The viscosities of microcrystalline cellulose dissolved in 1-ethyl-3-methylimidazolium acetate (EMIMAc) and in 1-butyl-3-methylimidazolium chloride (BMIMCl) were studied in detail as a function of polymer concentration and temperature. The goal was to compare the flow of solutions, macromolecule hydrodynamic properties in each solvent, and the activation energies of viscous flow. Intrinsic viscosities were determined using the truncated form of the general Huggins equation. In both solvents cellulose intrinsic viscosity decreases with increasing temperature, indicating the decrease of solvent thermodynamic quality. The activation energies for both types of cellulose solutions were calculated. For cellulose-EMIMAc the Arrhenius plot showed a concave shape, and thus the Vogel-Tamman-Fulcher (VTF) approach was used. We suggest an improved method of data analysis for the determination of VTF constants and demonstrate that cellulose-EMIMAc solution viscosity obeys VTF formalism. Once the dependences of Arrhenius activation energy and VTF pseudo-activation energy were obtained for the whole range of concentrations studied, they were all shown to be described by a simple power-law function of polymer concentration.

Mixtures of 1-ethyl-3-methyl-imidazolium acetate ([C2mim][OAc]) and water across the entire composition range, from pure [C2mim][OAc] to pure water, have been investigated using density, viscosity, and NMR spectroscopy, relaxometry, and diffusion measurements. These results have been compared to ideal mixing laws for the microscopic data obtained from the NMR results and macroscopic data through the viscosity and density. It was also found that the mixing of the two fluids is exothermal. The proton spectra indicate though that [C2mim][OAc] and water are interacting without the formation of new compounds. The maximal deviations of experimental data from theoretical mixing rules were all found to occur within the range 0.74 ± 0.06 mol fraction of water, corresponding to approximately three water molecules per [C2mim][OAc] molecule.

Macroscopic (steady-state viscosity, density) and microscopic (NMR chemical shifts, (1)H NMR relaxation times, and diffusion) properties of the 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc])-dimethyl sulfoxide (DMSO) mixture were studied in detail as a function of DMSO molar fraction at various temperatures. Temperature dependencies were used to calculate the activation energies. NMR results indicate that at low molar fraction of DMSO (<0.4), it weakly associates with the cation and in doing so disrupts the strong ion-ion association that exists in the pure ionic liquid. Stokes-Einstein equation, which linearly correlates the diffusion coefficient of a spherical molecule and macroscopic viscosity, was shown to work well for the [EMIM][OAc]-DMSO mixture. The influence of DMSO on the "anomalous" diffusion in [EMIM][OAc] ("quick" cation vs "slow" anion) was investigated; it was demonstrated that DMSO makes the cation diffusion slower. All parameters studied showed relatively small deviations from the ideal mixing rule behavior (from 20% to 50% difference between experimental and theoretically predicted results), confirming weak interactions between the components.

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International audienceThe influence of water on cellulose dissolved in 1-ethyl-3-methylimidazolium acetate (EMIMAc) is analysed by measuring steady state viscosity of dilute solutions. The goal is to determine: (a) the maximal water content allowing keeping cellulose dissolved (in dilute regime) and (b) the influence of water on solution flow and cellulose hydrodynamic properties. Mixing EMIMAc and water is exothermal and EMIMAc-water viscosity does not obey a logarithmic mixing rule suggesting strong interactions between the components. Newtonian flow of cellulose-EMIMAc-water solutions was recorded at water concentrations below 15 wt% and a shear thinning was observed for higher water content. It was suggested that above 15 wt% water cellulose is not completely dissolved: swollen aggregates form a sort of a "suspension" which is structuring under shear. Cellulose intrinsic viscosity showed a peak at 10 wt% water-90 wt% EMIMAc. It was hypothesised that the addition of water leads to the formation of large cellulose aggregates due to the preferential cellulose-cellulose interaction

Pulsed gradient spin-echo (PGSE) NMR, when coupled with the appropriate data processing algorithm, is a useful method for mixture analysis. Direct exponential curve resolution algorithm (DECRA) is demonstrated as a method that may be used to obtain polymer composition information as a function of molecular weight for a poly(urea-urethane). DECRA resolves both self-diffusion coefficients and corresponding spectral components from a single experiment without the need for physical separation. Molecular weight estimates from the NMR data are compared with that determined by size-exclusion chromatography (SEC). DECRA-resolved spectral components are directly compared with NMR spectra of SEC fractions. Subtle compositional changes among three different polymer solutions are clearly detected by the NMR analysis.

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Backgrounds: Physical violence in schools is a fairly common problem in Vietnam. However, current studies pay little attention to violence in private schools. Objectives: The study aims to estimate the prevalence and related sociodemographic factors of school physical violence among students at Hiep Hoa 5 private high school in Bac Giang province in Northern Vietnam. Methods: This was a school-based cross-sectional survey using a random sample technique with a multistage process from April to June 2019. Main findings: 412 students participated in the study, and the results indicated that 55/412 (13.3%) students were both perpetrators and victims of school violence. While 16.7% of students performed physical violence, 27.9% of students suffered physical violence by other students in the past six months. Experiencing physical violence was associated with sociodemographic characteristics such as gender, grade, exposure to physical violence in the media, time playing action games and witnessing violent events in the living place... Conclusions: More than 13% of students are perpetrators and victims of physical violence by their peers at a rural private high school. This prevalence is significantly correlated with individual factors. The results suggest that a greater focus on young people's educational activities should be provided to direct their development, including preventing physical violence. Keywords: Physical violence, high school students, perpetrators and victims.