Preparation of well-defined star polymer from hyperbranched macroinitiator based attapulgite by surface-initiated atom transfer radical polymerization technique

To prepare the well-defined star polymer grafted attapulgite nanofibrillar clay (WSP-ATP) with hydrophilic core and hydrophobic shell and higher percentage of grafting, the postgraft polymerization of vinyl polymer from hyperbranched macroinitiator based attapulgite (HMI-ATP) via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique was investigated for the first time. The HMI-ATP, with bromoacetic ester surface groups, was prepared by the bromoacetylation of the surface hydroxyl groups of the hyperbranched aliphatic polyester grafted attapulgite (HAPE-ATP). The HAPE-ATP was prepared by the one-pot polycondensation of the AB(2)-type monomer 2,2-bis(hydroxymethyl)propionic acid (bis-MPA), from the surfaces of the amino group modified attapulgite nanofibrillar clay (A-ATP) with p-toluenesulfonic acid (p-TSA) as catalyst. Then the SI-ATRP of methyl methacrylate (MMA) was conducted from the HMI-ATP made in the presence of 1,10-phenanthroline and Cu(I)Br as catalyst in toluene. The postgraft polymerization exhibited the characteristics of controlled/"living" radical polymerization. The product was characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM).