From a purely thermodynamic perspective, particle shape is a function of the interfacial tensions between the two polymers, as well as that between each of the polymers and the aqueous phase containing surfactant. It was found that a wide range of morphologies is attainable by simply tuning the type and concentration of surfactant. For example, when PVA was used as surfactant, biphasic Janus particles with approximately two equal halves were formed. However, when SDS, SDBS, or CTAB were used, particle shape varied from crescent moon to nearly two separated droplets depending on surfactant concentration. A thermodynamic model based on the minimization of free energy was developed in order to predict Janus particle morphology. The model also allows for extraction of polymer properties such as surface tension from Janus particle geometry as obtained by standard microscopy measurements