Polymer-Stabilized Blue Phases

In a polymer-stabilized self-assembled blue phase system, each material component plays an important role while interacting with the others. In the following, we will discuss the optimization of materials in terms of nematic LC host, chiral dopant, and monomers, respectively. 

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Both groups claimed that the mechanism of nanoparticle stabilization of blue phases is similar to that reported for polymer stabilized blue phases [412], with the nanoparticles accumulating or being trapped in the lattice disclinations, which finds support from numerical modeling of colloidal particles in blue phases recently described by Zumer and co-workers [429]. 

Fig. 8 Confocal laser scanning micrograph of polymer-stabilized blue phase I [16]...

Fig.11 Phase diagram of polymer-stabilized blue phases and schematic illustration of aggregation state of polymers [23]...

Fig. 16 Laser emission spectra from the polymer-stabilized blue phase of the (110) crystal [44]...

Kikuchi and coworkers found the rapid electro-optical effect in polymer-stabilized blue phases and presented the major potential of such phases in application to display devices and optical modulation devices [45,46]. Tra-... 

Fig. 17 Temperature dependence of electro-optical response time for the polymer-stabilized blue phases (polymer fraction a = 6.3, 10.5, 15.0 mol %) in the rise process (A) and decay process (B) [46]...

Jin Yan and Shin-Tson Wu, Polymer-stabilized blue phase liquid crystals a tutorial. Opt. Materials... 

Polymer-Stabilized Blue Phase Liquid Crystals... 

To widen BP temperature range, several approaches have been proposed [15-18] Here, we focus on the blue phases induced by incorporating chiral dopants into a nematic LC host. To make a polymer-stabilized blue phase liquid crystal, a small fraction of monomers (-8%) and photoinitiator (-0.5%) is added to the blue phase system. Figure 14.4 shows some exemplary nematic LC compounds, chiral dopants, and monomers [19]. Then we control the temperature within the narrow blue phase range to conduct UV curing. After UV irradiation, monomers are polymerized to form a polymer network, which stabilizes the blue phase lattice stmctures. 

Figure 14.7 shows the wavelength-dependent Kerr constant of a polymer-stabilized blue phase LC composite studied by Jiao, et al. Dots are the measured data and the solid line is the fitting result with Equation (14.21) using two adjustable parameters 2 216nm and proportionality constant G/E 2.62 X 10 nm This 2 - 216 nm agrees with that obtained from the employed LC host very well. 

Figure 14.7 Measured wavelength dependent Kerr constant (dots) of a polymer-stabilized blue phase liquid crystal and fitting results with Equation (14.21). Reproduced with permission from the American Physical Society.

L. Rao, J. Yan, S. T. Wu, et al., A large Kerr constant polymer-stabilized blue phase liquid crystal, Appl. Phys. Lett. 98, 081109 (2011). 

M. Wittek, N. Tanaka, M. Bremer, et al.. New materials for polymer-stabilized blue phase, SID Int. Symp. Digest Tech. Papers 42, 292-293 (2011). 

J. Yan and S. T. Wu, Effect of polymer concentration and composition on polymer-stabilized blue-phase liquid crystals, J. Display Technol. 7, 490-493 (2011). 

J. Yan, H. C. Cheng, S. Gauza, et al.. Extended Kerr effect of polymer-stabilized blue-phase liquid crystals, Appl Phys. Lett. 96, 071105 (2010). 

Y. Chen, and S.T. Wu, Recent advances on polymer-stabilized blue phase liquid crystal materials and... 

F. Peng, Y. Chen, J. Yuan, et al.. Low temperature and high frequency effects of polymer-stabilized blue phase liquid crystals with a large dielectric anisotropy, J. Mater. Chem. C. 2, 3597-3601 (2014). DOI 10.1039/c4tc00115j... 

Then in 2002, the author and coworkers reported that the temperature range of a blue phase could be increased to over 60 K by forming a small amount (7-8 wt%) of polymers in the blue phase the material was named the polymer-stabilized blue phase (Fig. 8.15) [17], The molecular dynamics are not lost in the polymer-stabilized blue phase, and moreover, the electro-optical response is very fast. It is believed that the polymers in the blue phase condense around disclinations and the blue phase is stabilized when the disclinations are thermally stabilized. 

Fig. 8.15 Polymer-stabilized blue phases. The monomers were 2-ethyl hexyl acrylate and 2-methyl-1,4-phenylene-bis(4(3(acryloyloxy)propyloxy)benzoate) (RM257, Merck)...

Let us consider the role of the polymer in the polymer-stabilized blue phase (PSBP) from the viewpoint of the thermodynamic interaction between the hquid crystal and the polymer. A feature of the blue phase is that it must coexist with disclination lines, and the very existence of the disclinations is the reason why the temperature range of the blue phase is small. Looking at it from the opposite direction, the blue phase could be stabilized by the disclinations. 

Fig. 8.18 Electro-optical response of polymer-stabilized blue phases. Precursor 1 is an acrylate monomer (11 %), precursor 2 is an acrylate monomer (8 %), precursor 3 is a methacrylate monomer (11 %), and precursor 4 is a methacrylate monomer (8 %). The liquid crystal was provided by JNC. The electrodes were simple interdigitated electrodes with a spacing of 10 mm...

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