Clickable Plastic Surfaces with Controllable Azide Surface Density

This study investigates the surface functionalization of plastic substrates through dip-coating in azide-functionalized polymer solutions, followed by a click reaction (i.e., strain-promoted azide–alkyne cycloaddition). Acrylic, poly(ethylene terephthalate) (PET), and nylon substrates are dip-coated with a series of polymers containing various azide groups grafted onto the poly(methyl methacrylate-co-hydroxyethyl methacrylate) backbone to examine structural effects on the surface density of clickable azide groups. X-ray photoelectron spectroscopy and fluorescence spectroscopy confirm the subsequent click-immobilization of cycloalkyne-tagged fluorescein, which is quantified to calculate the surface density of clickable azide groups. Further investigations demonstrate that the surface density of azide groups can be controlled by manipulating the polymer ratio during dip-coating, thus enabling the preparation of a linear surface gradient in terms of azide group density. Finally, the microcontact printing (µCP) method is employed to pattern the functionalized surfaces and quantify the functional molecules immobilized on the surface by µCP. This study highlights the adaptability of click chemistry and polymer coating techniques for the advanced functionalization of plastic surfaces for materials science and engineering applications.