Miktoarms hyperbranched polymer brushes: One-step fast synthesis by parallel click chemistry and hierarchical self-assembly

Abstract

Spherical molecular brushes with amphiphilic heteroarms were facilely synthesized by grafting the arms of hydrophobic 2-azidoethyle palmitate and hydrophilic monoazide-terminated poly(ethylene glycol) onto the core of alkyne-modified hyperbranched polyglycerol (HPG) with high molecular weight (Mn = 122 kDa) via one-pot parallel click chemistry. The parallel click grafting strategy was demonstrated to be highly efficient (∼100%), very fast (∼ 2 h) and well controllable to the amphilicity of molecular brushes. Through adjusting the feeding ratio of hydrophobic and hydrophilic arms, a series of brushes with different arm ratios were readily obtained. The resulting miktoarms hyperbranched polymer brushes (HPG-g-C16/PEG350) were characterized by hydrogen-nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) measurements. The spherical molecular brushes showed high molecular weights up to 230 kDa, and thus could be visualized by atomic force microscopy (AFM). AFM and dynamic laser light scattering (DLS) were employed to investigate the self-assembly properties of amphiphilic molecular brushes with closed proportion of hydrophobic and hydrophilic arms. The brushes could self-assemble hierarchically into spherical micelles, and network-like fibre structures, and again spherical micelles by addition of n-hexane into the dichloromethane or chloroform solution of brushes. In addition, this kind of miktoarms polymer brush also showed the ability of dye loading via host-guest encapsulation, which promises the potential application of spherical molecular brushes in supramolecular chemistry.