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