RESUMO
Understanding the polymer solubility in ionic liquids (ILs) is important for polymer processing or polymeric material preparation. Previously, two-parameter H-bonding analysis has been proposed to clarify that polymer solubility in ILs is dominated by H-bonding interactions (Y. F. Yuan et al., Phys. Chem. Chem. Phys., 2021, 23, 21893-21900). In the present work, 1H-NMR spectra are adopted to characterize the H-bonding interactions between polymers and ILs, which provide a microscopic relation between polymer solubility and two-parameter H-bonding analysis.
RESUMO
The 1 H nuclear magnetic resonance (1 H-NMR) spectrum is a useful tool for characterizing the hydrogen bonding (H-bonding) interactions in ionic liquids (ILs). As the main hydrogen bond (H-bond) donor of imidazolium-based ILs, the chemical shift (δH2 ) of the proton in the 2-position of the imidazolium ring (H2) exhibits significant and complex solvents, concentrations and anions dependence. In the present work, based on the dielectric constants (ϵ) and Kamlet-Taft (KT) parameters of solvents, we identified that the δH2 are dominated by the solvents polarity and the competitive H-bonding interactions between cations and anions or solvents. Besides, the solvents effects on δH2 are understood by the structure of ILs in solvents: 1) In diluted solutions of inoizable solvents, ILs exist as free ions and the cations will form H-bond with solvents, resulting in δH2 being independent with anions but positively correlated with ßS . 2) In diluted solutions of non-ionzable solvents, ILs exist as contact ion-pairs (CIPs) and H2 will form H-bond with anions. Since non-ionizable solvents hardly influence the H-bonding interactions between H2 and anions, the δH2 are not related to ßS but positively correlated with ßIL .
RESUMO
Polymer solubility in ionic liquids (ILs) cannot be predicted by the solubility parameter approach based on the "like dissolves like" principle. According to the Kamlet-Abraham-Taft (KAT) multi-parameter polarity scale, ILs can be categorized on the basis of hydrogen-bond acidity or basicity ones. The experimental observations, that acidic ILs easily dissolve basic polymers and basic ILs dissolve acidic polymers, reflect the complementary nature of hydrogen-bonding interactions. A quantitative hydrogen-bonding analysis is proposed for predicting the solubility by taking the product of ΔαΔß as an indicator of the competition between cross-association and self-association hydrogen bonding (H-bonding), where Δα is the difference of acidity parameters between the polymer and IL, and Δß is the difference of basicity. This solubility criterion has been validated by the solubility data of 19 polymers (11 acidic and 8 basic) in 11 ILs (7 acidic and 4 basic). These principles based on KAT parameters can be applied to other systems dominated by hydrogen bonding.
RESUMO
SCOPE: Mice are fed a soybean diet before or after fermentation in the present work to allow direct comparison of the antiobesity effect of fermentation. METHODS: C57BL6J mice were fed high-fat diets containing boiled soybeans (prefermentation) or Natto (postfermentation) for 4 weeks. Prefermented cooked soybeans or Natto was added at levels of 2.5 and 5%, which are the amounts that can be ingested in a normal diet once and twice a day. In addition, mice gut microbiota from fecal samples were analyzed to explore the mechanisms of effects caused by fermentation. RESULTS: Natto intake significantly reduced visceral fat in a dose-dependent manner, inhibited hypertrophy of adipocytes, improved carbohydrate metabolism, and reduced oxidative stress. These effects were seen in mice fed soybeans before fermentation, but were stronger in mice fed Natto. Therefore, soybean intake has beneficial effects and fermentation of soybeans enhances these effects. Natto was found to suppress fatty acid synthesis and promote fatty acid catabolism in the liver. These effects were also stronger with Natto compared with soybeans before fermentation. In addition, Natto had more potent beneficial effects on gut microbiota compared to soybeans. CONCLUSIONS: These results suggest that Natto intake supports maintenance of health.
