Aromatic polyazomethines

Research Focus Simplified method for preparing conjugated aromatic polyazomethine thiophene derivatives. 

Aromatic polyazomethines are apparently still the most interesting thermotropic polymers of classes other Aan aromatic polyesters for fabrication of high-strength fibers [72]. These polymers are prepared by polycondensation of aromatic diamines with dialdehydes ... 

Rotaxane polymers can also be deemed as polyrotaxanes or pseudopolyro-taxanes, because they have the common structural characteristics that is, many macrocycles reside on a polymer chain. However, unlike polyrotaxanes or polypseudorotaxanes, which are synthesized from the slipping of macrocycles into a polymer chain, rotaxane polymers are synthesized from the polymerization of rotaxane (or pseudorotaxane) monomer, and monomer unit on the polymer chain has one macrocycle. Harada [16] reported the preparation of a rotaxane polymer based on the homopolymerization of bithiophene (2T) pseudorotaxane. Bithiophene formed hrst inclusion compound a-CD-2T with a-CD, and then the polymerizations of a-CD-2T in water using EeCls as an oxidative initiator after centrifugation, the resulting powder was washed with water and THE to remove unreacted monomer and the corresponding rotaxane polymer was found as deep purple powder. Earcas et al. [17] developed a novel aromatic polyazomethine polymer with rotaxane architecture by the copolymerization of a diformylcarbazole derivative with a benzenediamine pseudorotaxane in DME. 

The synthesis of thermotropic polyurethanes, polyethers and aromatic polyazomethines has been reported by other researchers, but at present research on MCLCPs of the type described in this section is concentrated in academia and there has as yet been no major industrial exploitation. Block copolymers of polyarylsulphones and ketones " " are currently exciting interest in a number of laboratories. These have been prepared by synthesizing polyaryl sulphones or ketones with phenolic functionality, acetylating the end groups, and treating these functionalized blocks like a diphenol in a conventional LCP polymerization process. 

Representative classes are found in wholly aromatic polyesters, aromatic-aliphatic polyesters, wholly aromatic polyesteramides, aromatic-aliphatic polyesteramides, aromatic polyazomethines, aromatic polyester-carbonates, etc. 

Novel 1,3,4-oxadiazole-containing polyazomethines have been synthesized by the polycondensation of diamines, 2,5-bis(z -aminophenyl)-l,3,4-oxadiazole and 2,5-bis(/>-aminophenyl)-l,3,4-oxadiazole with aromatic dialdehydes, isophthaldehyde, and terephthalaldehyde (example follows), in -cresol at 20°C (54). 

Melt poly condensation is also the most popular method for other thermotropic condensation polymers, including the polyazomethines where the reaction between aromatic aldehydes or ketones and primary amines with elimination of water leads to azomethine (Schiffs base) formation 48). 

An aromatic polyazomethlne structure is shovm in the first line of Table 1. The literature of polyazomethines is voluminous but in general these materials have been reported to have poor solubility and to be unmeltable, and therefore difficult to characterize (1-9). On the other hand, mono and blsazomethlnes with appropriate terminal groups were among the early substances found to exhibit a liquid crystalline state. 

---