Surface gliding of the easy axis of a polymer-stabilized nematic liquid crystal and its dependence on the constituent monomers

Yang

Applied Physics Letters

et al. 2014

Self Cite

We examined the electrooptical properties of a nematic liquid crystal (LC) sample whose substrates were coated with a mixture of carbon nanotube (CNT) and polyimide (PI). The relaxation time of the sample coated with 1.5 wt. % CNT mixture was about 35% reduced compared to the pure polyimide sample. The elastic constant and the order parameter of the CNT-mixture sample were increased and the fast relaxation of LC could be approximated to the mean-field theory. We found the CNT-mixed polyimide formed more smooth surface than the pure PI from atomic force microscopy images, indicating the increased order parameter is related to the smooth surface topology of the CNT-polyimide mixture.

mentioning

confidence: 67%

Improvement of the relaxation time and the order parameter of nematic liquid crystal using a hybrid alignment mixture of carbon nanotube and polyimide

Yang

Applied Physics Letters

et al. 2014

Self Cite

ACS Appl. Polym. Mater.

“…LC anchoring, including gliding anchoring on the polymer-coated surface, was expected to depend on the reorientation of the polymer chains. , Therefore, to elucidate the anchoring mechanism, it is critical to understand the rheological properties of the polymer-coated layer. However, the cross-linked film fabricated in this study was too thin to obtain rheological measurements.…”

Section: Resultsmentioning

confidence: 99%

“…Sato and co-workers investigated the LC-anchoring property of the concentrated polymer brushes (CPBs), which are assemblies of densely end-grafted polymers on substrates, and demonstrated the following features: (i) exhibiting strong and weak azimuthal anchoring at low and high temperatures, respectively, on CPBs of both poly(ethyl methacrylate) (PEMA) and polystyrene (PSt); (ii) viscoelastic response to external fields at medium temperatures (possibly related to the concept of gliding anchoring); − and (iii) near-zero azimuthal anchoring on CPBs of poly(hexyl methacrylate) (PHMA) over a wide range of temperatures. , This strongly suggests that the mobility of the polymer layer should play an important role in the LC anchoring; however, the details surrounding this are still unclear.…”

Section: Introductionmentioning

confidence: 99%

Near-Zero Azimuthal Anchoring of Liquid Crystals Assisted by Viscoelastic Bottlebrush Polymers

Kinose

Sakakibara²,

Sato

et al. 2021

In this article, we revealed the mechanism of weak anchoring properties of liquid crystals (LCs) on cross-linked films of bottlebrushes consisting of poly(hexyl methacrylate) (PHMA) and poly(ethyl methacrylate) (PEMA). First, azimuthal anchoring coefficients, A 2 , of a LC were estimated using these two systems from the voltage−transmittance curves at different temperatures. The PHMA and PEMA systems showcased a temperaturedependent weak anchoring property, with A 2 decreasing as the temperature was increased. Second, the degree of swelling of these two systems (with cross-linked films) by the LCs was determined and compared with the phase diagrams of the corresponding mixtures without cross-linking, suggesting that the relaxation dynamics of side chains of bottlebrushes was retained even after the cross-linking. Finally, rheological measurements were conducted for the LC/bottlebrush mixtures to discuss the dynamics of the LCswollen cross-linked bottlebrush films, which clearly demonstrated the relaxation behavior of the side chains. Assuming the time scale for the determination of A 2 , the characteristic temperature corresponding to the side-chain motion was reasonably correlated with the decreasing temperature behavior of A 2 . As a consequence, weak anchoring could be explained by the polymer chain dynamics, which was revealed to be accelerated by the bottlebrush architecture as well as the swelling with LCs, depending on the affinity of the bottlebrush component with the target LC.

“…1 ), thank to a weak surface anchoring of the PMMA layer, E is able to realign the directors not only in the bulk but also in the surface region because ξ e decreases as the surface anchoring strength W becomes weaker. The reorientation of surface directors, the so-called surface gliding, has been studied using a range of techniques 11 12 13 14 15 16 17 18 19 20 21 22 23 24 . Furthermore, the relatively low phase transition T of PMMA from Cr to a glass (G) phase, , allows one to further reduce W by elevating T above .…”

Section: Resultsmentioning

confidence: 99%

Realization of Multi-Stable Ground States in a Nematic Liquid Crystal by Surface and Electric Field Modification

Gwag

Kim

et al. 2015

Sci Rep

Owing to the significant price drop of liquid crystal displays (LCDs) and the efforts to save natural resources, LCDs are even replacing paper to display static images such as price tags and advertising boards. Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption. However, the multi-stable LCD with industrial feasibility has not yet been successfully performed. In this paper, we propose a simple and novel configuration for the multi-stable LCD. We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring. The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.