The performance of the semiconducting component in organic field effect transistors (OFET's), is a key parameter in the advancement of organic electronic devices. This work describes the development of solution processible liquid crystalline semiconductors, both main chain rigid rod polymers and small molecule polymerisable liquid crystals, referred to as reactive mesogens. New conjugated main chain polymeric semiconductors have been designed, synthesised, and their performance in transistor devices is reported. Small molecule liquid crystalline semiconductors, which contain reactive end groups, were also prepared, and their design, characterisation, and performance in transistor devices is discussed.