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A Versatile Solvent-Free “One-Pot” Route to Polymer Nanocomposites and the in situ Formation of Calcium Phosphate/Layered Silicate Hybrid Nanoparticles

Authors

  • Hans Weickmann,

    1. Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany)
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  • Matthias Gurr,

    1. Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany)
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  • Olaf Meincke,

    1. Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany)
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  • Ralf Thomann,

    1. Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany)
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  • Rolf Mülhaupt

    Corresponding author
    1. Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany)
    2. Freiburg Institute for Advanced Studies, School of Soft Matter Research Albertstraße 19, 79104 Freiburg i. Br. (Germany)
    • Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Stefan-Maier-Str. 21/31, D-79104 Freiburg i. Br. (Germany).
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Abstract

Poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyurethane (PU) nanocomposites containing well-dispersed calcium phosphate/layered silicate hybrid nanoparticles were prepared in a versatile solvent-free “one-pot” process without requiring separate steps, such as organophilic modification, purification, drying, dispersing, and compounding, typical for many conventional organoclay nanocomposites. In this “one-pot” process, alkyl ammonium phosphates were added as swelling agents to a suspension of calcium/layered silicate in styrene, methyl methacrylate, or polyols prior to polymerization. Alkyl ammonium phosphates were prepared in situ by reacting phosphoric acid with an equivalent amount of alkyl amines such as stearyl amine (SA) or the corresponding ester- and methacrylate-functionalized tertiary alkyl amines, obtained via Michael Addition of SA with methyl acrylate or ethylene 2-methacryloxyethyl acrylate. Upon contact with the calcium bentonite suspension, the cation exchange of Ca2+ in the silicate interlayers for alkyl ammonium cations rendered the bentonite organophilic and enabled effective swelling in the monomer accompanied by intercalation and in situ precipitation of calcium phosphates. According to energy dispersive X-ray analysis, the calcium phosphate precipitated exclusively onto the surfaces of the bentonite nanoplatelets, thus forming easy-to-disperse calcium phosphate/layered silicate hybrid nanoparticles. Incorporation of 5–15 wt% of such hybrid nanoparticles into PMMA, PS, and PU afforded improved stiffness/toughness balances of the polymer nanocomposites. Functionalized alkyl ammonium phosphate addition enabled polymer attachment to the nanoparticle surfaces. Transmission electron microscopy (TEM) analyses of PU and PU-foam nanocomposites, prepared by dispersing hybrid nanoparticles in the polyols prior to isocyanate cure, revealed the formation of fully exfoliated hybrid nanoparticles.

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