Polymer surface modification by photografting of functional nitroxides

The UV-initiated photografting of X-TEMPO onto the surface of ethylene/α-olefin copolymer (EOC) and of styrene-b-(ethylene-co-butene)-b-styrene (SEBS) block copolymer films is here described. In particular, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO), 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO) and 4-(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononanoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (Fluo-TEMPO) were used as X-TEMPO derivatives to change the surface properties of the two polymer films. Infrared analysis (ATR-FTIR), electron paramagnetic resonance (EPR) and thermogravimetric analysis (TGA) confirmed the covalent immobilization of X-TEMPO onto the polymer surface. The fluorescence emission spectroscopy was used to investigate the optical properties of the NfO-TEMPO functionalized samples, while the contact angle measurements highlighted the wettability features of the surface modified with Fluo-TEMPO. A comparison of the data evidences that the properties of the free X-TEMPO derivatives have been completely transferred to the polymer giving “functional” films by a simple modification technique. Furthermore a discussion about the photografting mechanism as well as of the thermal robustness of the covalent bond between the X-TEMPO and the polymer is proposed.