کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5186156 | 1381097 | 2009 | 13 صفحه PDF | دانلود رایگان |
The chiral polymer P-1 was synthesized by the polymerization of (R)-6,6â²-dibutyl-3,3â²-diiodo-2,2â²-bisoctoxy-1,1â²-binaphthyl (R-M-1) with 5,5â²-divinyl-2,2â²-bipyridine (M-1) via Pd-catalyzed Heck reaction. P-2 and P-2â² were prepared by Wittig-Horner reaction of (R)-6,6â²-dibutyl-2,2â²-bisoctoxy-1,1â²-binaphthyl-3,3â²-dicarbaldehyde (R-M-2) with 5,5â²-bis (diethylphosphonomethyl)-2,2â²-bipyridine (M-2) in the presence of EtONa or NaH, respectively. P-3 was synthesized by Wittig-Horner reaction of (R)-6,6â²-di(4-trifluoromethylphenyl)-2,2â²-bisoctoxy-1,1â²-binaphthyl-3,3â²-dicarbaldehyde (R-M-3) with M-2 using NaH as a base. The four polymers have strong blue-green fluorescence due to the extended Ï-electronic structure between the chiral model compounds (R)-6,6â²-dibutyl-/di(4-trifluoromethylphenyl)-2,2â²-bisoctoxy-1,1â²-binaphthyl (R-1 or R-2) and the conjugated linker 2,2â²-bipyridyl group via vinylene bridge. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and circular dichroism (CD) spectroscopy. Based on the great differences of specific rotation values and CD spectra, P-1 and P-2 may adopt a zigzag chain configuration, while P-2â² and P-3 may adopt a helical configuration. The responsive optical properties of the two chiral helical polymers P-2â² and P-3 on transition metal ions were investigated by fluorescence, UV-vis and CD spectra. The results show that Ag+ and Ni2+ lead to nearly complete fluorescence quenching of P-2â² and P-3, Cu2+ and Fe2+ can cause obvious fluorescence quenching, but Zn2+ and Cd2+ can only produce slight fluorescence quenching. Ag+, Ni2+, Cu2+ and Fe2+ can also lead to the obvious changes of UV-vis spectra of P-2â² and P-3. On the contrary, Zn2+ and Cd2+ cause little changes. Most importantly, the CD intensities and wavelengths of the chiral helical polymers P-2â² and P-3 exhibit the pronounced changes upon addition of Ag+ and Ni2+.
Journal: Polymer - Volume 50, Issue 13, 19 June 2009, Pages 2793-2805