Macroscopic orientation in side-chain liquid crystalline polyacrylates
The whole work presented in this thesis is constituted by three research projects aimed at understanding the macroscopic orientation of the mesogenic groups in side-chain liquid crystalline polymers (LCPs) and exploiting the utility of the infrared dichroism technique in the orientation studies. A series of liquid crystalline polyacylates, with different mesogenic groups and lengths of the flexible spacer, were synthesized and used for investigations. In the first study, we proposed a new approach making it possible to mechanically stretch side-chain LCPs in their liquid crystalline state; we showed that a strong macroscopic orientation could be achieved at small deformations, and the mechanical stretching was particularly efficient for the LCPs containing a short flexible spacer, which orientation was difficult to develop in a strong magnetic field. This study clearly revealed an opposite effect of the spacer on the macroscopic orientation in the mechanical and magnetic fields. In the second study, our investigations were focused on polymer blend systems containing a side-chain LCP and a conventional polymer as matrix. We showed, with very different matrixes, that mechanically stretching an immiscible blend was also highly effective to induce a macroscopic orientation. In the third study, we demonstrated the high potential of using infrared dichroism to study the time-dependent magnetic orientation in thin side-chain LCP films.
- Sciences – Mémoires