Synthesis and blending behavior of an oligoarylenevinylene. Design towards processable materials for LED applications

A bisstyrenebenzene with improved solubility can be obtained by a lateral phenyl substituent on the phenylene ring. The phenyl substituted bisstyrenebenzene (PBSB) was synthesized by Pd-catalyzed coupling of 2,5-dibromobiphenyl and styrene. PBSB exhibits blue fluorescence in solution. Blends of PBSB and polystyrene or polycarbonate are homogeneous over a wide concentration range of PBSB, based on differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results were compared with the blending behavior of unsubstituted bisstyrenebenzene.     

Low-order modeling and dynamic characterization of rapid thermal processing

A low-order model of rapid thermal processing (RTP) of semiconductor wafers is derived. The first-principles nonlinear model describes the static and dynamic thermal behavior of a wafer with approximate spatial temperature uniformity undergoing rapid heating and cooling in a multilamp RTP chamber. The model is verified experimentally for a range of operating temperatures from 400° C to 900° C and pressures of 1 Torr and 1 atmosphere in an inert N₂ environment. Theoretical predictions suggest model validity over a still wider range of operating conditions. One advantage of the low-order model over previous high-order and statistical models is that the proposed model contains a small number of fundamental parameters and functions that, if necessary, are easily identifiable. Furthermore, because of reduced computational complexity, the low-order model can be used in real-time predictive applications including signal processing and process control design. In studying and verifying the model, the dynamic behavior of a semiconductor wafer undergoing rapid temperature changes is characterized. Close comparison between theory and experiment in terms of the wafer eigenvalue and dc gain is demonstrated; the strong nonlinear effects of temperature are shown. Convective heat transfer losses are also examined and are shown to increase with radial position on the wafer.     

Acrylonitrile polymerization by Cy3PCuMe and (Bipy)2FeEt2

Cy(3)PCuMe (1) undergoes reversible ligand redistribution at low temperature in solution to form the tight ion pair [Cu(PCy(3))(2)][CuMe(2)] (3). The structure of 3 was assigned on the basis of (i) the stoichiometry of the 1 = 3 equilibrium, (ii) the observation of a triplet for the PCy(3) C1 (13)C NMR resonance due to virtual coupling to two (31)P nuclei, and (iii) reverse synthesis of 1 by combining separately generated Cu(PCy(3))(2)(+) and CuMe(2)(-) ions. Complex 1 and [Cu(PCy(3))(2)][PF(6)] (5) coordinate additional PCy(3) to form (Cy(3)P)(2)CuMe and [Cu(PCy(3))(3)][PF(6)], respectively, while 3 does not. Complex 1, free PCy(3), and (bipy)(2)FeEt(2) (2) each initiate the polymerization of acrylonitrile. In each case, the polyacrylonitrile contains branches that are characteristic of an anionic polymerization mechanism. The major initiator in acrylonitrile polymerization by 1 is PCy(3), which is liberated from 1. A transient iron hydride complex is proposed to initiate acrylonitrile polymerization by 2.     

Substitutionsreaktionen mit Schwefeldiimiden

Substitution Reactions with Sulphur Diimides Substituted sulphur diimides are obtained by the reactions of (CH₃)₃Si? N?S?N? Si(CH₃)₃ with CH₃SO₂Cl and CCl₃SCl or with P₂O₃F₄ and (CH₃)₃Si? N?S?N? SN(CH₃)₂. S₄N₄ reacts with (CH₃)₂Si[N(CH₃)₂]₂ to from (CH₃)₂Si(N(CH₃)₂)? N?S?N? SN(CH₃)₂ while S₃N₂Cl₂ yields (CH₃)₂Si(Cl)? N?S?N? SN(CH₃)₂. It is possible to substitute the chlorine atom by diethylamine in the last compound. The new compounds are intermediates for the syntheses of cyclic sulphur-nitrogen compounds. They were characterized by mass-, ir-, ¹H-nmr spectra and elemental analysis.     

The electron microscope characterization of the fine structure of nylon 6: II. On the rearrangement of the structure during cold-drawing

The transmission electron microscope (TEM) visualization of the supermolecular structure of cold-drawn, oriented nylon 6 bulk material (bristles) by stained ultra-thin sections is reported. For evaluating the electron micrographs optical diffraction (OD) has been applied in comparison with small angle X-ray scattering (SAXS). The deformation of the spherulites was followed by polarization microscopy. In addition, investigations were carried out on commercial nylon 6 fibres. As the main result a transverse structure was revealed within the drawn samples at draw ratios between =4 and 4.5, consisting of mosaic crystals which show some lateral alignment. The structure is described by a modified layer lattice model. While the long period may increase slightly during drawing, the crystallite thickness remains almost constant. Fibres with =3.4 show a similarly oriented structure though the lateral alignment of the crystals is not so pronounced.     

4-Phosphoryl Pyrazolones for Highly Selective Lithium Separation from Alkali Metal Ions

Effective receptors for the separation of Li⁺ from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, H L ²-H L ⁴, in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li⁺ complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid-liquid extraction in the presence of TOPO revealed an unprecedented high Li⁺ extraction efficiency (78 %) for H L ⁴ compared to the use of the industrially employed acylpyrazolone H L ¹ (15 %) and benzoyl-1,1,1-trifluoroacetone (52 %) extractants. In addition, a high selectivity for Li⁺ over Na⁺, K⁺ and Cs⁺ under mild conditions (pH ∼8.2) confirms that H L ²-H L ⁴ represent a new class of ligands that are very effective extractants for use in lithium separation.     

Isotactic rac‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR¹=N,N‐dimethylamino ethoxide, OR²=2‐pyridyl methoxide), are active for the polymerization of rac‐lactide at ambient temperature in benzene to yield polymers with M_w/M_n=1.0–1.2. X‐ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR¹ provided only atactic polylactide, LCuOR² produced partially isotactic polylactide (P_m=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR² in contrast to a mononuclear species for LCuOR¹.