Signals were recorded by an interferometric refractometer (Agilent 1260 series). HEA was also polymerized in water as a control sample and compared to polymerization in the bulk phases. The number averaged molar mass (Mn) of poly-HEA formed by free radical polymerization in GMO60HEA5 cubic phase, and pure water was measured at 60°C in DMF at a flow rate of 1ml/min. The HEA/LAP ratio was kept at 10/1 and 5/1 for both samples (see Figure and Table in SI). For HEA polymerization in water, the sample was first sparged with Argon during 3 cycles of 5 min to remove dissolved oxygen and placed under UV light (365 nm) with constant stirring for 2h. The samples were dissolved in DMF to 2mg ml-1 and filtrated through a 0.45µm pore size polytetrafluoroethylene syringe membrane filter before injection.