| Summary: | 碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 106 === Direct arylation can carry out the coupling of C−H bond with electrophilic aryl halide with the transition metal catalytic system. In comparison to traditional cross-coupling reactions, direct arylation is considered a more atom-economy and environmental-friendly method and has been used to synthesize conjugated polymers in the recent years. Several mechanisms, such as Heck-type reaction, aromatic electrophilic substitution, and concerted metalation deprotonation (CMD) have been proposed to account for this reaction. Among all, CMD is the most likely one,as supported by numerous experimental results and theoretical calculations. The optimal reaction conditions often involve the use of catalyst, ligand, additive, and solvent.
Water-soluble conjugated polymers with π-electron conjugated backbone exhibit noticeable optoelectronic properties. They have attracted much attention in bio-related applications, such as biological sensing and cell imaging. To synthesize the water-soluble conjugated polymers by direct-arylation polymerizationin aqueous media has not been reported. It is therefore intriguing to examine its possibilities.
Herein, water-soluble polyfluorene is selected as the target polymer on account of its good fluorescence properties and easy structural modification. The catalytic conditions were optimized and polyfluorene with high average molar weight and narrow dispersity was obtained. During the optimization, we noticed that 1H NMR and fluorescence signals of fluorene monomer are quite sensitive to the reagents used the in the direct-arylation polymerization, which is linked with the variation of aggregation behavior in water. Moreover, the phosphine ligand could under ion-exchange reaction with the ammonia bromide functionality in both the monomer and polymer, thus increasing the diversity in the spatial structure of the polymers.
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