Surface Modification of Polypropylene Molded Sheets by Means of Surface-Initiated ATRP of Methacrylates

Structurally well-defined polypropylene-macroinitiator (PP-MI) sheets promoted the surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) under the mild conditions. There was no change in visual appearance on the surface during the surface-initiated ATRP. Surface analyses by attenuated total reflection infrared (ATR-IR) spectra and X-ray photoetectron spectra clearly showed the presence of PMMA segment grafting from the initiation sites on the surface of PP-MI sheet. Moreover, a uniform layer (ca. 60 nm) consisted of the grafted PMMA brush was directly observed by cross-sectional surface image of transmission electron micrograph measurement. The thicknesses of PMMA layers were linearly increased corresponding with the molecular weight of the grafted PMMA. and the graft densities of PMMA were estimated to be 0.36 chains/nm(2). A dynamic friction test of the resulting PMMA-grafted PP sheet was carried out by sliding a stainless ball probe to reveal higher wear resistance to abrasion characteristics compared to a PMMA-coated PP sheet. Utilizing this grafting technique, highly wettable poly (2-methacryloyloxyethyltrimethyl ammonium chloride) (PMTAC) was also successfully grafted from the PP-MI sheet. The contact angle against distilled water reached to 8 degrees, representing that the surface wettability was drastically improved by grafting highly wettable polymer chains. In addition, the sheet showed a high antibacterial property against Escherichia coli and Staphylococcus aureus.