Design of viscoelastic fluids with systematically controlled rheological properties

An ability to control viscoelastic properties of soft materials can provide benefits in laboratory and in industrial flow processes. However, predicting rheological parameters before the samples are made is challenging as any change in one design parameter (e.g. varying polymer molecular weight) can affect more than one rheological parameter. In idealized scenarios, various scaling theories predict the rheology of dilute polymer solutions in terms of polymer concentration, molecular weight, and solvent viscosity. Nonetheless, non-negligible deviations between the theoretical predictions and experimental observations have been reported.

In this work, we present a systematic method for controlling shear modulus, (the longest) relaxation time, and the first normal stress difference coefficient of a dilute polymer solution for varying polymer concentration, molecular weight, and solvent viscosity. We use polyisobutylene, a hydrocarbon-based polymer that appears in numerous experimental studies, for its stability, non-toxicity, and ease of access. We show that the three rheological parameters and the three design parameters can be put in a linear equation with experimentally verified matrix coefficients that result in a unique solution, which guarantees a linear mapping between the two sets of variables. This method offers the possibility to design in advance the range of viscoelastic flow behavior desired.