Surface properties and structures of diblock and random copolymers with perfluoroalkyl side chains

Polymers with perfluoroalkyl side chains have recently attracted a great deal of interest as additives to surface hydrophobicity to values higher than these corresponding to polytetrafluoroethylene. The structure and surface free energy of random and diblock copolymers of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA-r-PFEMA and PMMA-b-PFEMA, respectively) were compared using dynamic contact angle, X-ray photoelectron spectroscopy, X-ray diffraction, and reflection-adsorption FT-IR spectroscopy. The PMMA-b-PFEMA solution cast film showed a surface free energy of 7.8 mJ/m2. This value was lower than that of PMMA-r-PFEMA solution cast film (13.4 mJ/m2) but is comparable to the lowest value (6.7 mJ/m2) reported in literature. The surface of PMMA-b-PFEMA was almost covered with the CF3 groups of self-assembled perfluoroalkyl side chains. On the other hand, more CF2 groups and methacrylate main chain were exposed on the PMMA-r-PFEMA film surface due to parallel orientation of the perfluoroalkyl side chains, which determined the relatively higher surface free energy of the PMMA-r-PFEMA film.