Influence of polymer stabilization on the dielectric relaxations of an antiferroelectric liquid crystal

Abstract

Dielectric spectroscopic investigations are reported on an antiferroelectric liquid crystal in its pristine form and when stabilized by a polymer network without and with application of a DC bias field. While the inphase mode associated with the helix distortion is hardly affected, the high frequency mode connected with the antiphase fluctuations shows a large decrease with increasing concentration of the photoactive monomer used to generate the polymer stabilization. With the help of X-ray data, we rule out any interlayer nanophase segregation of the polymer strands, and argue that this strong effect is due to the large elastic interaction between the liquid crystal molecules and the polymer strands. Employing expression from a Landau theory we extract several relevant parameters, including the viscosities associated with the different relaxation modes, the elastic constant, and importantly the antiferroelectric interaction, which exhibits a substantial decrease upon polymer stabilization.

Confinement of an antiferroelectric liquid crystal in a polymer nanonetwork: thermal and dielectric behaviour

“…by mesogenic monomers (Type B) would have a strong tendency to follow the ordering of the LC molecules. These differences do alter the physical properties substantially, as was demonstrated by Madhuri et al [15] and Labeeb et al [17]. In this article we demonstrate the effect of the polymer confinement on the dielectric properties of an LC exhibiting a direct transition from the paraelectric SmA to the antiferroelectric SmC * A phase.…”

“…Evidently, two relaxation processes are present in both the samples. Our earlier analysis [15] has clearly established that the low-frequency mode, lying in the range of tens of kHz, is the IM mode, while the higher frequency one, in the MHz region, is the AM. The profiles in the SmA phase exhibit a single relaxation arising from the SM relaxation, as seen in figure 6a.…”

“…Taking the ratio of maximum f AM values of the pure TFM to those of the networked samples, it is seen that the reduction is 10% for TFM9HD1RM and 34% for TFM10HD samples. Interestingly, the data on TFM10RM reported by Madhuri et al [15] also exhibit 34% reduction. Thus, it appears that although the polymer content is approximately the same, the single-polymer systems are more efficient in lowering f AM , unlike in the case of the SM relaxation.…”

“…In contrast, the soft mode (SM) parameters were essentially unaltered [11]. As opposed to the focus on the nematic and ferroelectric LCs, studies on the polymer-stabilized antiferroelectric (PSAFLC) structure are only a few [12][13][14][15], with only one on the dielectric properties [15]. The nature of the polymer has an important say in the behaviour [16].…”

Hydrogen-bonded bent-core blue phase liquid crystal complexes containing various molar ratios of proton acceptors and donors

“…Previously, bent-core liquid crystal materials were widely applied in ferroelectric LC materials, 47 organic/inorganic composites 48,49 and chiral nanostructures. [50][51][52] Recently, the introduction of biaxialities to LC materials, such as: bent-core and di-mesogenic LCs, can induce BPs in LC mixtures.…”