SURFACE REDUCTION OF POLY(ARYL ETHER ETHER KETONE) FILM - UV SPECTROPHOTOMETRIC, H-3 RADIOCHEMICAL, AND X-RAY PHOTOELECTRON SPECTROSCOPIC ASSAYS OF THE HYDROXYL FUNCTIONS

The surface reduction of amorphous poly(aryl ether ether ketone) (PEEK ) film was successfully achieved by wet chemistry using a solution of NaBH4 in DMSO at 120 degrees C for 3 h. The resulting PEEK-OH film was fully characterized by MIR, W-visible, and H-1 NMR spectroscopies; al l the data were consistent with those of the references, 4-(4-methoxyp henoxy)benzhydrol and bulk-reduced PEEK (''PEEK-OH''). The surface of PEEK-OH film was analyzed by X-ray photoelectron spectroscopy (XPS). F rom the fine structures of the Cls and Ols peaks, we could determine a ratio of reduction reaching 75-85% of the monomer units contained in the 10 outermost atomic layers. The surface reactivity of the hydroxyl groups was assayed by derivatization with [H-3]acetic anhydride follo wed by liquid scintillation counting (LSC) of the sample-associated ra dioactivity. The PEEK-OH film was reacted with p-nitrophenyl chlorofor mate to furnish an activated surface (PEEK-OCO2PNP), the basic hydroly sis of which allowed the indirect spectrophotometric assay of the reac tive OH groups. The PEEK-OCO2PNP film was further used to covalently f ix amine derivatives via a carbamate Linkage. Using [H-3]lysine and tr ifluoroethylamine, we were able to assay the surface reactivity by LSC and XPS respectively. The ratios of surface derivatization were withi n 5-30%. The PEEK-OH film was used as substrate for the cultivation of CaCo2 epithelial cells; the presence of surface hydroxyl functions mo derately improves the polymer biocompatibility.