Science of Aerosol-to-Gel

Gelation is a result of sol-to-gel transition–a universal phenomenon–in irreversible non-coalescent aggregation systems . When the average size of aggregates reaches the length-scale of average nearest neighbor separation, an aerosol system is said to gel–this condition is defined as the ideal gel point (IGP). Beyond IGP, the kinetics of particle growth remains elusive because of the break down of the governing Smoluchowski equation. Dr. Chakrabarty and his group systematically studied the dynamics of gelling systems in this regime using the off-lattice diffusion limited cluster-cluster aggregation model. They showed that beyond IGP, the sol phase particles ceased to grow without forming into gels and their corresponding normalized mass distribution remained invariant with respect to the geometric mean and standard deviation. This invariant mass distribution also implied that the conversion of particles from the sol phase to gel phase during a unit time is independent of particle size. They elegantly parameterized the relationship between conversion rate and time using a power-law analytical expression which accurately predicts both the decrease in the total number of sol phase particles and the increase in average mass of the gel phase particles. It is to be noted that this complete, quantitative description of the time-evolution of monomers to aggregate to gel phase has not been accomplished before in our field.