The coordination polymer [Fe(NH2trz)3](2ns)2 exhibits the rare phenomenon of spin crossover in an attractive temperature range, i.e., somewhat above room temperature. Spin crossover in [Fe(NH2trz)3](2ns)2 is manifest by thermochromism,... more
The coordination polymer [Fe(NH2trz)3](2ns)2 exhibits the rare phenomenon of spin crossover in an attractive temperature range, i.e., somewhat above room temperature. Spin crossover in [Fe(NH2trz)3](2ns)2 is manifest by thermochromism, which is accompanied by a magnetic transition from diamagnetism to paramagnetism. However, [Fe(NH2trz)3](2ns)2 is brittle and difficult to process, which limits its use. In this study, we show that [Fe(NH2trz)3](2ns)2 can be co-processed with ultrahigh molecular weight polyethylene (UHMWPE), which possesses outstanding mechanical properties, particularly when tensile drawn. Therefore, [Fe(NH2trz)3](2ns)2–UHMWPE blends were gel-processed by extrusion, employing a relatively poor solvent, which has recently been shown to offer advantages compared to good solvents. Uniform and flexible films, ribbons and fibers with [Fe(NH2trz)3](2ns)2 fractions as high as 33.3% m/m were obtained that could be readily drawn. Spin crossover in the coordination polymer is ...
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Hydroxyl groups on silica surfaces can be removed partially or completely under mild conditions, including washing of silica with dry hexane, prolonged storage over phosphorous pentoxide, chemical reaction with phenyl isocyanate, ethyl... more
Hydroxyl groups on silica surfaces can be removed partially or completely under mild conditions, including washing of silica with dry hexane, prolonged storage over phosphorous pentoxide, chemical reaction with phenyl isocyanate, ethyl isocyanate or trimethylsilyl trifluoromethanesulfonate. The removal of these hydroxyl groups was performed at much lower temperatures than usually required for this process.
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Poly(phenylene methylene) (PPM) is a thermally stable, hydrophobic, fluorescent hydrocarbon polymer. PPM has been proposed earlier to be useful as a coating material but this polymer was isolated in relevant molar masses only recently,... more
Poly(phenylene methylene) (PPM) is a thermally stable, hydrophobic, fluorescent hydrocarbon polymer. PPM has been proposed earlier to be useful as a coating material but this polymer was isolated in relevant molar masses only recently, and in large quantities. Accordingly, the preparation of coatings based on PPM and their behavior was explored in this study, with the example of the metal alloy AA2024 as a common substrate for corrosion tests. Coatings free of bubbles and cracks were obtained by hot pressing and application of the following steps: Coating on AA2024 with a layer of polybenzylsiloxane to improve the adhesion between PPM and the metal surface, the addition of polybenzylsiloxane to PPM in order to enhance the viscosity of the molten PPM, and the addition of benzyl butyl phthalate as a plasticizer. Electrochemical corrosion tests showed good protection of the metal surface towards a NaCl solution, thanks to a passive-like behavior in a wide potential window and a very lo...
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Polystannanes are a unique class of materials as those inorganic polymers (more precisely organometallic polymers) appear to be hitherto the only characterized polymers with a backbone of covalently bound metal atoms.
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... also been used for decades, in particular carbon black, silicon dioxide (silica), titanium dioxide (titania), or aluminium oxide (alumina).1,2 ... 67 Since light scattering in nanocomposites is frequently irrelevant, polymer... more
... also been used for decades, in particular carbon black, silicon dioxide (silica), titanium dioxide (titania), or aluminium oxide (alumina).1,2 ... 67 Since light scattering in nanocomposites is frequently irrelevant, polymer composites containing coloured nano-particles can ...
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One of the most challenging aspects of using nanofibrillated cellulose (NFC) for membranes production is their limited permeance. When NFC membranes are produced from aqueous suspensions, depending on their grammage, the permeances are in... more
One of the most challenging aspects of using nanofibrillated cellulose (NFC) for membranes production is their limited permeance. When NFC membranes are produced from aqueous suspensions, depending on their grammage, the permeances are in the range of a few decades of L/(hm(2)MPa) not matching satisfactory filtration times. We present a fast and sustainable solution to increase the permeances of such membranes through a combination of solvent exchange of the NFC suspension with ethanol and the use of a removable template, a mixture of calcium compounds (CC). The effect of the CC/NFC ratio was screened for various concentrations. The permeance of water could be increased by as much as 2-3 times as compared to nontemplated membranes. Further, the membranes showed the ability for penetration of water-soluble macromolecules, contaminant rejection of suspended solid particles, and thus fluids (such as orange juice) could be concentrated, with a view to applications in food industry.
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... as strongly connected aggregates in the respective powders, in physical terms due to the high surface free energies (typically 5002000mJ/m2 for inorganic materials (Kinloch, 1987; Salmang and Scholze, 1982), compared to 2050mJ/m2... more
... as strongly connected aggregates in the respective powders, in physical terms due to the high surface free energies (typically 5002000mJ/m2 for inorganic materials (Kinloch, 1987; Salmang and Scholze, 1982), compared to 2050mJ/m2 for poly-mers (Lipatov and Feinerman ...
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... Leontidis,* Maria Orphanou, Tasoula Kyprianidou-Leodidou, Frank Krumeich, and Walter Caseri §. ... Chem., Int. Ed. Engl.1998, 37, 1263−1265. Krumeich, F.; Muhr, H.-J.; Niederberger, M.; Bieri, F.; Schnyder B.; Nesper R. J. Am.... more
... Leontidis,* Maria Orphanou, Tasoula Kyprianidou-Leodidou, Frank Krumeich, and Walter Caseri §. ... Chem., Int. Ed. Engl.1998, 37, 1263−1265. Krumeich, F.; Muhr, H.-J.; Niederberger, M.; Bieri, F.; Schnyder B.; Nesper R. J. Am. Chem. Soc.1999, 121, 8324. ...
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This work revisits the synthesis of the colloidal particles most commonly used for making model near hard suspensions or as building blocks of model colloidal gels, i.e. sterically stabilised poly(methyl methacrylate) (PMMA) particles.... more
This work revisits the synthesis of the colloidal particles most commonly used for making model near hard suspensions or as building blocks of model colloidal gels, i.e. sterically stabilised poly(methyl methacrylate) (PMMA) particles. The synthesis of these particles is notoriously hard to control and generally the problems are ascribed to the difficulty in synthesising the graft stabiliser (PMMA-g-PHSA). In the present work, it is shown that for improving the reliability of the synthesis as a whole, control over the polycondensation of the 12-polyhydroxystearic acid is the key. By changing the catalyst and performing the polycondensation in the melt, the chain length of the 12-polyhydroxystearic acid is better controlled, as confirmed by 1H-NMR spectroscopy. Control over the graft copolymer now enables us to make small variations of near hard sphere colloids, for example spherical PMMA particles with essentially the same core size and different stabilising layer thicknesses can no...
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Composite films of nanosized TiO2 particles, which contained rutile as the only detected crystal modification, and poly(vinyl alcohol), poly(vinyl pyrrolidone) or poly(4-vinylpyridine) were prepared from aqueous dispersions. During... more
Composite films of nanosized TiO2 particles, which contained rutile as the only detected crystal modification, and poly(vinyl alcohol), poly(vinyl pyrrolidone) or poly(4-vinylpyridine) were prepared from aqueous dispersions. During exposure to UV irradiation the nanocomposites comprising poly(vinyl alcohol) or poly(vinyl pyrrolidone) turned blue as a consequence of a partial reduction of TiIV to TiIII. The color intensity increased with increasing TiO2 content and irradiation time. This color did not fade after removal of the UV source in spite of the sensitivity of TiIII to atmospheric oxygen. By contrast, exposure to water caused the nanocomposites to adopt their original colorless appearance. These colorization-decolorization cycles could be repeated more than 10 times without apparent loss of intensity. Due to the small size of the TiO2 nanoparticles (ca. 3 nm), patterned blue structures of high resolution could be created in the polymeric materials, for instance with simple masking methods.
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ABSTRACT
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Page 1. 49 Hybrid Materials. Synthesis, Characterization, and Applications. Edited by Guido Kickelbick Copyright © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 978-3-527-31299-3 2 Nanocomposites of Polymers and Inorganic... more
Page 1. 49 Hybrid Materials. Synthesis, Characterization, and Applications. Edited by Guido Kickelbick Copyright © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 978-3-527-31299-3 2 Nanocomposites of Polymers and Inorganic Particles Walter Caseri ...
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Abstract: The optical properties of substituted phthalocyaninato-polysiloxanes and their copolymers having the chromophores separated by spacers are discussed in terms of the molecular exciton model. The shift of the Q band maximum of the... more
Abstract: The optical properties of substituted phthalocyaninato-polysiloxanes and their copolymers having the chromophores separated by spacers are discussed in terms of the molecular exciton model. The shift of the Q band maximum of the siloxane polymer compared to the ...
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ABSTRACTUniaxially oriented composites of high-density polyethylene and silver nanoparticles were prepared using solution-casting, melt-extrusion and solid-state drawing techniques. The absorption spectrum in the visible wavelength range... more
ABSTRACTUniaxially oriented composites of high-density polyethylene and silver nanoparticles were prepared using solution-casting, melt-extrusion and solid-state drawing techniques. The absorption spectrum in the visible wavelength range of the drawn nanocomposites was observed to strongly depend on the polarization direction of the incident light. For instance, the nanocomposites appear bright yellow or red when the vibration direction of linearly polarized light is perpendicular or parallel, respectively, to the drawing axis. The optical anisotropy of the drawn nanocomposites originates from uniaxially oriented, pearl-necklace type of arrays of nanoparticles of high aspect ratios. The absorption spectrum of the nanocomposites can be shifted to higher wavelengths using appropriate annealing procedures. The annealing results in an increased size of the primary silver particles, due to Ostwald ripening, and consequently a range of polarization-dependent colors can be generated in the...
Magnus green salt, [Pt(NH3)4][PtCl4], was first prepared by Gustav Magnus around 1830 by the dissolution of platinum(II) chloride in hydrochlo-ric acid followed by addition of ammonia (1, 2). The green crystals which slowly precipitated... more
Magnus green salt, [Pt(NH3)4][PtCl4], was first prepared by Gustav Magnus around 1830 by the dissolution of platinum(II) chloride in hydrochlo-ric acid followed by addition of ammonia (1, 2). The green crystals which slowly precipitated attracted considerable attention as ...
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ABSTRACT Scanning electron microscope images are presented of mica surfaces treated with an initiator and heated in the presence of styrene to obtain a grafted polymer. These images show “droplets” of size corresponding to that of... more
ABSTRACT Scanning electron microscope images are presented of mica surfaces treated with an initiator and heated in the presence of styrene to obtain a grafted polymer. These images show “droplets” of size corresponding to that of individual polystyrene molecules. Other experimental evidence is presented which suggests that the droplets are indeed individual molecules. The images are believed to be the first ever obtained of individual, “tethered” synthetic polymer molecules.
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Films of polymers comprising the quasi-one-dimensional compounds K