Facile Synthesis and Adsorption Properties of Phosphonated Cellulose Beads for Selective Removal of Low-density Lipoprotein

A novel low-density lipoprotein adsorbent was prepared simply by directly phosphonating porous cellulose beads. Tests in vitro demonstrated that this adsorbent showed quite good adsorption performance for selective removal of low-density lipoprotein from human plasma. The effects of preparation conditions on the lipoprotein sorption properties of the resulted adsorbent were investigated. The adsorption dynamics was also examined.

A CONFORMATION STUDY OF POLYELECTROLYTE-DENDRITIC SURFACTANT COMPLEXES IN DILUTE SOLUTIONS

Three dendronized polymers from generation one to generation three have been prepared by complexing negatively charged Frechet-type dendrons with a polyanion, poly（diallydimethylammoniurn chloride） （PDADMAC）. The gaffing degree has been confirmed mainly by elemental analysis. In dilute solutions of tetrahydrofuran, static light scattering studies indicate that the first generation complex has a coil-like conformation, even more flexible than PDADMAC. The second and third generation complexes exhibit polyelectrolyte behavior. Dynamic light scattering experiments indicate that all the three complexes have almost the same hydrodynamic radius, indicating that they might own similar coil conformation. Atomic force microscopy shows the existence of disordered globules formed by one or a couple of complex coils. All these observations can be explained by the flowerlike coil conformation, which is formed by the intra-molecular association. This is totally different from the stretched chain conformation formed by covalently connected dendronized polymers. This result also explains why some ordered supramolecular structures, found in condensed state of the similar complexes, are not as perfect as those of conventional dendronized polymers.

MOLECULAR WEIGHT DEPENDENCE OF CRYSTAL PATTERN TRANSITIONS OF POLY(ETHYLENE OXIDE)

Crystal patterns in ultrathin films of six poly（ethylene oxide） fractions with molecular weights from 25000 to 932000 g/mol were characterized within crystallization temperature range from 20 ℃to 60℃. Labyrinthine, dendritic and faceted crystal patterns were observed in different temperature ranges, and then labyrinthine-to-dendritic and dendritic-to- faceted transition temperatures T_L-D and T_D-F were quantitatively identified. Their molecular weight dependences are T_L-D（M_w） = T_L-D（∞） -K_L-D/M_w, where T_L-D（∞） = 38.2 ℃ and K_L-D = 253000 ℃.g/mol and T_D-F（M_w） = T_D-F（∞） -K_D-F/M_w, where T_D-F（∞） = 54.7 ℃ and K_D-F= 27000 ℃.g/mol. Quasi two-dimensional blob models were proposed to provide empirical explanations of the molecular weight dependences. The labyrinthine-to-dendritic transition is attributed to a molecular diffusion process change from a local-diffusion to diffusion-limited-aggregation （DLA） and a polymer chain with M_w ≈253000 g/mol within a blob can join crystals independently. The dendritic-to-faceted transition is attributed to a turnover of the pattern formation mechanism from DLA to crystallization control, and a polymer chain with a M_w ≈27000 g/tool as an independent blob crosses to a depletion zone to join crystals. These molecular weight dependences reveal a macromolecular effect on the crystal pattern formation and selection of crystalline polymers.

Sign of differential reflection and transmission in pump-probe spectroscopy of graphene on dielectric substrate

Pump-probe differential reflection and transmission spectroscopy is a very effective tool to study the nonequilibrium carrier dynamics of graphene. The reported sign of differential reflection from graphene is not explicitly explained and not consistent. Here, we study the differential reflection and transmission signals of graphene on a dielectric substrate. The results reveal the sign of differential reflection changes with the incident direction of the probe beam with respect to the substrate. The obtained theory can be applied to predict the differential signals of other two-dimensional materials placed on various dielectric substrates.

Fluorination-modulated end units for high-performance non-fullerene acceptors based organic solar cells

Organic solar cells (OSCs) have drawn great attention for their low cost, light weight, solution processability and flexibility [1-3]. Over the last decade, fullerene and their derivatives have been the dominant electron acceptors for OSCs due to their excellent electron-transport properties, but limited by their disadvantages of poor light absorption, high synthesis cost, and difficulties in property tunability.