In situ monitoring of energy release in real time during gelation of acrylamide (AAm)

Temperature variation and optical transmission was monitored in real time d uring the free radical crosslinking copolymerization (FCC) of acrylamide (A Am) and N,N-1-methylenebis(acrylamide) (Bis). Gelation experiments were ini tiated at various onset temperatures (T-on). During gelation the temperatur e rose then decreased to its initial value as the gelation time increased. That is explained with the energy release (Gelation activation energy) duri ng the polymerization process. Gelation activation energies, DeltaE(G) were measured and found to be increased as the onset temperature, T-on was incr eased. It was observed that transmitted photon intensities, I-sc, decreased dramatically at the reaction time, which were attributed to the increase i n scattered light intensity, I-sc during the formation of interconnected mi crogels in the system. Increase in I-sc was modeled using Rayleigh's equati on where reaction time was found to be proportional to the volume of the mi crogels. It was observed that a number of microgels increased as the onset temperature, T-on was increased. (C) 2001 Elsevier Science Ltd. All rights reserved.