The Interfacial Structure Of Complex Fluids:Polyelectrolytes And Nanobubbles

Complex fluids involve a number of matters in daily life and industrial manufacture and behave differently from ordinary solutions, comparing with which complex fluids exhibit more plentiful and variable properties as well as phase transitions, such as thixotropic and self-assembly driven by phase separation. Investigating these properties by computer simulation will allow us to have a deeper understanding to and make a better employing of them.Firstly, molecular dynamics simulation was adopted to investigate the formation and stability of bulk nanobubbles. Bulk nanobubbles were found to form in the solution with high gas supersaturation. With the increase of gas concentration, the density fluctuation of solution grew improving the formation of stable nucleus. If gas concentration was high enough, these stable nucleuses would collapse, which would speed up the growth of bulk nanobubbles. The present of curvature caused no effect on the adsorption of gas particles on vapor/liquid interface, but would lead to the increase of gas concentration in bulk solution. The increase ratio satisfied Krichevsky–Kasarnovsky equation. Under normal temperature and pressure, it was hard for the stability of bulk nanobubbles, and diffusive shielding model behaved no good enough in dealing with this problem.Based on the study above, we proceeded to study the influence of gas type on the formation of bulk nanobubbles. Our simulations showed that the weak-interaction gas particles triggered density fluctuation more efficiently than strong-interaction gas particles, and, therefore, were easier to form bulk nanobubbles. Furthermore, for the formation of bulk nanobubbles, the effect of increasing gas concentration can be reached by declining the interaction strength of gas particle, which would allow the formation of bulk nanobubbles under lower gas concentration. However, the relation between them is nonlinear.In the end, the adsorption of partially sulfated polystyrene(PSPS) on vapor/liquid interface was studied by Martini force field. The conformation of PSPS was a collapsed clew with hydrophilic sulfate decorating surface. The adsorption of PSPS was weak. The adsorption ratio of PSPS was around 50%. The adsorption didn't cause a large-scale variation of PSPS's conformation, yet leaded to the orientation of PSPS so that a larger hydrophobic surface adsorbed on vapor/liquid interface. In addition, both ionic strength and the curvature of vapor/liquid interface didn't have a significant effect on the adsorption of PSPS. But large positive curvature would suppress the adsorption to some degree.