Clickable Macroinitiator Strategy to Build Amphiphilic Polymer Brushes on Carbon Nanotubes

A novel and versatile Gemini-grafting strategy to modify surfaces/substrates is presented by a combination of conventional grafting to and grafting from strategies. As a typical example, carbon nanotubes (CNTs) were functionalized with amphiphilic/Janus polymer brushes by uniting click chemistry with a macroinitiator approach. A clickable macroinitiator, poly (3-azido-2-(2-bromo-2-methylpropanoyloxy)propyl methacrylate) (polyBrAzPMA), with alkyl bromo groups for initiating atom transfer radical polymerization (ATRP) and azido groups for the click reaction was first synthesized by postmodification of poly(glycidyl methacrylate) with sodium azide, followed by 2-bromoisobutyryl bromide. The clickable macroinitiator was clicked onto alkyne-containing multiwalled/single-walled CNTs via the Cu(I)-catalyzed click reaction of Huisgen 1,3-dipolar cycloaddition between azides and alkynes, resulting in a CNT-based clickable macroinitiator. Poly(n-butyl methacrylate), polystyrene, and poly(ethylene glycol) were subsequently grown on CNTs via ATRP grafting from and click grafting to approaches, affording CNT-supported amphiphilic polymer brushes. The functionalized CNTs were characterized by thermal gravimetric analysis (TGA), FTIR, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. All of the results demonstrated that it is feasible and facile to grow various multifunctional polymer brushes on CNTs by the clickable macroinitiator strategy, and the grafted polymer content can be well controlled. This versatile strategy can be readily extended to prepare other Janus/bifunctional polymer brushes, opening an avenue for building complex polymer architectures and tailoring surface