A novel synthetic method of a hyperbranched polymer possessing 100% branching was successfully developed by using 3,3-dibromo-1-hexyl-5-hydroxyindolin-2-one as a monomer in the presence of sodium hydride. The structure of the monomer is based upon an indolin-2-one core having geminal dibromide and hydroxyl functional groups which are designed to react together to form an irreversible ketal compound. A kinetic model reaction between 3,3-dibromo-1-hexylindolin-2-one with 4-methylphenol was studied in a base medium. The reaction followed second-order kinetics, indicating that the first reaction, that is, the formation of an intermediate from a reaction between 3,3-dibromo-1-hexylindolin-2-one and sodium 4-methylphenolate, is considerably slower than the second one-a reaction of the generated monobromide ether with sodium 4-methylphenolate. Therefore, a new monomer was designed and synthesized, aiming at a 100% hyperbranched polymer. The isolated polymer was characterized by C-13 NMR spectroscopy, which confirmed the 100% branching of the hyperbranched polymer.