Free radical cross-linking copolymerization of acrylamide and <i>N,N</i>^/ methylene-bis-acrylamide by using Fe(III)/thiourea and Ce(IV)/thiourea redox initiator systems

Abstract

Acrylamide (AM) and <i>N,N</i>^/ methylene-bis-acrylamide (Bis) copolymerization in water has been investigated at a total monomer concentration (AM + Bis) of 0.4 M. Extent of conversion of monomer into polymer was measured as a function of the reaction time upto the onset of macrogelation (gelation observed visually). The critical conversion at the gel point shows a minimum at ~5.7 mol% Bis concentration for Fe(III)/thiourea (TU) redox system whereas for Ce(IV)/TU redox system it occurs at ~2.6 mol% Bis concentration. It was found that polymer formed after gel points with different Bis% were not soluble in water, acetic acid, toluene or chloroform. In the copolymerization reaction involving Fe(III)/TU redox initiator system, no induction period is observed at 50°C. In the case of Ce(IV)/TU redox initiator system, however, a significant induction period is observed at 40°C, which depends upon the Bis% in the monomer mixture. Unlike Fe(III)/TU, the reaction takes only a few minutes to complete for Ce(IV)/TU redox initiator system after the induction period is over.