Development of polyolefin materials with biocompatible surface using supercritical carbon dioxide

To utilize polyolefins for biomaterials, biocompatible group was introduced onto polyolefins. Tn general, however, it is difficult to introduce biocompatible groups directly onto the hydrophobic surface of polyolefins. In this study, we paid attention to poly(vinyl acetate) (PVAc) of which the side group can be readily converted to the hydrophilic group. PVAc was immobilized onto polyethylene (PE) by in situ radical polymerization of vinyl acetate monomer using supercritical carbon dioxide as a solvent of monomer and swelling agent of polymer. The acetyl group on the surface of the prepared PE/PVAc blend was converted to the hydroxyl group by hydrolysis. The hydroxyl group on the surface of PE was reacted with 2-chloro-2-oxo-1,3,2-dioxaphospholane followed by adding trimethylamine, to form the phosphorylcholine (PC) group as a biocompatible surface of PE. The products were characterized by attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR), contact angle measurement, and X-ray photoelectron spectroscopy (XPS). ATR-FTIR and XRS measurement revealed that PC group was introduced onto the surface of PE. The contact angle decreased with the increase in polarity of functional group on the surface of PE. Thus, we could introduce the hydroxyl group on the surface of PE effectively. Various functional groups containing PC group can be also introduced on the surface of polyolefins based on this method.