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Effects of pH on structure and mechanical properties of dried pH-responsive latex particles

Abstract

Micrometer-sized, monodisperse polystyrene (PS) particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) colloidal stabilizer were synthesized by free radical dispersion polymerization. X-ray photoelectron spectroscopy and electrophoretic measurements verified that PDEA covered the PS particle surface. At pH 3.0 and 6.3, where the PDEA is protonated and cationically charged, the PDEA-PS particles were well dispersed in aqueous media thanks to water soluble PDEA stabilizer and slowly sedimented due to gravity and enriched on the bottom of glass vial. At pH 10.0, where the PDEA is non-protonated and neutral, the PDEA-PS particles weakly aggregated due to non-hydrated and collapsed PDEA. These PDEA-PS particles and aggregates relatively quickly sedimented on the bottom. Sediment height observed at pH 10.0 was larger than those observed at pH 3.0 and 6.3 in both wet and dry systems, which indicated that larger porosity was formed at pH 10.0. Mechanical testing experiments confirmed that fracture toughness of the dried materials decreased with an increase of pH. Fracture toughness was found to be correlated with the degree of particle ordering in the dried particulate materials: More ordered, dense packings lead to a higher fracture toughness than amorphous, less dense packings. Thus, we could tune fracture toughness and degree of particle ordering by controlling the pH.

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Publication details

The article was received on 12 Aug 2017, accepted on 15 Sep 2017 and first published on 15 Sep 2017


Article type: Paper
DOI: 10.1039/C7SM01625E
Citation: Soft Matter, 2017, Accepted Manuscript
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    Effects of pH on structure and mechanical properties of dried pH-responsive latex particles

    T. Sekido, M. Kappl, H. Butt, S. Yusa, Y. Nakamura and S. Fujii, Soft Matter, 2017, Accepted Manuscript , DOI: 10.1039/C7SM01625E

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