Novel Conjugated Polymer/Silica Nanocomposites with Tunable Mesostructure Synthesized by a Robust Pd Catalyst
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Novel Conjugated Polymer/Silica Nanocomposites with Tunable Mesostructure Synthesized by a Robust Pd Catalyst Byron McCaughey1, Chris Costello2, J. Eric Hampsey1, Donghai Wang1, Chaojun Li2, and Yunfeng Lu1* 1
300 Lindy Boggs, Chemical Engineering Department, Tulane University, New Orleans, LA 70118 2 2015 Percival Stern, Chemistry Department, Tulane University, New Orleans, LA 70118 ABSTRACT Conjugated poly(2,5-thienylene ethynylene) (PTE)/silica nanocomposites with cubic and lamellar mesostructures have been synthesized. Surfactant directed assembly coorganized 2,5diiodothiophene monomer and palladium-based catalyst within a silica matrix. Subsequent polymerization initiated by exposing the monomer/catalyst/silica nanostructures to acetylene gas resulted in the formation of an ordered, mesostructured poly(2,5-thienylene ethynylene)/silica nanocomposite as determined by XRD, UV-vis, FTIR, and TEM experiments. Mesostructured PTE with 287m2/g surface area is obtained after silica removal. Further polymerization of PTE oligomers occurs after exposure to acetylene gas due to active Pd catalyst attached to the polymer chains. This novel approach provides a unique route to synthesize mesostructured conjugated polymer/inorganic nanocomposites and porous mesostructured PTE. INTRODUCTION Nanocomposites are extremely promising materials due to their unique ability to combine and tailor overall physical properties and due to synergy, interfacial, and confinement effects between the constituent phases[1]. Nanocomposites that contain conjugated polymers confined within a silica matrix have shown enhanced conductivity, mechanical strength, processability, environmental stability, and other unique properties that allow for potential use in light emitting diodes[2], information storage devices, optical signal processors, battery substitutes, and solar energy converters[3]. Areneethynylene conjugated polymers such as poly(2,5-thienylene ethynylene) (PTE) are particularly interesting because they have exhibited high quantum yields[4], lower band gaps than benzene analogs[5], and stability to air and moisture[6]. However, because the synthesis and processing of PTE is often hindered by its low solubility, it is difficult to synthesize PTE/silica nanocomposites or high surface area PTE. Conjugated polymer/ceramic nanocomposites are typically created via a multiple-step synthesis process involving the formation of mesoporous material and subsequent monomer infiltration and polymerization[7-11]. One-step synthesis methods involving the simultaneous incorporation of monomer into the initial sol-gel solution have been studied much less frequently[12] because of the often require strict synthesis conditions required for many conjugated polymers[3,13]. Recently we developed a robust, one pot polymer synthesis procedure to prepare PTE via the palladium-catalyzed polymerization of aryl diodides with acetylene gas in aqueous media[14,15]. Because the reaction is carried out in water, a surfactant self-assembly synthesis route can be e
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