RATE CONSTANTS OF THE REACTION OF SILYL MACRORADICALS GENERATED BY CHAIN CLEAVAGE OF POLY(DIHEXYL SILYLENE) WITH OLEFINIC MONOMERS

Abstract

The flash photolysis of poly(dihexyl silylene), PDHeSi, in tetrahydrofuran solution at λ_inc = 347 nm (flash length: 20 ns) and ambient temperature yields silyl macroradicals that strongly absorb light at 370 nm. Recording the decay of the optical density at λ_obs = 370 nm rate constants of reactions of the silyl macroradicals were measured. The silyl macroradicals undergo a self reaction with a rate constant 2k_R+R = 1.9×10⁹dm³mol⁽¹s⁽¹⁾. Moreover, they are highly reactive towards olefinic monomers. The following rate constants k_R+M (in units of dm³mol⁽¹s⁽¹⁾ were determined: 1.6×10⁸, styrene; 1.0 × 10⁸, acrylonitrile; 7.6×10⁷, methyl methacrylate; 6.5×10⁷, vinyl acetate; 1.6×10⁷, butyl acrylate; 7.3×10⁶, methacrylonitrile; < 10⁵, n-butyl vinyl ether.

Keywords:

• Poly(Dihexyl Silylene)
• Main-Chain Cleavage
• Silyl Macroradicals
• Olefinic Monomers

ACKNOWLEDGEMENTS

This work was performed in the frame of the project Acciones Integradas that is financially supported by the Governments of both Spain and Germany. Some of the authors (A. A., C. P. and F. C.) would like to acknowledge the support provided by Plan Nacional de la CICYT, Spain (MAT 98-0797).