RIGID-ROD POLYMERS WITH FLEXIBLE SIDE-CHAINS .10. THERMOTROPIC MESOPHASES FROM AROMATIC STIFF-CHAIN POLYAMIDES BEARING N-ALKOXY SIDE-CHAINS

The synthesis of stiff-chain poly(1,4-phenylene terephthalamide)s subs tituted by two as well as by four flexible side chains per repeating u nit is described. The solubility of the materials bearing only two sid e chains is still very low. Appending of four side chains leads to pol yamides which dissolve in common organic solvents. All polyamides repo rted herein form layered structures in the solid state as well as in t he mesophase. Polyamides with two side chains have a very weak tendenc y for crystallization and do not exhibit a transition to the isotropic state even for the longest side chains. Polyamides with four side cha ins show three reversible thermal transitions: a disordering transitio n of the side chains, a transition to a layered, smectic-like mesophas e, and finally the transition to an isotropic melt. It is shown that t he phase behavior of these materials is mainly governed by the strong segregation of main- and side-chains which can be compared best to the microphase separation in block copolymers.