Morphology Of The Mixed Lb Films Of Ps And Ps-b-pmma

The Langmuir film balance technology and AFM were used to study the mixed Langmuir monolayers and LB films of homopolystyrene (h-PS) and polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), respectively. The effects of the compositions of blends and copolymers on the aggregation behavoir of h-PS/PS-b-PMMA at the air/water interface were studied.The result shown that similar to those of the PS-b-PMMA diblock copolymers, no obvious transition plateau exists in theπ-A isotherms of h-PS/PS-b-PMMA. The surface pressure increases slowly at the beginning of the compression and increases steeply in the late period. With the increase of h-PS content, theπ-A isotherms shift to the left, and the limiting mean molecular area decreases stepwisely; in the hysteresis curves, the hysteresis areas increase and the hysteresis becomes more evident. With the increase of the PMMA content in the diblock copolymers, theπ-A isotherms shift to the right, and the limiting mean molecular area increases stepwisely; in the hysteresis curves, the hysteresis areas decrease and the hysteresis becomes a little weaker.According to the AFM images of the LB films, when the content of h-PS is 20 wt %, it mainly exhibit circular micelles and their sizes decrease with the increase of the PMMA content in the diblock copolymers; the mixed LB films with the lower PMMA content exhibit the mixed structure of rod and circular micelles; with the increase of transfer pressure, the rod micelles appear and the size of the micelles increases. When the h-PS content is 40%, it mainly shows rod micelles. When the h-PS content is 60%, the mixed LB films respectively exhibit close-packed structure, necklace-network structure, and close-packed circular micelles with the increase of the PMMA content. When the h-PS content further increases to 80%, all of the LB films exhibit necklace-network structures, and the close-packed degree of the structure becomes larger with the increase of transfer pressure.