Structure and mobility in ferroelectric liquid crystalline elastomers as studied by time-resolved FTIR spectroscopy

The molecular structure and reorientation of ferroelectric liquid crystalli ne elastomers (FLCE) in response to an external electric field is studied o n a microsecond scale with time-resolved Fourier transform infrared (FTIR) spectroscopy. In order to analyze the influence of the network on the molec ular structure and mobility in FLCE, three similar FLC polysiloxanes are un der study that differ just in their crosslinking architecture: besides the uncrosslinked polymer we obtain by photocrosslinking FLCE in which the back bones of either adjacent smectic layers ("interlayer") or of the same smect ic layer ("intralayer") are preferably crosslinked. It is shown that the cr osslinking leads to a slowing down of the molecular mobility which is stron ger for the inter-than for the intralayer FLCE. Asymmetries in the reorient ation times and/or in the reorientation angles are observed (elastic memory effect). The intralayer crosslinking causes a "locomotive effect": the reo rientation of the mesogenic cores precedes that of the backbones.