Transparent precursors

Secondly, I would like to refer to the work of R. D. Michel 1, VJ. J. Nebe and W. II. Hardam (J. Imaging Sci., 10, 215, 1986). They obtained an active photosensitizer by irradiating transparent precursor molecules (inactive in photoreactions), which are mixed in polymer matrix. Further irradiation stimulated it for photoreactions, by which patterns were formed. These processes might be represented as two step photochemical amplification. These treatments shift "property" toward "sensibility" via "functionality". 

Figure 13.12 Images of ZnO nanoparticle synthesis. The transparent precursor solution (left) becomes translucent (middle) and turbid (right) during the synthesis of ZnO nanoparticles.

Mutually Transparent Precursors. According to equation 3, we expect the conditions for mutual transparency to be fuMlled in general when D < LS. In addition, since equation 3 assumes an infinite condensation rate, mutual transparency may also be realized under conditions where D somewhat exceeds L5 if the condensation rate is low. The ellipsometry results obtained for both the A2(fresh) and A2(aged) series of sols show low volume percent porosities and essentially no dependence of porosity on sol age. These observations are completely consistent with the idea of mutual transparency the ability of the pol3nners to freely interpenetrate as they are concentrated on the substrate surface should lead to dense pacing and should effectively hide any differences due to size and fractal dimension of the individual precursor species. For example, the differences noted in the scattering behavior of the A2(fresh) and A2(aged) sols are not manifested as differences in porosity in the ellipsometry data (Table I). 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Typical characterization of the thermal conversion process for a given molecular precursor involves the use of thermogravimetric analysis (TGA) to obtain ceramic yields, and solution NMR spectroscopy to identify soluble decomposition products. Analyses of the volatile species given off during solid phase decompositions have also been employed. The thermal conversions of complexes containing M - 0Si(0 Bu)3 and M - 02P(0 Bu)2 moieties invariably proceed via ehmination of isobutylene and the formation of M - O - Si - OH and M - O - P - OH linkages that immediately imdergo condensation processes (via ehmination of H2O), with subsequent formation of insoluble multi-component oxide materials. For example, thermolysis of Zr[OSi(O Bu)3]4 in toluene at 413 K results in ehmination of 12 equiv of isobutylene and formation of a transparent gel [67,68]. 

N3)2Ga (CH2)3NMe2 ] liquid precursor, nonpyrophoric, nonexplosive Horizontal cold-wall CVD Transparent 1 1 stoichiometric films. Growth temperature 773-1323 K, no additional N source 286... 

Prior to the addition of the silica precursor (TEOS), the acidic copolymer solution appears transparent and the SANS data shows that the copolymer forms spherical micelles of size 7.1 nm (figure 1-a). After the addition of TEOS, the solution becomes immediately turbid. Most probably, it is because TEOS is hydrophobic and forms an emulsion droplets under stirring when added to the solution [3], Then, the opacity increases with time (figure 1-b), until a thick white precipitate forms after about 23 minutes (figure 1-c). 

The precursor of poly(penzoxazole) (28), poly(o-hydroxy amide) (27) is amorphous and readily soluble in DMF, NMP, DMSO, pyridine, THF, and acetone.25 Transparent, flexible, and tough film of 27 can be obtained by casting. However, fluorine-containing poly(benzoxazole) (28) from 25 dissolves only in concentrated sulfuric acid and o-chlorophenol. 

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