Solvent effect on the film formation and the stability of the surface properties of poly(methyl methacrylate) end-capped with fluorinated units

The surface structure and stability (the resistance to surface reconstruction) of end-capped poly(methyl methacrylate) films were greatly affected by the solvents used for film preparation. Films of end-capped PMMA with about four 2-perfluorooctylethyl methacrylate units cast with benzotrifluoride solution exhibited excellent stability and resistance to polar environments compared with those cast with cyclohexanone and toluene solutions. The observed difference in stability between these fluorinated surfaces is attributed to their surface microstructures formed during the film formation processes, which are closely related to the associative behavior of the end-capped PMMA in the solution. A relatively perfect close-packed and well-ordered structure of the perfluoroalkyl side chains at the surface of the PMMA(857)-ec-FMA(3.3) film was formed when the film was cast with benzotrifluoride solution, in which only unimers existed. This study indicates that such a solvent effect may be used to promote the formation of a well-ordered packing structure of the fluorinated moieties at the film surface. The ordering of the packing structure is to a certain extent more important than the content of the fluorinated moieties at the surface for improving the surface stability.