In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate([OMIM][PF6])have been investigated under the pressure up to 5.86 GPa at room temperature.The results indicated that[OMIM][PF6]experienced a phase transition at about4.12 GPa during compression,and it was thought as a phase transition of liquid to a superpressurized glass.Upon decompression,from the obvious change of Raman spectra of[OMIM][PF6]at about 0.48 GPa,it could be inferred that a decompression-induced disorder to order phase transition in[OMIM][PF6]occurred.The phase behavior of[OMIM][PF6]at low temperature under atmospheric pressure was also investigated in detail.The result showed that Raman spectra of[OMIM][PF6]varied slightly and no crystallization occurred upon cooling.These facts suggested that a disorder to order phase transition was induced by decompression in[OMIM][PF6],and[OMIM][PF6]served as a superpressurized glass under the pressure above4.12 GPa,which was similar to the glassy state at low temperature.
Junyu LiLei SuXiang ZhuHaining LiXuerui ChengLiangbin Li
