Aromatic polyamides and polyhydrazides containing the oxalyl group

43 Aromatic polyamides and polyhydrazides containing the oxalyl group 

Fibres containing the oxalyl unit in the polymer chain are also newcomers to the scene. For convenience we describe them under a separate heading although formally they belong in the two classes already discussed. Two types of structure have been reported, one (XII) belonging to the polyamide class while the other (XIII) is a polyhydrazide.  

No doubt both the structures shown above are idealised since some block formation is to be expected in these polymers. Both polymers (J and K in Table 2) are prepared in the familiar way from terephthaloyl chloride and mixtures of the requisite diamines or diahydrazides in amide-LiQ solvents and wet spun from the same solvents. 

Like the polyhydrazide fibres described in the previous section these oxalyl-containing fibres develop their highest moduli on heat treatment and are capable of a limited amount of drawing. The polyoxamide XII seems to be able to stand the higher treatment temperature. After a pre-drawing at a moderate temperature it increases its modulus almost without drawing when heated to 500° in a way reminiscent of polymers A and B. 

Essentially we find in the literature just two polymers which have been spun to such fibres. Their preparation is simplicity itself merely requiring the bringing together of 2,5-dimethyl piperazine (XIV) and a bis-isocyanate of the type (XV) (where R = H or CH3) in a suitable solvent such as dimethylacetamide-lithium chloride. The resulting viscous polymer solution may be employed as the spinning dope. 

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