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

Temperature variation and optical transmission was monitored in real time during the free radical crosslinking copolymerization (FCC) of acrylamide (AAm) and N,N′-methylenebis(acrylamide) (Bis). Gelation experiments were initiated at various onset temperatures (Ton). During gelation the temperature rose then decreased to its initial value as the gelation time increased. That is explained with the energy release (Gelation activation energy) during the polymerization process. Gelation activation energies, ΔEG were measured and found to be increased as the onset temperature, Ton was increased. It was observed that transmitted photon intensities, Itr, decreased dramatically at the reaction time, which were attributed to the increase in scattered light intensity, Isc, during the formation of interconnected microgels in the system. Increase in Isc was modeled using Rayleighʹs equation where reaction time was found to be proportional to the volume of the microgels. It was observed that a number of microgels increased as the onset temperature, Ton was increased.