Energy distribution of the universe in the Bianchi type II cosmological models

Using the energy‐momentum complexes of Tolman, Papapetrou and Weinberg, the total energy of the universe in Locally Rotationally Symmetric (LRS) Bianchi type II models is calculated. The total energy is found to be zero due to the matter plus field. This result supports the viewpoint of Tryon, Rosen and Albrow.     

Photochemically Cross‐linked Poly(aryl ether ketone) Rings

Summary: Macrocyclic phenyl ether ketones were prepared via pseudo high dilution condensation. Irradiation of these rings with UV light in a solution containing isopropyl alcohol as hydrogen donor resulted in a photo‐induced reduction of benzophenone to benzopinacol and the formation linked macrocycles. These rings can be heated to undergo ring‐opening polymerization and produce a polymer network or they can be added to a polycondensation reaction to prepare poly(ether ether ketones) with variable degrees of cross‐linking.

Photochemical cross‐linking of PEK rings and ring opening polymerization (n: 2–6). (a) hν, iPrOH, DCM; (b) CsF, 260 °C (polymer 3 ); (c) 4,4′–difluorobenzophenone, hydroquinone, diphenylsulphone, K₂CO₃, 260 °C (2% polymer 4 ; 6% polymer 5 ).     

Synthesis of Conjugated Polymer Nanoparticles in Non‐Aqueous Emulsions

Summary: A novel non‐aqueous emulsion system, consisting of cyclohexane as the continuous and acetonitrile as the dispersed phase, is described. Stabilization of the system can be achieved by using polyisoprene‐block‐poly(methyl methacrylate) copolymers as emulsifiers. The suitability of this system for performing water‐sensitive, catalytic, and oxidative polymerizations and polycondensations is demonstrated by the synthesis of poly(3,4‐ethylenedioxythiophene), poly(thiophene‐3‐yl‐acetic acid), and polyacetylene. In all cases spherical nanoparticles with diameters as small as 23 nm can be obtained.

     

Precise Block‐Copolymers by Efficient Coupling of End‐Functionalized Polymers Using Phosgene

Summary: We report the synthesis of well‐defined block copolymers by covalent coupling of hydroxy end‐functionalized polymers. Using the high volatility of the coupling agent phosgene as compared to the solvent, very high conversion (up to 96%) is obtained in a one‐pot reaction with as little as 10⁻⁵ moles of each of the reacting polymers, even without prior purification of the as‐received reagents. This has potential as an alternative to the currently practiced method of sequential living polymerization of constituent monomers, with the added advantage of direct knowledge and control over the length distribution of each block.

Coupling of end‐functionalized polymers using phosgene to form block copolymers of controlled composition.     

Nanofibrous Membranes Containing Carbon Nanotubes: Electrospun for Redox Enzyme Immobilization

Summary: Nanofibrous membranes that possess reactive groups are fabricated by the electrospinning process from PANCAA solutions that contain MWCNTs. Field emission scanning electron microscopy is used to evaluate the morphology and diameter of the nanofibers. Potentials for applying these nanofibrous membranes to immobilize redox enzymes by covalent bonding are explored. It is envisaged that the electrospun nanofibrous membranes could provide a large specific area and the MWCNTs could donate/accept electrons for the immobilized redox enzymes. Results indicate that, after blending with MWCNTs, the diameter of the PANCAA nanofiber increases slightly. The PANCAA/MWCNT nanofibrous membranes immobilize more enzymes than that without MWCNTs. Moreover, as the concentration of the MWCNTs increases, the activity of the immobilized catalase is enhanced by about 42%, which is mainly attributed to the promoted electron transfer through charge‐transfer complexes and the π system of MWCNTs.

The covalent immobilization of redox enzymes, such as catalase, on a PANCAA/MWCNTs nanofiber.     

Influence of Microwave Irradiation on the Lipase‐Catalyzed Ring‐Opening Polymerization of ε‐Caprolactone

Summary: The microwave (MW)‐assisted lipase‐catalyzed ring‐opening polymerization of ε‐caprolactone in boiling solvents was investigated for the first time. In case of boiling toluene or benzene the MW‐assisted reaction proceeded significantly slower compared to oil bath heating. On the other hand, using boiling diethyl ether as solvent, an increase of the polymerization rate due to MW irradiation was found. Yield, molecular weight measurements, and MALDI‐TOF analysis supported the results.

Reactivity of the MW‐assisted ring‐opening polymerization of ε‐caprolactone compared with conventional thermal heating in different solvents.     

Molekül‐Detektive. Biosensoren

Biosensors are analytical devices incorporating biological material (receptor) intimately associated with or integrated within a physicochemical transducer. Advantages are the high selectivity for analyte detection. Examples given comprise the very successful commercial blood glucose biosensors made for the self‐control by the diabetic patients. Other biosensors are part of an analytic system, including the sensor chips of surface plasmon resonance or interferometry based devices, piezoelectric or reflectometric sensors capable of direct measurement of mass changes, and thermometric and other reagentless sensors. The development of nanotubes‐based devices allows for significant enhancment of the signal‐tonoise ratio of the biosensors. A milestone on the way towards miniaturization and parallelization of biosensors is the recently developed and prize‐winning electronic DNA chip.     

Electrically Conductive Poly(DL‐lactide)/Chitosan/Polypyrrole Complexes

Summary: The fabrication of novel conductive poly(DL ‐lactide)/chitosan/polypyrrole complex membranes is reported. Using poly(DL ‐lactide)/chitosan blends as matrices and polypyrrole as a conductive component, several kinds of membranes with various compositions are prepared. A percolation threshold of polypyrrole as low as 1.8 wt.‐% is achieved for some membranes by controlling the chitosan proportion between 40 and 50 wt.‐%. SEM images exhibit that the membranes with a low percolation threshold show a two‐phase structure which consists of poly(DL ‐lactide) and chitosan phases. Dielectric measurements indicate that there is limited miscibility between the poly(DL ‐lactide) and chitosan but polypyrrole is nearly immiscible with the other two components. Based on the structural characteristics of the membranes, the polypyrrole particles are suggested to be localized at the interface between two phases.

Dependence of conductivity of complex membranes on the PPy content. (○) PDLLA/PPy, (▪) PDLLA/ch(10)/PPy, (▵) PDLLA/ch(20)/PPy, (•) PDLLA/ch(30)/PPy, (□) PDLLA/ch(40)/PPy, and (▴) PDLLA/ch(50)‐PPy.     

Hydrophobicity of Polyaniline Microspheres Deposited on a Glass Substrate

Summary: A highly hydrophobic surface with a water contact angle of 148.0° has been constructed by depositing salicylic acid‐doped polyaniline (PANI‐SA) spheres on a glass substrate using a template‐free method. The hydrophobicity originates from the contribution of the air trapped in the inter‐space of a rough surface aggregated by micro‐ and nanospheres. Moreover, the deposition time strongly affects the hydrophobicity of the PANI‐SA spheres deposited on the substrate. The formation mechanism and hydrophobic origin of the PANI‐SA spheres deposited on the substrate are discussed.

The PANI films prepared at 60 min polymerization time is composed of co‐existing nano‐ and microspheres (left). The ability of the layers to trap large amounts of air makes the surface highly hydrophobic and results in a water contact angle of 148.0° (right).