INTRODUCING NH2 ONTO POLYMERIC FILMS VIA PHOTO-INDUCED C-H BOND TRANSFORMATION WITH PHENOL DERIVATIVES AS BUILDING BLOCKS

A one-step process to introduce both the aromatic and aliphatic primary amino groups with high chemoselectivity was developed. Triplet state acetone abstracts the hydrogen atoms from both the C-H bond of the polymeric film substrate and the O-H bond of phenol which is the building block and the amino group carrier. As a result, two kinds of free radicals, confined carbon-centered chain radicals of the polymer substrate and mobile oxygen-centered phenoxy radicals, were generated. Then the C-O bonds were formed by the coupling reaction between these two kinds of free radicals. p-Tyramine and p-aminophenol were used as amino carriers. The successful introduction of amino groups onto LDPE, BOPP and PET film substrates was demonstrated by measurements of water contract angle (CA), ultraviolet spectra (UV), X-ray photoelectron spectroscopy (XPS) and fluorescent microscopy. The processing factors, such as the UV-light intensity and irradiation time, concentrations of p-tyramine and p-aminophenol, and the ratio of acetone/water were investigated. The optimized process parameters are as follows: UV light intensity 9500 W/cm2; irradiation time 18 min for BOPP and LDPE, 22 min for PET; the ratio of acetone/water = 1; and concentration of p-tyramine and p-aminophenol 15% for BOPP and LDPE, 1% for PET. Based on the UV absorbance, the amino groups on the polymeric substrates were estimated to be in the range of 6.31016-9.510-6mmol/mm2.