Photoresponsive materials based on dithienylethenes

Photoresponsive molecules that undergo reversible isomerization reactions between two distinct forms that vary in their electronic and physical structure have the potential to significantly impact numerous applications in materials science. The dithienylethenes (DTEs) provide a versatile synthetic scaffold that can be tuned to display dramatic changes in colour, refractive index, luminescence and electrical conductance in response to light. The vast majority of research into the photoresponsive properties of these molecules has been limited to the solution phase, which is not useful for materials applications. The exploitation of this appealing platform in optoelectronic applications demands its physical attachment to a flexible polymeric architecture that will not negatively impact the photoresponsive component. The material must be convenient for processing into highly sensitive, photoresponsive thin films. Ring-opening metathesis polymerization (ROMP) is a general and mild technique that is amenable to the presence of numerous functional groups and many solvents and provides a modular and flexible polymer scaffold. The research presented in this thesis has focused on combining DTE and ROMP tecl~nology to develop effective strategies for constructing photoresponsive, tunable materials for potential use in optoelectronic applications. ROMP technology can be used to construct both pendant and main-chain photoresponsive dithienylethene polymers that contain a high content of the photoactive DTE component. These versatile materials can be used in both hydrophilic and lipophilic environments as well as the solid-state without sacrificing their marked photoactivity. The properties of these materials can be synthetically tailored, to obtain desirable properties such as intense colour, high refractive index or water solubility. Tailoring colour in DTE materials can also be achieved by strategically blending a series of monomers appended with three different DTE units, to create multi-component, multi-coloured, photoresponsive copolymers. Each component was preprogrammed to display the primary colours, blue, yellow and red in the ring-closed form. Strategically blending each component in the appropriate ratio creates materials that display a wide range of colours. The resulting multi-component copolymers can be selectively triggered, using the appropriate wavelengths of light, to display up to eight specific colours in a single off-the-shelf material