A methacrylate‐functionalized phosphorescent Ir(III)‐complex has been synthesized, characterized, and applied as a monomer in radical copolymerizations. Together with methyl methacrylate, the complex has been copolymerized under free radical polymerization conditions. Aiming for host‐guest‐systems, applicable e.g. in organic light emitting devices (OLEDs), the complex was further copolymerized with a methacrylate‐functionalized carbazole derivative using the atom transfer radical polymerization technique. Applying gel permeation chromatography, in combination with a photodiode array detector, could clearly prove the formation of the copolymers. The optical properties of the photoactive monomers as well as the copolymers were investigated by absorption and emission spectroscopy (in solution). For the carbazole‐copolymer, the emission originates almost exclusively from the complex. This provides evidence of an efficient intrachain energy transfer, which makes the system an interesting candidate for potential OLED applications.
Polystyrene microfibers containing lower‐rim substituted calix[4]arene with phosphinoyl pendant arms were easily prepared in one‐step procedure by electrospinning. A specific feature of the fibers is the difference in their functionality at the surface and in the bulk. The graded structure of the fibers was shown by XPS analyses. The calix[4]arene concentration in the 3–5 nm surface layer was 50% higher than the theoretically calculated if calix[4]arene was uniformly distributed in the fibers. A six‐coordinated complex was formed between the calix[4]arene included in the fibers and Ni2+ ions. The distribution of phosphorus along the fibers is uniform, as evidenced by X‐ray mapping.
Cystamine, when employed as a cross‐linking agent, leads to poly(amidoamine) networks, which on reaction with 2,2′‐dithiodipyridine turn into linear poly(amidoamine)s with side dithiopyridyl groups that easily undergo exchange reactions with reduced L ‐glutathione, a model thiol‐containing biologically active peptide. The resultant products represent the first examples of soluble poly(amidoamine)–peptide conjugates in which the peptide moieties are linked to the polymer chain by S S bonds stable in blood, but cleavable inside cells.
A polymeric film of a biodegradable poly(p‐dioxanone) was grown from 490 nm silica particles by monolayer formation via self‐assembly of hydroxy‐terminated triethoxysilane and subsequent surface‐initiated ring‐opening polymerization of p‐dioxanone. The resulting silica/poly(p‐dioxanone) hybrid particles were characterized by means of 1H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, field‐emission scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy.
The large‐deformation energetics of a single molecular chain of the rod‐like polyimide PMDA‐PDA was investigated using DFT, ab initio MO and semi‐empirical MO methods. The force/displacement curves were calculated from tensile testing simulations along the axis of the molecular chain, allowing a discussion of the distribution and change of local strain of the molecular chain. The deformation behavior of a single PMDA‐PDA molecular chain under finite deformations as functions of bending angle and dihedral angle between PMDA and PDA groups are compared. It is found that the semi‐empirical MO calculations provide sufficient accuracy to express the energetics of large deformations except for compressive deformation.
Summary: Novel hyperbranched poly(amine‐ester) (HPAE) cross‐linked films were prepared by cross‐linking the terminal hydroxyl groups of HPAE using glutaraldehyde (GA). Atom force microscope and scanning electron microscope revealed their smooth surfaces, dense and homogenous matrices. Property characterizations indicated that these cross‐linked films had good hydrophilicity, relative low protein adsorption, and high tensile strength. Also, their swelling behavior varied with the solvent.
Structure of the hyperbranched poly(amine‐ester). 相似文献
A novel approach is employed to produce core–corona nanospheres, which introduces a stereoregular hydrophilic part to an amphiphilic block copolymer. The resultant morphology is reported using isotactic‐poly(methacrylic acid)‐block‐poly(butyl acrylate). Infrared spectroscopy revealed a supramolecular interaction, and X ray diffraction revealed the crystallization of the outer isotactic‐poly(methacrylic acid) part. The nanostructure, which looks like a nanosized ‘grape’, was formed when nanospheres and nanofibers coexisted simultaneously and partially fused.
Attachment of triarylamino‐functional groups at the 9‐position of 2,7‐linked carbazole polymers results in blue‐emitting materials with two independent redox processes that were attributed to the triarylamino groups and the polymer backbone, respectively. This new class of blue‐emitting conjugated polymers was prepared via a Suzuki cross‐coupling reaction and showed low turn‐on voltages in electroluminescent devices as a result of their low ionisation potentials. The photophysical, electrochemical and electroluminescent properties of these materials are discussed.
Surfactant‐grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm‐co‐S180A) gels prepared using a chemical cross‐linker (bis‐PNS gels) exhibited rapid shrinking, as did PNS gels prepared by γ‐ray irradiation (γ‐PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main‐chain structure. The shrinking kinetics of the bis‐PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis‐PNS gel.
The importance of taking into account the principle of microscopic reversibility in the analysis of complex copolymerization systems is demonstrated. The analysis of a reversible copolymerization system in which segmental exchange is possible from the point of view of the reaction microreversibility proves that hetero‐reshuffling rate constants depend on homo‐reshuffling rate constants and copolymerization thermodynamics.
Summary: The first example of a room temperature reversible addition‐fragmentation chain transfer polymerization conducted directly in aqueous media is detailed. Under these conditions acrylamide and N,N‐dimethylacrylamide may be polymerized in a controlled fashion to near quantitative conversions employing a difunctional trithiocarbonate chain transfer agent (CTA). Hydrolysis studies conducted at pH 5.5 suggest that the CTA is stable up to approximately 50 °C.
Summary: High‐resolution FT‐IR spectroscopy has been used for the first time to characterize the variation of the unit cell dimensions of high‐density polyethylene (HDPE). In combination with the unit cell parameters of HDPE measured at different temperatures by Swan using wide‐angle X‐ray diffraction, the relationship between the rocking band shift (730 cm−1) and the change of the unit cell volume of HDPE has been established.
High‐resolution variable‐temperature FT‐IR spectra of HDPE rocking bands with decreasing temperature. 相似文献
Summary: A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual‐scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an ‘intelligent’ wettability property can be utilized to separate oil and water systems efficiently.
The composite film can be used to separate diesel oil and water. 相似文献
A branched copolymer containing a degradable polyperoxide linkage at a branching point was synthesized by the radical copolymerization of dienyl‐functionalized polystyrene and polyisoprene macromonomers with molecular oxygen. The ternary mixture of the branched copolymer and the macromonomers showed phase‐separated structure after annealing at 45 and 90 °C. The adjacent spacing of the phase‐separated structure was in the order of submicron to micrometer, which is larger than that of general microphase separated structures, due to the presence of homopolymers (macromonomers). Annealing at 110 °C induced thermal decomposition of the polyperoxide followed by in‐situ collapse and a drastic morphology change in the phase‐separated structure.
The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer–living radical polymerization (SET‐LRP) mechanism. The polymerizations proceeded quickly, reaching 67% conversion at a residence time of 16 min. Ligand concentration could also be reduced without a sharp drop in polymerization rate, demonstrating the potential for decreased raw material and post‐process purification costs. Chain extension experiments conducted using synthesized polymer showed high livingness. The combination of living polymer produced at high polymerization rates at ambient temperature and low volatile organic solvent content demonstrate the potential of a copper reactor for scale up of SET‐LRP.
Oligomeric guanidines can be obtained by polycondensation of guanidine hydrochloride and 1,2‐bis(2‐aminoethoxy)ethane. A comparative MALDI‐TOF mass spectrometry/NMR spectroscopy study with a 13C‐labeled sample enabled the unambiguous analysis of a guanidine‐based polymer. Among the four major product series unprecedented macrocyclic compounds were detected. The minimum inhibition concentrations for four different microorganisms were determined, showing excellent biocidal activities.
Deposition of hole injection layers including a perfluorinated ionomer has been demonstrated using layer‐by‐layer spin self‐assembly for enhanced device efficiency and lifetime in PLEDs. We show that the LBL spin self‐assembled thin films enable to control work functions of indium‐tin oxide anodes by changing the PFI concentration and that a resulting green‐emitting device has an enhanced luminescence efficiency and 18 times longer half lifetime than a device using a conventional HIL. We also fabricate a gradient of energy levels by the LBL self‐assembly of the PFI that results in a work function of 5.74 eV, which can be used to improve carrier injection even for an emitting layer whose ionization potential is over 5.7 eV.
The synthesis of nanosized poly(methyl methacrylate) initiated by 2,2′‐azoisobutyronitrile via differential microemulsion polymerization has been investigated. Poly(methyl methacrylate) with a molecular weight of around 1 × 106 and a particle size of about 20 nm was achieved under mild reaction conditions. A typical condition was that the surfactant amount required could be as low as 1/130 of the monomer amount in weight, and the surfactant/water ratio could be as low as 1/600, which is much less than the corresponding amounts reported in the literature. “Molecular bricks”, i.e., nanoparticles in which there are only one or two polymer chains, can be achieved using mild conditions by differential microemulsion polymerization, which may have potential applications for making molecular devices.
Summary: The synthesis and thermal, redox and photoluminescence properties of a soluble donor‐acceptor polyplatinayne with the electron‐accepting silole ring and its model compound are described. The polymer has an optical band gap of 2.10 eV which is much lower than that of thienyl‐ or silyl‐bridged congeners. The incorporation of electron‐accepting silole unit in the metallopolymer main chain creates a new π‐conjugated system that features unique donor‐acceptor characteristics.
