Oleg Grinevich

VIBRATIONAL OVERTONE ENHANCEMENT OF METHYL METHACRYLATE POLYMERIZATION INITIATED BY BENZOYL PEROXIDE DECOMPOSITION

Abstract Vibrational overtone initiated polymerization has been demonstrated using intracavity photolysis of a benzoyl peroxide/methyl methacrylate mixture. Excitation of the 6 ν CH overtone transition of the ground electronic state of benzoyl peroxide creates radicals which subsequently begin the polymerization process. Polymer yield was monitored by comparison of the 2 ν CH overtone absorptions for the methyl, methylenic and olefinic CH stretches at 5946 and 6170 cm −1 , respectively. Plots of polymer yield versus time demonstrate an autoacceleration of the polymerization rate commencing many hours after the photolysis period. The delay before autoacceleration depends on the duration of the photolysis.

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.

Laser vibrational overtone activation of ethyl acrylate/benzoyl peroxide mixture

Abstract Intra- and extracavity laser vibrational overtone polymerization of ethyl acrylate/benzoyl peroxide mixture has been demonstrated. Five photolysis wavenumbers on and near the fifth CH stretch overtone absorption of benzoyl peroxide was investigated. The polymer yield was monitored by observing the decrease in the intensity ratio of the olefinic/methyl and methylenic first CH stretch overtone absorptions of ethyl acrylate. The rate of the polymerization did not depend on the photolysis wavenumber. Molecular weights of the overtone initiated polymers were an order of magnitude larger than those obtained by thermal polymerization. The polymerization rate is compared to the intracavity laser vibrational overtone polymerization of methyl methacrylate.

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.

REVERSIBLE ISOMERIZATION OF METHYLCYCLOPENTADIENES DIRECTED BY SELECTIVE EXCITATION OF THE METHYL OUT-OF-PLANE FOURTH OVERTONE TRANSITION

Abstract Laser vibrational overtone excitation has been employed to study the reversible isomerization of 2-methylcyclopentadiene and 1-methylcyclopentadiene. Spectroscopy of the third through fifth overtones is reported for both isomers. The specific rate coefficients for the energies corresponding to the fourth overtone methyl out-of-plane CH stretch transitions have been derived and compared to those calculated from RRKM theory for the forward and reverse reactions. It is demonstrated that selective overtone excitation of one isomer in the 50:50 mixture enriches the mixture with another isomer.