46620-G7
Synthesis and Design of Novel Electro-Active, Site-Isolated Nanostructures
We have developed a method for the formation of stable organic conjugated nanoparticles that are comprised from a single linear polymeric precursor utilizing an intramolecular chain collapse process. The two key elements of the linear conjugated precursors involved the design of an ABA triblock copolymer with incorporated crosslinking units in the A block copolymers to site-isolate the embedded semiconducting core block and form distinctive well-defined particles in nanoscopic dimensions of 5-10 nm. The increased photoluminescence is a direct measure of the efficiency in the confinement of the semiconducting block depending on the length of the A block copolymers and represents the first example of cross-linked ‘organic quantum’ dots from individual polymer chains as the result of the nanoparticle formation technique.
In particular, we prepared and analyzed two types of linear precursors differentiated first by the central B block prepared as macroinitiator from bromo-functionalized alkoxyamine initiators with dibromofluorene as monomer in a Yamamoto reaction. A second macroinitiator was prepared with the same initiator as a block copolymer with dibromofluorene and dibromothiophene as monomers. The second differentiation was made with the length of the copolymers which were grown as A block from the macroinitiator block with styrene and 10% of vinylbenzosulfon as crosslinking unit. The final block copolymer ABA precursors with 8:1:8 PS:fluorene:PS and 5:1:5 PS:fluorene/thiophene:PS were then transformed into nanoparticles in nanoscopic size dimensions equivalent to quantum dots. After the particles were tested for a successful intramolecular chain collapse process with techniques such as gel permeation chromatography (GPC), dynamic light scattering (DLS), Atomic Force Microscopy (AFM) and also Nuclear Magnetic Resonance (NMR), we investigated the result of the site isolation of the semiconducting block in the 3-D nanostructure. It was observed that the photoluminescence increase is strongly dependent on the the length of the A block copolymer and a ratio of 8:1:8 can facilitate a more comprehensive site isolation of the center block.
The current work inludes watersoluble equivalent nanoparticles that can be post-modified to cross-cellular barriers and and target specific tissues.
