Effect of Pressure on Local Order in Liquid Dimethyl Sulfoxide

Abstract

Raman spectroscopy was used to study intermolecular interactions, dynamics and the structure of neat liquid dimethyl sulfoxide (DMSO). Isotropic and anisotropic spectra were recorded in the SO stretching vibration region at temperatures between 30 and 70 °C and under pressures up to 2200 bar. To separate the temperature and density effects, the density of DMSO was also determined over the same region of temperature and pressure. By analyzing the isotropic and anisotropic spectra, the Raman noncoincidence effect was measured. This coupling parameter which reflects intermolecular interactions exhibits a nonlinear increase with density but is relatively insensitive to temperature. With increasing density, drastic changes in the first moment and the shape of the isotropic SO band were detected. The SO stretching vibration band shifts to lower wavenumbers, whereas its full width at half-height increases significantly with increasing pressure. The isotropic SO stretching band is resolved into three components which show markedly different intensity changes upon pressurization. The results are discussed in terms of pressure-induced formation of stronger molecular aggregates leading to an enhanced local order in liquid DMSO at elevated pressures. In a general sense, the results of this study provide yet another example of the dominance of volume effects over kinetic effects on the dynamic structure of liquids.

The non-coincidence effect in glass

“…The importance of the orientational pair correlation function in considering the existence of intermediate range order comes from the fact that attractive forces are more effective in the coordination picture indicating a larger coordination range due to possible domain formation in the glass. This is in agreement with the Boson peak observations for clustering of molecular groups that leads to the universal property of the intermediate range order for glasses [7,8]. The effect may be calculated for simple systems as given by Zerda, et al [9].…”

“…were under a constant pressure and varying temperature or sometimes at constant density [2][3][4][7][8][9][10]. Typical spectra showing Raman scattering results from NBS-710 glass are given in Fig.…”

Intermolecular Interactions in Aqueous Dimethyl Sulphoxide and Acetic Acid Probed by High‐Pressure FTIR

“…Wa ter and dimethyl sulfoxide (DMSO) in ter act with each other and with other sol utes through hy dro gen bonding, [3][4][5][6][7][8][9][10][11] but de tails of such in ter ac tions are not well char ac terized. Vi bra tional spec tra of aque ous DMSO, spe cif i cally of the S=O stretch ing vi bra tion, 3,7,[12][13][14] has been stud ied at wide con cen tra tion in ter vals, while DMSO has been de scribed as en hanc ing wa ter struc ture. 1,5 The en hanced hy dro gen bonding be tween wa ter mol e cules in aque ous DMSO com pared to bulk wa ter was at trib uted by Soper et al 5 to the pres ence of a strong hy dro gen-bonding site on the DMSO ox y gen and not to any spe cial or der ing around the methyl head groups.…”

“…[19][20][21] In or der to as sess the in di vid ual ef fects of the aliphatic res i dues on the wa ter struc tures, the pres ent ar ti cle de scribes the ap pli ca tion of the high-pressure method to aque ous DMSO and aque ous ace tic acid, as a pre lude to the in ves ti ga tion of their hy drated mo lec u lar con for ma tions. Liq uid DMSO was char ac ter ized by pres sure in di cat ing sig nif i cant struc tural lo cal or der, 12 while short-range or der in liq uid DMSO is strongly in creased at higher den si ties due to a re ar range ment of neigh bor ing mol e cules to form strongly as so ci ated clus ters. 12,13 In a re cent study of the high-pressure phase of ace tic acid, 15 de spite a low freez ing pres sure of only 0.2 GPa, the high-pressure crys tal struc ture of ace tic acid seems to be quite dif fer ent from that formed at low tem per ature, show ing the va ri ety of hy dro gen bonds which ace tic acid can form.…”

“…Liq uid DMSO was char ac ter ized by pres sure in di cat ing sig nif i cant struc tural lo cal or der, 12 while short-range or der in liq uid DMSO is strongly in creased at higher den si ties due to a re ar range ment of neigh bor ing mol e cules to form strongly as so ci ated clus ters. 12,13 In a re cent study of the high-pressure phase of ace tic acid, 15 de spite a low freez ing pres sure of only 0.2 GPa, the high-pressure crys tal struc ture of ace tic acid seems to be quite dif fer ent from that formed at low tem per ature, show ing the va ri ety of hy dro gen bonds which ace tic acid can form. As such, pres sure rep re sents a very in for mative ap proach to the study of bi nary mix ture struc tures.…”