OXIDATION OF POLY[BIS(4-METHYLPHENOXY)PHOSPHAZENE] SURFACES AND CHEMISTRY OF THE SURFACE CARBOXYLIC-ACID GROUPS

Surfaces of poly[bis(4-methylphenoxy)phosphazene], [NP(OC6H4CH3)2]n, were oxidized with an aqueous KMnO4/NaOH solution, analyzed, and used as substrates for surface reactions. The small-molecule cyclic trimer, [NP(OC6H4CH3)2]3, was also oxidized as a model system. Analysis of the small-molecule reactions by solution state C-13, P-31, and H-1 NMR spectroscopy and mass spectrometry confirmed that the methyl groups were oxidized to carboxylate groups. The oxidized polymer film surfaces were examined by contact angle measurements, ATR-IR, SEM, TEM, and XPS methods. The maximum depth of oxidation was 1-mu-m. Relationships between the reaction parameters, percent oxidation, and the contact angle have been established. The oxidized surfaces were also examined for cation exchange capability. Carboxylic acid surface units were reduced to benzylic alcohol groups. In addition, various coupling reactions were used to link 4-nitrofuroic acid and the tetrapeptide, Arg-Gly-Asp-Ser, to the polymer surfaces.