Wettability improvement of bacterial polyhydroxyalkanoates via ion implantation

Water wettability of polyhydroxyalkanoates (PHAs), which were produced by b acteria, were improved by carboxyl ion implantation. Ion implantation was p erformed at an energy of 150 keV with fluences ranging from 5 x 10(12) to 1 x 10(15) ions/cm(2). The surface properties were characterized by means of contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scan ning electron microscopy (SEM). Similar contact angle changes were observed on polyhydroxybutyrate (PHB) and poly (hydroxybutyrate-co-hydroxyhexanoate ) (FHBHHx). For PHB, the contact angle of water decreased from the original 68.5 degrees to zero at the fluence of 1 x 10(15) ions/cm(2). For PHBHHx, it decreased from 91.5 degrees to 68.5 degrees. The results revealed that i on implantation improved water wettability of the PHAs. Furthermore, it was found that the intensities of three components C-C, C-O and C=O, which wer e resolved from the Cls spectra for pristine PHAs, decreased after the COOH + implantation. Notably, a new component at 284.6 eV, which corresponds to the amorphous carbon structure, appeared after implantation. The present st udy suggests that the improvement of water wettability of the PHAs might co me from the destruction of original surface chemical bonds and formation of an amorphous carbon phase by ion implantation. The influence of surface mo rphology on wettability is also discussed. (C) 2000 Elsevier Science B.V. A ll rights reserved.