International audienceThe photoredox catalysis approach is used to initiate the free radical promoted cationic photopolymerization of N-vinylcarbazole (NVK) under very soft irradiation conditions (halogen lamp, blue or green LED bulbs) using visible-light harvesting photocatalysts (mainly Ir(III) complexes) in iodonium salt and silane containing photoinitiating systems. The reactions were shown to proceed via an oxidative catalytic cycle where the generated free radicals are oxidized into cations. The effect of NVK on this catalytic cycle is discussed. Epoxy/NVK matrixes can also be polymerized. The luminescent properties of the synthesized polymers are presented
Constitutional self-instructed membranes were developed and used for mimicking the adaptive structural functionality of natural ionchannel systems. These membranes are based on dynamic hybrid materials in which the functional self-organized macrocycles are reversibly connected with the inorganic silica through hydrophobic noncovalent interactions. Supramolecular columnar ion-channel architectures can be generated by reversible confinement within scaffolding hydrophobic silica mesopores. They can be structurally determined by using X-ray diffraction and morphologically tuned by alkali-salts templating. From the conceptual point of view, these membranes express a synergistic adaptive behavior: the simultaneous binding of the fittest cation and its anion would be a case of ''homotropic allosteric interactions,'' because in time it increases the transport efficiency of the pore-contained superstructures by a selective evolving process toward the fittest ion channel. The hybrid membranes presented here represent dynamic constitutional systems evolving over time to form the fittest ion channels from a library of molecular and supramolecular components, or selecting the fittest ion pairs from a mixture of salts demonstrating flexible adaptation.crown-ethers ͉ ion channels ͉ self-assembly
Thin films of crosslinked polymethylhydrosiloxane (PMHS) have been grafted on silica using the sol-gel process allowing further functionalization by effective quantitative hydrosilylation of SiH groups by olefins within the network. Postfunctionalization gives the polysiloxane network with n-alkyl side chains. The PMHS coating was prepared by room temperature polycondensation of a mixture of methyldiethoxysilane HSiMe(OEt) 2 monomer and triethoxysilane HSi(OEt) 3 (TH) as crosslinker. The surface-attached films are chemically stable and covalently bonded to the silica surface. Subsequently, films were functionalized without delamination. We showed by FTIR spectroscopy how the crosslinking ratio and the molecular size of the alkenes precursors influence the extent of the hydrosilylation reaction of SiH groups in the PMHS network. We have determined that quasi-full olefin addition catalyzed by a platinum complex occurred within soft networks of less than 5% TH with 1-alkenes CH 2 ¼ ¼CH(CH 2 ) n-2 CH 3 of various alkyl chain lengths (n ¼ 5, 11, 17). Powders of PMHS gel were also modified with 1-alkenes by hydrosilylation. The SiH groups within the soft gel (5% crosslinked) were fully functionalized as shown by 29 Si and 1 H solid-state NMR. The structure of functionalized polysiloxane with n-octadecyl and n-dodecyl side chains was studied by FTIR, wide angle X-ray diffraction, and DSC showing crystallization of the long n-alkyl chains in the network. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [3546][3547][3548][3549][3550][3551][3552][3553][3554][3555][3556][3557][3558][3559][3560][3561][3562] 2008
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