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Dopierala K.,Poznan University of Technology | Maciejewski H.,Poznan Science and Technology Park | Maciejewski H.,Adam Mickiewicz University | Karasiewicz J.,Poznan Science and Technology Park | Prochaska K.,Poznan University of Technology
Applied Surface Science | Year: 2013

Alkyl- and fluoroalkyltriethoxysilanes were investigated as potential surface modifiers. Many aspects concerning trialkoxysilanes were discussed, starting from hydrolysis of silanes in water solutions, the effect of this hydrolysis on the surface tension, wettability of the modified surface to the morphology of the modified surface. Surface tension and contact angle measurements as well as scanning electron microscopy were used to characterise alkyl- and fluoroalkyltriethoxysilanes and their ability to modify the wettability of glass. The effect of such modification was superhydrophobic surface with high values of contact angles. Superhydrophobic behaviour was observed as a result of two-step modification providing increased surface roughness thanks to the use of different size silica particles and surface chemical modification with fluorosilane molecules. © 2013 Elsevier B.V. All rights reserved. Source


Przybylak M.,Poznan Science and Technology Park | Maciejewski H.,Poznan Science and Technology Park | Maciejewski H.,Adam Mickiewicz University | Dutkiewicz A.,Poznan Science and Technology Park | And 2 more authors.
Cellulose | Year: 2016

Hydrophobization of cotton fabrics was carried out with the use of bifunctional polysiloxanes with various contents of functional groups. Polysiloxanes contained in their structure groups capable of bonding to substrates (trialkoxysilyl or glycidyl ones) and fluoroalkyl groups showing surface activity. Two methods of surface modification were compared: (1) a one-step method via the chemical modification of fabrics with solutions of bifunctional polysiloxanes and (2) a two-step method—via preliminary modification of fabrics with silica sol followed by chemical modification with solutions of bifunctional polysiloxanes. The hydrophobicity was determined by measuring the water contact angle by drop profile tensiometry. Changes in the surface topography were examined by scanning electron microscopy. Superhydrophobic fabrics were obtained by a simple one-step method by the chemical modification in solutions of bifunctional polysiloxanes. The fabrics maintained their superhydrophobic properties even after multiple washings. The modification does not cause any changes visible to the naked eye, such as stiffening, color changes or a decrease in mechanical properties. © 2016 The Author(s) Source


Szwarc-Rzepka K.,Poznan University of Technology | Ciesielczyk F.,Poznan University of Technology | Zawisza M.,Poznan University of Technology | Kaczmarek M.,Poznan University of Technology | And 4 more authors.
Physicochemical Problems of Mineral Processing | Year: 2012

Hepta(isobuthyl)ethyltriethoxysilyloctasilsesquioxane was synthesized by hydro-silylation of hepta(isobuthyl)vinyloctasilsesquioxane with triethoxysilane, over Karstedt catalyst and tetrahydrofuran. Hybrid systems of silica and monofunctional silsesquioxane (SiO2/POSS) were obtained by solvent evaporation, using emulsion silica (ES) and hydrated silica (HS), obtained by precipitation in emulsion or water media. For their surface modification hepta(isobuthyl)ethyltriethoxysilyloctasilsesquioxane was used. The hybrids were characterized by dispersion analysis (NIBS method and laser diffraction technique) and morphological analysis (transmission electron microscopy) as well as wettability profiles in an aqueous system. The adsorptive properties of the hybrids were evaluated on the basis of surface area BET, pore volume and size. The effectiveness of modification of the hybrid fillers was tested by FTIR and 29Si CP MAS NMR. Source


Jancelewicz M.,Adam Mickiewicz University | Nowaczyk G.,Adam Mickiewicz University | Makrocka-Rydzyk M.,Adam Mickiewicz University | Wypych A.,Adam Mickiewicz University | And 3 more authors.
Journal of Non-Crystalline Solids | Year: 2010

Rheological and dielectric behavior of linear PDMS and alkyl-modified PDMS melts has been studied. Molecular dynamics of linear PDMS, being a model of grafted polydimethylsiloxanes studied, has been examined carefully with particular attention paid to its ability to form the semicrystalline phase. Random incorporation of alkyl groups into PDMS chain has been shown to prevent the polymer crystallization. The glass transition temperature of the grafted PDMS changes proportionally to the modifier content. Both techniques allow characterization of the main α-relaxation, which is related to the glass transition and exhibits similar behavior in all systems. This relaxation is discussed in terms of the Vogel-Fulcher-Tammann-Hesse (VFTH) approach. The fragility of grafted PDMS materials was found to be higher as compared to the linear polymer. The analysis of the rheological data shows the existence of additional slow relaxation, which has been interpreted as the polymer chain motion. © 2010 Elsevier B.V. All rights reserved. Source


Maciejewski H.,Adam Mickiewicz University | Dabek I.,Poznan Science and Technology Park | Fiedorow R.,Adam Mickiewicz University | Dutkiewicz M.,Adam Mickiewicz University | Majchrzak M.,Adam Mickiewicz University
Journal of Thermal Analysis and Calorimetry | Year: 2012

Epoxy functional (poly)siloxanes are one of the most important classes of modified silicones. Due to high reactivity of epoxy group and specific features of siloxane chain, they can make an excellent raw material for synthesis of hybrid materials. Results obtained in this study have shown that both the modification of epoxy resins with epoxy functional disiloxanes as well as the application of polysiloxanes with long polysiloxane chains and a specified content of epoxy groups makes it possible to produce hybrid materials of very good thermal stability. Crosslinking reactions were carried out with use of four diamines of which the best one appeared to be 4,4′- diaminodiphenylmethane. The highest thermal stability was found in the case of hybrid materials obtained from epoxy functional polysiloxanes. © The Author(s) 2011. Source

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