PREPARATION AND THERMAL-DECOMPOSITION OF CYCLIC AZOAMIDINIUM SALTS AS WATER-SOLUBLE RADICAL INITIATORS FOR POLYMERIZATION OVER A WIDE TEMPERATURE-RANGE

A series of cyclic azoamidinium chlorides as water-soluble initiators were prepared by reactions of the iminoether derived from 2,2'-azobisisobutyronitrile with substituted alkylene diamines. The first-order rate constants for the decomposition of the azoamidinium salts varied from 0.59 x 10(-5) to 14.1 x 10(-5) s-1 with the ring size and the alkyl substitution of the ring. Decomposition of 2,2'-azobis[2-(imidazoline-2-yl)propane] dihydrochloride was found to be accelerated by alkyl substitution on the imidazolinium ring. However, the azoamidinium compounds having larger rings, 2,2'-azobis[2-(3,4,5-trihydropyrimidine-2-yl)propane] dihydrochloride and 2,2'-azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepine-2-yl)propane] dihydrochloride, decomposed at a slower rate than the unsubstituted azobis[2-(imidazoline-2-yl)propane] dihydrochloride. These new initiators were found to be capable of initiating radical polymerizations of acrylamide and vinyl acetate.