Enhanced Forster resonance energy transfer in electrostatically self-assembled multilayer films made from new fluorescently labeled polycations

The synthesis of two new complementary fluorescently labeled polycations, which are derived from 4-(vinylbenzyl chloride) and coumarin, and their use for layer-by-layer multilayers films applying electrostatic self-assembly (ESA) are reported. The alternating polyelectrolyte deposition cycles were followed by UV-vis spectroscopy, ellipsometry, and X-ray reflectivity. Regular growth was observed. Fluorescence and UV-vis measurements showed the formation of fluorescent dye aggregates for one coumarin derivative in the ESA multilayers. The resulting shift in the spectra enhances the spectral overlap between the two fluorescently labeled polycations when used in mixed thin films, improving the efficiency of the Forster resonance energy transfer between the chromophores. The nonradiative nature of the energy transfer was confirmed by fluorescence decay time measurements

New chain transfer agents for reversible addition-fragmentation chain transfer (RAFT) polymerisation in aqueous solution

New chain transfer agents for free radical polymerisation via reversible addition-fragmentation chain transfer (RAFT) were synthesised that are particularly suited for aqueous solution polymerisation. The new compounds bear dithioester and trithiocarbonate moieties as well as permanently ionic groups to confer solubility in water. Their stability against hydrolysis was studied, and compared with the one of a frequently employed water-soluble RAFT agent, using UV-Vis-spectroscopy and H-1-NMR measurements. An improved resistance to hydrolysis was found for the new RAFT agents compared to the reference one, providing good stabilities in the pH range between 1 and 8, and up to temperatures of 70 degreesC. (C) 2004 Elsevier Ltd. All rights reserved