title: Raman spectroscopic study of temperature and pressure effects on the ionic liquid propylammonium nitrate.
abstract: Raman spectroscopy has been used to decipher structural rearrangements in the protic ionic liquid propylammonium nitrate, [C3H7NH3][NO3], as a function of temperature (180-420 K) at atmospheric pressure and as a function of pressure (0.1 MPa-2.0 GPa) at room temperature. Spectral modifications of the Raman bands belonging to the anion and cation normal modes indicate structural changes occurring in both the polar and nonpolar nanoscale domains of [C3H7NH3][NO3]. The crystalline phase of [C3H7NH3][NO3] at low temperature has cations in the anti conformation and undertakes a transition with increasing temperature to a phase with cations mostly in the gauche conformation. The distorted network of hydrogen bonds gives a distribution of local environments around the anions that remains in the normal liquid phase at high temperature. The sample under high pressure might become microscopically heterogeneous, allowing for micro-Raman imaging of different ordered phases of [C3H7NH3][NO3] in a diamond anvil cell.
authors: Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo , CP 26077, CEP 05513-970, São Paulo, SP, Brazil.
authors: Luiz F O
authors: LF
authors: Faria
authors: Tatiana C
authors: TC
authors: Penna
authors: Mauro C C
authors: MC
authors: Ribeiro