Polyaniline nanodisks have been synthesized successfully by the chemical oxidation polymerization of aniline by a self‐assembly process without the use of any acid. The thickness and lateral dimensions of the polyaniline nanodisks are in the range of 20–30 nm and 1–2 µm, respectively. The influence of synthetic parameters, such as the concentration of ammonium peroxydisulfate and pH, on the morphologies of polyaniline nanostructures have been investigated.
Summary: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor‐induced phase separation occurred during the solidifying process and a rough surface with a micro‐nano‐binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.
Multiwalled carbon nanotubes (MWNT) are introduced into thermoplastic matrices (polycarbonate and polyamide) by melt blending using polyethylene (PE) based concentrates with high MWNT loadings (24–44 wt.‐%). MWNT surfaces were treated with a metallocene‐based complex to afford the in‐situ polymerization of ethylene directly from the surface. The resulting concentrates showed excellent MWNT pre‐dispersion. Due to the high interfacial energy between MWNT and PE, the nanotubes migrate into matrix polymers with lower interfacial energies, like polycarbonate and polyamide, and thereby remain in their excellent dispersion state. Thus, electrical percolation is achieved at lower MWNT contents as compared to direct incorporation. For polycarbonate it is shifted from 0.75 to 0.25 wt.‐%.
The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.
Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro‐2‐propanol. Simple binary mixtures of phosphate‐buffered saline and ethanol have been found to be highly effective for electrospinning. FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning. Crosslinking of the electrospun collagen scaffolds was achieved with standard methods.
Alternating copolymers comprised of (meth)acrylates and vinyl ethers with controlled molecular weights and polydispersities were synthesized for the first time by living radical polymerization using organotellurium, stibine, and bismuthine chain transfer agents. Combining living alternating copolymerization and living radical or living cationic polymerization afforded hitherto unavailable block copolymers with controlled macromolecular structures.
The random end linking of different amounts of trifunctional crosslinkers with 3 000 prepolymer linear chains, with length varying from 10 to 30 monomers, to form networks at different system number densities was dynamically simulated by the molecular dynamics method. Investigation of the crosslinking kinetics shows that, with a stoichiometric number of crosslinkers present, the time evolution of free ends fraction decays as a power law in time t−3/4. This scaling behavior is different from the one in a dense polymer melt. Structural analyses of the resulting networks indicate that the imperfections of the network structure strongly depend on the initial synthesis conditions including the initial system number density and the ratio of crosslinkers to precursor polymer chain ends.
Copolymerization of hepta‐1,6‐diene with ethylene using a cobalt–bis(imino)pyridine complex affords a polymer that contains trans‐1,2‐five‐membered rings in the repeating unit from hepta‐1,6‐diene. The ratio of the repeating units of diene to those of ethylene is controlled from 3: 97 to 50:50, depending on the reaction conditions. Isotope‐labeling reactions reveal that the major chain transfer pathway involves β‐hydrogen elimination of the polymer end formed after ethylene insertion.
An in‐situ refractive index method is applied to study the diffusion process of sucrose in hydrogels. Diffusion was monitored by recording the refraction of a laser beam when passing through a triangular hydrogel cell. The distribution of refractive index changes was obtained from the deviated distance of the linear beam and converted to the distribution of concentration. By employing Fick's second law, the diffusion behavior was investigated and the diffusion coefficient was obtained.
Schematic picture of the refractive index equipment to study the diffusion process. 相似文献
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.
New photosensitive alkoxyamines have been designed using molecular orbital calculations to improve the selective C O versus N O cleavage. The targeted light‐sensitive alkoxyamine is synthesized in one step and its reactivity under UV has been investigated using both ESR and LFP. The ability of this alkoxyamine to control the photopolymerization of n‐butyl acrylate is evidenced through a process called nitroxide‐mediated photopolymerization NMP2. The selected alkoxyamine is finally used to prepare covalently bonded multilayered micropatterns. This original application highlights the high potential of this technique for some specific applications that require spatial control.
We describe an enzyme‐responsive polymeric vehicle, which is of great interest in controlled drug delivery, biosensing, and other related areas. The polymer synthesized using lipase as catalyst in DMSO has a favorable molecular structure that is quickly hydrolyzed by lipase in aqueous phase, and allows a fast release of encapsulated molecules.
Grafted conjugated polyelectrolytes were synthesized for the first time and characterized. The polymers demonstrated properties of a convenient and efficient protocol for creating Hg2+ sensors. The unique character of the new material comes from an anionic counterion nature with no external cofactors, and imparts high selectivity and fast detection for mercury ion in a fluorescence probe. The concept may be potentially applied to create new sensors for monitoring other ions.
The use of PSU‐Py prepared by click chemistry as a platform in membrane‐bottom microwell plates for oxidase and hydrolase/oxidase‐based enzyme assays is studied. For the GOx assay, the postulated fluorescence mechanism is based on the consumption of glucose by dissolved oxygen and GOx in the microwell plates covered with the PSU‐Py membrane. For the AG‐GOx assay, maltose is used as AG substrate and hydrolyzed to glucose which is then oxidized by the GOx activity. It is shown that the PSU‐Py membrane acts as a fluorescence indicator of the enzymatic reactions, and both GOx and AG/GOx enzyme assays are successfully applied for glucose, maltose and acorbose analysis in the range 0.125–2.0 × 10?3 M glucose, 0.05–0.5 × 10?3 M maltose, and 0.0125–0.1 mg · mL?1 acorbose, respectively.
SS phages are genetically enginnered by replacing 2 N‐terminal amino acids of the p8 coat protein of the fd phage. AGE and zeta potential measurements show that SS phages carry at least 1/4 less net negative surface charge than fd phages. Morphology and thickness of phages are studied at different counterion concentrations (10?3, 10?2 and 10?1 M ) by AFM, SEM and immunofluorescence analyses. Bundles induced by CoCl2 and CaCl2 are either metallized by chemical reduction or biomineralized for apatite‐like material formation. EDX spectroscopy confirms the presence of Co, P and Ca peaks in mineralized samples. Such bottom‐up manufactured phage scaffolds might be applied in bioengineering studies.
Two new “H” type of indole‐based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of “H” type chromophore moieties. And they could be promising candidates for the practical applications as new photonic materials.
A cationic water‐soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg · mL−1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three‐fold enhancement in the electroluminescence (EL) efficiency.
Summary: The existence of liquid‐crystalline (LC) phases in dilute methylcellulose solutions is demonstrated by exothermic peaks in differential scanning calorimetry (DSC) curves upon heating and is evidenced by a discontinuity of the dynamic storage modulus when the concentration of methylcellulose increases. This crystalline phenomenon is further confirmed by polarized light microscopy and optical rotatory dispersion measurements. It is found that the appearance of the LC formation is related to the temperature, concentration, and molecular weight of methylcellulose.
The exothermic peaks in DSC curves upon heating and cooling, and conformational transitions in ORD profiles for 2.5 g · L−1 SM4000 methylcellulose aqueous solutions. 相似文献
