Synthesis and properties of long‐chain branched poly(ether sulfone)s by self‐polycondensation of AB2 type macromonomers

Long‐chain branched poly(ether sulfone)s (PESs) were synthesized via self‐polycondensation of AB₂ macromonomers. The linear PES oligomers synthesized by self‐polycondensation of 4‐chloro‐4′‐(4‐hydroxyphenyloxy)diphenyl sulfone were terminated with 4‐(3,5‐methoxyphenoxy)‐4′‐fluorodiphenyl sulfone to form AB₂ macromonomer precursors. After conversion from methoxy to hydroxy groups, the AB₂ macromonomers were self‐polycondensed to form long‐chain branched PESs. NMR measurements support the formation of the target macromonomers ( = 2930–67,800 (g mol^?1); M_n = number average molecular weight) and long‐chain branched PESs. Gel permeation chromatography with multiangle light scattering measurements indicated the formation of high‐molecular‐weight (M_w) polymers over 10⁴. The root‐mean‐square radius of gyration (R_g) suggests that the shape of the long‐chain branched PES synthesized from small AB₂ macromonomers in solution is similar to that of hyperbranched polymers. Increasing resulted in larger R_g, suggesting a transition from hyperbranched to a linear‐like architecture in the resulting long‐chain branched PESs. Rheological measurements suggested the presence of strongly entangled chains in the long‐chain branched PES. Higher tensile modulus and smaller elongation at the break were observed in the tensile tests of the long‐chain branched PESs. It is assumed that the enhanced molecular entanglement points may act as physical crosslinks at room temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1825–1831