Several 3‐alkoxy‐5, 7‐diiodo‐6‐fluorones (λmax ≈ 470 nm) have been synthesized and evaluated as initiators for photopolymerization triggered with the 515.5 nm line of an Ar+ laser. 2‐Acyl‐ and 2‐alkyl‐4,5,7‐triiodo‐3‐hydroxy‐6‐fluorones were also tested at 515.5 nm. 9‐Cyano‐2‐Acyl‐ and 9‐cyano‐2‐alkyl‐4,5,7‐triiodo‐3‐hydroxy‐6‐fluorones were studied and could be excited with the 632 nm line of a He–Ne laser. Dyes with long linear carbon chain alkoxy groups at C‐6 showed larger molar extinction coefficients and formed polymers with better mechanical properties than did compounds with shorter carbon chains, or did the corresponding C‐6 phenols. The optimum side chain length of the C‐6 ether alkyl group is between 4–7 carbon atoms. With longer carbon chain alkoxy groups at C‐8, e.g., octyl, the mechanical properties of the formed polymers are inferior to systems formed with the butyl isomer as photoinitiator. In the case of alkoxy groups with branched alkyl groups (e.g., 2‐ethylbutyl), the relationship between dye structure and the properties of the polymers formed is less straightforward. Though the dyes react from their triplet state, the fluorescence quantum yields of the dyes and the performance of the dyes as photoinitiators appear directly related. © 1995 John Wiley & Sons, Inc.

The crosslinking reaction of an epoxy‐based resin has been monitored by observing the time evolution of the thermal diffusivity of the mixture, using photoacoustic spectroscopy. The results are interpreted in terms of the expected thermal properties of liquids, polymers and solids, and a comparison with the reported viscosity behavior in similar systems is also made. The potential of the technique for following the curing process is discussed.

HF gas molecules in 11 = 2 are produced in a beam-gas reaction system using an intracavity, multiply resonant HF chemical laser to consecutively pump HF(11 = 0) using the PI (4) and P 2 (3) HF lasing lines. A beam of Ba or Sr reacts with the perturbed reagent gas to form the metal monohalide. The internal state distribution of the MF product is probed using pulsed laser induced fluorescence. In both reactions, products are seen with internal energies out to nearly the exothermic limit, but fractional vibrational energy releases are small and apparently decrease with increasing reagent vibration. State-ta-state cross sections for 11 = 2 reagents, relative to those for 11 = 1 and 11 = 0 are reported.

The kinetics of iodine doping of atactic polystyrene films is investigated using photoacoustic spectroscopy. The changes in the photoacoustically measured physical properties, such as nonradiative relaxation time and thermal diffusivity, are present as a function of the doping time. The results show strong evidence that an order-disorder transition is taking place as a function of the doping time. The suggested order-disorder transition is also evident in the dielectric constant measurements of the doped films.

laser-induced polymerization of multifunctional acrylates, were studied as a function of some of the photopolymerization parameters. The properties investigated were the Young's modulus of elasticity and the stress-at-break, both derived from the stress versus strain test of dogbone-shaped photopolymerized samples. The parameters studied included the dye and co-initiator concentrations, and the laser power. We also compared the mechanical properties of samples made using different types of fluorone dyes and using two different amines as co-initiator. Better polymers are formed by the dyes with low fluorescence quantum yield. The three photopolymerization parameters modify the mechanical properties in a very similar way: they initially tend to increase both the Young's modulus and the stress-at-break but have a deleterious effect on the material strength if used in excess. Nphenylglycine, NPG, was shown to form stronger polymers (higher Young's modulus) than if N,N-dimethyl-2,6-diisopropylaniline, DIDMA, was used as co-initiator. We discuss the possible molecular mechanisms for such observations.

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The vibrationally resolved state-to-state kinetics of the molecular beam reaction Ba + HF--.BaF + H has been investigated using a unique dual reaction differencing technique which is sensitive to 0.04 cm -I Doppler shifts and allows detection of the full distribution of products from low fractionally excited reagents. Contrary to earlier results, BaF at low vibrational levels is found to dominate the product distribution in reaction proceeding from HF (v = I). The difference spectrum also reveals that the total reaction rate increases by a factor of three by vibrationally exciting the reagents.

Deoxygenation of vanadyl Schiff's base complexes by SOCl2 gave the corresponding dichloro-derivatives of vanadium(IV)