Generation mechanism from irradiation

Acid-catalyzed photoresist films acid diffusion, 35 acid generation, 303233/341 advantages, 28 catalytic chain length, 3435r development of classes of cationic photoinitiators, 28 experimental procedure, 35-36 generation mechanism from irradiation of triphenylsulfonium salts, 28-29 merocyanine dye method for acid analysis, 30,31/33/... 

Photolysis of sugar oximes produces iminolactones.178,179 These are the compounds proposed to arise from irradiation of glycosyl azides however, the mechanism leading to formation of iminolactones from these two starting-materials (azides and oximes) must be quite different (see Scheme 30). Photolysis of azides is considered to generate a nitrene, whereas photolysis of oximes produces an iminolactone that... 

Onium salts have been widely used as an acid generator for photo-, EB, and x-ray resist. In addition, aromatic polymers such as novolak and polyhydroxystyrene have been often used as a base polymer for EB and x-ray resist. The reaction mechanisms in a typical resist system have been investigated by pulse radiolysis [43,52,77-88], SR exposure [79,80,83-85], and product analysis [88]. Figure 6 shows the acid-generation mechanisms induced by ionizing radiation in triphenylsulfonium triflate solution in acetonitrile. The yields of products from electron beam and KrF excimer laser irradiation of 10 mM triphenylsulfonium triflate solution in acetonitrile are shown in Fig. 7 to clarify the... 

Diazo-compounds can in turn be generated photochemically from sodium salts of toluenesulphonyl hydrazones. Irradiation of the cyclobutane tosylhydrazone (44) gave trans-tricyclo[5.1.0.0 ]-octane (45 R=Me) by the pathway shown in Scheme 4 44 the tricycle (45 R=H) can also be obtained by photoelimination of nitrogen from the diazatricyclo[ 5.2.1.0 4]decene (46). The unexpected conversion of the anthracenocycloheptatriene derivative (47) into triptycene with loss of one carbon atom was observed on irradiation in tetrahydrofuran 4 the mechanism of this unusual reaction remains obscure and merits further investigation, but neither 1-triptycenyl nor 2-triptycenyl carbene appears to be an intermediate in this transformation. 

Since radicals arc neither formed nor destroyed during reversible chain transfer, RAFT polymerization must, like conventional radical polymerization, be initiated by a source of free radicals as shown in Scheme 9.38. RAFT polymerization is usually carried out with conventional radical initiators. Most often thermal initiators (e.g. AIBN, ACP, BPO, K2SnOs) are used. S polymerization may be initiated thermally between 100-130°C. Polymerizations initiated with UV irradiation, a gamma source " or a plasma tleld have been reported. In these polymerizations, radicals generated directly from the RAFT agent may be responsible for initiation. It was initially suggested by Pan and coworkers that the mechanism for molecular weight control in and y-... 

Aromatic plants are usually constituted from cellulose, essential oil, and water. If these three compounds are heated by microwaves at a fixed radiation power and for a set time, the heating rate will be the highest for water, followed by essential oil and cellulose, respectively. One of the interactions of the microwave energy with the matrix is called the dipolar polarization mechanism. A substance can generate heat when irradiated with microwaves if it has a dipole moment, for example that of the water molecule. A dipole is sensitive to external electric fields and will attempt to align itself with the field by rotation. 

The similar rates of photooxidation of (NADP)2 in the presence or absence of oxygen pointed to the presence of an electron acceptor other than the latter, suggesting the presence of H2O2 as a possible intermediate. And, in fact, as previously noted for photooxidation of NADH and (NAD) 2, irradiation of NADPH or (NADP)2 in the presence of O2 was accompanied by appearance of H2O2, the level of which was proportional to the amount of NADP product. In line with the mechanism proposed for photooxidation of NADH and (NAD)2 , the level of generated H2O2 would be expected to equal the amount of NADP formed from irradiated NADPH, and 50% of that formed from irradiated (NADP)2. The observed level of H2O2... 

The chemical pathways leading to acid generation for both direct irradiation and photosensitization (both electron transfer and triplet mechanisms) are complex and at present not fully characterized. Radicals, cations, and radical cations aH have been proposed as reactive intermediates, with the latter two species beHeved to be sources of the photogenerated acid (Fig. 20) (53). In the case of electron-transfer photosensitization, aromatic radical cations (generated from the photosensitizer) are beHeved to be a proton source as weU (54). 

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