Variable - angle ATR-FTIR studies of depth distribution of amidation in surface modified poly(ethylene terephthalate)

Variable - angle ATR-FTIR spectroscopy was applied to the evaluation of the in-depth homogeneity of amidation within superficial layers of poly(ethylene terephthalate) (PET) surfaces. Thin films of PET were subjected to aminolysis with triethylenetetramine and tetraethylenepentamine by wet chemistry and using air plasma as precursor, respectively, in order to create surface functionalities. By varying the incidence angle of the infrared radiation, chemical changes were investigated from layers of different thicknesses. The amide II band has been selected as a marker for monitoring the aminolysis products and for depth profiling. The choice of an exponential decay of the in-depth amide distribution was justified by the quite regular decreasing of the angular absorbance with depth of penetration of the evanescent wave.