Synthesis, structures and properties of functional polyhedral oligomeric silsesquioxane (POSS)-based conjugated materials

Polyhedral oligomeric silsesquioxane (POSS) is a cage-like molecule with a well-defined and highly symmetric structure having a size of 0.5 nm diagonally. The POSS material demonstrates a truly hybrid inorganic core / organic shell architecture with one or more vertexes covalently substituted by a wide range of functional groups which render materials with versatile properties for many applications. Recent studies indicate POSS incorporated conjugated polymers show improved performance due to less aggregation caused by the cubic cage which interrupts close packed linear polymers. Our previous work indicated that molecules consisting of a POSS cage and rigid organic short chains exhibit strong quantum confinement effects which imply organic-quantum-dot-like properties. In this research, a systematic study on the effect of incorporation of POSS on the properties, especially optical characteristics, of luminescent nano-particles and hyper-branched polymers was conducted in three areas: 1) Well defined blue POSS luminescent dots were designed and synthesized where conjugated oligomers are directly grafted onto eight vertexes of POSS cage. It was found that excitons are confined in each arm of emissive units and hence excitons are confined within each dot and isolated chromospheres are obtained. 2) Highly regioselective bromination of octaphenyl-POSS was achieved. The green POSS light emitting dots based on this structure were synthesized to achieve well defined nano-particles with precisely controlled structures and sizes. DOCTOR OF PHILOSOPHY (MSE)