The Physics and Application of Liquid Crystal/ferroelectric Particles Colloids PDF Download

Author: Fenghua Li
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 264

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Book Description
The liquid crystalline phases have been of great fundamental interest and at the same time found enormous recent application in display and photonic devices. Much effort has been put into developing new type liquid crystals, with fast response times, higher birefringence, low driving voltage and so on, but the chemical synthesis of obtaining such LCs can often be difficult. By contrast, this thesis utilizes ferroelectric colloidal dispersions to dope liquid crystals. Colloids in liquid crystalline hosts present new physical features as the anisotropic intermolecular interactions compete against colloidal interactions. These dilute colloids are stable since the particles were coated with surfactant. Most particles remain separated at a certain stable distance. Because the particles are so small, they do not disturb the LC orientation. The colloids therefore are macroscopically homogeneous and appear similar to a pure liquid crystal with no visible evidence of the dispersed particles. At the same time, nanoparticles are large enough to maintain their ferroelectricity and integrate these intrinsic properties with the LC host. In this thesis, I focus on physics of these ferroelectric liquid crystals colloids and describe a new non-synthetic method of modifying the properties of existing liquid crystals by doping them with surfactant-processed ferroelectric nanoparticles. Special attention was paid to investigate the electro-optic properties of ferroelectric nematic colloids for display applications. At very low concentration, sub-micron ferroelectric particles show very fascinating enhancement to liquid crystal mixtures, such as, higher birefringence ([delta]n), higher dielectric anisotropy, and T[subscript ni] temperature and so on. These results indicate that low concentrated ferroelectric nanoparticles may enhance the orientational ordering of nematic liquid crystals. Traditionally, by changing the molecular structure, the molecular type, and polarizability, people can synthesize and modify the long-rang macroscopic properties of LC mixtures. Not only the time and effort are huge, but also the results of synthesis, such as clearing point and viscoelastic properties, can not be predicted. Doping ferroelectric nanoparticles is a simple and effective approach to control and modify LC properties.