Two-dimensional aggregation of rod-like particles:: A model investigation

In this work, a 2D computer model was created for the aggregation of rodlike particles, on the basis of a molecular-dynamic approach. With the help of the model, it is possible to visualize the motion of the aggregating particles, clearly and faithfully, offering the possibility of structural, kinetic, and dynamic analysis of the aggregation. The aggregation, in the model, is governed by long-range and short-range attractive particle-particle forces, two-dimensional streams, breaking forces, and the degree of particle-anisometry. The long-range forces initiate the motions of the particles and clusters and also cause restructuring in the growing aggregates, which process can be hindered by sufficiently strong short-range, attractive forces. The off-lattice computer simulation of the aggregation revealed that (i) the greater extent of restructuring resulted in the formation of denser and more compact clusters with higher fractal dimensions. Interestingly, the attractive short-range forces, through the restructuring, could also influence the driving force of aggregation. It was found that the more intensive the restructuring, the weaker the driving force is in the second stage of aggregation. (ii) An increase in the effective range of long-range forces (without restructuring) resulted in higher fractal dimensions and kinetic constants. The increase of D-f with the effective range of forces was interpreted in terms of a percolation-like aggregation. (iii) Moreover, increasing anisometry of the particles (without restructuring) also resulted in an increase of fractal dimensions, confirming that the investigated aggregations take place in a transition range between the diffusion-limited-like aggregation and percolation (gelation). Our model was implemented successfully in a real phenomenon, the aggregation of cylindrical-shaped carbon particles at water (aqueous surfactant solution)/air interfaces. The effectiveness of the computer model was proved by comparing the structural, kinetics, and mechanism-related parameters obtained for the simulations with those of the real experiments.