Connecting Curable Siloxanes to Luminescent Organic Semiconductors - Monomers for Functional Hybrid Materials
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0939-O03-27
Connecting Curable Siloxanes to Luminescent Organic Semiconductors - Monomers for Functional Hybrid Materials Heiner Detert1, and Erli Sugiono2 1 Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10 - 14, Mainz, Rheinland-Pfalz, 55099, Germany 2 Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt/Main, 60444, Germany
ABSTRACT Luminescent stilbenoid chromophores with two alkoxysilane end groups are prepared via hydrosilylation or condensation / reduction of substituted 5-ring oligo-phenylenevinylenes (OPV) with hydro- and aminopropylsilanes. Chromophore and curable units are connected via flexible spacers. To obtain compounds with a rigid connection between silane and π-system, iodo- or bromo-OPVs were coupled to alkoxysilanes carrying vinyl- or p-vinylphenyl moieties under Heck conditions. This approach allowed a combined connection of the chromophore to the silane moiety with an extension of the π-system. Hydrolysis of the alkoxysilanes yields silanols condensing to curable three-dimensional networks, thus allowing the transformation of small molecules to transparent and fluorescent films with well-defined chromophores.
INTRODUCTION In addition to conjugated polymers [1,2], well-defined, monodisperse oligomers [3 - 5] have received considerable attention as active materials for the use in a variety of electro-optical devices. Initally, the oligomers had been prepared as model compounds for a better understanding of the properties of the homologous polymers [6], but in some applications the well-defined chromophores proved to perform superior to their macromolecular homologues. Advantages of compounds with a low molecular weight are a better control of the effective conjugation length, the relatively easy fine tuning of electrical and optical properties [2, 7, 8] as well as solubility and the possibility to form layers by vacuum deposition. Despite these benefits, their strong tendency towards crystallisation is a major drawback for their application e.g. as emissive layers in LEDs. Successful strategies to stabilise amorphous films of monodisperse chromophores are linking conjugated units to form molecules with a tetrahedral shape [9, 10], the connection of rigid π-systems with flexible polymers, either as side groups [11] or segments in the main chain [12], and embedding the electroactive compounds in a polymeric matrix like polysiloxane [13]. Linking conjugated oligomers to alkoxysilanes results in curable compounds for the synthesis of cyclosiloxanes, linear polymers or organic-inorganic hybrid materials [14]. A device-oriented approach uses the immobilisation of the functional units on the substrate, often on surfaces pretreated with reactive silanes [15, 16], and also with siloxane-functionalized chromophores [17]. In connection with our work on luminescent materials [8, 9, 19], we describe here the syntheses and some properties of oligo(phenylenevinylene)s directly or via flexible spacers
connected with reactive alkoxysilanes. These monomers are interesting
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