Six novel perfluoroalkyl-activated bishalo monomers 4a,b−6a,b have been synthesized successfully using Pd(0)-catalyzed cross-coupling reaction of 4-chloro- or 4-fluoro-3-trifluoromethylphenylboronic acid with 1,4-dibromobenzene, 2,6-dibromopyridine, and 2,5-dibromothiophene. These monomers were converted to poly(arylene ether)s by nucleophilic displacement of the halogen atoms on the benzene ring with several bisphenols. The products obtained by displacement of the fluorine atoms exhibit weight-average molar masses up to 3.52 × 105 g mol-1 in GPC. Displacement of the chlorine atoms from the analogous monomer structures by bisphenols was not successful in obtaining high molar mass products. These poly(arylene ether)s showed very high thermal stability even up to 536 °C for 5% weight loss in TGA in synthetic air. Comparatively low thermal stability for the thiophene ring containing polymers was attributed to the oxidation of the sulfur atom of the thiophene ring at high temperature in air, which destroyed the aromatic character of the thiophene ring. This was confirmed by investigating the thermal stability of these polymers in an inert environment. The polymers exhibit glass transition temperatures (T g) up to 234 °C in DSC. The glass transition temperatures taken as peak in tan δ in DMTA measurements are in good agreement with the DSC T g values. All the polymers are soluble in a wide range of organic solvents, e.g., CHCl3, THF, NMP, and DMF. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 70 MPa, a modulus of elasticity up to 2.69 GPa, and elongation at break up to 30% depending on their exact repeating unit structures.

In this work, we report on the optical properties and amplified spontaneous emissions (ASE) of polystyrene opals engineered with planar structural defects containing a conjugated polymer emitter. Defects in opals give rise to allowed states inside the photonic stop band, which are probed by transmittance and reflectance spectroscopy. The emission spectrum of the polymer embedded in the defect layer is strongly modified and fingerprints of defect states located inside the stop band are recognized. Amplified spontaneous emission for these engineered photonic crystals is clearly observed.

Abstract. Research in distributed problem solving in the last years focused on distributed applications which cooperate to accomplish a task. Another level of distributed problem solving is that of human teams which are distributed in space and cooperate in solving a problem. In this paper we will introduce distributed problem solving from the 'human level', briefly present the accompanying research area of ComputerSupported Cooperative Work (CSCW) and the different basic mechanisms of computer support for workgroup computing, and then focus on the awareness information that is of special importance for supporting coordinated cooperation of groups with unstructured tasks.

Ring the changes: Experimental Raman spectra of fluorinated and non-fluorinated polyphenylenevinylenes are assigned according to quantum chemical calculations for oligomer model systems [picture: see text]. Characteristic differences in the spectra can be traced back to strong inter-ring distortion of the fluorinated compounds.The Raman spectrum of poly{2-methoxy-5-[(2-ethylhexyl)oxy]-1,4-phenylenedifluorovinylene} (MEH-PPDFV) is reported and compared with that of a well-known non-fluorinated reference polymer, namely poly{2-methoxy-5-[(2-ethylhexyl)oxy]-1,4-phenylenevinylene} (MEH-PPV). The Raman spectra of both polymers are assigned on the basis of density functional theory calculations of the corresponding oligomers. The main differences between vinylene fluorinated and non-fluorinated structures deal with the intensity, frequency shift and broadening of C--C vinylene stretching. Additional differences concern the relative intensities of C-C phenylene and vinylene stretching as well as the deformation modes in the range 1250-1350 cm(-1). It is shown that these effects are due to the larger distortion from planarity of the fluorinated polymer, compared with the non-fluorinated counterpart, induced by repulsive interactions between the fluorine atoms on the vinylene units and the oxygen atoms of the alkoxy groups on the aromatic rings.