Liquid Crystal (LC) Building Blocks

Liquid crystal (LC) building blocks are building blocks that use liquid crystals as raw materials to achieve specific functions and actually exist in the system. Liquid crystal is an intermediate substance between the crystalline state and the liquid state. It combines some characteristics of liquid and crystal, and shows some unique properties. Most liquid crystals are organic compounds and consist of long rod-shaped molecules. In a natural state, the long axes of these rod-shaped molecules are roughly parallel.

Applications:

The liquid crystal building module has the advantages of unique properties, abundant types, and relatively simple preparation method. It has a wide range of applications in the fields of optoelectronic materials, biology, medicine and environmental monitoring.

• Optoelectronic materials: Liquid crystal building blocks are widely used in the field of optoelectronic materials. At present, liquid crystals are used as display materials in daily necessities such as computer display screens, smartphone screens, and LCD TVs. Liquid crystal display materials have the advantages of the low driving voltage, small power consumption, high reliability, large amount of displayed information, color display, no flicker, no harm to human body and low cost. Benzophene-based liquid crystals have high mechanical strength, good chemical stability and thermal stability, and are commonly used in optoelectronic materials. Benzophene-based liquid crystal small molecules and polymers are applied to organic photodiodes, and significant application effects are achieved. Benzophene liquid crystal is used as the preparation of transistor materials, and the resulting transistor has good dynamic stability and thermal stability.

Figure 1. Light-emitting diode manufactured by liquid crystal building blocks

• Medicine: The molecular alignment of the cholesteric liquid crystal is obviously affected by temperature. When the ambient temperature changes, the color change of the liquid crystal can be observed. The mechanism of cholesteric liquid crystal color display and temperature display is because the pitch of its layered spiral structure changes with temperature, and changes in the molecular structure of the liquid crystal definitely cause changes in its optical properties. Using this feature, new chiral liquid crystal monomers and cholesteric elastomers can be successfully used in medicine and other fields. For example, using the temperature effect of cholesteric liquid crystal, a liquid crystal thermometer can be successfully manufactured. This thermometer is placed on the patient's forehead according to the color of the thermometer to get the patient's temperature. After the mercury thermometer breaks, the outflow of mercury will bring harm to human health and the environment, but the liquid crystal thermometer successfully avoids these shortcomings. Based on the fact that the temperature of tumor tissue is slightly higher than that of normal tissue, cholesteric liquid crystal has also been successfully used to diagnose tumors. By coating a layer of cholesteric liquid crystal film on the site to be examined, the exact location of the tumor can be accurately diagnosed according to their color difference. Now, this method has been used clinically for the diagnosis of various cancers, and timely excision treatment for patients to relieve patients. In addition, cubic phase liquid crystal and hexagonal phase liquid crystal can coexist with excessive water, and have been widely studied as a drug carrier for oral, injection, and transdermal administration.

Figure 2. Liquid crystal thermometer manufactured by liquid crystal building blocks

• Biology: Liquid crystals have both liquid fluidity and solid optical anisotropy. In the melting point and clearing point temperature range, there are many different intermediate phase states due to different molecular orientations. Changes in temperature, surface morphology and chemical structure will affect the short-range interactions between molecules and the long-range orientation order, which in turn will cause molecular orientation changes and propagate into the surrounding tens of micrometers. This orientation change has a certain signal amplification effect and can convert the bonding between biomolecules into a macroscopic optical signal. Therefore, liquid crystal is an excellent biosensing material. In the field of biology, liquid crystal biosensors are widely used in the detection of small molecules such as glucose, proteins, nucleic acids and other biomolecules. For example, using the principle of protein-aptamer and antigen-antibody specific binding, liquid crystal biosensors are used to detect proteins such as goat immunoglobulin G and ischemic modified proteins.

Figure 3. Biosensor manufactured by liquid crystal building blocks

References:

1. XU Xiao-peng. (2006), "Development and Domestic Application of Liquid Crystal Materials." New Chemical Materials 34(11), 81-83.
2. ZABAＲA A. (2014), "Controlling molecular transport andsustained drug release in lipid-based liquid crystalline mesophases." J Controlled Release 188(6), 31-43.
3. NGUYEN T H. (2010), "Phytantriol and glyceryl monooleate cubic liquid crystalline phases as sustained-release oral drug delivery systems for poorly water soluble drugs I. Phase behaviour in physiologically-relevant media." J Pharm Pharmacol  62(7), 844-855.