Hyperbranched polyphenylenes

Abstract

Highly branched polyphenylenes were synthesized from AB2 type monomers, e.g., 3,5dibromophenylboronic acid (1A) and 3,5-dihalophenyl Grignard reagents (IB and 2). Monomers 1 and 2 were polymerized by Pd(0) and Ni(II) catalyzed aryl-aryl coupling reactions, respectively. Polymers obtained from 1 had molecular weights in the 5000-35 000 range with polydispersities less than 1.5. They are thermally stable to 550 aC and soluble in many organic solvents. 13C NMR indicates about 70% branching efficiency. A Tt at 236 °C was observed, but the polymer was brittle and did not form films. The melt viscosity of polystyrene was reduced, and the modulus was improved as a bromo functional hyperbranched polymer was added. The bromo polymer was metalated with butyllithium. The resulting lithio polymer reacted with various electrophiles to provide polymers with other end groups which control solubility as well as thermal properties. Some of these derivatives were used as multifunctional initiators to prepare star polymers, for example, via ring-opening polymerization of propiolactone and anionic polymerization of methyl methacrylate.

Nanoscale assembly into extended and continuous structures and hybrid materials

“…Phenyl-based AB 2 -type monomers undergo Suzuki coupling to give globular hyperbranched polyphenylenes that can be combined with organic small molecules 65 or surface-functionalized for tailored applications. 66 By the FeCl 3 dehydrogenation of dendritic polyphenylene, Mullen and co-workers 67 achieved the preparation of PAHs much larger than HBC. The geometry of the initial polyphenylene dendrimer strongly influenced product distribution, as dehydrogenation started independently on each dendron arm and proceeded to the core.…”

Synthesis of hyperbranched polymers with controlled degree of branching

“…Therefore, the glass transition for HBPs is strongly affected by the translational movement of the entire molecule instead of a segmental movement. 36,42 The chemical natures also affect the T g values; for example, an aliphatic polyester generally has a much lower T g value than the aromatic polyester. 43 Mechanical and rheological properties The rheological properties of HBPs are characterized by a Newtonian behavior in the melt state; that is, no shear thinning or thickening is observed, 44,45 indicating the lack of entanglements for these polymers.…”

Preparation And Characterization Of Photosensitive Hyperbranched Aliphatic Polyester

“…One of the exciting and promising developments in material science today is the design and synthesis of hyperbranched polymer materials which are found to have potential applications in the field of functional materials [1][2][3], such as films [4][5], coatings [6], adesive agents [7], modifiers and so on [8].The candidate materials include polyurethane acrylateand hyperbranched polyester polyamide etc [9]. It is well known that hyperbranched polyester possesses a variety of unique proprieties such as good solubility, low viscosity, multivalence, and encapsulation effects, which mainly are caused by the branching and spherical architecture.…”