High-Density Packing of Spherical Microdomains from A(AB3)3 Dendron-like Miktoarm Star Copolymer.

An A(AB3)3 dendron-like miktoarm star copolymer consisting of polystyrene (PS, A) and poly(2-vinylpyridine) (P2VP, B) was synthesized using a series of anionic polymerization, atom-transfer radical polymerization (ATRP), and click reaction. The morphology of A(AB3)3 changed greatly depending on the volume fraction of A and the chain asymmetry. Interestingly, a body-centered cubic spherical phase was found even at fA = 0.51 because the chain architecture of A(AB3)3 stabilizes the large interfacial curvature toward A domains. On the other hand, when the length difference between the end and middle A blocks decreased, a hexagonally packed cylindrical phase was formed at fA = 0.50. This is attributed to the fact that the middle A chains are arranged in a more relaxed way, resulting in a milder interfacial curvature toward A domains. The experimental observations are well-consistent with the predictions based on self-consistent-field theory.

Synthesis and photoluminescence of novel Ba9Y2Si6O24:Eu2+ green phosphor.

Novel (Ba1_xEu(x))9Y2Si6O24 green phosphors were successfully prepared by a solid-state reaction method. The prepared (Ba1_xEu(x))9Y2Si6O24 green phosphors showed a single intense broadband emission in a range from 502 to 510 nm. The effects of the Eu2+ doping concentration on the optical properties were discussed under consideration of concentration quenching. The experimental results clearly indicates that the prepared (Ba1_xEu(x))9Y2Si6O24 green phosphors have great potentials as a down-conversion green phosphor for white light emitting diodes (LEDs) utilizing blue LEDs as the primary light source.