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The photochemical polymerization reactions of isoprene with the use of H2O2 as the photoinitiator have been studied in benzene, acetone, and tetrahydrofuran solutions. Hydrogen peroxide is photodecomposed to form hydroxyl radicals which may initiate the polymerization of isoprene with hydroxyl terminated polyisoprene as the product. Average molecular weight, microstructure, and the functionality of the hydroxyl terminated polyisoprene are determined. A suitable reaction mechanism and the polymerization rate equations are proposed. The overall activations energy is evaluated to be about 3.8 kcal/mol.

BACKGROUND: Crosslinkable hyperbranched polymers have great potential for use in organic light‐emitting devices and photovoltaics. With this in mind, two crosslinkable hyperbranched polyfluorenes, P5 and P6, containing oxadiazole as the core, and linear polyfluorene P0 were synthesized via palladium‐catalyzed Suzuki coupling. A device was also made. RESULTS: The resulting polymers were characterized using NMR, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The spectral behavior of the polymers was also investigated. Compared with uncrosslinked P5 and P6, the photoluminescence spectra of crosslinked P5 and P6 were little influenced by the crosslinking. After annealing for 3 h at 200 °C in air, the photoluminescence of P6 (with a greater content of branched units) showed excellent stability compared with that of P5 and P0. The results for the device revealed that photocrosslinking improves the stability of the electroluminescence. CONCLUSION: The crosslinkable polymers obtained can be used in multilayer devices. Copyright © 2008 Society of Chemical Industry

A series of cadmium telluride (CdTe) nanocrystals were synthesized by a modified organometallic synthesis method at various reaction temperatures ranging from 130 to 250 • C. In this method, octadecylamine (ODA) was introduced as an additional coordinating component to the mixture of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP). CdO was used as a precursor. The prepared CdTe nanocrystals were studied by the absorption and emission spectra as well as the powder X-ray diffraction (XRD) patterns. The result shows that besides the traditional continuous-growth mode observed frequently at relatively high reaction temperature, a discontinuous-growth mode was confirmed at the initial growth stage of CdTe nanocrystals, arising from the change of the absorption spectra of CdTe nanocrystals with the reaction time at relatively low reaction temperature. The structures of CdTe nanocrystals, e.g., the cubic zinc blende structure at 160 • C and the hexagonal wurtzite structure at 250 • C, were characterized by XRD.

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