Syntheses and properties of related polyoxadiazoles and polytriazoles

Abstract

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...

A New Class of Aromatic Poly(1,3,4-oxadiazole)s and Poly(amide-1,3,4-oxadiazole)s Containing (Naphthalenedioxy)diphenylene Groups

“…Many efforts have been made to improve the solubility and lower the T g , hence to make such polymers more easily processable, for example by incorporating flexible linkages in the backbone or bulky pendant group on the aromatic rings. [12][13][14][15][16][17][18] Several different reaction pathways have been developed to prepare poly(1,3,4-oxadiazole)s. The most popular synthesis involves the preparation of a precursor polyhydrazide by the reaction of a diacyl chloride or derivative with hydrazine or a dihydrazide compound. This precursor polyhydrazide is cyclized to the polyoxadiazole by heating to 200-300 • C under vacuum or heating in a dehydrating solvent such as sulfuric acid, polyphosphoric acid, or phosphoryl chloride.…”

Synthesis and Properties of Novel High-Electron-Affinity Polymers for Electroluminescent Devices

“…In order to obtain processible and colorless main chain oxadiazole polymers, the introduction of a flexible linkage on the main chain has proven effective, as the flexible linkage not only interrupts the conjugation, but also induces torsion of the molecular chain (32). A typical example is poly(phenylene-1,3,4-oxadiazole-phenylene-hexafluoroisopropylidene) (PPOPH) (Figure 7) which is soluble in chlorinated solvents (33,34). Yang and Pei reported the use of PPOPH as the electron injection layer in MEH-PPV based LEDs (35).…”

Novel thermally stable poly(amine hydrazide)s and poly(amine‐1,3,4‐oxadiazole)s for luminescent and electrochromic materials

“…Highly aromatic polyoxadiazoles and their precursors (polyhydrazides) are generally difficult to process because of their infusible and insoluble properties. Many efforts have been made to improve the solubility and lower the glass‐transition temperature ( T g ) and, therefore, make such polymers more easily processable, for example, by the incorporation of flexible linkages into the backbone or bulky pendant groups onto the aromatic rings 12–18…”