Fig. 1.

Polymer chain scission scaling based on the assumption that the flow is laminar. Scission theories in laminar flows suggest that data plotted on these coordinates should yield universal behavior. Effective laminar stress represents the viscous stress on the chain, assuming that the flow is laminar. PS/CS and PS/CE represent the classical scaling data for polystyrene (PS) in cross-slot (CS) and contraction–expansion (CE) flows that were deemed to be in good agreement with the laminar flow scission theories. The lines denote the best fits for these data. Also shown are the anomalous experimental data that probed the effect of solvent viscosity (PS/viscosity, green circles) and geometry (PS/geometry, black circles) on chain scission. The anomalous geometric effect is also evident in scission data of DNA molecules in CE geometries of varied inlet dimensions (labeled d = 63–380 μm). Here ε̇_c ≡ U/d. The details of the studies are given in Table 1.