Lithographic design of photosensitive polyarylates based on reaction development patterning

The factors affecting pattern‐forming properties in reaction development patterning were examined with polyarylates with various bisphenol moieties. The developability of the photosensitive polyarylates was dependent on the properties of the subtituent (R) in the bisphenol moieties. The development time decreased in the following order: R?C(CH₃)₂ > fluorenyl unit ? phenolphthalein unit > C(CF₃)₂ > SO₂. This order agreed with that of the reactivity between the polyarylates and ethanolamine, and these orders can be explained by pK_a of the bisphenol used to prepare the polyarylates. The development with NH₂? R′? OH resulted in successful positive‐tone pattern formation. However, pattern formation with the developers containing NH₂? R′? OCH₃ was unsuccessful. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2694–2706, 2006     

Pd-catalyzed selective addition of heteroaromatic C-H bonds to C-C triple bonds under mild conditions

Simple heteroarenes such as pyrroles and indoles undergo addition reactions to C-C triple bonds in the presence of a catalytic amount of Pd(OAc)(2) under very mild conditions, affording cis-heteroarylalkenes in most cases. The cleavage of aromatic C-H bonds is the possible rate-determining step in CH(2)Cl(2), and the addition of heteroaromatic C-H bonds to C-C triple bonds is in a trans-fashion.     

Computer simulation for the cooligomerization system

In order to clarify the kinetic features of the styrene (A)–methyl methacrylate (B)–CCl₄(S) cooligomerization system, a computer simulation was carried out. The experimental data on the degree of polymerization and the deviation of the cooligomer composition from the statistical steady-state composition were comparatively well explained by calculations based on the kinetic equations derived from the assumed reaction scheme and the values of the velocity coefficients, although the values of the four velocity coefficients in the initiation step and the velocity coefficient of the termination by the coupling of two solvent radicals were estimated. The results of the calculation of the rate of each component reaction show that the following two reactions are the most important in the initiation and in the transfer and termination steps when the [S]/([A] + [B]) ratio is large: where, A, A*, and P are styrene, polystyryl radical, and the cooligomer, respectively. Moreover, it was concluded that the deviation of the cooligomer composition from the statistical steady-state composition was caused by these two reactions.     

2-Oxo-1,3-dioxoles as specific substrates for measurement of arylesterase activity

Various 4-arylthiomethyl-2-oxo-1,3-dioxole derivatives IIIa-o were synthesized. Their hydrolysis rates by arylesterase (EC 3.1.1.2) and cholinesterase (EC 3.1.1.8) in human serum were evaluated. Some of them were not hydrolyzed by cholinesterase, but were hydrolyzed easily by arylesterase. Among the substrates, sodium 4-((5-methyl-2-oxo-1,3-dioxol-4-yl)methylthio)benzenesulfonate (IIIg) was selected for its substrate reactivity toward arylesterase and its good water solubility. In addition, neither aliesterase (EC 3.1.1.1), acetylesterase (EC 3.1.1.6) nor cholesterol esterase (EC 3.1.1.13) hydrolyzed the compound. IIIg is thus concluded to be a specific substrate for arylesterase. Our assay system for serum arylesterase using IIIg can be readily applied to an automatic analyzer in the diagnosis of liver cirrhosis.     

Photo-induced dimerization of 1-naphthoxide anion: Electron transfer mechanism

Irradiation of sodium 1-naphthoxide in MeOH gave selectively 1,4-dihydro-4',8-dihydroxy-1,1'-binaphthyl 2. A similar reaction in PhH afforded the regioisomer 5, along with 6, Structural proof is presented for these hitherto unknown dimers. The reaction is completely quenched in the presence of naphthalene, a good electron scavenger. This new type of photodimerization was proved to be initiated by intermolecular electron-transfer from the excited 1-naphthoxide anion to the ground state one to give the oxidation-reduction dimers.     

Structure in the emission from pyrene evaporated films

Emission spectra and decay times of fluorescence of pyrene thin films prepared by evaporation onto substrates at liquid nitrogen temperature were measured. Structure in the emission from films warmed slowly up to higher temperature is found to the higher energy side of the excimer emission band. The decay time is about 410 ns at temperatures between 110 K and 210 K. But the emission from the film warmed up to a temperature above 210 K shows only the excimer emission. These results are discussed in relation to an amorphous structure in the pyrene evaporated thin film.     

An anomalous emission excited near the absorption edge of pyrene crystals

Emission spectra and decay times of the fluorescence excited at the absorption edge region in pyrene crystals were measured. At liquid nitrogen temperature, the fluorescence under the excitation at 390 nm is considered as the excimer emission and its band peak shifts a little to the short wavelength in comparison with that of the excimer emission under the excitation at 360 nm. The emission decay times under the excitation at the 390 nm and 360 nm are about 155 ns and 180 ns, respectively, at liquid nitrogen temperature. The former decay time changes its value abruptly near 127 K. This abrupt change of the decay time may be due to the phase transition in pyrene crystals.     

Migration of excimers in pyrene crystals

Emission decay times of the new excimer were measured for undoped and perylene doped pyrene crystals. From the decay times obtained, the temperature dependence of the diffusion coefficient of the excimers was deduced by assuming a model in which two electronic states of the new excimer are involved in the energy transfer process. Within this model, it was found that in the upper excimer state the excimers migrated by a hopping process, while in the lower excimer state they migrated as free excimer excitons while undergoing phonon scattering.