Study On Synthesis Of AB-Type Amphiphilic Block Copolymer By Atom Transfer Radical Polymerization And Its Dispersibility As Hyperdispersants

In recent years, more and more researches have been focused on the synthesis of hyperdispersants (as are often called highly efficient polymeric dispersants) in the field of pigment-dispersing additives .They have a better dispersibility than the conventional surfactants and had been put into practice in industry . However, little researches for the synthesis of hyperdispersants has been carried out in our country, plenty of products are still mainly depended on import. Based on the analysis of the molecular structure of hyperdispersants and the corresponding mechanisms of dispersion and stabilization for pigment suspension, a series of A-block-B hyperdispersants MPES were synthesized by atom transfer radical polymerization (ATRP) method. The MPES were charactered by IR, UV, and the dispersion and stabilization properties of carbon black suspension with the hyperdispersants were studied.The major works and conclusions are described as followings:First, a macroiniator MPEG-Br was prepared by the reaction of methoxypolyethylene glycol(MPEG1000) with 2-Bromopropionyl bromide, and under the catalysis of CuX/2,2'-bipyridine, the monomer styrene was initiated and polymerized with MPEG-Br through ATRP to produce amphiphilic diblock copolymer MPES. The structure of MPES was characterized by Fourier-Transform Infrared spectroscopy(IR) and Ultraviolet spectroscopy(UV), and the molecular weight was determined by Gel Permeation Chromatography(GPC). The effects of catalysts, ligand, initiator and reaction temperature on the conversation of styrene and the molecular weight of the MPES were discussed respectively.The dispersion property of MPES for carbon black pigment in water was also investigated by Spectrophotometer, Scanning Electron Microscope (SEM), Particle size analyzer and electrophoresis meter respectively. The results showed that when the content of styrene in MPES was about 73% and the mass ratio of carbon black to MPES was 3:1, carbon black can disperse in water in a best state, in which the carbon black particles has a well-distribution and the carbon black suspension has a long-term stability. The SEM of dispersions indicated that the hyperdispersant made the carbon black microparticles smaller and well-distributed.This understanding dispersibility is contributed basically to the steric hindrance of solventable chain (i.e. the poly ethylene glycol group)which stretched in the water and the tightly absorbed function on the surface of carbon blackof anchoring group(i.e. polystyrene) ,and this effectively prevented the reconglomeration of carbon black particles.