Various surface functionalizations of ultra-high-molecular-weight polyethylene based on fluorine-activation behavior

Abstract

Ultra-high-molecular-weight-polyethylene (UHMWPE) is an excellent biological material, but covalently introducing a variety of functional groups on its surface is very difficult owing to its inherently inert structure. In this study, the surface functionalization of UHMWPE based on fluorine-activation and subsequent derivatization reactions is reported, and offers a simple and convenient pathway to the incorporation of useful functional groups and patterned surface functionality. A large number of carboxyl groups, –C–F_x and CC bonds are covalently bonded to the macromolecular chain structure through a fluorine-activated process in the presence of oxygen, greatly increasing the surface polarity and wettability. Its surface energy is increased from 34.5 mN m⁻¹ to 57.5 mN m⁻¹, and the polar component arises from 4.0 to 23.8 mN m⁻¹. In contrast, only stable C–F forms when treated with only fluorine (no oxygen), producing a hydrophobic Teflon-like surface structure and poor wettability. Moreover, UHMWPE with carboxyl groups and double bonds, used as precursor, were further covalently functionalized through subsequent derivatization reactions with fluorine, bromine and amine-terminated molecules, by which the carbon–bromine bond and amino groups were successfully grafted onto a UHWMPE surface. The results demonstrate that the fluorine-activated strategy developed in this work is an effective means to improve the surface hydrophilicity and derivatization reaction capacity of UHMWPE.