The site‐specific attachment of nanoparticles is of interest for biomaterials or biosensor applications. Polymer brushes can be used to regulate this adsorption, so the conditions for selective adsorption of phosphonate‐functionalized nanoparticles onto micropatterned polymer brushes with different functional groups are optimized. By choosing the strong polyelectrolytes poly(3‐sulfopropyl methacrylate), poly(sulfobetaine methacrylate), and poly[2‐(methacryloyloxy)ethyl trimethylammonium chloride], it is possible to direct the adsorption of nanoparticles to specific regions of the patterned substrates. A pH‐dependent adsorption can be achieved by using the polycarboxylate brush poly(methacrylic acid) (PMAA) as substrate coating. On PMAA brushes, the nanoparticles switch from attachment to the brush regions to attachment to the grooves of a patterned substrate on changing the pH from 3 to 7. In this manner, patterned substrates are realized that assemble nanoparticles in pattern grooves, in polymer brush areas, or substrates that resist the deposition of the nanoparticles. The nanoparticle deposition can be directed in a pH‐dependent manner on a weak polyelectrolyte, or is solely charge‐dependent on strong polyelectrolytes. These results are correlated with surface potential measurements and show that an optical trap is a versatile method to directly probe interactions between nanoparticles and polymer brushes. A model for these interactions is proposed based on the optical trap measurements. 相似文献
A new kind of a fibrous material is produced by controlled self‐rolling of patterned thin poly(4‐vinyl)pyridine films in acidic water. Self‐rolling is induced by unequal swelling of the top and the bottom layers of the films in the solvent. Rolling starts from parallel scratches in the film and results in twin‐scroll fibers. The fibers are stabilized by staining with CuCl2 salt and freeze‐dried. The output of the fiber material production is of the order of 1 cm3 from approximately 50 cm2 of the patterned polymer film. The approach opens new broad opportunities for creation of smart fibrous materials via loading the fibers with functional micro‐ and nanoparticles. 相似文献
A poly(2-(2-bromopropionyloxy)ethyl methacrylate) (PBPEM) was used as macroinitiator in the synthesis of molecular brushes with poly(4-vinylpyridine) side chains, (P(BPEM-g-4VP). Atom transfer radical polymerization (ATRP) was employed as the polymerization technique. The polymerizations were carried out in DMF at 30 °C using a copper-chloride-based ATRP catalyst, which converted all the dormant polymer chain ends to alkyl chloride groups, thus minimizing branching and crosslinking, which occurred when a copper bromide-based catalyst was employed. Tris(2-pyridylmethyl)amine was selected as the ligand due to the high activity of its CuI complex in ATRP as well as its strong binding to both CuI and CuII, which prevented competitive complexation of the monomer or polymer to the metal center. In order to prevent crosslinking via radical coupling, the monomer conversion was kept low (under 3%) and the alkyl chloride end groups of P4VP side chains were converted to alkoxyamines upon activation followed by a reaction with TEMPO radical. Dynamic light scattering measurements showed the hydrodynamic diameter (DH) of the brushes was pH-dependent. Aggregation of single P(BPEM-g-4VP) brushes in water was very pronounced at high pH values but was observed even when the amount of added HCl was enough to completely protonate the pyridine units (DH = 278 nm). 相似文献
In this study, we present nanowear studies using surface force microscopy (SFM), on nanoscopic thin films of reversibly switchable binary polymer brushes [polystyrene (PS) + poly(2-vinylpyridine) (P2VP)] and respective monobrushes [polystyrene and poly(2-vinylpyridine)] synthesized via “grafting to” method. The aim was to tune the wear in nanothin polymer brush surfaces. Therefore, the effect of conformational switching of PS + P2VP brush on treatment with selective solvents for PS and P2VP chains on the wear process was investigated. Wear process on thick spin-coated films of PS and P2VP was also investigated for comparison. Nanowear experiments were performed using SFM tip by repeating scans over the surface to follow the wear process closely. The wear process on different surfaces was explained on the basis of molecular entanglement as well as adhesion and friction on the sample surface. For spin-coated PS film as well as PS and PS + P2VP brush surfaces (treated with toluene) with molecular entanglements at surface, wear mechanism involved formation of ripples. However, in case of spin-coated P2VP films as well as P2VP and PS + P2VP brush surfaces (treated with ethanol) with no molecular entanglements at surface, wear occurred via removal of polymer chains and their accumulation at the rim. For PS + P2VP surface treated with acidic water, wear mechanism was complex and inhomogeneous ripple formation was followed by formation of heaps of polymeric material in the center of scanned area. The extent of wear as measured either by root mean square roughness of the surface or spacing between the ripples, increased with the number of scans for all the surfaces. Our study shows that wear mode of polymer brush surfaces is different for different polymers and can be controlled/tuned by the use of binary polymer brushes. 相似文献
Argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were solution coated with a thin layer of poly(4-vinyl pyridine) (P4VP). Subsequent exposure of the films to argon plasma resulted in the grafting of P4VP on the PTFE films. Electroless plating of copper could be carried out effectively on the P4VP-grafted PTFE (P4VP-g-PTFE) surface after PdCl2 activation and in the absence of SnCl2 sensitization (the Sn-free process). The catalytic processes of the electroless plating of copper in the presence and absence of sensitization by SnCl2 were also compared. The effect of glow discharge conditions on the P4VP concentration and the adhesion strength of the electrolessly deposited copper was investigated. The T-peel adhesion strength of the electrolessly deposited copper with the graft-modified PTFE film was improved in the absence of SnCl2 sensitization and could reach about 3 N/cm. PdCl2 activation and electroless deposition of copper could not be carried out on the pristine or the Ar plasma-treated PTFE surface in the absence of prior sensitization by SnCl2. X-ray photoelectron spectroscopic (XPS) analysis revealed that the electrolessly deposited copper delaminated from the P4VP-g-PTFE film by cohesive failure inside the PTFE film. 相似文献
Summary: A simple route to an ordered array of metal/semiconductor oxide composite nanodots is presented. Micellar monolayer films of polystyrene‐block‐poly(2‐vinyl pyridine) (PS‐b‐P2VP) loaded with HAuCl4 in the P2VP nanodomains are used as templates. TiO2 is generated selectively within the polar P2VP domains of PS‐b‐P2VP/HAuCl4 films by chemical vapor deposition of TiCl4. Subsequent removal of the organic matrix by oxygen plasma or UV light leads to an array of Au/TiO2 composite nanoparticles on the substrate surface.
Schematic illustration of the process to fabricate an array of Au/titania composite nanodots. 相似文献
In this work, an open‐tubular capillary liquid‐phase column was prepared by modifying chain polymer on the inner surface of capillary and chemical bonding of metal organic frameworks, NH2‐UiO‐66, to the brushes of chain polymer (poly(glycidyl methacrylate)). Besides advantages of facial preparation and good permeability, the chain polymer effectively increases the modification amount of NH2‐UiO‐66 nanoparticles to increase the phase ratio of open‐tubular capillary column and enhance the interactions with analytes. The results of scanning electron microscope energy‐dispersive X‐ray spectra indicated that NH2‐UiO‐66 nanoparticles were successfully bonded to the chain polymer. Because of the hydrophobic interaction and hydrogen bonding interaction between the analytes and the ligand of NH2‐UiO‐66, different analytes were well separated on the NH2‐UiO‐66‐modified poly(glycidyl methacrylate) capillary (1.12 m × 25 μm id × 365 μm od) with the high absolute column efficiency reaching 121 477 plates, benefiting from an open‐tubular column and low mass transfer resistance provided by polymer brush and metal–organic framework crystal. The relative standard deviations of the retention time for run‐to‐run, day‐to‐day, and column‐to‐column (n = 3) runs are below 4.28%, exhibiting good repeatability. Finally, the column was successfully applied to separation of flavonoids in licorice. 相似文献
Thermally stable mesoporous TiO2/SiO2 hybrid films with pore size of 50 nm have been synthesized by adopting the polymeric micelle‐assembly method. A triblock copolymer, poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide), which serves as a template for the mesopores, was utilized to form polymeric micelles. The effective interaction of titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) with the polymeric micelles enabled us to fabricate stable mesoporous films. By changing the molar ratio of TEOS and TTIP, several mesoporous TiO2/SiO2 hybrid films with different compositions can be synthesized. The presence of amorphous SiO2 phase effectively retards the growth of anatase TiO2 crystal in the pore walls and retains the original mesoporous structure, even at higher temperature (650 °C). These TiO2/SiO2 hybrid films are of very high quality, without any cracks or voids. The addition of SiO2 phase to mesoporous TiO2 films not only adsorbs more organic dyes, but also significantly enhances the photocatalytic activity compared to mesoporous pure TiO2 film without SiO2 phase. 相似文献
A new strategy toward patterned polymer brushes combining the spatially controlled deposition of poly[(hydroxymethyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ) by chemical vapor deposition (CVD) polymerization of 4‐(hydroxymethyl)[2.2]paracyclophane and surface‐initiated ring‐opening polymerization was developed. Patterns of polymer brushes with thicknesses between 53 and 538 Å were created. The approach does not require photolithographic tools and has potential applicability to a wide range of different substrates, such as glasses, polymers, metals or composites. 相似文献
Surface‐initiated atom transfer radical polymerization (SI‐ATRP) was used to graft poly(N‐isopropylacrylamide) (PNIPAM) brush layers with a controllable thickness in the 10‐nm range from silicon substrates. The rate of polymerization of N‐isopropylacrylamide was tuned by the [Cu(II)]0/[Cu(I)]0 ratio between the deactivating and activating species. The polymer layer thickness was characterized by atomic force microscopy (AFM) and ellipsometry. PNIPAM layers with a dry thickness between 5.5 and 16 nm were obtained. Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) confirmed that the chemical structure is PNIPAM brushes. Analysis of the AFM data showed that our procedure leads to polymer grafts in the “mushroom‐to‐brush” transition regime. 相似文献
The title compound, poly[μ3‐bromido‐(pyridine‐3‐carboxylato‐κN)copper(I)], [CuBr(C6H5NO2)]n, is a novel coordination polymer based on a copper–bromide net and nicotinic acid ligands. The asymmetric unit contains one copper(I) ion, one bromide ligand and one nicotinic acid ligand, all on general positions. The CuI atom is tetrahedral and coordinated by three bridging Br atoms and the N atom from the nicotinic acid ligand. The Cu–Br units form alternating six‐membered chair‐patterned rings in net‐like layers. The attached nicotinic acid units point alternately up and down. The layers are assembled into a three‐dimensional network via intermolecular O—H...O and C—H...Br hydrogen‐bonding interactions. 相似文献
Herein, nanometer‐scale morphologies of graft‐copolymer‐like supramolecular thin films, composed of sulfonic acid terminated polystyrene (SPS) and poly(2‐vinylpyridine) (P2VP), and their application to antireflection coatings were investigated. The intermolecular complexes of SPS and P2VP, formed through nonstoichiometric multiple hydrogen bonding between the sulfonic acid group of SPS and the nitrogen atom in pyridine unit of P2VP, occurring in film deposition allowed for the formation of spherical micelles (with SPS and P2VP as the corona and core, respectively) in the thin film. Interestingly, the domain size of the micelles was tunable from approximately 20 to 90 nm on average by controlling either the blend ratio of components or the concentration of polymer solution. Furthermore, nanoporous thin films could be easily prepared by removing the core of micelle‐based nanostructures by using a simple solvent etching process, leaving sulfonic acid groups on the surface of nanopores, which can be utilized as potential functional sites. Those resultant nanoporous thin films were conveniently employed as an antireflection layer on a glass substrate, giving a maximum 97.8 % transmittance in the visible wavelength range. 相似文献
ABTS, 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate), a colorless dianion that forms a colored radical upon oxidation, was characterized with electrochemistry and spectroscopy and demonstrated to be a detectable analyte in a polymer‐modified spectroelectrochemical sensor. Three positively charged polymers were incorporated into a thin film on an indium tin oxide (ITO) optically transparent electrode and used to concentrate ABTS at the electrode surface. Of the three films, poly(vinylbenzyl trimethyl ammonium chloride)‐poly(vinyl alcohol) (PVTAC‐PVA), poly(diallyldimethylammonium chloride)‐silica (PDMDAAC‐SiO2), and quaternized poly(4‐vinyl‐N‐methylpyridinium nitrate)‐silica (QPVP‐SiO2), PVTAC‐PVA demonstrated the best ability to absorb ABTS. Within 20 min, a change of 0.2 absorbance units at 417 nm and 13.6 μA/cm2 in anodic peak current density in cyclic voltammetry at a scan rate of 0.025 V/s were observed. 相似文献