Optically anisotropic aromatic polyamide dopes

Abstract

Compositions or dopes comprising carbocyclic aromatic polyamides in suitable liquid media are prepared which are optically anisotropic (exhibit different light transmission properties in different directions in the dope). These dopes, and related isotropic dopes, are used in preparing fibers of unique internal structure (evidenced by low orientation angle and/or high sonic velocity) and exceptionally high tensile properties (e.g., initial modulus).

What is claimed is: 
     
       1. Optically anisotropic dope consisting essentially of: I. at least about 5 percent by weight of a polymer having an inherent viscosity of at least 0.7 and consisting essentially of at least one type of carbocyclic aromatic homo- or copolyamide having chain extending bonds from each aromatic nucleus which are coaxial or parallel and oppositely directed, and   II. at least one liquid medium selected from the group consisting of: A. amides and ureas selected from the group consisting of: N,N-dimethylacetamide, N,N-dimethylpropionamide, N,N-dimethylbutyramide, N,N-dimethylisobutyramide, N,N-dimethylmethoxyacetamide, N,N-diethylacetamide, N-methylpyrrolidone-2, N-methylpiperidone-2, N-methylcaprolactam, N-ethylpyrrolidone-2, .[.N-acetylpyrrolidone.]..Iadd.N-acetylpyrrolidine.Iaddend., N-acetylpiperidine, N,N'-dimethylethyleneurea, N,N'-dimethylpropyleneurea hexamethylphosphoramide, and N,N,N',N'-tetramethylurea and containing a salt from the group consisting of lithium chloride and calcium chloride   B. concentrated sulfuric acid,   C. hydrofluoric acid, and   D. chloro-, fluoro- or methane-sulfonic acids, said polymer being present in the dope in a concentration above the level at which there is a decrease in viscosity with increasing concentration represented by a sharp discontinuity in the slope of the plot of the dope viscosity vs. polymer concentration curve without the formation of a solid phase.     
     
     
       2. Dope of claim 1 wherein said liquid medium is concentrated (greater than about 98 percent by weight) sulfuric acid which may contain free SO 3 .