Radical Addition Rate Constants to Acrylates and Oxygen: α-Hydroxy and α-Amino Radicals Produced by Photolysis of Photoinitiators

Abstract

Laser flash photolysis of R-hydroxy and R-amino ketones, which are used as photoinitiators in free radical polymerization, lead to the generation of a series of nucleophilic R-hydroxy and R-amino radicals. Absolute addition rate constants of these radicals to n-butylacrylate and oxygen were measured by laser flash photolysis employing an indirect probe technique. Crystal violet and N,N'-bis(2,5-di-tert-butylphenyl)-3,4,9,- 10-perylenedicarboximide were used as selective probe molecules for these nucleophilic initiator radicals to measure the addition rate constants to n-butylacrylate and oxygen, respectively. High acrylate addition rate constants of some initiator radicals were found in acetonitrile solution, e.g., dimethylketyl radical ( kacrylate ) 1.3 10 7 M -1 s -1 ) and 2-morpholino propan-2-yl radical (kacrylate ) 2.9 10 7 M -1 s -1 ).