POLYMERIZATION INITIATION BY N-P-TOLYLGLYCINE - FREE-RADICAL REACTIONS STUDIED BY PULSE AND STEADY-STATE RADIOLYSIS

The extensive use of N-p-tolylglycine (NTG) and analogous compounds in adhesive bonding technologies requires a better understanding of thei r role in initiating free-radical polymerization. The fast oxidation a nd reduction reactions of NTG proceed via the formation of various fre e radicals and radical cation and anion intermediates. These intermedi ates were identified and their reactivity with oxygen, to produce the corresponding peroxyl radicals, was measured. Hydroxyl radicals (OH) w ere used to initiate oxidation reactions of NTG, while the reduction r eactions were initiated with hydrated electrons (e(aq)(-)). OH radical s react with NTG predominately by addition to the aromatic ring follow ed by OH-elimination to produce NTG(+). radical cations. In the presen ce of oxygen, the OH-NTG(.) adduct also reacts with oxygen to produce peroxyl radicals. The reaction of NTG with e(aq)(-) forms the radical anion, which subsequently protonates on the aromatic ring to produce c yclohexadienyl radicals, or undergoes an amine elimination to yield an acetic acid free radical and 4-methylaniline. Hydroperoxyl radicals ( HO2.) abstract hydrogen from the alpha position of NTG to form the cor responding alkyl free radical. (C) 1994 John Wiley and Sons, Inc.