The aqueous polymer solutions of the water-soluble samples were further investigated with the turbidimetry. The polymers (except S42) were soluble in water at lower temperatures, and phase separate upon heating. It should be noted that a liquid-liquid phase separation or coacervate formation was observed for S0 when stored at 4 °C for overnight. For PEtOx with high molecular weight, coacervation has been reported. A similar behavior was observed for thionated polymers, but their phase separation appears more like classical aggregation/sedimentation, possibly due to increased hydrophobicity because of thionation.