How do polymers stretch in stagnation point extensional flow-fields?

In this paper we present an analysis of salient existing evidence on the nature of the coil-stretch transition for dilute polymer solutions in extensional flows around stagnation points. Some experiments support the idea of a transition which is critical in strain-rate to a highly extended final state, other studies report a non-critical extension and only a low degree of final strain. This situation is mirrored by theoretical and computational approaches, where the existence of a critical transition has long been a controversy. We also present new experimental evidence which leads us to maintain our previous arguments for criticality of the transition and close to full stretching.