Silica microparticles surface coating by layer-by-layer or polyelectrolyte complex adsorption
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ORIGINAL PAPER
Silica microparticles surface coating by layer-by-layer or polyelectrolyte complex adsorption Marcela Mihai & Simona Schwarz & Andreas Janke & Claudiu Augustin Ghiorghiţă & Ecaterina Stela Drăgan
Received: 24 September 2012 / Accepted: 15 January 2013 / Published online: 24 January 2013 # Springer Science+Business Media Dordrecht 2013
Abstract This study follows the surface properties modification of some silica particles, by coating with complementary polyelectrolytes by layer-by-layer deposition or by the adsorption of preformed polyelectrolyte complexes. Two polyanions, alginic acid and poly(2-acrylamido-2-methylpropanesulfonic acid - co - acrylic acid), and chitosan as polycation are used. The influence of the polyelectrolytes structure and the molar ratio between ionic charges on the polyelectrolyte complexes characteristics is investigated by turbidimetry, dynamic light scattering and electrophoresis. The properties of the formed inorganic/organic materials are evaluated comparing the size distribution and zeta and streaming potential of the samples prepared by layer-by-layer or preformed polyelectrolyte complexes adsorption. The surface morphology is evidenced by atomic force microscopy, and some specific surface parameters are discussed. A special attention is paid to the responsiveness of the new composite materials to environmental pH changes, as a function of preparation conditions.
Dh DLS K ha LbL NPEC
Keywords Silica particles . Surface modification . Polyelectrolyte multilayer . Polyelectrolyte complex . pH sensitive polymers
Introduction
Abbreviations AFM ALG CS
Atomic force microscopy Alginic acid Chitosan
M. Mihai (*) : C. A. Ghiorghiţă : E. S. Drăgan “Petru Poni” Institute of Macromolecular Chemistry of Romanian Academy, Grigore Ghica Voda Alley 41 A, 700487 Iasi, Romania e-mail: [email protected] S. Schwarz : A. Janke Leibniz-Institut für Polymerforschung Dresden e. V., Hohe Strasse 6, 01069 Dresden, Germany
NTU P(AMPS-co-AA)
PEC pzc Ra RMS SK ZP
Hydrodynamic diameter Dynamic light scattering Kurtosis Surface height Layer-by-layer Non-stoichiometric polyelectrolyte complexes Nephelometric Turbidity Units Poly(2-acrylamido-2methylpropanesulfonic acid - co - acrylic acid) Polyelectrolyte complex Point of zero charge Average surface roughness Root-mean-square roughness Skewness Zeta potential
Different methods can be applied for materials surface coating, usually classified into three groups: physical, chemical and bulk modifications [1, 2]. The alternate deposition of polyanions and polycations onto a solid substrate has been proposed as a reliable, flexible and simple method to buildup multilayered polyelectrolyte films on planar surfaces or three-dimensional substrates, with fine control over thickness, composition, morphology, and chemical functionality [3–8]. As a function of the last adsorbed layer, with positive or negative charges, the films can adsorb a great variety of compounds such as dyes, particles, or clay microplates [9–12]. The formation of polyelectrolyt
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