The regulation of polymer topology and the precise control over the monomer sequence is crucial and challenging in polymer science. Herein, we report an efficient solution-phase synthetic strategy to prepare regio- and sequence-controlled conjugated polymers with topological variations via the usage of methyliminodiacetic acid (MIDA) boronates. Based on the solubility of MIDA boronates and their unusual binary affinity for silica gel, the synthesized regio- and sequence-defined conjugated oligomers can be rapidly purified via precipitation or automatic liquid chromatography. These synthesized discrete oligomers can be used for iterative exponential and sequential growth to obtain linear and dendrimer-like star polymers. Moreover, different topological sequence-controlled conjugated polymers are conveniently prepared from these discrete oligomers via condensation polymerization. By investigating the structure-property relationship of these polymers, we find that the optical properties are strongly influenced by the regiochemistry, which may give inspiration to the design of optoelectronic polymeric materials.

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Utilizations of alkylboranes reagents in radical polymerization are summarized in this minireview. Alkylboranes act as conventional radical initiators or radical chain‐transfer agents in free‐radical polymerization and controlled radical polymerization. This review discusses various polymerizations operating through different alkylborane reagents with their accompanying mechanisms. The aim of this minireview is to present the state of art of alkylboranes in radical polymerization and to provide the future aspects of this direction. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 14–19

A new synthesis route was developed to produce the diamine monomer containing benzimidazole units, 6,4 0 -diamino-2-phenylbenzimidazole (BIA), which was easily prepared by the reduction of 6,4 0 -dinitro-2-phenylbenzimidazole synthesized via a reaction between 4-nitro-1,2-phenylenediamine and 4-nitrobenzoyl chloride. The composition and structure of the products were confirmed by Fourier transform infrared, NMR, and elemental analysis. A series of polyimides were prepared by the polycondensation of BIA and various dehydrates, pyromellitic dianhydride, 3,3 0 ,4,4 0 -biphenyl tetracarboxylic dianhydride, 4,4 0 -oxydiphthalic anhydride, and benzophenone tetracarboxylic dianhydride via a traditional two-step procedure. The polyimides exhibit excellent thermal stability up to 540 C and high glass transition temperature (T g ) in the range of 382-409 C. The polyimide films are tough and flexible and possess good mechanical properties of tensile strength of 222-232 MPa and modulus of 3.1-5.6 GPa without stretching. The polyimides are amorphous state in wide-angle X-ray diffraction patterns, whereas small-angle X-ray diffraction patterns show the existence of molecular aggregation. The rigid-rod structure and intermacromolecular hydrogen bond are likely responsible for the excellent properties of the polyimides.

Manganese oxide/carbon nanofiber (MnO x /CNF) composites were successfully fabricated as freestanding electrodes through incorporating different manganese sources of nanostructured MnO 2 or Mn(CH 3 COO) 2 $4H 2 O into polyacrylonitrile (PAN) solution by electrospinning and a subsequent carbonization method. The MnO 2 with a rod-like hierarchical core-corona nanostructure was selfprepared by a hydrothermal method using polyvinylpyrrolidone (PVP) to control the size and morphology of nanoparticles. The morphologies and structures of the MnO x /CNF composites were characterized by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. MnO x /CNFs produced from Mn(CH 3 COO) 2 $4H 2 O exhibited good flexibility with uniform dispersion of small MnO x particles in the loose structures of the CNFs. In contrast, MnO x /CNFs derived from MnO 2 displayed relative brittle mechanical properties. The electrochemical performances of the two composites were investigated by cyclic voltammetry, galvanostatic charging/discharging and impedance measurement techniques. The resulting MnO x /CNFs demonstrated excellent electrochemical performance with great rate capability, low internal resistance and long-term cycling stability. Composites produced from Mn(CH 3 COO) 2 $4H 2 O delivered a specific capacitance of 211 F g À1 at 0.25A g À1 in 0.5 M Na 2 SO 4 electrolyte These results suggest that such freestanding MnO x /CNF composites would be promising electrodes for highperformance supercapacitors.