Preparation And Characterization Of N,N-Dialkylated Perfluoroalkanesulfonamides

The carbonate solvents, such as EC, DMC, EMC, PC and so on, are often used assolvent for the Li-ion battery electrolytes. However, volatility and inflammability of thetraditional organic electrolytes are unfavorable to rechargeable lithium batteries forpopular use, because these properties may cause serious accidents, such as explosion andcombustion. The fluoro-substituted solvents, used as the additives or co-solvents, havebeen investigated to improve the flash point and applied as the flam retardant of theelectrolytes, thus enhancing the thermal and over-charging safety problems.A serial novel N,N-dialkylated perfluoroalkanesulfonamides （R_fSO₂NR₁R₂） havebeen synthesized by substituting perfluoroalkanesulfonyl fluorides （chloride） with the secondaryamines. And all of them were confirmed by means of1H NMR,19F NMR, ESI-MS and FTIR.Furthermore, correlations between the physicochemical properties and construct of theresulted products were studied extensively including the thermal analysis, density,refractive index, dielectric constant, viscosity and polarity.It shows that, R_fSO₂NR₁R₂which containing a common R₁and R₂, the viscosity,density and melting points were raised as enlarging the Rfgroups, while the results wereinverse for refractive index and dielectric constant. On the other hand, when R_fSO₂NR₁R₂sharing the same Rf, it could be concluded that the viscosity and refractive index tended toincrease as enlarging the alkyl chain, while a contrary change would be obtained for thedensity and dielectric constant. The polarity of R_fSO₂NR₁R₂was roughly located betweenacetonitrile （46.0） and methanol （55.5）, which would decrease when the alkyl orperfluoroalkyl chain prolonged. Dipolarity/polarizability is lower than methanol,hyrogen-bond-donating is close to water and methanol, hydrogen-bond-accepting ofordinary alkyl R_fSO₂NR₁R₂is lower than water, however, as alkyl contain oxygen, thehydrogen-bond-accepting is higher than methanol. Kamlet-Taft parameter （except β）decrease as the alkyl or perfluoroalkyl chain prolonged.