Research On Graphical Interface Of Polymer Droplets Evaporation

It is a common physical phenomenon in the nature that a spilled drop on a solid surface. Evaporation-induced self-assembly of the droplets dispersed or dissolved in solvent has been used of creating regular, repetitive, and well-defined patterns. For the evaporation of droplets from a solution or suspension to the substrate, and then evaporated to the environment, wherein the change in a variable, so that the final pattern will change accordingly at the interface. Regulates evaporation of the droplets formed at the interface pattern is the focus of this study.The effects of temperature, concentration, molecular weight, external field and the adding of the equal SiO2 on the evaporative deposition patterns of hydrosoluble polymer droplets were investigated in this paper. The pictures of the deposition patterns, which were took by the polarization microscope and the Scope Image, were deal with through Image-Pro Plus and Origin, To sum up, we can draw the conclusion as follow.We have discovered patterns formed by drying aqueous drops of sodium chloride and the mixture of sodium chloride containing SiO2.Sodium chloride inhibited the formation of a cyclic pattern, with sodium chloride concentration change will have other dendritic structures and fragmented crystallization. This is due to the presence of sodium chloride changes the stress distribution of the droplet surface, weakened radial capillary flow compensation, so that the Marangoni flow is dominant, and sodium chloride inhibited the formation of a cyclic pattern. The mixture of sodium chloride containing SiO2 formed a new pattern not a single cyclic deposition after evaporation. With increasing of SiO2 concentration, deposition of particles inside the droplets increases, larger particles is more and more intensive, and the edge of the deposit grows ever wider. This is related with the charge of the solute and the evaporation kinetics.Study on evaporation process of the droplets with SiO2, PVA, PVP, the mixture of PVA and SiO2 or the mixture of PVA and NaCl. It analyzed the pattern formation and influence factors of polymer droplet evaporation process. It was found that during the evaporation progress of SiO2 droplets, the contact line of the droplet is fixed, does not slip. With concentration increasing, the edge of the droplet deposition from disorder into order, and those related to Brownian motion. In addition, it found that the concentration and temperature have a major impact on the pattern after the formation of PVA droplet evaporation. When the concentration increases and the temperature decreases, the pinning effect increases, sediment thickness and width of the edge of the droplet increases. In the mixed system of SiO2 and PVA, there is competition between SiO2 and PVA. During the evaporation-induced self-assembly of NaCl and PVA particles mixed system, dendritic deposition of droplets were formed along the radial direction, fragment deposition patterns were formed along the outer edge of the formation of the dendritic deposition. This is because after adding NaCl, ionic strength of the solution and the instability of the evaporation system is increased, thus affecting the concentration gradient and sophisticated growth.Further exploration of the polymer solution evaporation process is that the droplet is restricted between the substrate and the pushpin or steel ball. It analyzes the pattern evaporation under restricted space and the factors affect the formation. It was found that the concentric rings will not formed under unrestricted conditions, but there were concentric rings under restricted conditions. When droplet evaporation under limited conditions the greater the radius of curvature of restricted space, the thinner the droplets between the restricted space, the faster the droplet evaporates. Therefore concentric ring structure is formed more uniformly.