Site-Selective Functionalization of Polydopamine Films via Aryl Azide-Based Photochemical Reaction

Abstract

Although the post functionalization of versatile polydopamine (pD) films enables the expression of functional groups of interest on target substrates, their immobilization generally lacks site-selectivity within a surface platform. In this paper, we report a site-selective conjugation method to functionalize pD films based on the combination of simple photolithographic techniques. The essence of the chemical functionalization strategy was the use of the aryl azide group, whose photolysis induces the generation of reactive nitrene groups that functionalize hydrocarbon networks of pD films. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses indicated that the pD film was functionalized primarily with aryl azide groups under UV irradiation and the introduction of a photomask enabled the pattern generation of the initiator that was tethered with the aryl azide group. A subsequent surface-initiated polymerization on their substrates produced a patterned polymer brush, expressing their own functionality on the surface platform.