E. Gebhard et R. Zentel, Ferroelectric liquid crystalline elastomers, 2 - Variation of mesogens andnetwork density, MACRO CH P, 201(8), 2000, pp. 911-922
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.