Preparation of the water-soluble fluorene-containing fluorescent polymer by one-pot method

Abstract

A water-soluble fluorescent polymer, 2,7-di}4'-[3''-(S-poly(acryloyl ethylene diamine hydrochloride)-2'''- methyl propionic acid)propionyloxy hexyloxy]phenyl{-9,9-di(n-octyl)fluorene (P3) with regular and ordered structure, was designed and synthesized with high conversion using click reaction between thiols and carbon-carbon double bonds. Because the S-H bond is relatively weak, thiol groups are subject to rapid oxidation during purification and storage and thereby result in the low conversion in the following click reaction. To circumvent this limitation, the synthesis of thiol groups and click reaction were simultaneously performed in one system (one-pot method). The intermediate products P1 (S-1-dodecyl-S'-[poly(N-Boc-acryloyl ethylene diamine)-2'-methyl propionic acid]trithiocarbonate) and M2 (2,7-di[4-(acryloyloxy hexyloxy)phenyl]-9,9-di(n-octyl)fluorene) were prepared via reversible addition fragmentation chain transfer (RAFT) polymerization and Williamson synthesis, respectively. Then, 2,7- di}4'-[3''-(S-poly(N-Boc-acryloyl ethylene diamine)-2'''-methyl propionic acid)propionyloxy hexyloxy]phenyl{-9,9-di(n-octyl)fluorene (P2) was synthesized with high conversion (83%) by employing a click reaction with P1 and M2 as starting materials. Finally, water-soluble fluorescent polymer P3 was obtained after the deprotection of P2. M2, P1, P2 and P3 were characterized by Fourier transform infrared (FTIR) spectrum, nuclear magnetic resonance (NMR), high-resolution mass spectroscopy (MS), gel permeation chromatograph (GPC), UV-Visible (UV-Vis) spectrum, and fluorescence, respectively. The results revealed that P3 displayed good solubility in water and not only exhibited a blue fluorescence emission band in water but also had a similar photoluminescent spectra to those of M2 and P2 in dichloromethane. The fluorescence quantum yield of P3 in aqueous solution could reach 0.10. In addition, the result of cell cytotoxicity indicates that P3 has low cytotoxicity and exhibits potential for biomedical applications. This work provides a new insight into the study of water-soluble fluorescent polymer. Open image in new window