Poly aromatics pyrrole

Poly(N-phenyl-3,4-dimethylenepyrroline) had a higher melting point than poly(N-phenyl-3,4-dimethylenepyrrole) (171° vs 130°C). However, the oxidized polymer showed a better heat stability in the thermogravimetric analysis. This may be attributed to the aromatic pyrrole ring structures present in the oxidized polymer, because the oxidized polymer was thermodynamically more stable than the original polymer. Poly(N-phenyl-3,4-dimethylenepyrroline) behaved as a polyelectrolyte in formic acid and had an intrinsic viscosity of 0.157 (dL/g) whereas, poly(N-pheny1-3,4-dimethylenepyrrole) behaved as a polyelectrolyte in DMF and had an intrinsic viscosity of 0.099 (dL/g). No common solvent for these two polymers could be found, therefore, a comparison of the viscosities before and after the oxidation was not possible. 

VV -values for bromoform and pyrrole, acidic liquids, against poly(vinyl chloride), an acidic polymer, and dimethyl sulfoxide, a predominantly basic liquid, against polyfmethyl methacrylate), a basic polymer, but large values for the acidic liquids against PMMA and the basic liquid against PVC. 2-Iodoethanol, a bifunctional liquid, showed appreciable -values with both polymers. Despite these results in line with expectations, other results based on wettability measurements are not so clear-cut. For example, Vrbanac [94] found significant apparent acid-base interactions of various aromatic liquids against poly(ethylene), presumably a neutral substrate. 

The oxidation of poly(N-phenyl-3,4-dimethylenepyrroline) with DDQ or Pd/C in nitrobenzene gave in a cyclic aromatic amine polymer with repeating pyrrole rings in the polymer backbone. Using Pd/C in... 

These polymers, particularly poly(pyrrole), are most conveniently prepared from the parent molecule via electrolysis. So far, furan, pyrrole, thiophene, and various methylated derivatives have been polymerized by this procedure (10). The anodic polymerization apparently also works for relatively electron rich aromatic compounds such as aniline and azulene (11). 

Following the application of 3-cresol and anisole, induction of P. putida TVA8 was achieved and there are some studies (e.g., Boyd and Sheldrake, 1998), suggesting several substrates and mono- and poly-cyclic aromatic rings may be cleaved by toluene dioxygenase. Other cyclic compounds (e.g., pyrrole, pyridine, and furan) also induce P. putida TVA8, but the specific mechanism and enzymes involved are unknown. Further studies on this aspect are required to comprehensively address this question. 

Recently, it was found that poly(phospholes) provide an even better perspective for such devices (06CRV4681). Indeed, the calculated aromaticity of the unsubstituted phosphole is quite low in comparison with that of pyrrole in terms of aromatic stabilization energy (ASE) and nucleus-independent chemical shift (NICS) pyrrole, ASE = 25.5 (kcal/mol), NICS =—15.1 (ppm) phosphole, ASE 7.0 (kcal/mol), NICS = -5.3 (ppm) (06CRV4681). 

Beller and coworkers recently reported a new strategy for the synthesis of poly-substituted anilines based on a three-component-coupling reaction and a domino deprotec-tion/aromatization reaction (equation l)44. A mixture of O-benzyl carbamate, p-toluene-sulfonic acid, aldehyde, AC2O and dienophile in /V-rnclhy I pyrrol idone was allowed to react for 24 h at 120 °C, followed by Pd/C catalyzed dehydrogenation in triglyme at 140 °C. A variety of tri-, tetra- and penta-substituted anilines were efficiently created by this domino process. 

Poly(phenylenebutadiynylene)s, PPBs, having small substituents at the phenylene moiety, are almost insoluble in most organic solvents. Substitution of the phenylene to another unsubstituted aromatic moiety such as pyrrole, pyridine or thiophene is not effective in solubilizing the polymer. These insoluble PABs are difficult to use in optolectronic applications because of poor processability, but they can be used as precursor polymers for carbon [40]. 

The improved electrochemical synthesis (7) of poly pyrrole has led to its use as coating for the protection of n-type semiconductors against photocorrosion in photoelectrochemical cells. (8,9) Recently, it was announced that pyrrole was not the only five-membered heterocyclic aromatic ring compound to undergo simultaneous oxidation and polymerization. Thiophene, furan, indole, and azulene all undergo electrochemical polymerization and oxidation to yield oxidized polymers of varying conductivities (5 x 10 3 to 102 cm- ). (10-13) The purpose... 

Arylene-bis-(pyrrole dicarboxylic acid anhydrides) were prepared by the condensation of two moles of diethyl diacetyl succinate with one mole of aromatic diamine, followed by hydrolysis and dehydration. Condensation of these novel dianhydrides with various aromatic diamines resulted in the formation of poly (amic acids) which were further condensed to polyimides. If the diethyl diacetyl succinate and aromatic diamine were reacted in equimolar quantities an N-(amino aryl) pyrrole diester was formed which can be further condensed to give polyimide directly. 

Biswas and Roy [126] also studied the thermal stability characteristics (Table 16.7) of chemically prepared pyrrole (PY) modified poly-N-vinylcarbazole (NVC) composite P(PY-NVC) and reported the percentage weight losses for PPY, PNVC and P(PY-NVC) during thermal degradation. It was observed that the thermal stability of P(PY-NVC) was intermediate between those of individual components. 50% weight loss was recorded at 400°C in the case of PPY, at 450°C for PNVC and at 425°C for P(PY-NVC) respectively. They inferred that the thermo-oxidative breakdown of aromatic linkages of the polymer matrix occurs in the temperature range of 300-550°C in case of P(PY-NVC)... 

The electrodeposition method is particularly useful for preparation of poly pyrroles since a wide range of materials can be prepared. For example in our laboratories a range of polymers containing sulfonated aromatics (Table 1) have been prepared as have composite polymers based on incorporation of polyelectrolytes such as polyvinylsulfonate or Nafion (4). This flexibility in synthesis is extremely important since the polymer composition determines the transport properties that can be achieved. 

A number of conjugated heterocyclic polymers, viz., poly(pyrrole) [9], poly(p-phenylene) [10], poly(thiophene) [11], and poly(aniline) [12] are also electrically conducting and continue to be developed and studied for electrochromic devices [13-14 see also the companion chapter in this volume] and ion switching devices [15-16], among others. Polymer films with high electrical conductivity have been generated by electrochemical polymerization of benzenoid, nonbenzenoid and heterocyclic aromatics, in particular from the derivatives of pyrrole, thiophene, carbazole, azulene, pyrene, triphenylene and aniline. The electrochemical approach for making these films is very versatile and it provides a facile way to vary the properties of the films. The realization of the applications for each electroactive polymer depends on the control and particularly the enhancement of the... 

Polymers with heteroaromatic units such as PT and poly(pyrrole) and their derivatives are nondegenerate in their ground state and possess two possible types of structure the aromatic and the quinoid structure (Fig. 2). 

In general, one anion is incorporated for every three pyrrole units. Exceptions are pyrrole- or thiophenesulfonic acids where the counterion is coupled directly to the monomer (self doping) [55]. Some typical conducting anions are fluoroborate, perchlorate, aromatic sulfonic acids, penicillin, -dodecyl sulfate phthalocyanine sulfonic acid, poly(styrenesulfonicacid), styrene sulfonic acid, and heparin [13]. 

Other groups developed alternative methods toward the synthesis of poly(arylenemethine)s. For example, the condensation of 2-(chloromethyl)-5-formylfuran with pyrrole and thiophene, or the reaction of a,a,a -trichloro-p-xylene with aromatic compounds in the presence of Friedel-Crafts catalyst [842], was reported. The condensation of 2-lithiothiophene with 2,5 -dithiophenedicarbox-aldehyde or 2,5-dilithiothiophene with 2-formylthiophene gives a... 

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