Highly dispersed ZnO nanoparticles with variable particle sizes were successfully prepared within an amphiphilic hyperbranched polyetherpolyol matrix via decomposition of an organometallic precursor in the presence of air leading to stable nanocomposites. The high degree of stabilization during and after the synthesis by the polymer permits control over the nanoparticle size and therefore, due to the quantum‐size‐effect, the particle properties. Furthermore, these polymer‐inorganic nanocomposites can easily be dispersed in apolar solvents to yield highly transparent, stable solutions.
We report syntheses of phenylene‐, biphenylene‐, and terphenylene‐layered polymers with a xanthene scaffold by the modified Suzuki‐Miyaura coupling reaction. Their optical properties were studied in detail. The polymer end‐capped by nitrobenzene units, which act as fluorescence quenchers, exhibited the photo‐excited energy transfer from the layered oligophenylenes to the terminal units.
Summary: In the present communication we describe a photolithographic method to produce polyaniline (PANI) patterns using PANI modified with a traceless removable functional group (nitrosated polyaniline, PANI‐NO) and external inexpensive polymeric photoacid generators (poly(vinyl chloride), PVC). Therefore, residual sub‐products created by irradiation of the plate do not remain occluded in the polymeric films. The borders of the patterns are better defined than in the case of chemical lithography using inorganic acids as the hydrolyzing agent.
A new route consisting of simultaneous centrifugal spinning and solution blowing to form polymer nanofibers is reported. The fiber diameter (60–1000 nm) is shown to be a function of polymer concentration, rotational speed, and working pressure of the processing system. The fiber length is dependent on the rotational speed. The process can deliver 6 kg of fiber per hour and therefore offers mass production capabilities compared with other established polymer nanofiber generation methods such as electrospinning, centrifugal spinning, and blowing.
Blue‐light‐emitting 2,7‐carbazole‐based conjugated copolymers have been prepared by Yamamoto or Suzuki cross‐coupling reactions. By introducing highly substituted aromatic comonomers, fully soluble high‐molecular‐weight copolymers have been obtained. Moreover, these amorphous polymeric materials exhibit good thermal stability and interesting redox properties. All these features make these new conjugated polymers highly promising for the development of single‐polymer‐layer blue‐light‐emitting diodes.
Macroporous temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPA) hydrogels were prepared by a novel phase‐separation technique to improve the response properties. In comparison with a conventional PNIPA hydrogel prepared in water, these macroporous hydrogels, prepared by polymerization in aqueous sucrose solutions, have higher swelling ratios at temperatures below the lower critical solution temperature and exhibit much faster response rates to temperature changes.
Scanning electron microscopy image of the surface of a PNIPA hydrogel, prepared in 1.50 M aqueous sucrose solution. 相似文献
The Michael reaction of chitosan with acrylic acid was carried out successfully, even in water alone as the reaction medium. As a consequence of its good solubility in water, the reaction product, N‐carboxyethylchitosan, showed excellent biodegradable properties with standard activated sludge.
In contrast to the conventional two‐step method, which involves the generation of reactive functional groups followed by incubation in a dye solution (a wet developing process), the “precursor approach” enables the rapid and cost‐effective generation of patterned images in one step, without the need for an additional wet process. By using the “precursor approach”, the fluorescence of precursor molecules in polymer films can be effectively manipulated by: (1) photoinduced removal of transient protecting groups; (2) photoinduced protonation or intramolecular proton transfer; (3) photochromism; (4) photoinduced formation of fluorophores; (5) photoinduced oxidative degradation or molecular orientation.
The synthesis of high conductivity poly(3,4‐ethylenedioxythiophene) (PEDOT) films using vacuum vapour phase polymerisation is reported. Water vapour is introduced into the chamber and results suggest that it acts as a proton scavenger during polymerisation. Process optimisation leads to PEDOT films that have high conductivity and a blue‐black appearance. Poor quality films have lower conductivity and a characteristic greenish colour. UV‐vis‐NIR spectra show that poor PEDOT films are characterised by higher absorption in the UV‐vis region and an absorption plateau in the NIR region, which suggests an increased level of disrupted conjugation along the polymer backbone or higher oligomer content. Conversely, high quality PEDOT is characterised by an extended NIR absorption tail and lower absorption in the UV‐vis region.
Nonlinear optical vinyl polymers with high glass transition temperature (Tg) were prepared by the functionalization of a fluorinated acrylate‐methyl vinyl isocyanate copolymer. A modified pathway to obtain a thiophene bridged chromophore was worked out. Poled films of the polymers show a fairly high and stable nonlinear optical response, even at elevated temperatures.
The thiophene‐bridged chromophore, based on a substituted dicyanomethylene‐dihydrofuran acceptor, synthesized here. 相似文献
Microporous films consisting of two‐dimensionally ordered void structures ‐ so‐called honeycomb films ‐ were produced by evaporation of polymer solutions under high humidity. Two types of poly(vinyl cinnamate)s were used: A newly synthesized amphiphilic poly(vinyl cinnamate) and a mixture of a commercial poly(vinyl cinnamate) and an amphiphilic polyion complex. Photo‐crosslinking of the honeycomb structure could be achieved by UV irradiation while completely retaining the film morphology. The crosslinked films showed excellent stability against organic solvents.
Spherical polyelectrolyte brushes consisting of a magnetite/polystyrene nanocomposite core and a poly(acrylic acid) brush shell were prepared by photo‐emulsion polymerization. They are narrowly dispersed, superparamagnetic and redispersible after aggregating by external magnetic field, as determined by transmission electron microscopy, dynamic light scattering, thermal gravimetric analysis and a vibrating sample magnetometer. Magnetic control is thus introduced into nano‐sized spherical polyelectrolyte brushes to achieve recovery and controllable delivery in applications. This approach opens up the way for cost‐effective applications of spherical polyelectrolyte brushes.
A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.
A generalized silica coating scheme is used to functionalize and protect sub‐micron and micron size dicyclopentadiene monomer‐filled capsules and polymer‐protected Grubbs' catalyst particles. These capsules and particles are used for self‐healing of microscale damage in an epoxy‐based polymer. The silica layer both protects the capsules and particles, and limits their aggregation when added to an epoxy matrix, enabling the capsules and particles to be dispersed at high concentrations with little loss of reactivity.
Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl3 and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.
TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min. 相似文献
Plasma Enhanced Chemical Vapor Deposition (PECVD) of poly‐2‐hydroxyethyl methacrylate (pHEMA) biocompatible, biodegradable polymer films were produced alone and cross‐linked with ethylene glycol diacrylate (EGDA). Degree of cross‐linking was controlled via manipulation of the EGDA flow rate, which influenced the amount of swelling and the extent of degradation of the films in an aqueous solution over time. Noncross‐linked pHEMA films swelled 10% more than cross‐linked films after 24 h of incubation in an aqueous environment. Increasing degree of film cross‐linking decreased degradation over time. Thus, PECVD pHEMA films with variable cross‐linking properties enable tuning of gel formation and degradation properties, making these films useful in a variety of biologically significant applications.
Perfectly alternating copolymers can be synthesised by reacting diacrylates with terminal dienes using alternating diene metathesis polycondensation (ALTMET). This novel method is very versatile and allows preparation of diverse structures of polymers, including main‐chain liquid crystalline polymers.
Main‐chain liquid crystalline polymer obtained by ALTMET. 相似文献
Superhydrophobic conducting polyaniline (PAni) films were electrochemically deposited in acetonitrile‐H2O electrolyte containing aniline monomer and perfluorooctanesulfonic (PFOS) acid. The films exhibited an extended network structure composed of helical PAni sub‐micron fibers. The helical fibrous structure is thought to form through a supermolecular templating process. The surface of the PFOS‐doped PAni films showed a water contact angle of 153°. Reducing the PFOS‐doped PAni (in emeraldine salt form) by negative potential led to de‐doped PAni films (in leucoemeraldine base form) which were superhydrophilic (water contact angle close to 0°). By controlling the electrical potential, PAni films were changed between the doped state and de‐doped state, resulting in reversibly switchable superhydrophobic and superhydrophilic surfaces.
