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

Abstract

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

Long‐Chain Hyperbranched Polymers: Synthesis, Properties, and Applications

“…This esterification polycondensation condition was further modified by Choi and coworkers into continuous water removal by using p ‐toluenesulfonic acid in a moisture‐sensitive catalyst‐free way from the standpoint of applicability in industrial scale production . Similarly, LCHBPs based on poly(ether sulfone)s were prepared via a similar polycondensation reaction of AB 2 ‐type linear poly(ether sulfone) macromonomers …”

“…It should be noted that the entangled feature that usually did not occur in conventional HBPs might even be introduced to LCHBPs, but the length of the subchain should be substantially above the entanglement molecular weight . The strongly entangled chains may also act as physical cross‐links . Based on several polylactide LCHBPs, it was apparent that the long‐chain branching structures led to an increase of the melt elasticity and melt strength of HBPs, and a shorter induction period and a higher crystallization speed during isothermal crystallization, while resulting in less perfect crystals .…”

“…Although excellent achievements have been made on HBPs, in contrast with linear polymers, the quite low viscosity and amorphous nature or high brittleness of HBP materials arising from their dendritic topologies with subchain lengths much shorter than the critical molecular weight for entanglement, give rise to poor processability and inferior mechanical properties, that are not possible for structural applications . Nevertheless, long‐chain hyperbranched polymers (LCHBPs), essentially the long‐chain analogs of HBPs with a linear long subchain segment between branching points, may combine the advantageous properties of HBPs and linear polymers, which may allow the formation of entanglements and also crystallinity like their linear segments, making them less brittle materials than their short‐chain analogs . When compared with linear polymers, LCHBPs possess lower solution and melt viscosity, better solubility, and a large number of terminal functional groups because of their hyperbranched architectures.…”

“…Besides their unique synthetic strategies and novel structural features or topologies, LCHBPs have displayed some novel properties in both bulk and solution states. The chain entanglements have turned out to probably occur in LCHBPs via rheological measurements, which make them feasible in structural applications . They also display some unique assembly morphologies or crystallinity behaviors due to their long‐chain topological architectures .…”

Intramolecular cyclization of long-chain hyperbranched polymers (HyperMacs) from A2 + Bn step-wise polymerization

“…15,16 Especially, for hyperbranched polymers, [17][18][19][20][21][22][23] if the macromonomers are employed, the well-defined hyperbranched polymers with linear long-chain backbone between branched points can be formed as the so-called HyperMacs or Hyperblocks. 26,29,[41][42][43][44][45] However, the fine identification and quantitative characterization of long chain hyperbranched topology are difficult. Thus HyperMacs have received more and more attention in polymer rheology, [32][33][34] coating, 35,36 biomaterials and biomedicine engineering.…”