| Abstract: | Wetting behavior of perfluoroalkylethyl acrylate (FA)/n-alkyl acrylate (AA) copolymers with the various length of side chains of the AAs is discussed from a standpoint of surface molecular mobility. The copolymerization reactivity ratio indicates that these polymers are random copolymers. The surface properties were studied by measuring dynamic contact angle, static contact angle and freeze-dried X-ray photoelectron spectroscopy, and the bulk properties by wide-angle X-ray diffraction and differential scanning calorimetry. The advancing contact angles for water were independent of side-chain length of AAs and were almost constant at 120°. We have attributed this phenomenon to the orientation of perfluoroalkyl groups (Rf groups, CxF2x+1) in air, which is independent of side-chain length of AAs. On the contrary, the receding contact angles showed small values of about 45° when n numbers below 8 and increased when n numbers above 12. This can be explained as follows. High wettability during the receding process at the n numbers below 8 results from regression of Rf groups at the water–solid interface caused by minimization of the interface free energy. The low wettability during the receding process at the n numbers above 12 shows that Rf groups cannot regress due to its crystallization. This mechanism is also supported by other measurements. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1741–1749, 1999 |
