科研之友
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摘要
Aggregation behavior of three star-shaped fluoropolymers containing polyhedral oligomeric silsesquioxane (POSS) and different monomers poly(methyl methacrylate) (PMMA), poly(trifluoroethyl methacrylate) (PTFEMA) and poly[poly(ethylene glycol)methyl ether methacrylate] (PMPEGMA), POSS-(PMMA-b-PTFEMA)(8), POSS-(PTFEMA-b-PMMA)(8), and POSS-(PTFEMA-b-PMPEGMA)(8)) was investigated at the air-water interface. The interfacial rheology and surface morphology were studied through surface pressure and compression modulus measurements, hysteresis, relaxation, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The surface pressure-mean molecular area (I -MMA) isotherms exhibited four regions, and it was found that the pseudoplateau observed corresponds to a "pancake-to-brush" transition. The compression modulus isotherms showed two peak values which were related to the phase transition of the monolayer. The hysteresis behaviors were compared in two different regions during the compression-expansion process. In addition, the relaxation of the monolayer was discussed using the step compression method. The relaxation process was proposed that related to the adsorption-desorption exchange of molecules and polymer segments on the surface (fast relaxation process) and the reconformation of the adsorbed macromolecules inside the adsorption layer (slow relaxation process). Furthermore, the Langmuir-Blodgett (LB) films prepared at different surface pressures from the three copolymers were scanned by AFM and a variety of morphologies were observed. Finally, the structure evolutions for the three star-shaped copolymers that aggregate at the air-water interface were proposed.
