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- Living polymerization (3)
- Micelles (3)
- ATRP (2)
- Amyloid beta-peptide (1)
- Azulen (1)
- Bauwesen (1)
- Block copolymers (1)
- Chain folding (1)
- Confocal fluorescence microscopy (1)
- Copolymerization (1)
Organisationseinheit der BAM
Covalent bridges play a crucial role in the folding process of sequence-defined biopolymers. This feature, however, has not been recreated in synthetic polymers because, apart from some simple regular arrangements (such as block co-polymers), these macromolecules generally do not exhibit a controlled primary structure—that is, it is difficult to predetermine precisely the sequence of their monomers. Herein, we introduce a versatile strategy for preparing foldable linear polymer chains. Well-defined polymers were synthesized by the atom transfer radical polymerization of styrene. The controlled addition of discrete amounts of protected maleimide at precise times during the synthesis enabled the formation of polystyrene chains that contained positionable reactive alkyne functions. Intramolecular reactions between these functions subsequently led to the formation of different types of covalently folded polymer chains. For example, tadpole (P-shaped), pseudocyclic (Q-shaped), bicyclic (8-shaped) and knotted (α-shaped) macromolecular origamis were prepared in a relatively straightforward manner.
Four azulene dyads have been synthesized and studied by spectroscopic and electrochemical methods. A triarylamine, a boron-dipyrromethene (BDP or BODIPY), a porphyrin, and an isoalloxazine moiety have been linked to an extended π electron system at the 2-position of azulene, leading to the dyads 1–4, respectively. For the synthesis of 1–4, first 2-(4-ethynyl-phenyl)azulene (EPA) was prepared, which was further reacted with the halogenated chromophores by Pd-catalyzed cross-coupling reactions. The dyads 1–4 exhibit strong absorption bands in the visible range, which are dominated by the absorption spectra of the individual subchromophores. Fluorometric studies of 2–4 revealed that after excitation of the subchromophoric unit attached to the parent azulene moiety, quenching mainly through energy transfer to azulene is effective, whereas possible charge-transfer interactions play only a minor role. Potentiodynamic oxidation of the dyads 1–4 leads to the formation of polymer films, which are deposited at the electrode. The polymer film derived from 1 was further characterized by spectroelectrochemistry. During positive doping of poly-1, a strong absorption band appears at 13,200 cm1, which is typical for triarylamine radical cations. This band is overlapping with a broad absorption band in the low-energy region that might be caused by charge-transfer interactions within the polymer.