Determination of interfacial tension between two immiscible polymers with and without surfactants at the interface.

A second-order drop deformation method for inferring interfacial tension between two immiscible polymers is proposed and shown to improve the accuracy of tension estimate appreciably. A small step-strain method, which uses a strong flow (capillary number >1) and short flow time approximately O(0.1s), is successfully developed to avoid complications caused by the surfactants for surfactant-laden drops. This method is demonstrated to give good tension estimates for a range of viscosity ratios and surface coverage.