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SYNOPSISNew aromatic poly-1,2,4-triazoles and poly-l,3,4-oxadiazoles are studied as thermally stable membrane materials. Various groups were introduced onto the pendant phenyl groups of poly-1,2,4-triazoles. Glass transition temperature, degradation temperature, and cold crystallization behavior were studied as a function of these groups. Cold crystallization appeared to be highly sensitive to macromolecular regularity. The solubility of poly-l,3,4-oxadiazoles was highly improved upon incorporation of 5-t-butylisophthalic, 1,1,3-trimethyl-3-phenylindane, 4,4'-( 2,2'-diphenyl) hexafluoro propane, and diphenyl ether groups into the polymeric main chain, whereas the high glass transition temperatures and degradation temperatures typical for aromatic poly-1,3,4-oxadiazoles were maintained. 0 1994 John Wiley & Sons, Inc.Keywords: poly-1,3,4-oxadiazoles polyhydrazide poly-1,2,4-triazoles cold crystallization I NTRODU CTl O N Aromatic poly-1,2,4-triazoles and poly-1,3,4-oxadiazoles are studied as new thermally stable membrane materials for gas separation applications, especially poly [ p -, n-phenylene-(4-phenyl) -1,2,4-triazole], which is known for its excellent gas separation properties.' The use of these polymers as membrane materials is hampered due to their poor solubility, which limits the number of possibilities of fabricating membranes with a desired morphology, like asymmetric structures. For example, poly ( p -, nphenylene ) -1,3,4-oxadiazole is soluble only in concentrated sulphuric acid, which is a very difficult solvent to handle in practice.In this article we wish to report the syntheses and physical properties of poly-1,3,4-oxadiazoles and poly-1,2,4-triazoles where various functional groups are incorporated into and onto the polymer backbone with the aim of increasing their solubility while maintaining their thermal stability. The relationship between the gas separation properties and these molecular structures was also studied and is reported elsewhere.2 The solubility of polymers is often increased when flexible bonds, large pendant groups, or polar substituents are incorporated in the polymer backbone. The introduction of large pendant bulky groups along the polymer backbone results in a less ordered polymer matrix increasing the solubility characteristics. This is nicely illustrated by the fact that poly ( p -, m-phenylene) -1,3,4-oxadiazoles are soluble only in concentrated sulphuric acid while poly [ p -, m-phenylene-(4-phenyl) -1,2,4-triazoles], having an extra pendant phenyl group, are also soluble in mcresol and formic acid.Solubility is also highly increased if, instead of aromatic groups, aliphatic groups are incorporated into the polymer backbone, but a significant reduction in thermal stability is also observed. Incorporation of aliphatic groups for that reason was avoided. ( Nonetheless, cyclohexane was incorporated as a comparison to the aromatic poly(p-, mphenylene-1,3,4-oxadiazoles. ) A number of authors have reported poly ( 1,3,4-oxadiazoles ) with increased solubility characteris-ti...

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New thermally stable conducting materials can be obtained by dispersing conducting carbon black into poly(4,4Ј-diphenylether-1,3,4-oxadiazole) (POD-DPE) solution in NMP. The blend preparation process resulted in quite good dispersed composite and a relatively low percolation threshold (around 5 wt % of CB). The effect of the compressive stress on the resistivity of composite has been evaluated. The resistivity decreases continuously as the applied pressure is increased. In addition to the electrical conductivity, the presence of carbon black resulted in higher thermally stable materials. The thermal stability, electrical conductivity, and pressure-sensible characteristics make this conducting material a good candidate for application in manufacture of pressure sensors for high temperature ambient. This material shows a typical semiconductor behavior, characterized by an increase of conductivity with the temperature.

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