Alexander Mejiritski

Quantum yield determination for photolysis of photoimageable polymer in thin films

We have established a procedure for quantum yield determination for the photolysis of photoimageable polymers in thin films. Previously, we have discovered that electron transfer in polymers bearing benzophenone ammonium borate salt pendants is followed by bond cleavage leading to the formation of the polymeric amine. A measured solid state quantum efficiency of 0.15 makes this class of compounds interesting as precursors for polymeric amine generation.

Tetrakis(pentafluorophenyl)gallates (I)

Abstract The synthesis of certain iodonium tetrakis(perfluorophenyl)gallate salts is reported. The rates of acid formation when these compounds are irradiated with a broad spectrum mercury arc in EtOH are compared.

Solid state studies on the effect of fillers on the mechanical behaviour of photocured composites

Abstract Various fillers (cellulose triacetate, glass fibres, Al(OH) 3 powder, and Kevlar pulp) were added in different loadings to a dimethacrylic monomer (DEGDMA) and the systems were photopolymerized. The composites thus photoformed were then mechanically tested (Youngs modulus of elasticity and stress-at-break) and the results compared with theory. Scanning electron microscopy (SEM) and lateral force atomic force microscopy (AFM) were used to obtain information about the intimate structure and the surfaces of these composites.

Perturbation of the luminescent silicon emission by adsorbed dyes

Fluorescent dyes have been used to impregnate partially oxidized porous silicon produced by stain etching. The properties of the structures produced have been studied by photoluminescence (PL) and IR spectroscopies before and after extensive solvent extraction of the dye. PL spectra from extracted wafers are different from nonextracted ones and show, most of the time, three peaks. One peak at 700 nm is assigned to luminescent silicon before the dye impregnation; a second emission peak resembles the dye luminescence from solution, and a third peak at 630–670 nm is attributed to silicon emission perturbed by the adsorbed dye. A model is proposed to account for this new peak, by including band splitting due to the adsorption of the dye molecules.

Tetraorganylborate salts as convenient precursors for photogeneration of tertiary amines

Photoreactions of p-(benzoyl)benzyl trisubstituted ammonium tetraorganylborate salts for the generation of tertiary amines in solution and rigid matrices are described. Structural modification of the complexes allows study of the influence of steric and electronic effects on the photogeneration of amines. Flash photolysis, cyclic voltammetry and product analysis indicate that single electron transfer from borate to excited benzophenone is followed by homolytic C–N bond cleavage. Photoliberation of the tertiary amine is controlled by the rate of the electron transfer reaction.

Transient Spectroscopy of 5,7-diiodo-3-butoxy-6-fluorone (DIBF)†

DIBF (5,7‐diiodo‐3‐butoxy‐6‐fluorone) is a visible light photosensitizer for diaryliodonium salts, the latter being used in cationic photopolymerizations. Although photopolymerization of cycloaliphatic epoxide resins can be initiated by direct excitation of UV‐absorbing diaryliodonium salts, such as (p‐octyloxy)phenyliodonium hexafluoroantimonate (OPPI), the short wavelengths required cause some practical problems. Sensitizers, of which DIBF is among the best, obviate the deep UV problem by allowing visible‐wavelength activation of the photoinitiator. Addition of 9,10‐diethoxyanthracene (AN 910 E) dramatically accelerates photopolymerization under visible irradiation of the DIBF/OPPI system. We report herein the transient spectroscopy of the photosensitizer DIBF and discuss likely mechanisms for sensitization of OPPI.