Structure And Morphology Of The LB Films Of Homo-PS And PS/PS-b-PEO Blends

In this paper, the Langmuir film balance technology and atomic force microscopy (AFM) were respectively used to study the aggregation behavior of the Langmuir monolayers and the morphology of the LB films of homo-polystyrene (h-PS) and its blends with polystyrene-b-poly(ethylene oxide) (PS-b-PEO, SEO19K).According to theπ-A isotherms, for the h-PS system,it could be found that when the solution volume was fixed, the surface collapse pressure increased with the increasing of solution concentration. When the solute quality was fixed, the isotherms moved to the left with the increasing of solution concentration and the spread ability of solution was worse. The AFM height images of the LB films showed that h-PS could form necklace-netwok structure at the air/water interface under the general condition. With the increasing of solution concentration and transfer pressure, the density of netwok structure and the size of micelle increased. With the increasing of dipping pressure, the feature of the LB films changed from noodle network structure to flat film with holes when the concentration was 0.1 mg/mL.With the increasing of h-PS content, for the h-PS/SEO19K blend system, the surface micelles increased in number and decreased in size, and the platforms of the isotherms moved to the lower pressures and became shallower when the solute quality was fixed. When the h-PS content was larger than 80 wt%, the platform disappeared, that was, the isotherms of blends were similar to that of h-PS. When the h-PS content was fixed, the isotherms move to the left and the surface collapse pressure increased with the increase of spreading volume. The features of the LB film of h-PS/SEO19K blends changed from isolated circular micelle structure to microphase separation structure. The features of the LB film present necklace-netwok structure when the content of h-PS was 90%. Furthermore, when the h-PS content was certain, spreading methods affected the isotherms obviously for the high content of h-PS but unconspicuously for the low content of h-PS. The solution spreading order influnced the features of the LB film by different spreading methods.