Synthesis of New Star-Shaped Liquid Crystalline Cyclotriphosphazene Derivatives with Fire Retardancy Bearing Amide-Azo and Azo-Azo Linking Units

Abstract

Two series of new hexasubstituted cyclotriphosphazene derivatives were successfully synthesized and characterized. These derivatives are differentiated by two types of linking units in the molecules such as amide-azo (6a–j) and azo-azo (8a–j). The homologues of the same series contain different terminal substituents such as heptyl, nonyl, decyl, dodecyl, tetradecyl, hydroxyl, carboxyl, chloro, nitro, and amino groups. All the intermediates and final compounds were characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), and Carbon, Hydrogen, and Nitrogen (CHN) elemental analysis. Liquid crystal properties for all compounds were determined using polarized optical microscope (POM). It was found that only intermediates 2a–e with nitro and alkoxyl terminal chains showed a smectic A phase. All the final compounds with alkoxyl substituents are mesogenic with either smectic A or C phases. However, other intermediates and compounds were found to be non-mesogenic. The study on the fire retardancy of final compounds was determined using limiting oxygen index (LOI) method. The LOI value of pure polyester resin (22.53%) was increased up to 24.71% after treating with 1 wt% of hexachlorocyclotriphosphazene (HCCP). Moreover, all the compounds gave positive results on the LOI values and compound 6i with the nitro terminal substituent showed the highest LOI value of 27.54%.

Synthesis and Determination of Thermotropic Liquid Crystalline Behavior of Cinnamaldehyde-Based Molecules with Two Schiff Base Linking Units

“…The synthesis of calamitic molecules with a liquid crystal mesophase requires at least two aromatic rings—either cycloaliphatic or a combination of one aromatic and one cycloaliphatic ring—which are connected directly or through a suitable linking unit. Calamitic molecules containing a rigid core have been regarded as the most suitable geometry to exhibit mesogenic behavior [ 34 ]. Therefore, the study of the structure–property relationship is very important in designing new liquid crystal materials.…”

“…Halogen groups are polar substituents possessing strong dipole moments, and thus have the ability to promote mesomorphic properties. The increased dipole moment can enhance the stability of lattice and melting temperatures [ 34 ]. Moreover, the electronegativity of the halogen atom reduces the degree of molecular order, which enhances a higher clearing temperature [ 31 , 35 ].…”

Liquid Crystals Investigation Behavior on Azo-Based Compounds: A Review

“…Over the years, the use of electronic devices has increased to meet the demand of easing our lives. The most common liquid crystal used is the liquid crystal display (LCD) that is present on our mobile phones, computers, laptops, and many more [ 51 , 52 ]. LCD is an electronic display device with a flat panel that uses a liquid crystal as its main operation medium [ 53 ].…”

Synthesis, Structural Elucidation and Mesophase Behaviour of Hexasubstituted Cyclotriphosphazene Molecules with Amide Linking Unit

“…215 Zuhair Jamain, Melati Khairuddean, Synthesis, Structural Elucidation and Mesophase Nur Kamarina Kamaruddin, Yeoh Zhi Rui Behaviour of Hexasubstituted Cyclotriphosphazene Molecules with Amide Linking Unit Scheme 2. Synthesis of hexasubstituted cyclotriphosphazene derivatives, 5a-d [22][23][24].…”