A novel co‐assembly based on the block copolymer bearing photocleavable groups and macroanionic polyoxometalates Na9[Ln(W5O18)2] (LnW10, Ln = Eu, Dy) triggered by UV light is realized in aqueous solution. The copolymer synthesized by atom transfer radical polymerization (ATRP) undergoes irreversible cleavage upon UV irradiation to generate primary amine (pKa ≈ 8–9) residues which are completely protonated under a neutral pH in aqueous solution. Electrostatic attractions between the resulting positively charged copolymers and anionic LnW10 drive the formation of assemblies. In situ small angle X‐ray scattering and transmission electron microscopy are used to characterize the morphology of the assemblies. The microenvironments around polyoxometalates in the core of hybrid assemblies become highly hydrophobic, resulting in dramatically enhanced photoluminescence with the obvious intensity enhancement. The solution parameters pH and salt additives show great effects on the formation of assemblies.
Summary: A systematic investigation of the microstructure of ethylene copolymers has been carried out as a function of the comonomer type and content, employing small‐angle X‐ray scattering (SAXS) experiments to study the lamellar structure, and solid‐state NMR to study the local conformational freedom. The SAXS results clearly show that the major consequence of incorporating comonomers (butene and octene) is the absence of lamellar thickening during the crystallization. From solid‐state NMR study, applying the rotor‐encoded rotational echo double resonance technique (REREDOR), it is found that the extent of the orientational order in the noncrystalline region of semicrystalline polyethylene is substantial but this order is not significantly affected by the incorporation of comonomer units. Therefore, the major cause for the significant improvements of mechanical properties observed for ethylene copolymers is not a change in the thermodynamic state of the noncrystalline region, but most likely a significant change in the intermolecular topological structure due to the blocking of disentanglement processes required by the lamellar thickening step during crystallization.
Photovoltaic performance of dye sensitized solar cells fabricated with a commercially available thiophene based copolymer was investigated. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)], a highly soluble polythiophene, was used as a sensitizer. An open-circuit voltage of 0.64 V and a short-circuit current density of 0.36 mA/cm2 were measured. The incident photon to current conversion efficiency for the polymer was measured. Fluorescence from the other polythiophene, poly(3,3′-didodecyl quarter thiophene) was found to be quenched when blended with phenyl C61 butyric acid methyl ester (PCBM) (1:1 wt ratio), indicating the charge transfer from the conjugated polymer to PCBM. 相似文献
