Polymer-Nanocrystal Composites: Copolymers, Polymeric Particles and Hybrid Systems

摘要

Poly(fluorene)s (PFs) containing functional monomers as building blocks that can interact via their end-functionalities with optically active species such as semiconductor nanocrystals are of increasing interest in the modern light-emitting and display technology. Incorporation of carbazole-based building blocks in the backbone of PFs can contribute to a higher hole-transporting mobility and to a raise of the energy level of the highest occupied molecular orbital. A new trend in the materials’ design is the combination of fluorene derivatives with inorganic semiconductor nanocrystals in hybrid structures or the preparation of conjugated polymers in the form of nanoparticles. In the last case, groups with amphiphilic character like phosphonates can play a significant role, due to their strong chemical affinity to quantum dots allowing the preparation of nanocomposite systems.Within the framework of this thesis, fluorene- and carbazole-based building blocks were synthesized and incorporated in Yamamoto or Suzuki polymerizations, targeting to post-modified copolymers, polymer microparticles or hybrids. Aim of this approach was the development of poly(fluorene)-nanocrystal composite systems and the subsequent performance of energy transfer investigations in order to gain insight in a phenomenon, which still remains a subject of extensive research. For this purpose, in addition to fabricating composites by simply mixing the synthesized fluorene-based copolymers with inorganic quantum dots, two more sophisticated approaches, namely, the ‘grafting-from’ and the ‘microparticle’ methodology were applied as well. The blending strategy was performed with copolymers possessing amino-functionalized side-chains, which render an interconnection with nanocrystals like CdTe feasible. The ‘grafting-from’ approach represents an innovative but simple way in order to grow oligo(fluorene) or poly(fluorene) moieties from the surface of nanocrystals via a facile polymerization protocol. In this way, direct linkage between the two counterparts is created and the consequence of this environmental circumstance on the energy transfer process can be investigated. Finally, PFs with phosphonate-functionalized side-chains were targeted. Their bringing-together with water-stable nanocrystals via a precipitation methodology would be to the best of our knowledge the first time that such microparticulate composites in an aqueous medium would be reported, exhibiting excellent stability and optical properties.