| dc.description.abstract | Recently, the temperature range and stabilization of structures with the application of external voltages of blue phase liquid crystals (BP-LCs) have become two of the key research topics for BP-LCs. Both of them have been paying much attention significantly by scientists. Since the temperature range of BP-LCs is extremely narrow, it is clear that the extension of temperature range is one of the key points in BP-LCs field. Currently, polymer-stabilized BP-LCs (PSBP-LCs), reported by H. Kikuchi in 2002, becomes the most commonly used method to extend the temperature range of BP-LCs.[1] In this thesis, we do lots of experiments about chiral polymer-doped BP-LCs but not achiral polymer-doped BP-LCs. The reported stabilization of BP-LCs is based on the polymerization of chiral polymer at various temperature of LCs at blue and isotropic phases.
According to the experimental results, the polymerized chiral polymer onto the substrates can be used to extend the temperature ranges of BP-LCs significantly. To elucidate the mechanism for extending the temperature ranges of BP-LCs, several factors for the processes of photo-polymerization are considered. They include (1) the concentrations of chiral polymer; (2) the temperatures of LCs (blue and isotropic phases) during photo-polymerization; (3) the UV-curing durations; (4) the cell gaps, and others. It turns out that the temperature ranges of BP-LCs can be extended by the polymerized chiral polymer of 6 wt% by UV illumination at isotropic phase. The mechanism of extending the temperature ranges of BP-LCs by chiral polymer-doped BP-LCs is based on the polymerized chiral polymer structures onto the substrates, which is different from that of PSBP-LCs. Such a stabilization approach is called “Surface-stabilized blue phase liquid crystals (SSBP-LCs)”. According to the references, PSBP-LCs can only be achieved by polymerizing the doped polymers at the temperature of blue phase, thus the processes for achieving SSBP-LCs is much easier than PSBP-LCs by polymerizing the doped chiral polymers at isotropic phases.
Finally, we have also compared the electro-optical properties of SSBP-LCs with those of PSBP-LCs, and the results show that the properties of SSBP-LCs are as good as those of PSBP-LCs. Notably, the response time of SSBP-LCs is shorter than that of PSBP-LCs. Accordingly, we believe that such a novel approach can improve the development of BP-LCs in LC technology. | en_US |