Igor I. Ponomarev

Novel composite Zr/PBI-O-PhT membranes for HT-PEFC applications.

Summary Novel composite membranes for high temperature polymer-electrolyte fuel cells (HT-PEFC) based on a poly[oxy-3,3-bis(4′-benzimidazol-2″-ylphenyl)phtalide-5″(6″)-diyl] (PBI-O-PhT) polymer with small amounts of added Zr were prepared. It was shown in a model reaction between zirconium acetylacetonate (Zr(acac)4) and benzimidazole (BI) that Zr-atoms are capable to form chemical bonds with BI. Thus, Zr may be used as a crosslinking agent for PBI membranes. The obtained Zr/PBI-O-PhT composite membranes were examined by means of SAXS, thermomechanical analysis (TMA), and were tested in operating fuel cells by means of stationary voltammetry and impedance spectroscopy. The new membranes showed excellent stability in a 2000-hour fuel cell (FC) durability test. The modification of the PBI-O-PhT films with Zr facilitated an increase of the phosphoric acid (PA) uptake by the membranes, which resulted in an up to 2.5 times increased proton conductivity. The existence of an optimal amount of Zr content in the modified PBI-O-PhT film was shown. Larger amounts of Zr lead to a lower PA doping level and a reduced conductivity due to an excessively high degree of crosslinking.

Synthesis and properties of 10-hydroxy-10-oxo-10H-10λ5-phenoxaphosphine-2,8-dicarboxylic acid and related polybenzoimidazoles

Oxidation of 10-hydroxy-2,8-dimethyl-10H-10λ5-phenoxaphosphine 10-oxide (1) with potassium permanganate in an alkaline medium afforded 10-hydroxy-10-oxo-10H-10λ5-phenoxaphosphine-2,8-dicarboxylic acid (2). The latter exists as a stable crystal hydrate containing two water molecules. With the aim of examining the possibility of performing the synthesis of polybenzoazoles based on acid 2, the model reaction of the latter with o-phenylenediamine in polyphosphoric acid (PPA) was studied. New high-molecular-weight phosphorus-containing polybenzoimidazoles were prepared by the reaction of 2 with various aromatic tetraamines in PPA and Eaton’s reagent.

Molecular Design of Rigid-Chain Polyheteroarylenes and the Effect of Substituents at the Central Heterocyclic Fragment on the Polyheteroarylene Equilibrium Rigidity

Quantum-chemical calculations and calculations by the Monte Carlo method were used for conformational analysis of heterocyclic polymers. The steric effect of various substituents on the equilibrium geometry and conformational dynamics of 1, 4, 5, 8-naphthalenetetracarboxydiimide was studied using the AM1 semiempirical quantum-chemical method. It was shown that addition of bulky groups to the naphthalene moiety of 1, 4, 5, 8-naphthalenetetracarboxydiimide increases conformational rigidity of the imide rings. Using the example of rigid-chain polymers containing the naphthoileneimide ring, it was demonstrated that the introduction of four bulky substituents into the structure of 1, 4, 5, 8-naphthalenetetracarboxydiimide results in a considerable increase in the equilibrium rigidity of the polymer.

Molecular structure and conformational dynamics of 3,12-dichloro-5,14-diphenyl-7,9a,16,18a-tetrazadibenzo[a,l]pentacene-9, 18-dione

The X-ray study of 3,12-dichloro-5,14-diphenyl-7,9a,16,18a-tetrazadibenzo[a,l]pentacene-9,18-dione (1), a model compound for a novel class of thermostable polyheteroarylenes, polyquinoquinazolones, has been carried out. The nonsymmetric flattened structure of the molecule observed is a result of intermolecular interactions. It was established using quantum-chemical calculations by the semiempirical AM1 method that the annelation of the 1,6-dihydropyrimidinone ring by aromatic cycles results in increasing the conformational flexibility of the dihydrocycle due to weakening the conjugation between the carbonyl group and the remaining π-system of the molecule. It was shown by X-ray study and quantum-chemical calculations that protonation of1 results in a substantial change in the molecular structure due to the large contribution of the 1,4-dihydro tautomeric form to the structure of the 1,6-dihydropyrimidinone ring. A tendency for the conformational flexibility of the heterocycle to increase upon protonation was revealed.

Benz[4,5]Isoquino[1,2- b ]Quinazoline-7,9-Dione and a Rearrangement Product of its Hydrolysis, 2-(1,8-Naphthalenedicarboximido)benzamide

Benz[4,5]isoquino[1,2-b]quinazoline-7,9-dione, (1), C 19 H 10 N 2 O 2 , was isolated as a product of the reaction between naphthalic anhydride and anthranylamide after crystallization from dimethylformamide. Recrystallization from concentrated (95%) formic acid resulted in 2-(1,8-naphthalenedicarboximido)benzamide, (2), C 19 H 12 N 2 O 3 , as a rearrangement product of hydrolysis [alternative systematic name: 2-(1,3-dioxo-2,3-dihydro-1H-benz[de]isoquinol-2-yl)benzamide]. The two crystallographically independent molecules of (1) [(1a) and (1b)] are substantially non-planar as a result of strong intramolecular steric repulsion between their cis-arranged carbonyl groups [the O...O distances are 2.584(3) and 2.664(3)A, and the dihedral angles between the naphthalene and benzene nuclei are 8.75 (7) and 14.46 (7)°, respectively]. Molecule (2) is also sterically hindered with an approximately orthogonal orientation of the naphthalenedicarboximide and o-phenylene groups [dihedral angle 87.05 (4)°] and absence of π-conjugation between the o-phenylene and amide groups [dihedral angle 40.02 (6)°].

Synthesis of block copolymers based on poly(p-benzamide) with a polyamide benzimidazole

Abstract A diblock copolymer based on poly( p -benzamide) (PBA) and poly(2-phenylene-(5-benzimidazole))isophthalamide (PABI) was synthesized by direct coupling reaction between acylchloride and amino end groups of the two homopolymers. Soxhlet extraction with N,N 1- dimethylacetamide completely removed unreacted PABI and allowed determination of copolymer content and composition of the unextracted fraction (by u.v. data and viscosity measurements). Preliminary results on phase behaviour are given and analysed in terms of block length.

Direct synthesis of aromatic polyamides using the imidazole-triphenylphosphite system

Abstract The possibility of using imidazole as a catalytic component in the direct synthesis of poly( p -phenyleneterephthalamide) and poly( p -benzamide) by phosphorylation with triphenylphosphite was investigated. In the presence of imidazole it was possible to perform the whole synthesis in a homogeneous solution, thus avoiding the formation of a precipitate or a swollen gel, as usually described in literature, particularly for poly( p -phenyleneterephthalamide). Higher molecular weights were obtained in our systems, as compared to typical values from the direct synthesis method.

Synthesis and structure of 6-chloro-2,3-trimethylene-4-phenylquinoline

An X-ray structural investigation of 6-chloro- 2,3-trimethylene-4- phe nylquinoli ne obtained by the reaction of 2-amino-5-chlorobenzophenone with cyclopentanone was carried out. At 20 °C, a = 23.750,b = 9,242, c = 14.018 A, β = 112,68° space group (21c,Z = 8, 2647 reflections,R = 0.047 He five-membered ring has an envelope conformation Conjugation between the quinohne fragment and the phenyl substituent is significantly distorted dm to the rotation of the latter by -62.9°

Poly[2-phenylene-(5-benzimidazole)] isophthalamide : macromolecular characterization

Two different synthetic routes have been used to synthesize poly[2-phenylene-(5-benzimidazole)] isophthalamide (PABI), an aromatic polyamide that shows good compatibility with rigid chain polymers such as poly(p-benzamide). The influence of the conditions of synthesis in determining the molecular weight of PABI has been investigated in order to use this polymer for rigid—flexible copolymers with specific characteristics. Values of [η] and Mw have been determined in 96% H2SO4 and dimethylacetamide, and conformational properties have been investigated by viscometry and molecular dynamics simulations.

Synthesis and X-ray structural investigation of 6-chloro-10-phenyl-1,2,3,4-tetrahydroacridine

An X-ray structural study of 6-chloro-10-phenyl-1,2,3,4-tetrahydroacridine prepared by the reaction of cyclohexanone with 2-amino-5-chlorobenzofenone was carried out. At 20°Ca=24.215(6),b=8.967(2),c=15.006(3) Å, β=115.57(2)°,V= 2939(1) Å3,dcalc=1.310 g cm−3,Z=4, space groupC2/c, 1324 reflections, λMoKα,R=0.038. The cyclohexene ring has a half-chair conformation. The phenyl substituent is rotated 71.2° with respect to the plane of the quinoline fragment.