Structure and mobility in ferroelectric liquid crystalline elastomers

Time-resolved Fourier transform infrared (FTIR) spectroscopy with polarized light was employed to study the structure and mobility of a homologous ser ies of ferroelectric liquid crystalline polymers (FLCPs) and ferroelectric liquid crystalline elastomers (FLCEs) in response to an external electric f ield. The chemical composition of the samples, besides the cross-linking un its, is similar. For the elastomers, two different cross-linking architectu res are realized: "intralayer" cross-linking leads to the formation of two- dimensional networks, whereas "interlayer" cross-linking forms three-dimens ional networks. Due to its specificity, FTIR spectroscopy enables analysis of the reorientational dynamics for the different molecular moieties in det ail, thus revealing information about reorientation times, angular excursio n, and the phase relationship in the rearrangement of the various molecular groups. In comparison to the un-cross-linked FLCP, both elastomeric sample s exhibited smaller reorientation angles and an increase of the reorientati on times. In the case of the interlayer cross-linked FLCE, an elastic memor y effect was observed: For the reversal from negative to positive field pol arity, the reorientation times were longer than for these in the opposite d irection. For the intralayer cross-linked sample, it was shown that the bac kbone molecules reorient slower than the other molecular units ("locomotive effect"). For the un-cross-linked FLCP and the two FLCE samples, different coupling mechanisms between the network and the mesogenic parts are derive d from the measurements.