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Polymers 2016, 8(3), 96; doi:10.3390/polym8030096

Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations

1
Laboratory of Polymer Chemistry, Department of Chemistry, University of Helsinki, A.I. Virtasen aukio 1, P.O. Box 55, FIN-00014 HY Helsinki, Finland
2
Limnological Institute Siberian Branch of the Russian Academy of Sciences, 3, Ulan-Bator Str., Irkutsk 664033, Russia
*
Author to whom correspondence should be addressed.
Academic Editor: André Laschewsky
Received: 26 February 2016 / Revised: 11 March 2016 / Accepted: 16 March 2016 / Published: 22 March 2016
(This article belongs to the Special Issue Polymers for Aqueous Media)
View Full-Text   |   Download PDF [4895 KB, uploaded 22 March 2016]   |  

Abstract

The present work describes the acid-triggered condensation of silicic acid, Si(OH)4, as directed by selected polycations in aqueous solution in the pH range of 6.5–8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the formation of silica-polyelectrolyte (S-PE) nanocomposites in the form of precipitate or water-dispersible particles. The mean hydrodynamic diameter (dh) of size distributions of the prepared water-dispersible S-PE composites is presented as a function of the solution pH at which the composite formation was achieved. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and block copolymers of DMAEMA and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) were used as weak polyelectrolytes in S-PE composite formation. The activity of the strong polyelectrolytes poly(methacryloxyethyl trimethylammonium iodide) (PMOTAI) and PMOTAI-b-POEGMA in S-PE formation is also examined. The effect of polyelectrolyte strength and the OEGMA block on the formation of the S-PE composites is assessed with respect to the S-PE composites prepared using the PDMAEMA homopolymer. In the presence of the PDMAEMA60 homopolymer (Mw = 9400 g/mol), the size of the dispersible S-PE composites increases with solution pH in the range pH 6.6–8.1, from dh = 30 nm to dh = 800 nm. S-PDMAEMA60 prepared at pH 7.8 contained 66% silica by mass (TGA). The increase in dispersible S-PE particle size is diminished when directed by PDMAEMA300 (Mw = 47,000 g/mol), reaching a maximum of dh = 75 nm. S-PE composites formed using PDMAEMA-b-POEGMA remain in the range dh = 20–30 nm across this same pH regime. Precipitated S-PE composites were obtained as spheres of up to 200 nm in diameter (SEM) and up to 65% mass content of silica (TGA). The conditions of pH for the preparation of dispersible and precipitate S-PE nanocomposites, as directed by the five selected polyelectrolytes PDMAEMA60, PDMAEMA300, PMOTAI60, PDMAEMA60-b-POEGMA38 and PMOTAI60-b-POEGMA38 is summarized. View Full-Text
Keywords: silica; nanoparticles; polyelectrolyte; polycations; condensation; colloid; sodium metasilicate; PDMAEMA; PMOTAI; OEGMA; POEGMA silica; nanoparticles; polyelectrolyte; polycations; condensation; colloid; sodium metasilicate; PDMAEMA; PMOTAI; OEGMA; POEGMA
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Overton, P.; Danilovtseva, E.; Karjalainen, E.; Karesoja, M.; Annenkov, V.; Tenhu, H.; Aseyev, V. Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations. Polymers 2016, 8, 96.

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