No abstract

A novel aromatic diacid, 3, 5‐dicarboxyl‐4′‐amino diphenyl ether, containing pendant phenoxy amine group was synthesized. Homo‐ and co‐polybenzimidazoles containing different content of pendant phenoxyamine groups were synthesized by condensation of 3,3′‐diaminobenzidine with this acid and a mixture of this acid and isophthalic acid in different ratio in polyphosphoric acid. Copolybenzimidazoles with structural variations were also synthesized based on this acid and pyridine dicarboxylic acid, terephthalic acid, adipic acid, or sebacic acid. The polymers have good solubility in polar aprotic solvents and strong acids and they form tough flexible films by solution casting. The polymers were characterized by different instrumental techniques (FTIR, TGA, DSC, XRD, etc.) and for solvent solubility, mechanical properties, inherent viscosity, and proton conductivity. The inherent viscosities of the polymers vary in the range of 0.62–1.52 dL/g. They have high thermal stability up to 475–506 °C (IDT) in nitrogen, high glass transition temperatures (Tg) ranging from 313 to 435 °C and good tensile strength ranging from 58 to 125 MPa. Proton conductivity of homo polymer is 3.72 × 10−3 S/cm at 25 °C and 2.45 × 10−2 S/cm at 200 °C © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5776–5793, 2008

Polybenzimidazole (PBI) polymers tethered with N-phenyl 1,2,4-triazole (NPT) groups were prepared from a newly synthesized aromatic diacid, 3 0 -(4-phenyl-4H-1,2,4-triazole-3,5-diyl) dibenzoic acid (PTDBA). The obtained polymers show superior thermal and chemical stability and good solubility in many aprotic solvents. The inherent viscosities of all polymers were around 1 dL/g. They exhibit high thermal stability with initial decomposition temperature ranging from 515 to 530 C, high glass transition temperature ranging from 375 to 410 C, and good mechanical properties with tensile stress in the range of 66-98 MPa and modulus 1897-2600 MPa. XRD analysis indicates that these polymers are amorphous in nature. Physicochemical properties such as water and phosphoric acid-uptake, oxidative stability, and proton conductivity of membranes of these polymers have also been determined. The proton conductivity ranged from 4.7 Â 10 À3 to 1.8 Â 10 À2 S cm À1 at 175 C in dry conditions.

The present state-of-the-art in anticorrosive coatings technology is a multistep process where multilayered hybrid coatings are applied on metallic substrates with each layer having certain functionality and properties. These layers are mainly an interfacial layer, such as inorganic phosphate coatings and/or sol-gel hybrid coatings, which are accompanied by a paint/polymer topcoat. While the main characteristic of the polymer topcoat is a "barrier" role to prevent the diffusion of corrosive species to the metal surface, the primer or the first layer in contact with metal surface is of significant importance due to its role in "active" corrosion prevention capability and promotion of strong adhesion between the substrate surface and subsequent layers. In this article, recent developments in processing and functional properties of zinc-phosphate sacrificial primers and sol-gel-based hybrid coatings will be overviewed. Finally, some of the innovative advancements in this area developed by this research group and others will also be discussed.

Polybenzimidazoles containing different contents of pendant nitrophenoxy groups were prepared by condensation of 3,3 0 -diamino-benzidine with a mixture of 3,5-dicarboxyl-4 0 -nitro diphenyl ether and isophthalic acid (IPA) in different ratios in polyphosphoric acid. The polymers are soluble in polar aprotic solvents, they have inherent viscosities in the range of 0.75-1.10 dL g À1 and they form tough and transparent films on solution casting. They have good thermal stability with initial decomposition temperature ranging from 380 to 416 C in nitrogen, good tensile strength ranging from 56 to 65 MPa and reasonably good oxidative stability. Phosphoric acid uptake of these polymers is low compared with PBI and membranes doped with phosphoric acid exhibit good proton conductivity in the range of 6.6Â 10 À3 to 1.9Â 10 À2 S/cm at 25 C and 1.2Â 10 À2 to 4.9Â 10 À2 S/cm at 175 C, compared with 3.9Â 10 À3 S/cm at 25 C and 3.2Â 10 À2 S/cm at 175 C for PBI. These membranes are suitable for applications as polymer electrolyte for fuel cell and presumably for gas separation at high temperature.