Electric-field-induced segmental reorientation in ferroelectric liquid crystalline polymers and elastomers

Macroscopically oriented ferroelectric liquid crystalline elastomers were p repared by UV-induced cross-linking of the corresponding polymer. Time-reso lved FT-IR spectroscopy is employed to analyze structure and mobility in th ese materials on the level of the different molecular moieties. The influen ce of cross-linking is analyzed in detail in its effect on the molecular mo tion and its time dependence in response to an external electric field. The angular excursion of the motion of the spacer in response to an external e lectric field is much smaller than that of the mesogen. This is in pronounc ed contrast to low molecular FLC. The angle between the mesogen and the spa cer changes continuously during the reorientation in the Sm A phase, sugges ting continuous changes in the spacer conformation. It is shown that the fe rroelectric order is frozen by the cross-linking reaction. A new method is described to detect the phase transition Sm C*- Sm A in ferroelectric liqui d crystalline elastomers. It is based on a direct determination of the bias ed rotation for the polar (carbonyl) groups being the molecular origin of t he observed ferroelectricity.