Spin-coating is a facile, straightforward, solution processing technique for the production of uniform thin films, which has been utilised for a wide range of applications including organic electronic and photonic devices, sensors, membranes and optical coatings. Many of the applications of spin-coated polymer films utilise the propensity of polymers to self-assemble, resulting in the formation of well-ordered, intricate morphologies that evolve towards thermodynamic equilibrium. Understanding the interplay between processes such as phase-separation and crystallisation, which control the final morphology, has therefore been the topic of intense theoretical and experimental studies in the field of polymer science. In particular the potential of spun-cast organic electronic devices to help alleviate the world's dependence upon fossil fuels in terms of energy generation and energy efficiencies has driven the need for greater control over the final morphology, in order to produce more efficient devices.
I have developed the technique of stroboscopic microscopy, which facilitates direct imaging during spin-coating, allowing us to directly observe, in real-time, the processes of self-assembly at the microscale. I have advanced the technique to operate in three different modes, which allow observations of topography, composition and crystallisation.
This thesis presents the direct observations of self-assembly processes that occur during the spin-coating of model polymer systems [polystyrene:poly(methyl methacrylate) and polystyrene:poly(ethylene glycol)], systems relevant to organic electronics [polystyrene:poly 9,9’-dioctlyflourene] and polystyrene colloidal dispersions. A number of key parameters have been investigated including the effects of; rotation rate, composition, polydispersity and the interplay between crystallisation and phase separation. The observation that of have been made may be utilised to either, rationally design processing conditions that will allow targeted morphologies to be attained or information obtained in real-time may be used to direct and control self-assembly processes in order to achieve desired morphologies.
