Polycyclocondensation

There are two possibilities for practical implementation. If the polymers with the heterocyclic groups are to be isolated in powder form, the polycyclocondensation can be achieved in the same reaction mixture, i.e., in solution. However, if the polymer is to be isolated in the form of fibers, foils, coatings, or adhesives, the following procedure is appropriate The soluble, still reactive polymers of the first reaction step are poured out, e.g., as a film, or spun into a fiber. Then the solvent is evaporated and afterwards the polycyclocondensation is carried out by heating the finished article in the solid state. 

Preparation of a Polyimide from Pyromellitic Dianhydride and 4,4 -0xydianiline by Polycyclocondensation... 

The polyimide is formed by the thermal polycyclocondensation of the poly(amide acid). For this purpose, 5 ml of poly(amide acid) solution are placed on a watch glass (diameter 10 cm) and kept in a vacuum oven at 50 °C for 24 h.The solvent evaporates and at the same time cyclization to the polyimide takes place the resulting film is insoluble in dimethylformamide.The formation of the polyimide can be followed by IR spectroscopy the NH-band at 3250 cm disappears while imide bands appear at 1775 and 720 cm" Once the initial drying process has raised the solid content to 65-75%, the polyimide formation can be accelerated by heating the poly(amide acid) film to 300 °C in a vacuum oven for about 45 min.The polyimide made from pyromellitic dianhydride and 4,4 -oxydianiline exhibits long-term stability in air above 200 °C. 

The technical production of poly(benzimidazole) (PBI) is also carried out in two steps. In the first step an aromatic tetramine is condensed with the diphenyl ester of an aromatic dicarboxylic acid at 220-260 °C, yielding a poly(amino amid) with elimination of phenol. Ring closure with elimination of water occurs in the second step (solid-phase polycyclocondensation), conducted at 400 °C and yielding the polybenzimidazole (experimental procedure, see Table 2.3). 

High-temperature (160-180 °C) polycyclocondensation of the starting monomers in w-cresol, using quinoline as catalyst. In almost all cases polyimides obtained in w-cresol demonstrated higher solution viscosities than the same polymers synthesised in NMP. 

Synthesis of polyimides containing benzothiazole-2-sulfide groups was carried out using high-temperature polycyclocondensation in w-cresol in accordance with Scheme 5.7 [41, 44]. All the polyimide synthesis reactions were homogeneous and yielded polymers having reduced viscosities Pred = 0.29-0.42 dl/g, Tg = 215-265 °C and 10% weight loss temperature = 325-400 °C (Table 5.9). 

The fact that all bis(naphthalic anhydrides) display lower reactivity than naphthalene-1,4,5,8-tetracarboxylic acid dianhydride, has predetermined an expedient synthesis of their polyheteroarylenes. It involves catalytic processes which find wide application in polycondensation and polycyclocondensation reactions [154, 155]. 

Synthesis of polynaphthoykiKbenzimidazoks based on 3,3, 4,4 -tetraamino-diphenyl oxide was a heterogeneous proce irrespective of the nature of the applied bis(naphthalic anhydride), while synth is of polynaphthoylenebenzimidazoles based on 2,2-bis(3,4-diaminophenyl)-hexafluoropropane was a homogeneous one. Irrespective of homogeneity or heterogeneity of the polycyclocondensation processes, the d ired polymere were obtained in quantitative yields and were characterized by high degree of cyclization. Some characteristics of the synthesized polynaphthoylenebenzimidazoles are set out in Table 17. 

Polycyclocondensation, high-temperature catalytic 142, 146, 148-162 Polydimethylacrylamide 19 Polyelectrolytes, water-soluble 49 Polyethylene glycol nonyl phenol 58 Polyheteroarylenes 158, 162, 167 Polynaphthoylenebenzimidazoles 118,146-165... 

Sulfonated ACPs are prepared both by direct sulfonation and by polycondensation and polycyclocondensation of sulfonated compounds. Synthesis of the first sulfonated poly(p-phenylene) was reported by Wegner and co-workers [103]. The Suzuki coupling of diboronic ethers with dibromo-aromatic monomers furnished poly(p-phenylene) with 95% yield. 

PBI membranes loaded with high levels of phosphoric acid were prepared using a new sol-gel process [190]. This process, termed the PPA process, uses PPA as the condensing agent for the polycyclocondensation and the membrane casting solvent. After casting, absorption of water from the atmosphere causes hydrolysis of the PPA to phosphoric acid. 

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