LYOTROPIC LIQUID-CRYSTALS OF A SOLUBLE POLYDIACETYLENE - A COMPARATIVE INVESTIGATION BY MEANS OF OPTICAL AND ELECTRON-MICROSCOPY

The liquid crystalline properties of a concentrated solution of poly{5 ,7-dodecadiyne-1,12-diol bis[((4-butoxycarbonyl)methyl)urethane]} (P-4 -BCMU) -a soluble polydiacetylene- in chloroform, beyond the critical concentration, have been investigated. Optical microscopy shows the an isotropic liquid crystal solution of P-4-BCMU in chloroform to be a po lymer nematic. Disclinations with strengths of s= +1/2 and -1/2 are th e most frequent type. Some disclinations with s = +1 were observed, bu t rarely disclinations with s = -1. Therefore, the liquid crystal text ure usually displays a schlieren with two brushes in the vicinity of t he singularities. The supramolecular structure observed by transmissio n electron microscopy shows a lamellar type morphology. As previously shown, the thickness of the lamellae is correlated to the molecular ch ain length. The chain length distribution leads to segregation with re spect to molecular length and can be observed by thickness variations of both individual and subsequent lamellae. A kinetic study of disclin ation annihilation induced by isothermal relaxation in the liquid crys talline phase is presented. Possible mechanisms of the relation of the lamellar texture and the disclination annihilation are discussed. A s tripe texture observed over large regions of the solid film is suggest ed to be a decoration effect due to internal stress as a result of sol vent evaporation when the films are prepared by solution casting.