Py-PBI

Fig. 26 (a) Structures of pyridine-, terpyridine-, and thiol-terminated PBI derivatives with different substituents at the bay positions X and X . The inset illustrates the alternation of optical properties of the PBIs with different bay-area substituents, (b) Plateau data-point histogram of Py-PBI in a mixture of mesitylene/THF (4 1). bias = 0.1 V, tip retraction rate was 60 nm s-1. The inset show the bias voltage dependence of the current through a molecular junction... 

The PBI molecules studied include pyridyl-(P-PBI), terpyridyl (TP-PBI), and thiol-terminated (T-PBI) perylene-3,4 9,10-tetra-carboxylic acid bisimides, that contain bulky ferf-butylphenoxy substituents at 1,6,7,12 bay positions, and pyridyl-(Py-PBI) and terpyridyl- (TPy-PBI) terminated perylene-3,4 9,10-tetra-carboxylic acid bisimides, that contain bulky pyrrolidinyl substituents at 1,7 bay positions (Fig. 26a) [327-329]. 

Jana et al. prepared alternative tetraamine monomer, 2,6-bis(3, 4 -diaminophenyl)-4-phenylpyridine (Py-TAB), for synthesizing pyridine bridge polybenzimidazole (Py-PBI) (Figure 5.15) [42]. 

Jana et al. reported that HFA containing PBI polymer (Figure 5.15) absorbed less water and also that the swelling ratio was low due to the presence of hydrophobic fluorine atoms in the polymer chain. This polymer was chemically stable, with only -10% weight loss after 120h in Fenton s reagent. The Py-PBI membrane was doped with a different percent of... 

Pyridine polybenzimidazoles (py-PBIs, Fig. 5d) have been investigated for their use in fuel cells because of their high concentration of basic sites (amine and imine groups). Similar to AB-PBI, the high concentration of basic sites allow these polymers to have a high affinity to acids. The pyridine moiety is commonly combined with the traditional PBI stmcture by including it as part of the backbone structure. 

Fig. 13.8 Polarization curves under hydrogen and oxygen gases at various temperatures of PA-doped 2,5-py-PBI membranes [30]...

Other PBIs CaroUo et al. [ 109] synthesized a series of PBls with different numbers of N-atoms, that is, different basicities, including poly(2,2 -(2,6-naphthalin)-5,5 -bibenzimidazole) (naphthalin-PBI) (Fig. 4.6d) and poly(2,2 -(2,6-pyridin)5,5 -bibenzimidazole) (Py-PBI) (Fig. 4.6b). They found that both the acid doping level and the proton conductivity remarkably increased with the membrane molecular weight and basicity, which depend on the amount of NH groups as well as on their position in the polymer backbone. In addition to Py-O-PBI (Fig. 4.6c), OO-PBI (Fig. 4.6e) was synthesized by a standard polycondensation reaction of 3,3, 4,4 -tetraaminodiphenyl... 

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