Ferroelectric liquid crystalline elastomers, 2 - Variation of mesogens andnetwork density

Oriented smectic-C* elastomers have been made by performing radical photo-c rosslinking reactions in a polar state of the ferroelectric phase. This pap er aims at the evaluation of structure-property-relationships, Two polymer systems - varying in the length of the mesogens, the ferroelectric polariza tion and the amount of crosslinkable groups - were synthesized. The ferroel ectric properties of the resulting elastomers were studied using electro-op tical investigations. The crosslinking of ferroelectric polysiloxanes with a modest polarization (50-105 nC/cm(2)) and 15 or 25 mol-% of crosslinkable groups leads to polar elastomers, which can no longer be switched complete ly (voltages up to 400 V are not enough to reach the second, destabilized s witching state). Ferroelectric polysiloxanes with a higher polarization (90 -150 nC/cm(2)) lead to elastomers, which can be switched again completely. This happens because the torque (P-s . E) acting on the liquid crystalline director is - this time - large enough to overcome the elastic field of the polymer network.