Aminated poly(ethylene terephthalate) (PET) surfaces were characterized for their use as substrates for the attachment of biologically active molecules. Amines of different chain lengths, tetraethylenepentamine, triethylenetetraamine (TTETA), and diethylenetriamine (DETA), were investigated. X-ray photoelectron spectroscopy was used to show that each amine introduced a comparable amount of nitrogen (5 atom %) to the PET surface. Contact-angle and titration analyses indicated that the amination reaction was not restricted to the surface, with evidence of diffusion into the polymer by TTETA and DETA. As a result, degradation of the PET substrate, evidenced by mass loss, was observed to occur. Annealing of the PET films before amination at a temperature of 200 degrees C reduced the extent of degradation without producing a decrease in the nitrogen content produced. (c) 2007 Wiley Periodicals, Inc.