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Self-encapsulation of poly-2,7-fluorenes in a dendrimer matrix
D Marsitzky1, R Vestberg, P Blainey
1Contribution from the IBM Almaden Research Center, NSF Center for Polymeric Interfaces and Macromolecular Assemblies, 650 Harry Road, San Jose, California 95120-6099.
Journal of the American Chemical Society
|July 19, 2001
Summary
Researchers synthesized dendritic poly-2,7-fluorene polymers using a macromonomer approach. Dendritic side groups influenced conjugation and electronic properties, with optimal size observed for generation 2 dendrons in rigid rod polymers.
Area of Science:
- Polymer Chemistry
- Organic Electronics
- Materials Science
Background:
- Rigid rod polymers like poly-2,7-fluorene offer excellent charge transport properties.
- Controlling polymer morphology and electronic characteristics is crucial for device applications.
- Dendritic side groups can influence polymer solubility, processability, and optoelectronic behavior.
Purpose of the Study:
- To synthesize and characterize novel dendritic poly-2,7-fluorene homopolymers and copolymers.
- To investigate the effect of dendritic side group size on polymer conjugation and solid-state properties.
- To evaluate the optoelectronic performance, including electroluminescence, of these new materials.
Main Methods:
- Preparation of 2,7-dibromofluorene monomers with varying generations (1, 2, 3) of benzyl ether dendrons.
- Condensation polymerization to create homopolymers and copolymers with diethylhexylfluorene.
- Characterization using fluorescence spectroscopy, solid-state photoluminescence (PL) spectra, quantum efficiency measurements, Atomic Force Microscopy (AFM), and Differential Scanning Calorimetry (DSC).
- Electroluminescence (EL) measurements to assess device performance.
Main Results:
- Successful synthesis of dendritic poly-2,7-fluorene homopolymers and copolymers.
- Fluorescence measurements indicated extensive conjugation along the polymer backbone.
- An optimal size of dendritic side groups (generation 2) was identified, correlating with high reactivity and site isolation of the conjugated chain.
- AFM and DSC confirmed the absence of microphase separation in the hybrid polymers and copolymers.
- Homopolymers exhibited higher turn-on voltages compared to copolymers in initial electroluminescence tests.
Conclusions:
- The macromonomer approach enables the synthesis of well-defined dendritic poly-2,7-fluorene materials.
- Dendritic side group engineering provides a route to tune the optoelectronic properties of conjugated polymers.
- Generation 2 dendritic side groups appear optimal for balancing reactivity and conjugation in these rigid rod systems.
- The synthesized polymers show potential for applications in organic electronic devices, although further optimization is needed to reduce turn-on voltages.
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