Synthesis, Morphology and Properties of Rod-coil Block Copolymers, Poly(fluorene)-block-Poly(4-vinylpyridine)
Date Issued
2009
Date
2009
Author(s)
Sun, Han-Sheng
Abstract
π-conjugated rod-coil block copolymers have been widely investigated recently since they have great potential applications in many aspects, including electronic devices, sensors, optical materials, biotechnology and etc. Such block copolymers could not only manipulate the electron and optoelectronic properties but also provide the flexibility on morphology control. In this thesis, the main objective is to synthesize a series of different rod/coil ratios polyfluorene-based block copolymers and form the hierarchical self-organized structures in order to control the orientation of PF nanodomains. Furthermore, the thin film state morphologies of those polymers and photophysical properties were explored. In the first part of this thesis (chapter 2), an amphiphilic rod-coil block copolymer, poly[2,7-(9,9-dihexylfluorene)]-block-poly(4-vinylpyridine) (PF-b-P4VP) with diverse rod/coil ratios was synthesized and characterized. Various self-assemble morphologies, including lamellar and irregular structure, were observed using AFM, as the PF and P4VP blocks compositions are similar to each other. The morphological transformation led to a significant variation on fluorescence characteristics due to the intermolecular aggregation of rigid segment PF. In the second part of this thesis (chapter 3), the hierarchical self-organized supramolecular materials were prepared from poly[2,7-(9,9-dihexylfluorene)]-block-poly(4-vinylpyridine) (PF-b-P4VP) and 3-Pentadecylphenol (PDP) with different PDP content by hydrogen bonding. The FTIR experimental results showed that hydrogen bonding existed between the nitrogen of 4-vinylpyridine ring and hydroxyl group of PDP. After the PDP was added, the morphologies changed to disorderly cylinder, cylinder-sphere complex and sphere with a domain size of approximately 15-20 nm. The fluorescence characteristics also varied with the diverse hierarchical structures. In the PL spectra, the decrease in the intensity of PF excimer was obtained, as the P4VP(PDP)x matrix content increased. It is the result of the inhibition of the intermolecular aggregation of PF blocks.
Subjects
Rod-coil block copolymer
Thin film morphology
Anionic polymerization
Type
thesis
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