Jurnal ILMU DASAR, Vol. 24 No. 2, Juli 2023 : 101-112 101 Journal homepage: https://jurnal.unej.ac.id/index.php/JID A Review on Physical, Chemical and Optical Properties of Liquid Crystal Vinod Kumar Singh 1 , R. K. Singh 2*) , Reena Dhyani 3 , B. S. Rawat 3 , P. S. Rawat 3 , Hemlata Sharma 3 , Narinder Kumar 3 1 Deparment of Chemistry, Shivpati Degree College, Shohrat Garh, Siddharth Nagar (U.P.) 272205 India 2 Deparment of Chemistry, M. L. K. P. G. College Balrampur (U.P.) 271201 India 3 Department of Physics, School of Applied & Life Sciences, Uttaranchal University, Dehradun, Uttarakhand-248007, India *E-mail: rksmlk25@gmail.com ABSTRACT The foundation of the upcoming generation of cutting-edge gadgets and digitally augmented technologies is expected to be smart soft materials. Because of their responsiveness and adaptability, liquid crystals (LCs) are promising smart soft materials. In the 20th century, LCs were crucial to changing the information display sector. However, several beyond-display uses for LCs have been proven at the turn of the twentieth century, neatly using their controlled stimuli-responsive and adaptable properties. New LC materials have been developed and engineered for such applications. The review comes close with a summary and viewpoints on the potential and problems facing LCs as smart soft materials. This review is expected to inspire a wide range of concepts for the application of nature's delicate phase of matter in the generation and beyond of smart and augmented devices. Keywords: Liquid Crystal, Optical Properties, Physical and Chemical Parameters. INTRODUCTION Structure and Classification of LCs The materials known as LCs are those that simultaneously exhibit certain physical characteristics common to liquids and others common to crystals (De Gennes, 1993). Mesomorphic materials, or materials exhibiting mesomorphic states, are a more accurate term for them. These states of aggregation arise between the liquid and solid phases (Demus, 2011). In the mesomorphic form, they typically resemble liquids from a macroscopic perspective, but in contrast to typical liquids, they exhibit a significant anisotropy in the physical characteristics, making them more like to crystals in this regard. "Anisotropic fluids" is another term that is applicable (Demus, 2001). By altering the thermodynamic parameter for a particular material, the mesomorphic state (perhaps more than one) is manifest. LC materials are often classified as thermotropic or lyotropic under constant pressure and volume (Foelen, 2023). While others achieve these states by adjusting the concentration ratio of components, the first exhibit a mesomorphic behaviour when the temperature is varied (Gao, 2022). Because moststudies on nonlinear optical characteristics have been conducted onne matic states, we shall solely discuss thermotropics in the sections that follow. Mesomorphism is seen in compounds where the orientational order of LC molecules is produced by the chemical composition. Only when each molecule is lengthened in a single, distinct direction can orientation be understood. For this reason, the typical molecules of thermotropic LCs are represented by stiff rods with lengths of 20 to 40A and widths of 4 to 5A (Jakli, 2006). These chemicals fall into a wide variety of categories, and more are continually being created. However, a general standard for the chemical makeup of an organic substance showing mesomorphic states may be provided (Kelker, 1980). Through chemistry and the study of LCs, physics is extended to the biosciences (Demus, 1984). Both fundamental and applied research have seen remarkable linkages and changes as a result of borderline status (Fratini, 2016). When P.G. de Gennes received the 1991 Nobel Prize in Physics for his contribution to our knowledge of the LCline state, the public was made aware of the rapidly developing field of study and application (Brown, 1973). Additionally, LC phases and their technological application are necessary for displays in a variety of commonly used devices and equipment (Dunmur, 2001). Membrane development, stability, molecular- molecular interactions, and recognition are areas of biochemistry, bioorganic, and organic chemistry that are seeing a lot of attention and research. Detergents, lipids, and steroids are associated with LC phenomena (Lu, 2022).