Grafting of Branched Polymers onto Carbon Black Surface: Radical Postpolymerization Initiated by Pendant Azo Groups of Grafted Polymer on the Surface

The grafting of highly branched polymer onto carbon black surface by postpolymerization of glycidyl methacrylate (GMA) initiated by pendant azo groups introduced to grafted polyGMA on the surface was investigated. The graft polymerization of GMA onto carbon black was achieved by use of azo groups introduced onto the surface: the percentage of grafting (the proportion of grafted polymer to carbon black) and surface density of grafted polymer to carbon black were determined to be 35.4% and 0.39 mg/m2, respectively. The introduction of pendant azo groups to grafted polyGMA chain on carbon black was successfully achieved by the reaction of pendant glycidyl groups with 4,4′-azobis(4-cyanopentanoic acid) using (α-picolin as a catalyst: the amount of pendant azo groups was determined to be 0.23 mmol/g. It was found that the postpolymerization of GMA was initiated by the pendant azo groups of polyGMA-grafted carbon black and branched polymer was grafted onto carbon black surface: the total grafting of polyGMA was increased from 35.4% (0.39 mg/m2) to 47.5% (0.52 mg/m2) after the postpolymerization. By repeating the above procedure, i.e., introduction of pendant azo groups and and postpolymerization, highly branched polymers were grafted onto carbon black surface. Branched polymer-grafted carbon black gave a stable colloidal dispersion in good solvents for grafted polymer.