Synthesis of Hyperbranched Poly(phenylene oxide) by Ullmann Polycondensation and Subsequent Utilization as Unimolecular Micelle

A new hyperbranched poly(phenylene oxide) was synthesized from a simple AB2 type monomer, 3,5‐dibromophenol, by Ullmann polycondensation. The bromo‐terminated hyperbranched poly(phenylene oxide) was amorphous (Tg = 120 °C), but showed high thermal stability (T5d = 480 °C in nitrogen). The polymer with the degree of branching of 0.61 showed good solubility in organic solvents. The highly branched nature of the polymer effectively disrupted the crystalline characteristics of the linear poly(phenylene oxide) (Tm = 285 °C). When the bromine end groups of the polymer were transformed to lithium carboxylate groups, the resulting polymer became soluble in water. This carboxylate‐terminated hyperbranched poly(phenylene oxide) showed the characteristics of an unimolecular micelle in aqueous solution and behaved as a host for nonpolar organic guest molecules such as 1,4‐diaminoanthraquinone even under the critical micelle concentration of conventional surfactants. DSC and TGA curves of the hyperbranched poly(phenylene oxide) 2. magnified image DSC and TGA curves of the hyperbranched poly(phenylene oxide) 2.