Liquid crystalline materials containing pyrimidine rings

Liquid crystals with their unique ordered mesophases and anisotropic physical properties, such as optical, magnetic and dielectric anisotropy, have found wide opto-electronic applications, especially liquid crystal displays (LCDs) in digital electronic devices, such as smart phones, tablets, laptops, TVs, etc. Liquid crystals incorporating 2,5-disubstituted pyrimidine rings in their aromatic cores are often used in commercial LCDs. They are also critical building blocks of liquid crystalline organic semiconductors designed for use in novel organic electronic devices, such as organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), sensors, etc. This review will focus specifically on pyrimidine-based liquid crystals, such as calamitic, bent, discotic, taper-shaped, small molecules, oligomers and polymers. It will highlight the relationships between molecular structure and liquid crystalline behaviour, i.e. mesomorphism of relevance to organic and opto-electronic applications. It will highlight the development, optimisation and innovation of liquid crystalline materials containing pyrimidine rings, thereby stimulating the potential for new structural design and applications, such as sensors, flexible electronics, 4D printing and subsequently opening up completely new markets for these advanced functional materials.