechanism proposed is based on the photoexcitation of TiC>2 to generate an electron and a positive hole (equations 2 and 3). Aliphatic nitro compounds such as 12-nitrododecanoic acid can be reduced to 12-amino dodecanoic acid in 90% yield by this method. 

More recent results support the view that Lewis acids, on the interaction with metal carbonyls, may facilitate dissociation of a ligand to leave a vacant site for alkene coordination.75 Photochemical generation of carbene species [Eq. (12.20)], the crucial step in photoinduced metathesis, is a complicated, multistep process 74,76,77... 

Photoinduced proton transfer may be generated through the large variation in acidity or basicity of functional groups in the excited states of specific structures [8.226] and lead to photoinduced pH jumps [8.227,8.228]. Changes of optical properties by tautomerisation in the excited state [8.229] occur, for instance, in the fluorescent states of bipyridyl diols [8.230a] and form the basis of a proton transfer laser process [8.230b]. 

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