We report on a facile, robust and rapid method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified while avoiding chemical degradation. Specifically, we demonstrate that brief exposure of PET surfaces to ultraviolet/ozone (UVO) generates a large surface concentration of hydrophilic moieties that serve as points of chemical attachment, thereby facilitating subsequent chemisorption of organosilane precursors. The feasibility of this methodology is tested by decorating UVO-modified PET surfaces with semifluorinated organosilane (SFOS) molecules, which serve to alter the surface energy of PET without compromising its bulk characteristics. The physico-chemical properties of the SFOS layers attached to PET are studied with a palette of experimental probes, including near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron (XPS) spectroscopy, contact angle, atomic force microscopy (AFM), and ellipsometry. Experimental results indicate that ≈2 min of UVO treatment is optimal for covering PET with dense self-assembled monolayers (SAMs) of SFOS. Longer UVO treatment times contaminate and correspondingly roughen PET surfaces with low-molecular weight organic compounds (LMWOCs) generated from degradation of the topmost PET material. As a consequence, SFOS SAMs attached to the LMWOC layer wash off readily from UVO-treated PET.
Citation: Journal of Electron Spectroscopy and Related Phenomena
Pub Type: Journals
poly(ethylene terephthalate) (PET), ultraviolet/ozone (UVO), polymer surface modification, SAM, NEXAFS