The synthesis of various polybenzimidazoles (PBIs) in condensation media such as polyphosphoric acid and Eaton’s reagent was accomplished. Molecular weight distribution of the synthesized polymers ...was examined with respect to the process conditions and the chemical structure of the monomers. It was found that during the synthesis of PBIs a side acylation reaction occurs which leads to the formation of branched macromolecules with Mw up to 2.3 × 106 and higher and even crosslinking, resulting in gelation of the polymers during synthesis. Fraction of the side reaction in the overall process appeared to be dependant on both the chemical structure of the monomers and the condensation media used. The orientation of the acylation reaction was determined by quantum-mechanical calculations.
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We have fulfilled modeling of molecular and electronic structure of nanotubes B x N x C y (x ≥ 0, y ≥ 0) with various atom dispositions in the hexagonal lattice points on cylinder surfaces. ...Electronic spectra of such systems with a quasi-one-dimensional superlattice structure have been investigated in the topological and valence approximations. We suppose that these nanotubes consist of alternating carbon and boron nitride ring-like or chain-like structures. We have demonstrated that these systems with different extent of minizones in the electronic spectrum can be produced by means of a change of belt-like fragment width. Quasi-localized states were found in C 2 m symmetry nanotubes.
This article describes a computer simulation of the geometrical and electronic structure of a quasi-two-dimensional carbon layer with a trigonal lattice consisting of fullerenes C36 (1) with ...topological symmetry D6h. Every polyhedral cluster 1 of this polymeric layer (2) is surrounded by six similar fullerenes and connected with every such a fullerene by two covalent bonds. Atomic coordinates of the repeating unit are estimated on the basis of MNDO/PM3 calculations of hydrocarbon molecule (D6h)-C132H48 (3). The carbon skeleton of 3 coincides with a sufficiently large fragment of the polymeric layer 2. The electronic spectrum of the quasi-two-dimensional layer 2 is calculated by the crystalline orbital method in the EHT approximation. The band gap in the electronic spectrum of 2 was found to be equal to 1.5 eV. The geometric and electronic structure of some oligomers of cluster C36, quasi-linear macromolecule C36n, and "hypergraphite" layer is also discussed.
This article describes a computer simulation of the geometrical and electronic structure of a quasi-two-dimensional carbon layer with a trigonal lattice consisting of fullerenes C
36 (1) with ...topological symmetry
D
6h. Every polyhedral cluster 1 of this polymeric layer (2) is surrounded by six similar fullerenes and connected with every such a fullerene by two covalent bonds. Atomic coordinates of the repeating unit are estimated on the basis of MNDO/PM3 calculations of hydrocarbon molecule (
D
6h)-C
132H
48 (3). The carbon skeleton of 3 coincides with a sufficiently large fragment of the polymeric layer 2. The electronic spectrum of the quasi-two-dimensional layer 2 is calculated by the crystalline orbital method in the EHT approximation. The band gap in the electronic spectrum of 2 was found to be equal to 1.5 eV. The geometric and electronic structure of some oligomers of cluster C
36, quasi-linear macromolecule C
36
n, and “hypergraphite” layer is also discussed.
