We present fluorocarbon-free block copolymer brushes as potential systems for dual-action, i.e., ... more We present fluorocarbon-free block copolymer brushes as potential systems for dual-action, i.e., soil-repellent and soil-releasing textile finishes. Polymer brushes were prepared by employing specifically engineered triblock copolymers consisting of a hydrophobic, a hydrophilic, and either a central or a terminal anchor block bearing several anchoring groups for sustainable immobilization using the "grafting to" approach on both flat Si wafers and rough cotton fabrics. The switching characteristics of both types of block copolymer brushes were investigated by exposing the brushes to conditions and stimuli that are similar to those applied during laundering in a washing machine and drying in a laundry dryer, respectively. Contact angle measurements were performed to evaluate the polarity and wettability of the block copolymer brushes after treatment in hot water and in air, or in a vacuum at elevated temperatures simulating the washing and the drying procedure of a textile fabric. While the block copolymer brush with the terminal anchor showed only minor changes in terms of the wetting characteristics and the brush morphology upon the applied stimuli, the block copolymer brush with the central anchoring block exhibited a significant change from a hydrophilic (soil-releasing) to a hydrophobic (stain-repellent) surface. This switching behavior was reversible and could be achieved on both, flat Si wafers, and much more pronounced on rough cotton fabrics. Atomic force microscopy and angle-resolved X-ray photoelectron spectroscopy investigations further indicated a complete rearrangement of the brush morphology. Accordingly, we regard this type of block copolymer brushes as a system that fully meets the basic requirements for an application as a dual-action textile finish, which can be reversibly switched with respect to water repulsion.
The authors report on highly swellable, stable layers of spherical dendritic glycopolymers, compo... more The authors report on highly swellable, stable layers of spherical dendritic glycopolymers, composed of hyperbranched poly(ethylene imine) (PEI) as core and two different maltose shells (A = dense shell and B = open shell). These glycopolymers are cross-linked and attached with poly(ethylene--maleic anhydride) (PEMA) or citric acid on SiO substrates. The swelling and adsorption of biomolecules were analyzed by spectroscopic ellipsometry and quartz crystal microbalance with dissipation. The swelling degree and complexation with the drug molecule adenosine triphosphate (ATP) were found to be up to 10 times higher for dendritic glycopolymer layers cross-linked with PEMA than for layers cross-linked with citric acid. ATP complexation by electrostatic interaction with the PEI cores was confirmed by x-ray photoelectron spectroscopy analysis. Complexation led to partial collapsing, stiffening, and increase of polymer layer viscosity of the PEMA cross-linked layers. From modeling of ellipso...
New types of composites were obtained by an autotemplate method for assembling hollow CaCOcapsule... more New types of composites were obtained by an autotemplate method for assembling hollow CaCOcapsules by using pH-sensitive polymers. Five pectin samples, which differ in the methylation degree and/or amide content, and some nonstoichiometric polyelectrolyte complex dispersions, prepared with the pectin samples and poly(allylamine hydrochloride), were used to control the crystal growth. The morphology of the composites was investigated by scanning electron microscopy, and the polymorphs characteristics were investigated by FTIR spectroscopy. The presence of the polymer in the composite particles was evidenced by X-ray photoelectron spectroscopy, particle charge density, and zeta-potential. The new CaCO/pectin hollow capsules were tested as a possible matrix for a tetracycline hydrochloride carrier. The kinetics of the drug release mechanism was followed using Higuchi and Korsmeyer-Peppas mathematical models.
Advanced materials (Deerfield Beach, Fla.), Jan 31, 2017
Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to t... more Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed-dimensional (2D/3D) metal-free van der Waals (vdW) heterostructures based on triazine (C3 N3 ) linkers grow as large area, transparent yellow-orange membranes on copper surfaces from solution. The membranes have an indirect band gap (Eg,opt = 1.91 eV, Eg,elec = 1.84 eV) and are moderately porous (124 m(2) g(-1) ). The material consists of a crystalline 2D phase that is fully sp(2) hybridized and provides structural stability, and an amorphous, porous phase with mixed sp(2) -sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one-pot reaction mixture: unprecedented for metal-free frameworks and a direct consequence of on-catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the mater...
ABSTRACT The influence of metal pretreating on the properties of adhesively bonded joints was inv... more ABSTRACT The influence of metal pretreating on the properties of adhesively bonded joints was investigated. AlMg3 and several pre-treatment methods were used.The pre-treated surfaces and the joints were characterized using: SEM/EDX, XPS, EIS, surface tension, DMA, μTA and the determination of mechanical parameters. The highest bond strengths were obtained using anodic oxidation in phosphoric acid as the pre-treatment method.
A readily synthetic route to endow the surface of hydrophobic carbon black (CB) particles with pr... more A readily synthetic route to endow the surface of hydrophobic carbon black (CB) particles with primary amino groups has been developed. The adsorption of the water-borne polyelectrolyte copolymer poly(vinyl amine-co-vinyl amide) (PVAm) on CB was studied as function of pH and polyelectrolyte concentration. The amino-functionalization process of CB with PVAm strongly depends on pH. As shown by electrokinetic measurement as function of pH, the content of accessible primary amino groups on the surface of CB increases with increasing the OH- concentration. The alternative functionalization of the CB surface with an anionic polyelectrolyte is demonstrated for the adsorption of poly(ethylene-alt-maleic anhydride) (PEMSA). About 50 mg of PVAm can be adsorbed on 1.0 g of CB, which is sufficient to completely alter the surface net charge. The aim of the introduced functional amino groups is their ability to act as anchoring groups for subsequent surface reactions improving the CB's process ability, compatibility, and adhesion properties.
We report a simple method to synthesize binary polymer brushes from two incompatible polymers of ... more We report a simple method to synthesize binary polymer brushes from two incompatible polymers of different polarity. The synthetic route is based on a subsequent step-by-step grafting of carboxyl-terminated polystyrene and poly(2-vinylpyridine) to the surface of a Si wafer functionalized with 3-glycidoxypropyltrimethoxysilane. The end-functional polymers were spin-coated on the substrate, and grafting was carried out at a temperature higher than the glass transition temperature of the polymers. The composition of the binary brushes can be regulated based on grafting kinetics of the first polymer by the change of time or/and temperature of grafting. This method reveals a smooth and homogeneous polymer film on the macroscopic scale, while at the nanoscopic scale the system undergoes phase segregation effecting switching/ adaptive properties of the film. Upon exposure to different solvents, the film morphology reversibly switches from "ripple" to "dimple" structures as well as the surface energetic state switches from hydrophobic to hydrophilic. The same switching of hydrophilic/hydrophobic properties was obtained for the different ratios between two grafted polymers in the binary brush.
ABSTRACT Für viele Anwendungen ist die gezielte Einstellung der Benetzbarkeit von Festkörperoberf... more ABSTRACT Für viele Anwendungen ist die gezielte Einstellung der Benetzbarkeit von Festkörperoberflächen von großer Bedeutung. Ein aktueller Forschungsschwerpunkt ist die Herstellung ultrahydrophober Oberflächen, deren Anwendungspotenzial sich von selbstreinigenden Beschichtungen bis hin zum oberflächenspannungskontrollierten Flüssigkeitstransport in der Mikrofluidik erstreckt. Im Folgenden werden ausgewählte Strategien zur Erzeugung ultrahydrophober Oberflächen vorgestellt und das Wechselspiel zwischen gezielter Änderung der chemischen Zusammensetzung und der Strukturierung der Festkörperoberfläche auf die Benetzbarkeit näher beleuchtet. Am Beispiel von Kern-Schale-Partikeln wurden zum einen die freie Oberflächenenergie der Partikel durch das Anbinden kovalenter Polymerbürsten gezielt verändert und zum anderen hochgeordnete, aber auch ungeordnete, Oberflächentopographien aus dicht gepackten Partikeln mit unterschiedlichen Rauheiten hergestellt. Dabei wurde die Rauheit durch Verwendung von Partikeln mit unterschiedlichem Durchmesser (200 nm bis 20 μm) variiert. Oberflächen mit hierarchisch rauen Topographien wurden durch eine anodische Oxidation von Aluminium erhalten. Auf solchen Oberflächen applizierte Copolymere unterliegen einer molekularen Selbstorganisation, bei der sich hydrophobe Segmente an der Grenzfläche Polymer/Luft anreichern und so dem Material ultrahydrophobe Eigenschaften verleihen. Hydrophile Segmente reichern sich in der Grenzschicht Metalloxid/Polymer an und sorgen so für eine gute Haftungfestigkeit der polymeren Beschichtung. Hierarchisch raue Oberflächen konnten auch durch ein Plasmaätzen von Polymeren erreicht werden. Binäre Polymerbürsten, die an so vorbehandelte Oberflächen kovalent angebunden wurden, ermöglichten ein reversibles Schalten zwischen vollständiger Benetzung und Ultrahydrophobie.
... OH-Terminated Polyester on a Silicon Surface Senta Reichelt, Lothar Jakisch, Frank Simon, Kar... more ... OH-Terminated Polyester on a Silicon Surface Senta Reichelt, Lothar Jakisch, Frank Simon, Karina Grundke, Klaus-Jochen Eichhorn,* Brigitte Voit ... Streaming potential measurements were carried out using an Electrokinetic Analyzer EKA (Anton Paar KG, Austria). ...
Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a ... more Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface's top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique "triple-sized" structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method.
Angewandte Chemie International Edition, Feb 1, 2009
The use of conjugated polymers (CPs) in integrated circuits, solar cells, light emitting diodes, ... more The use of conjugated polymers (CPs) in integrated circuits, solar cells, light emitting diodes, or sensors often requires their covalent fixation and patterning on various surfaces. [1] CPs can be grafted to functionalized surfaces by (electro)chemical cross-linking, [2] however, it is difficult to control a structural order within the cross-linked films. The attachment of CP chains to substrates by their end-points to form polymer brushes would be an interesting alternative, possibly helping charge injection and charge transport processes that are crucial for many devices. [1b] A "polymerization onto" procedure consisting of a Yamamoto step-growth polycondensation combined with a grafting of in situ growing polyfluorene molecules onto properly functionalized polymer supports was recently developed by Carter et al. [3] According to this approach, however, only thin grafted layers are forming even in hard reaction conditions and a predominant quantity of the monomer forms ungrafted polymers. The surfaceinitiated polymerization (SIP, or "grafting-from") technique usually results in significantly thicker grafted films and can be easily applied for patterning of polymers. The SIP concept has been implemented for the grafting of various nonconjugated polymers obtainable by chain-growth polyadditions. [4] However, examples of SIP of CPs are scarce owing to the intrinsic obstacles of the step-growth route to such polymers. [5] Nowadays, chain-growth cross-coupling polycondensations, such as nickel-catalyzed Kumada polycondensation, have become powerful tools in synthesis of well-defined polythiophenes, polyfluorenes, and some block copolymers. [6] Recently, taking advantage of the chain-growth mechanism of Kumada polycondensation, we developed SIP of regioregular poly(3-hexylthiophenes) from cross-linked poly(4-bromostyrene) (PS(Br)). [7] On the other hand, palladium-catalyzed Suzuki-coupling polycondensation of aryl halides with organoboron reagents is another remarkably efficient, versatile, route to conjugated polymers which is tolerant to various functional groups and solvents. [8] In the classical reaction, the Suzuki polycondensation is catalyzed by [Pd(PPh 3) 4 ] or similar complexes and involves the step-growth mechanism. [8] Recently, Yokozawa et al. reported the chain-growth Suzuki Scheme 1. a) Chain-growth Suzuki polycondensation and b) surfaceinitiated grafting of poly[9,9-bis(2-ethylhexyl)fluorene].
Http Dx Doi Org 10 1163 156856108x388399, Apr 2, 2012
... Katharina Fink a,b, Susanne Höhne a, Stefan Spange b and Frank Simon a,∗ a Leibniz Institute ... more ... Katharina Fink a,b, Susanne Höhne a, Stefan Spange b and Frank Simon a,∗ a Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden, Germany b Chemnitz University of Technology, Department of Polymer Chemistry, Strasse der Nationen 62, D ...
A controlled assembly of natural beta-cyclodextrin modified Au NPs mediated by dopamine is demons... more A controlled assembly of natural beta-cyclodextrin modified Au NPs mediated by dopamine is demonstrated. Furthermore, a simple and sensitive colorimetric detection for dopamine is established by the concentration-dependent assembly.
The method for producing chitosan coatings on solid surfaces with anchoring layers of poly(gly ci... more The method for producing chitosan coatings on solid surfaces with anchoring layers of poly(gly cidyl methacrylate) and maleic anhydride copolymers has been proposed. It is shown that, owing to a high reactivity of epoxy and anhydride groups, the efficiency of immobilization and the stability of the coatings are considerably higher than those prepared by the conventional method of chitosan grafting onto the surface modified by poly(acrylic acid). The properties of chitosan coatings are examined via atomic force micros copy, X ray photoelectron spectroscopy, ellipsometry, and electrokinetic measurements. Depending on the anchoring layer used, the total thickness of the coatings is 6-16 nm with an rms roughness less than 1.2 nm, while the isoelectric points of the surfaces modified with chitosan are located in the pH range 5-6.
We present fluorocarbon-free block copolymer brushes as potential systems for dual-action, i.e., ... more We present fluorocarbon-free block copolymer brushes as potential systems for dual-action, i.e., soil-repellent and soil-releasing textile finishes. Polymer brushes were prepared by employing specifically engineered triblock copolymers consisting of a hydrophobic, a hydrophilic, and either a central or a terminal anchor block bearing several anchoring groups for sustainable immobilization using the "grafting to" approach on both flat Si wafers and rough cotton fabrics. The switching characteristics of both types of block copolymer brushes were investigated by exposing the brushes to conditions and stimuli that are similar to those applied during laundering in a washing machine and drying in a laundry dryer, respectively. Contact angle measurements were performed to evaluate the polarity and wettability of the block copolymer brushes after treatment in hot water and in air, or in a vacuum at elevated temperatures simulating the washing and the drying procedure of a textile fabric. While the block copolymer brush with the terminal anchor showed only minor changes in terms of the wetting characteristics and the brush morphology upon the applied stimuli, the block copolymer brush with the central anchoring block exhibited a significant change from a hydrophilic (soil-releasing) to a hydrophobic (stain-repellent) surface. This switching behavior was reversible and could be achieved on both, flat Si wafers, and much more pronounced on rough cotton fabrics. Atomic force microscopy and angle-resolved X-ray photoelectron spectroscopy investigations further indicated a complete rearrangement of the brush morphology. Accordingly, we regard this type of block copolymer brushes as a system that fully meets the basic requirements for an application as a dual-action textile finish, which can be reversibly switched with respect to water repulsion.
The authors report on highly swellable, stable layers of spherical dendritic glycopolymers, compo... more The authors report on highly swellable, stable layers of spherical dendritic glycopolymers, composed of hyperbranched poly(ethylene imine) (PEI) as core and two different maltose shells (A = dense shell and B = open shell). These glycopolymers are cross-linked and attached with poly(ethylene--maleic anhydride) (PEMA) or citric acid on SiO substrates. The swelling and adsorption of biomolecules were analyzed by spectroscopic ellipsometry and quartz crystal microbalance with dissipation. The swelling degree and complexation with the drug molecule adenosine triphosphate (ATP) were found to be up to 10 times higher for dendritic glycopolymer layers cross-linked with PEMA than for layers cross-linked with citric acid. ATP complexation by electrostatic interaction with the PEI cores was confirmed by x-ray photoelectron spectroscopy analysis. Complexation led to partial collapsing, stiffening, and increase of polymer layer viscosity of the PEMA cross-linked layers. From modeling of ellipso...
New types of composites were obtained by an autotemplate method for assembling hollow CaCOcapsule... more New types of composites were obtained by an autotemplate method for assembling hollow CaCOcapsules by using pH-sensitive polymers. Five pectin samples, which differ in the methylation degree and/or amide content, and some nonstoichiometric polyelectrolyte complex dispersions, prepared with the pectin samples and poly(allylamine hydrochloride), were used to control the crystal growth. The morphology of the composites was investigated by scanning electron microscopy, and the polymorphs characteristics were investigated by FTIR spectroscopy. The presence of the polymer in the composite particles was evidenced by X-ray photoelectron spectroscopy, particle charge density, and zeta-potential. The new CaCO/pectin hollow capsules were tested as a possible matrix for a tetracycline hydrochloride carrier. The kinetics of the drug release mechanism was followed using Higuchi and Korsmeyer-Peppas mathematical models.
Advanced materials (Deerfield Beach, Fla.), Jan 31, 2017
Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to t... more Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed-dimensional (2D/3D) metal-free van der Waals (vdW) heterostructures based on triazine (C3 N3 ) linkers grow as large area, transparent yellow-orange membranes on copper surfaces from solution. The membranes have an indirect band gap (Eg,opt = 1.91 eV, Eg,elec = 1.84 eV) and are moderately porous (124 m(2) g(-1) ). The material consists of a crystalline 2D phase that is fully sp(2) hybridized and provides structural stability, and an amorphous, porous phase with mixed sp(2) -sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one-pot reaction mixture: unprecedented for metal-free frameworks and a direct consequence of on-catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the mater...
ABSTRACT The influence of metal pretreating on the properties of adhesively bonded joints was inv... more ABSTRACT The influence of metal pretreating on the properties of adhesively bonded joints was investigated. AlMg3 and several pre-treatment methods were used.The pre-treated surfaces and the joints were characterized using: SEM/EDX, XPS, EIS, surface tension, DMA, μTA and the determination of mechanical parameters. The highest bond strengths were obtained using anodic oxidation in phosphoric acid as the pre-treatment method.
A readily synthetic route to endow the surface of hydrophobic carbon black (CB) particles with pr... more A readily synthetic route to endow the surface of hydrophobic carbon black (CB) particles with primary amino groups has been developed. The adsorption of the water-borne polyelectrolyte copolymer poly(vinyl amine-co-vinyl amide) (PVAm) on CB was studied as function of pH and polyelectrolyte concentration. The amino-functionalization process of CB with PVAm strongly depends on pH. As shown by electrokinetic measurement as function of pH, the content of accessible primary amino groups on the surface of CB increases with increasing the OH- concentration. The alternative functionalization of the CB surface with an anionic polyelectrolyte is demonstrated for the adsorption of poly(ethylene-alt-maleic anhydride) (PEMSA). About 50 mg of PVAm can be adsorbed on 1.0 g of CB, which is sufficient to completely alter the surface net charge. The aim of the introduced functional amino groups is their ability to act as anchoring groups for subsequent surface reactions improving the CB's process ability, compatibility, and adhesion properties.
We report a simple method to synthesize binary polymer brushes from two incompatible polymers of ... more We report a simple method to synthesize binary polymer brushes from two incompatible polymers of different polarity. The synthetic route is based on a subsequent step-by-step grafting of carboxyl-terminated polystyrene and poly(2-vinylpyridine) to the surface of a Si wafer functionalized with 3-glycidoxypropyltrimethoxysilane. The end-functional polymers were spin-coated on the substrate, and grafting was carried out at a temperature higher than the glass transition temperature of the polymers. The composition of the binary brushes can be regulated based on grafting kinetics of the first polymer by the change of time or/and temperature of grafting. This method reveals a smooth and homogeneous polymer film on the macroscopic scale, while at the nanoscopic scale the system undergoes phase segregation effecting switching/ adaptive properties of the film. Upon exposure to different solvents, the film morphology reversibly switches from "ripple" to "dimple" structures as well as the surface energetic state switches from hydrophobic to hydrophilic. The same switching of hydrophilic/hydrophobic properties was obtained for the different ratios between two grafted polymers in the binary brush.
ABSTRACT Für viele Anwendungen ist die gezielte Einstellung der Benetzbarkeit von Festkörperoberf... more ABSTRACT Für viele Anwendungen ist die gezielte Einstellung der Benetzbarkeit von Festkörperoberflächen von großer Bedeutung. Ein aktueller Forschungsschwerpunkt ist die Herstellung ultrahydrophober Oberflächen, deren Anwendungspotenzial sich von selbstreinigenden Beschichtungen bis hin zum oberflächenspannungskontrollierten Flüssigkeitstransport in der Mikrofluidik erstreckt. Im Folgenden werden ausgewählte Strategien zur Erzeugung ultrahydrophober Oberflächen vorgestellt und das Wechselspiel zwischen gezielter Änderung der chemischen Zusammensetzung und der Strukturierung der Festkörperoberfläche auf die Benetzbarkeit näher beleuchtet. Am Beispiel von Kern-Schale-Partikeln wurden zum einen die freie Oberflächenenergie der Partikel durch das Anbinden kovalenter Polymerbürsten gezielt verändert und zum anderen hochgeordnete, aber auch ungeordnete, Oberflächentopographien aus dicht gepackten Partikeln mit unterschiedlichen Rauheiten hergestellt. Dabei wurde die Rauheit durch Verwendung von Partikeln mit unterschiedlichem Durchmesser (200 nm bis 20 μm) variiert. Oberflächen mit hierarchisch rauen Topographien wurden durch eine anodische Oxidation von Aluminium erhalten. Auf solchen Oberflächen applizierte Copolymere unterliegen einer molekularen Selbstorganisation, bei der sich hydrophobe Segmente an der Grenzfläche Polymer/Luft anreichern und so dem Material ultrahydrophobe Eigenschaften verleihen. Hydrophile Segmente reichern sich in der Grenzschicht Metalloxid/Polymer an und sorgen so für eine gute Haftungfestigkeit der polymeren Beschichtung. Hierarchisch raue Oberflächen konnten auch durch ein Plasmaätzen von Polymeren erreicht werden. Binäre Polymerbürsten, die an so vorbehandelte Oberflächen kovalent angebunden wurden, ermöglichten ein reversibles Schalten zwischen vollständiger Benetzung und Ultrahydrophobie.
... OH-Terminated Polyester on a Silicon Surface Senta Reichelt, Lothar Jakisch, Frank Simon, Kar... more ... OH-Terminated Polyester on a Silicon Surface Senta Reichelt, Lothar Jakisch, Frank Simon, Karina Grundke, Klaus-Jochen Eichhorn,* Brigitte Voit ... Streaming potential measurements were carried out using an Electrokinetic Analyzer EKA (Anton Paar KG, Austria). ...
Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a ... more Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface's top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique "triple-sized" structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method.
Angewandte Chemie International Edition, Feb 1, 2009
The use of conjugated polymers (CPs) in integrated circuits, solar cells, light emitting diodes, ... more The use of conjugated polymers (CPs) in integrated circuits, solar cells, light emitting diodes, or sensors often requires their covalent fixation and patterning on various surfaces. [1] CPs can be grafted to functionalized surfaces by (electro)chemical cross-linking, [2] however, it is difficult to control a structural order within the cross-linked films. The attachment of CP chains to substrates by their end-points to form polymer brushes would be an interesting alternative, possibly helping charge injection and charge transport processes that are crucial for many devices. [1b] A "polymerization onto" procedure consisting of a Yamamoto step-growth polycondensation combined with a grafting of in situ growing polyfluorene molecules onto properly functionalized polymer supports was recently developed by Carter et al. [3] According to this approach, however, only thin grafted layers are forming even in hard reaction conditions and a predominant quantity of the monomer forms ungrafted polymers. The surfaceinitiated polymerization (SIP, or "grafting-from") technique usually results in significantly thicker grafted films and can be easily applied for patterning of polymers. The SIP concept has been implemented for the grafting of various nonconjugated polymers obtainable by chain-growth polyadditions. [4] However, examples of SIP of CPs are scarce owing to the intrinsic obstacles of the step-growth route to such polymers. [5] Nowadays, chain-growth cross-coupling polycondensations, such as nickel-catalyzed Kumada polycondensation, have become powerful tools in synthesis of well-defined polythiophenes, polyfluorenes, and some block copolymers. [6] Recently, taking advantage of the chain-growth mechanism of Kumada polycondensation, we developed SIP of regioregular poly(3-hexylthiophenes) from cross-linked poly(4-bromostyrene) (PS(Br)). [7] On the other hand, palladium-catalyzed Suzuki-coupling polycondensation of aryl halides with organoboron reagents is another remarkably efficient, versatile, route to conjugated polymers which is tolerant to various functional groups and solvents. [8] In the classical reaction, the Suzuki polycondensation is catalyzed by [Pd(PPh 3) 4 ] or similar complexes and involves the step-growth mechanism. [8] Recently, Yokozawa et al. reported the chain-growth Suzuki Scheme 1. a) Chain-growth Suzuki polycondensation and b) surfaceinitiated grafting of poly[9,9-bis(2-ethylhexyl)fluorene].
Http Dx Doi Org 10 1163 156856108x388399, Apr 2, 2012
... Katharina Fink a,b, Susanne Höhne a, Stefan Spange b and Frank Simon a,∗ a Leibniz Institute ... more ... Katharina Fink a,b, Susanne Höhne a, Stefan Spange b and Frank Simon a,∗ a Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden, Germany b Chemnitz University of Technology, Department of Polymer Chemistry, Strasse der Nationen 62, D ...
A controlled assembly of natural beta-cyclodextrin modified Au NPs mediated by dopamine is demons... more A controlled assembly of natural beta-cyclodextrin modified Au NPs mediated by dopamine is demonstrated. Furthermore, a simple and sensitive colorimetric detection for dopamine is established by the concentration-dependent assembly.
The method for producing chitosan coatings on solid surfaces with anchoring layers of poly(gly ci... more The method for producing chitosan coatings on solid surfaces with anchoring layers of poly(gly cidyl methacrylate) and maleic anhydride copolymers has been proposed. It is shown that, owing to a high reactivity of epoxy and anhydride groups, the efficiency of immobilization and the stability of the coatings are considerably higher than those prepared by the conventional method of chitosan grafting onto the surface modified by poly(acrylic acid). The properties of chitosan coatings are examined via atomic force micros copy, X ray photoelectron spectroscopy, ellipsometry, and electrokinetic measurements. Depending on the anchoring layer used, the total thickness of the coatings is 6-16 nm with an rms roughness less than 1.2 nm, while the isoelectric points of the surfaces modified with chitosan are located in the pH range 5-6.
Uploads
Papers by Frank Simon