Fracture of flexible polymer chains in dilute solution under transient extensional flow

Applying the technique of Brownian dynamics simulation, we have studied the fracture process of flexible polymer chains when they encounter an extensional flow field of transient character. For this purpose, a mathematical model was made of an experimental device used earlier by other authors to study fracture of polystyrene in dilute solution. The polymer/solvent system studied was a very dilute solution in theta conditions. The polymer molecule was modeled as a FENE bead-spring chain, including a modification to allow for chain fracture. The simulation results showed that the fracture yield depended strongly on flow rate and on molecular weight. We have characterized the molecular-weight dependence of the critical flow rate which is necessary for fracture to occur. The distribution of the resulting fragments is interpreted in terms of the conformation of the chains prior to fracture.