Thermally stable, photoactive polymerizable diazenes. Applications in polymer technology

Abstract

New and useful nonpolymerizable and polymerizable diazene free radical initiators have been designed, based on molecular orbital and empirical linear free energy calculations. The design of the polymerizable diazenes has been based on four requirements: independent reactivities of azo and vinyl moieties, high thermal stability of the trans‐diazene isomers, efficient convertability of the trans isomer to the cis isomer, and high thermal reactivity (to produce free radicals) of the cis‐diazene isomers. The cis‐diazene isomers are obtained from the trans isomers by irradiation with visible light. A new free radical initiator has been shown to be useful in preparing graft copolymers and in crosslinking polymer chains by visible light activation. Poly(styrene‐co‐2‐(meta‐styrylazo)‐2‐methoxypropane) (2) was prepared by the copolymerization of styrene monomer and 2‐(meta‐styrylazo)‐2‐methoxypropane (1), either thermally or via a free radical initiator. Copolymer 2 then was reacted with methyl methacrylate monomer in the presence of visible light, to produce poly (styrene‐g‐methyl methacrylate) (6). Poly(styrene‐co‐2‐(meta‐styrylazo)‐2‐methylpropane) (17), prepared by the copolymerization of styrene monomer and 2‐(meta‐styrylazo)‐2‐methylpropane (15), was successfully crosslinked at elevated temperatures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3203–3213, 1999

Hydrazone initiators for vinyl polymerizations

“…The DSC exotherm maximum temperatures do not correlate well with the calculated DSC exotherm maximum temperatures for the isomeric diazenes (see column 4 of Table III and refs. 18 and 19). This suggests that the hydrazones do not decompose by rearrangement to the isomeric diazenes (Scheme ) unless the DSC peaks are masking an endothermic rearrangement of hydrazones to diazenes, superimposed on the resulting diazenes' decomposition.…”