RIGID-BACKBONE POLYMERS .18. STRICTLY ALTERNATING RIGID-FLEXIBLE POLYAMIDES

Experimental data are presented which show that in strictly alternating rigid-flexible copolyamides with the axial ratio x of their rigid elements between 3 and 3. 5, lyotropic liquid crystallinity exists in solutions of 25-40% polymer. For polymers having 4. 0 less than x less than 4. 5, anisotropic solutions appear in the concentration range 15-25%. These axial ratios are substantially smaller than the value of x//c equals 6. 4 predicted by theories for independent rodlike particles, but are in qualitative agreement with recent theoretical calculations taking cognizance of the connection of rodlike elements by flexible residues in the polymer chain. It is further shown that solid solutions of a model compound in an alternating rigid-flexible polymer may be prepared, provided there exists shape and size similarity between the model compound and the polymeric repeat unit.