Accessing local dynamics within a single macromolecule is the key to understand the physical origin of the viscoelasticity and especially the glass transition. In order to extract specific information on the dynamics ...Accessing local dynamics within a single macromolecule is the key to understand the physical origin of the viscoelasticity and especially the glass transition. In order to extract specific information on the dynamics of the branch point of a star polymer around its glass transition temperature, four-arm star poly （n-butyl methacrylate） with a fluorescent core was synthesized using perylene diimide as initiator and polymerization conducted via atom transfer radical polymerization. The process is found to be effective in positioning the fluorophore at the branch point with the fluorophore intact, which allows the successful application of single molecule fluorescence defocus imaging in examining the local site- sensitive dynamics. The power spectra of rotation trajectories, the population of rotating fluorophores as well as the distribution of angular displacement were used to revel the difference in local dynamics between branch point and the arm＇s end. It is discovered that the local dynamics at the core of the star polymer is much less activated than that at the arm＇s end. The results demonstrate the strong effect dues to the topological constrain at the branch point and the more free space at the arm＇s end.展开更多
Y/Bi co-doped silicate glasses were prepared,and the effects of Y 2 O 3 on the absorption and emission properties were investigated by spectrum measurement.It was found that the absorption intensity in visible region ...Y/Bi co-doped silicate glasses were prepared,and the effects of Y 2 O 3 on the absorption and emission properties were investigated by spectrum measurement.It was found that the absorption intensity in visible region decreases with increase of Y 3＋ concentration in（70-x）SiO 2 xY 2 O 3-30CaO-1.5Bi 2 O 3（x=0 mol.%,1 mol.%,3 mol.%,5 mol.%,7 mol.%） glasses.The emissions centered at 410,630,1200 and 1290 nm were observed under 280,470,514 and 808 nm excitation,respectively.The emission intensity had the similar change tendency in the visible and near infrared region.We also discussed the actual role of Y 3＋ ions playing in the visible and near infrared emissions of the silicate glasses.展开更多
基金supported by National Basic Research Program of China(No. 2014CB643601)
文摘Accessing local dynamics within a single macromolecule is the key to understand the physical origin of the viscoelasticity and especially the glass transition. In order to extract specific information on the dynamics of the branch point of a star polymer around its glass transition temperature, four-arm star poly （n-butyl methacrylate） with a fluorescent core was synthesized using perylene diimide as initiator and polymerization conducted via atom transfer radical polymerization. The process is found to be effective in positioning the fluorophore at the branch point with the fluorophore intact, which allows the successful application of single molecule fluorescence defocus imaging in examining the local site- sensitive dynamics. The power spectra of rotation trajectories, the population of rotating fluorophores as well as the distribution of angular displacement were used to revel the difference in local dynamics between branch point and the arm＇s end. It is discovered that the local dynamics at the core of the star polymer is much less activated than that at the arm＇s end. The results demonstrate the strong effect dues to the topological constrain at the branch point and the more free space at the arm＇s end.
基金supported by Science and Technology Project of Guangdong (2009A090100044)National High-Technology Research and Development Program of China ("863"Program) (2011AA030201)
文摘Y/Bi co-doped silicate glasses were prepared,and the effects of Y 2 O 3 on the absorption and emission properties were investigated by spectrum measurement.It was found that the absorption intensity in visible region decreases with increase of Y 3＋ concentration in（70-x）SiO 2 xY 2 O 3-30CaO-1.5Bi 2 O 3（x=0 mol.%,1 mol.%,3 mol.%,5 mol.%,7 mol.%） glasses.The emissions centered at 410,630,1200 and 1290 nm were observed under 280,470,514 and 808 nm excitation,respectively.The emission intensity had the similar change tendency in the visible and near infrared region.We also discussed the actual role of Y 3＋ ions playing in the visible and near infrared emissions of the silicate glasses.
