title: Nuclear Magnetic Resonance Spectroscopy Investigation on Ultralow Melting Temperature Behavior of Dimethyl Sulfoxide-Water Solutions.
abstract: On the basis of the molecular understanding that DMSO has a trigonal pyramidal geometry with one highly polarized sulfinyl group and two hydrophobic methyl groups, we used NMR technology to rationalize why DMSO can act as antifreeze for aqueous solutions. A series of DMSO-water, DMSO-methanol, and acetone-water binary solutions with various molar ratios were tested in specified low temperature conditions. The freezing test results indicated that only DMSO-water solutions with the DMSO-water molar ratio (nDMSO) in a specific range can form apparent ultralow freezing temperature solutions. Among all DMSO-water solutions, the apparent freezing temperature lower than -130 °C was obtained for nDMSOvalues of 0.25, 0.30, and 0.35, respectively. Multinuclear NMR chemical shifts,1H diffusion experiment results, and viscosity measurements suggested that molecular rearrangement resulted in the formation of the water-core DMSO-shell aggregation unit in DMSO-water solutions. The weak methyl-methyl London dispersion forces among water-core DMSO-shell aggregation units can explain the apparent ultralow freezing temperatures of these DMSO-water solutions.
authors.affiliation: Department of Chemistry, Chung Yuan Christian University , Chung-Li District, Tauyuan City, Taiwan 32023, R.O.C.
authors.forename: Yuan-Chun
authors.initials: YC
authors.lastname: Wen
authors.affiliation: Department of Chemistry, Chung Yuan Christian University , Chung-Li District, Tauyuan City, Taiwan 32023, R.O.C.
authors.forename: Hsiao-Ching
authors.initials: HC
authors.lastname: Kuo
authors.affiliation: Department of Chemistry, Chung Yuan Christian University , Chung-Li District, Tauyuan City, Taiwan 32023, R.O.C.
authors.forename: Jhong-Lin
authors.initials: JL
authors.lastname: Guo
authors.affiliation: Department of Chemistry, Chung Yuan Christian University , Chung-Li District, Tauyuan City, Taiwan 32023, R.O.C.|Research Center for Analysis and Identification, Chung Yuan Christian University , Chung-Li District, Tauyuan City, Taiwan 32023, R.O.C.
authors.forename: Hsi-Wei
authors.initials: HW
authors.lastname: Jia