Representative molecular structures of four N-type polymer semiconductors materials (a: N2000; b: PPDI-DTT, c: TBDI-DT and d: PDTzTIT) based on NDI, PDI, BTI and BTzI, respectively.
Rheological properties of water films nanoconfined in two parallel Au plates are
investigated with the aid of molecular dynamics simulations. The density distribution, velocity
profile, and diffusion coefficients of the water film in a Couette flow are studied. Shear viscosity
and its dependence on the shear rate of the water film are also examined in the present research. It is
found that the density of the water molecules near the plates is much higher than that in the other
regions. This indicates that many water molecules are adsorbed by the plates and adsorbed layers
are formed in the vicinity of the plates. The diffusion of the whole film increases dramatically as the
shear rate becomes greater than 1010 s-1. The shear viscosity decreases as the shear rate increases,
especially for the water film with a small thickness, which indicates the shear-thinning behavior for
viscosity of the nanoconfined film. Moreover, an increase in shear viscosity with a decrease in the
film thickness can also be found in the present study.
Surfactants are very often used in tertiary oil production. However, the conventional surfactants cannot be used in high salinity reservoirs of tertiary oil production because the high salinity leads to the deactivation of the surfactants. Gemini sulpho-betaine surfactants have been developed to meet the requirements of tertiary oil production in such reservoirs. In this study, the Gemini sulphobetaine surfactant (bis{[(N-methyl-N-(3-alkoxy-2-hydroxy)propyl-N-(3-sulfonate)propyl]methylene}) was prepared by etherification, ring opening reaction and sulfonation reaction with decyl alcohol, epichlorohydrin, N,N’-dimethyl ethylene diamine and 1,3-propanesultone. The experimental conditions obtained are: the ratio of 1,3-propanesulfonic acid lactone to tertiary amine intermediate = 2.3 : 1, reaction temperature = 70°C and reaction time = 11 h. The analysis of the infrared spectrum showed that the structure of the synthesised substance corresponds to that of a Gemini sulphobetaine surfactant. The chemical shifts of the groups were determined by 1HNMR structural characterisation of the products. The surface tension, emulsifying properties, foaming properties and wetting properties were investigated. The results showed that the surfactant has good foaming properties and good compatibility in a high salt environment.
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