The main objective of this proposal is to study the structure of the interface between a semiconducting liquid crystal (LC) and a soft dielectric substrate for their potential application in opto-electronic devices. The performance of such devices is determined by the interface; for LCs the degree of order in the first few molecular layers of the semiconducting channel and the smoothness of the interface with the gate insulator is crucial. We will perform experiments on previously characterised semiconducting, dialkylterthiophene thin-film systems with fully deuterated side chains, which exhibit complex phase behaviour close to interfaces. We will use neutron reflectometry to probe, in-situ, structuring and phase transitions near the buried LC/polymer or substrate interface as a function of temperature, starting from the isotropic state through a transition to various smectic phases.