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摘要
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 DMSOwater, DMSOmethanol, and acetonewater binary solutions with various molar ratios were tested in specified low temperature conditions. The freezing test results indicated that only DMSOwater solutions with the DMSOwater molar ratio (n(DMSO)) in a specific range can form apparent ultralow freezing temperature solutions. Among all DMSOwater solutions, the apparent freezing temperature lower than -130 degrees C was obtained for n(DMSO) values of 0.25, 0.30, and 0.35, respectively. Multinuclear NMR chemical shifts, H-1 diffusion experiment results, and viscosity measurements suggested that molecular rearrangement resulted in the formation of the watercore DMSOshell aggregation unit in DMSOwater solutions. The weak methylmethyl London dispersion forces among watercore DMSOshell aggregation units can explain the apparent ultralow freezing temperatures of these DMSOwater solutions.
- 出版日期2016-12-29
