Polyalkplisocyanates so as aromatic polyamides have great importance for their ability to show liquid crystal properties. And so many of them are used for very high - strength synthetical Fibre materials. This work deals with delute solutions of polyisocyanates, their copolymers, aromatic polyamides and macromolecules with heterocycles in main chain. Hydrodynamic and optical properties of these polyamides are investigated by viscometry and flow birefringence methods. Experimental results are compared with those for different polyamides studied. LC macromolecules show rigid worm - like chains behavior.