Poly Azole s

Several routes have been reported for the synthesis of aromatic poly(azole)s such as poly(benzimidazole), poly(benzoaxazole), and poly(benzthiazole) melt polycondensation of dicarboxylic acid diphenyl esters with tetramines21 and high-temperature solution polycondensation of dicarboxylic acids or their derivatives with tetramine hydrochlorides in PPA.22 PPA acts as condensing agent and solvent. Ueda etal.23 developed a modified method for the synthesis ofpolyazoles with the use of PPM A. 

The effects of various reaction conditions are examined in detail, in which 1 mmol oftetramine (23) or (24) is reacted with 1 mmol ofdicarboxylic acid (15). As for the amount of solvent, 5 ml of PPMA is appropriate for the 1-mmol scale reaction. A higher concentration makes it difficult for the reaction to proceed homogeneously, whereas a lower concentration reduces the rate of reaction. The reduced viscosity markedly increases with increasing temperature, and the polycondensation of 15 and benzidine (23) at 140°C results in a sufficiently high reduced viscosity of 0.90 dl/g in 24 h. The reaction of 2,2-bis(4-carboxyphenyl)-1,1,1,3,3,3-hexafluoropropane (15) with tetramines occurs slowly, requiring more than 24 h for completion, because (15) has the highly negative hexafluoroisopro-pylidene unit. 

The reduced viscosity ofpoly(benzimidazole) from 15 and tetramine (24) is not high enough under the reaction conditions described above in PPMA. The reaction at 200°C for 24 h in PPMA affords only a low-molecular-weight polymer in a low yield owing to low solubility in PPMA and sublimination of dicarboxylic acid (15). However, an improved reduced viscosity of 0.59 dl/g is attained by a two-step method, first at 140°C for 24 h and then at 200°C for 24 h. 

High-molecular-weight fluorine-containing aromatic poly(benzoxazole)s have not been obtained either by the direct solution polycondensation in PPA at 200°C or by the low-temperature solution polycondensation in DMAc at 0 to 5°C from 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoropropane and aromatic diacid derivatives because the fluorine-containing monomer has low nucleophilicity owing to the presence of the electron-withdrawing hexafluoroiso-propylidene unit. 

Mamyama et al.25 have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A,A 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoro-propane (25) with aromatic diacids and subsequent thermal cyclodehydration of the resulting poly(o-hydroxy amide)s in vacuo. In this method, aromatic diamines with low nucleophilicity are activated more positively through the conversion to the /V-silylated diamines, and the nucleophilicity of the fluorine-containing bis(o-aminophenol) can be improved by silylation. 

Maruyamaera/. have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A/Al 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3 -amino-4-hydroxy phenyl)-1,1,1,3,3,3-hexafluoro- 

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In polymer solar cells, poly(9,9-dialkylfluorene-alt-dithienylbenzothiadi-azole)s (PFTBTs) have been developed to achieve power conversion efficiencies (PCEs) of 4.5%. Upon changing the alkyl side chains, the performance of... 

As high temperature PEMs, random copolymers containing poly(imide benzimid-azole)s (PI-PBIs) and poly(benzimidazole-amide)s were synthesized by Fang et al. [128]... 

Finally, it should be mentioned that the aromatic polyimides were the forerunners of a diversified group of thermostable polymers having heterocyclic moieties in their repeat units, for example, poly(benzimidazole)s, poly(benzox-azole)s, poly(benzthiazole)s, poly(benzobisthiazole)s, poly(l,3,4-oxadiazole)s. 

Scheme 4 Proposed stacking structure. The plane-to-plane distance d for the polymer shown in No. 19 is about 3.8 A [93-95], which is somewhat shorter than the d value (about 3.85 A) reported for head-to-tail-type poly(3-alkylthiophene) HT-P3RTh [128,129] and somewhat longer than the d values (3.6-3.65 A) observed with head-to-head-type poly(4-alkylthiazole-2,5-diyl) [124,129,130] and the charge-transfer-type copolymer of thiophene and 4-alkylthi-azole [131]. Poly(ethylenedioxythiophene) gives a similar d value (3.8 A) [132]. The existence of S in the aromatic ring seems to make the distance d longer...

M. Baibarac, P. Gomez-Romero, M. Lira-Cantu, N. Casan-Pastor, N. Mestres, and S. Lefrant. Electrosynthesis of the poly(V-vinyl carb-azole)/carbon nanotubes composite for applications in the supercapacitors field. Eur Polym. J., 42(10) 2302-2312, October 2006. 

N. Blouin, A. Michaud, D. Gendron, S. Wakim, E. Blair, R. Neagu-Plesu, M. Belletete, G. Durocher, Y. Tao, M. Leclerc, Toward a Rational Design of Poly( 2,7-Carb azole) Derivatives for Solar Cells. /. Am. Chem. Soc. 2008,130, 732-742. 

J.A. Asensio, S. Borrows, P. Go mez-Romero, Polymer electrolyte fuel cells based on phosphoric acid-impregnated poly[2,5-benzimid-azole] membranes, J. Electrochem. Soc. 151 (2)(2004)A304-A310. 

FIGURE 7.25 P NMR spectrum of poly-VPCP (a) in CDCI3 and PVTP (b) in OMSO-d. (Reprinted from Polymer, 54, Alidagi, H.A., Girgic, O.M., Zorlu, Y., Hacivelioglu, R, Celik, S.U., Bozkurt, A., Kilic, A., and Yesilot, S., Synthesis and proton conductivity of azole-substituted cyclic and polymeric phosphazenes, 2250-2256, Copyright 2013, with permission from Elsevier.)... 

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