Liquid Crystals Material Characterization

Liquid crystals are matters in a state which have properties between those of conventional liquids and those of solid crystals^[1]. Liquid crystal is partially ordered and anisotropic. In terms of molecular order, liquid crystal molecules have one-dimensional or two-dimensional long - range order.

The discovery of crystal liquid can date back to the year of 1888^[2]. Friedrich Reinitzer is an Austrian botanical physiologist who worked at the Karl-Ferdinands-Universit?t. He found that cholesteryl benzoate does not melt in the same manner as other compounds, and it has two melting points. At 145.5 °C (293.9 °F) it melts into a cloudy liquid, and at 178.5 °C (353.3 °F) it melts again and the cloudy liquid becomes clear. The phenomenon is reversible. In fact, the phenomenon that he observed is the light scattering phenomenon of liquid crystals and the selective reflection of visible light in the cholesteric structure. Moreover, the various derivatives of cholesterol that he studied now belong to the class of materials known as cholesteric liquid crystals.

Generally, a matter has three states: gas, liquid and solid. However, liquid crystal is a strange phase which is between liquid and solid. It is called mesomorphic - liquid crystal state. Liquid crystal materials can be divided into thermatropic liquid crystal and lyotropic liquid crystal. Thermatropic liquid crystal is a mixture, and lyotropic liquid crystal is a pure substance. In order to meet the requirements of actual applications, the liquid crystals can be blended to improve the performances. According to the transformation and orientation of liquid crystal molecules, liquid crystal can be divided into three phases: Nematic, Cholesteric and Semitic.

Fig.1 The position of liquid crystal in matter states.

With the development of technology, liquid crystal has entered into our daily life. For example, the display devices of mobile phones, televisions, laptops and computers are constituted by liquid crystal. Furthermore, due to high strength, high modulus and low thermal expansion coefficient, liquid crystal polymers are widely used in manufacturing cable, body armor, high strength fiber and spacecraft large structure parts. Moreover, crystal polymer can also be used in wide line covered and microwave ovens. Besides the application in flat panel displays, liquid crystal has a unique and attractive property that offers great potential in fundamental science and innovative applications. Recently, new directions for applied and fundamental liquid crystal science gradually become the interests of scientists. The new directions mainly include liquid crystals for organic electronics and energy conversion applications, liquid crystal templating for creating nanostructured materials or ordering nano- and microparticles, composite materials containing thermotropic liquid crystals as functional additive, actuators made from liquid crystal elastomers and liquid crystals in biology, biotechnology, food science and pharmacology^[3].

Fig.2 Cartoon illustrating the transition from individual energy levels to energy bands as the extension of p electron overlap grows along the columns of a columnar discotic liquid crystal phase^[3].

It is very important to understand the properties of liquid crystal materials before mass production. Therefore, professional testing of liquid crystal material is critical. Alfa Chemistry is a professional testing company and can provide many testing services about liquid crystal materials. Alfa Chemistry has many professional instruments. Below is the instruments list.

• Polarimeter and Polarizing Microscope

• Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM)

• Fourier Transform Infrared Spectrometer (FTIR Spectrometer)

• 1H Nuclear Magnetic Resonance (NMR)

• Differential Scanning Calorimetry (DSC)

• Thermomechanical Analysis (TMA)

• X Ray Diffraction

Alfa Chemistry is professional in liquid crystal characterizations and we can provide accurate and reliable tests results within the time constraint. Please feel free to contact us if you have any concern or would like us to perform any liquid crystal material testing. Check our instruments list for our capabilities.

References

• Chandrasekhar, S. (1992). Liquid Crystals (2nd ed.). Cambridge: Cambridge University Press. ISBN 0-521-41747-3.

• Lagerwall J P F, Scalia G. A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology[J]. Current Applied Physics, 2012, 12(6):1387-1412.

• Reinitzer F, Zur Kenernis des Cholesterins [J], Monathsh Chem, 1988,9:421-441.