Mild photochemical surface modification of fluoropolymer by aliphatic amine under UV irradiation

Abstract

Developing a simple and mild strategy for surface modification of chemically inert polytetrafluoroethylene (PTFE) remains highly desirable for applications involving adhesion and surface bioactivity. In this work, we successfully surface-functionalized PTFE using a solution of commonly used aliphatic amine under UV irradiation. The water contact angle (WCA) of PTFE film decreased from 122° to 42° after 9 min of UV irradiation in the presence of a solution of triethylenetetramine in dimethylformamide. Attenuated total reflectance Fourier transform infrared spectra suggested the introduction of aliphatic C–H, –NH₂, –OH and C = C groups on the modified PTFE. X-ray photoelectron spectroscopy and time-of-flight secondary-ion mass spectrometry tests further verified the occurrence of defluorination and introduction of oxygen and nitrogen species. Patterned modification of PTFE can be achieved by using a photomask and regionally selective immobilization of protein on patterned substrate demonstrated the reactivity of modified surface. The peel strength for modified PTFE/stainless steel is 12 times higher than that of the pristine film. This strategy is also applicable to other perfluoropolymers such as poly(tetrafluoroethylene-co-hexafluoropropylene), for which the F content was reduced to 0.7 % and the WCA was reduced to about 10° after photochemical modification.