SYNOPSISThe synthesis and structure-property relations of a number of novel substituted paralinked aromatic homopolyamides and copolyamides are described. The synthesis of the polyamides was carried out by polycondensation of activated N,N'-bis-( trimethylsilyl ) substituted aromatic diamines and aromatic diacid chlorides. In order to improve the solubility and to lower melting temperatures, novel arylsubstituted terephthalic acids moieties, such asp -terphenyl-2,5-dicarboxylic acid and o-terphenyl-2,5-dicarboxylic acid, were used in combination with substituted and noncoplanar diamines. Depending on the chemical structure, polyamides with very high solubility ( u p to 40% w/w) in polar aprotic solvents such as N,N-dimethylacetamide without the addition of inorganic salts were obtained. Lyotropic liquid crystalline behavior was observed for the first time in polyamides which contain noncoplanar biphenylene units.
The substitution of poly@-phenylene terephthalate) and poly@-phenylene terephthalamide) with phenyl and biphenylyl substituents (Cbiphenylyl and 2-biphenylyl) in the terephthalic acid unit lowers the melting temperatures and crystallization tendency and increases the solubility. The melting temperatures of the polyesters are in the range of 285 -350 "C. Melting of the polyamides occurs between 440-490 "C. The polyamides begin to decompose in the same temperature range. In polyesters as well as in polyamides the 2-biphenylyl substituent was found to be more effective in decreasing the crystallinity, lowering the melt transition temperatures and increasing the solubility.
The arylation of monomers for high-performance polymers is described. The reaction of dibenzoyl peroxide with various 1,4-disubstituted benzene derivatives results in phenylation. Minimization of side reactions is discussed. The Ni-promoted reaction of Grignard compounds with iodoarenes was used to introduce the phenyl, biphenyl, and naphthyl substituent.
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