MOLECULAR-DYNAMICS STUDY OF CLUSTER GROWTH AND POLYMER DEGRADATION

This work is an overview on two molecular dynamics studies of processes at temperatures characteristic of a flame -- growth of silicon clusters from binary cluster collisions and thermal degradation of polymers. In the first study, silicon clusters grow as a consequence of cluster-cluster collisions by forming transient agglomerates that coalesce in a few picoseconds. The collision energy accommodates within the cluster favoring the formation of globular larger clusters regardless of the collision energy and of the impact parameter. On the average the probability for the clusters to stick upon collision is almost 1, showing clearly that die process is irreversible. The second study concerns simple polymeric chains undergoing fragmentation when they burn. These fragments are products of thermal degradation. The consorted sequence of depolymerization reactions arises after fragmentation. As a result, a sample of degrading fragments is formed where the polymer chains have dramatically coiled. These fragments self trap themselves in coiled conformations due to the cooling effect produced by the depolymerization reaction.