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 ( Mntrue(AB 2true) = 2930–67,800 (g mol−1); Mn = number average molecular weight) and long‐chain branched PESs. Gel permeation chromatography with multiangle light scattering measurements indicated the formation of high‐molecular‐weight (Mw) polymers over 104. The root‐mean‐square radius of gyration (Rg) 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 Mntrue(AB 2true) resulted in larger Rg, 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

Slip at the interface between immiscible polymer melts remains poorly understood. A method that relies solely on rheological measurements to obtain the interfacial slip velocity uses the slip-induced deviation in the flow variables. To use the method, accurate estimates of the flow variables under the assumption of no-slip are necessary. Although such estimates can be easily derived under some cases, in general, this is not straightforward. Therefore, methods to determine the interfacial slip velocity without using estimates for the flow variables under no-slip conditions are desirable. In this work, we focus on investigations of slip at the interface between two immiscible polymer melts undergoing two-phase coaxial flow. To enable such investigations, we have adapted the Mooney method, usually used to investigate wall slip, to investigate polymer/polymer interfacial slip. Using this method, we have measured the slip velocity at the interface between polypropylene and polystyrene as a function of the interfacial stress. To determine the validity of the modified Mooney method, we also determine the slip velocity using the slip-induced deviation in the flow variables. To enable this determination, we use polypropylene and polystyrene with almost identical shear rate-dependent viscosities over a range of shear rates. The slip velocity obtained from the modified Mooney method displayed excellent agreement with that determined using the deviation from no-slip. In agreement with prior work, the dependence of the slip velocity on the interfacial stress is a power-law. Our investigation spans a sufficiently wide range of interfacial stress R. Komuro · S. K. Sukumaran ( ) · M. Sugimoto · K. Koyama Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata, 992-8510, Japan e-mail: sa.k.sukumaran@gmail.com to enable the direct observation of two power-law regimes and also the transition between the two regimes. We also find that the power-law exponent of approximately 3 at low stresses decreases to approximately 2 at high stresses.

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