Nanoscopic hydrophilic/hydrophilic phase-separation well below the LCST of polyphosphoesters.

The complex phase separation process of thermoresponsive polyphosphoesters (PPEs) with an identical side-group structure but different copolymer compositions is characterized by electron paramagnetic resonance (EPR) spectroscopy. In water these PPEs show LCST-type behavior, in which water-rich and slightly polymer-enriched nanoscopic regions are highly water swollen, and nanoscopic inhomogeneities with the lowest polarity contrast measured so far develop 8 °C below the macroscopic cloud point.