where is the volumetric flowrate, is the channel width, and is the channel height. The µ-PTV shear experiments were performed using the highest concentration in this work (10 mg/mL) in order to check for rheology induced instabilities or modifications to the flow profile. The experimental and theoretical shear rates are shown in Figure for PII-2T solutions in both chlorobenzene (CB) and 90% chlorobenzene/ 10% dimethylformamide (CB/DMF), which exhibit different aggregation states. From our prior work , the solution state of PII-2T in pure CB consists of elongated, semiflexible fibril aggregates in addition to a separate population of dispersed polymer chains. As will be discussed later, the solution state in CB/DMF is similar but consists of fibril aggregates that are more rigid, have improved lamellar order and also form large agglomerates. For both 10 mg/mL solutions, the experimental shear rate agrees well with the theoretical Newtonian shear rate for the accessible flowrates. We therefore use this relation to determine the shear rates for the retardance experiments over the full flowrate range. Likewise, we used µ-PTV to determine the experimental extensional strain rates in the cross-slot microchannels for flowrates up to 35 µL/min (full range up to 140 µL/min). For a Newtonian fluid, the extensional strain rate at the cross-slot's stagnation point ̇ has been shown to follow , ̇