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Calcium Phosphate Mineralization beneath a Polycationic Monolayer at the Air–Water Interface

Authors

  • Mathias Junginger,

    1. University of Potsdam, Institute of Chemistry, 14476 Potsdam, Germany
    2. Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
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  • Katarzyna Kita-Tokarczyk,

    1. Department of Chemistry, University of Basel, 4056 Basel, Switzerland
    2. Current address: Centre for Molecular Nanoscience, School of Chemistry, University of Leeds, Leeds LS2 9JT, UK
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  • Thomas Schuster,

    1. Department of Chemistry, University of Basel, 4056 Basel, Switzerland
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  • Jürgen Reiche,

    1. University of Potsdam, Institute of Physics and Astronomy, 14476 Potsdam, Germany
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  • Felix Schacher,

    1. Makromolekulare Chemie II, University of Bayreuth, Naturwissenschaften II (NW II), 95440 Bayreuth, Germany
    2. Current address: School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
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  • Axel H. E. Müller,

    1. Makromolekulare Chemie II, University of Bayreuth, Naturwissenschaften II (NW II), 95440 Bayreuth, Germany
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  • Helmut Cölfen,

    1. Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
    2. Current address: University of Konstanz, Physical Chemistry, 78457 Konstanz, Germany
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  • Andreas Taubert

    Corresponding author
    1. University of Potsdam, Institute of Chemistry, 14476 Potsdam, Germany
    2. Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
    • University of Potsdam, Institute of Chemistry, 14476 Potsdam, Germany.
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Abstract

The self-assembly of the amphiphilic block copolymer poly(n-butyl methacrylate)-block-poly[2-(dimethylamino)ethyl methacrylate] at the air–water interface has been investigated at different pH values. Similar to Rehfeldt et al. (J. Phys. Chem. B2006, 110, 9171), the subphase pH strongly affects the monolayer properties. The formation of calcium phosphate beneath the monolayer can be tuned by the subphase pH and hence the monolayer charge. After 12 h of mineralization at pH 5, the polymer monolayers are still transparent, but transmission electron microscopy (TEM) shows that very thin calcium phosphate fibers form, which aggregate into cotton ball-like features with diameters of 20 to 50 nm. In contrast, after 12 h of mineralization at pH 8, the polymer film is very slightly turbid and TEM shows dense aggregates with sizes between 200 and 700 nm. The formation of calcium phosphate is further confirmed by Raman and energy dispersive X-ray spectroscopy. The calcium phosphate architectures can be assigned to the monolayer charge, which is high at low pH and low at high pH. The study demonstrates that the effects of polycations should not be ignored if attempting to understand the colloid chemistry of biomimetic mineralization. It also shows that basic block copolymers are useful complementary systems to the much more commonly studied acidic block copolymer templates.

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