A novel method to prepare polymer-ionic liquid gel under high pressure and its electrochemical properties

Sol–gel transition behavior of ionic liquid gel based on poly (ethylene glycol) (PEG) and ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO 4 ] has been investigated under the pressure up to 250 MPa. The Temperature versus Pressure phase diagram of PEG/[EMIM][EtSO 4 ] gel is constructed, and it indicates that the melting point is an increasing function of pressure. Based on the phase diagram, the PEG/[EMIM][EtSO 4 ] gels are prepared by cooling under the pressure of 300 MPa and atmospheric pressure, respectively. From the differential scanning calorimetry result of the recovered samples, it is found that PEG/[EMIM][EtSO 4 ] gel prepared under high pressure has a higher crystallinity and smaller crystal size polymer network, comparing with under atmospheric pressure. The cyclic voltammograms and impedance spectra tests indicate that the PEG/[EMIM][EtSO 4 ] gel prepared under high pressure exhibit higher ionic conductivity comparing with atmospheric pressure. It could be speculated these excellent properties might be attributed to the loose gel structure and high ionic density induced by high pressure.