Search results for "Phenylene"
showing 10 items of 457 documents
Blends of poly(2,6-dimethyl-1,4-phenylene oxide) with styrene copolymers
1994
Binary blends of poly(2,6–dimethyl–1,4–phenylene oxide) (PPE) with various styrene copolymers were investigated. Poly(styrene–co–acrylonitrile) (SAN), poly[styrene–co–(methyl methacrylate)] (SMMA), poly[styrene–co–(acrylic acid)] (SAA) and poly[styrene–co–(maleic anhydride)] (SMA) are only miscible with PPE when the amount of comonomer is rather small. From calculated binary interaction densities it can be concluded that the strong repulsion between PPE and comonomer limits miscibility. In blends of PPE with SAN, as well as with ABS, the inter-facial tension between the blend components is significantly reduced upon addition of polystyrene–block–poly–(methyl methacrylate) diblock copolymers…
Dynamic mechanical properties of semi-interpenetrating networks based on poly(styrene-co-maleic anhydride): 3. Poly(2,6-dimethyl-1,4-phenylene ether)…
1994
Semi-IPN's based on linear poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and diamine crosslinked poly(styrene-co-maleic anhydride) (PScoMA) copolymers containing small amounts of maleic anhydride (PSA=4.7wt.-% MA, PSB=5.8 wt-% MA) are studied with respect to the influence of cross-linking on the phase behavior. Temperature-dependent dynamic mechanical analysis (DMA) and DSC show that the semi-IPN's prepared from concentrated solution show weak crystallinity of the PPE phase. After heating above the PPE melting transition the semi-IPN's remain amorphous and the relaxation in the glass transition region as well as the terminal relaxation of the free PPE chains in the network is studied as a fu…
Poly(styrene-b-methyl methacrylate) block copolymers as compatibilizing agents in blends of poly(styrene-co-acrylonitrile) and poly(2,6-dimethyl-1,4-…
1993
Abstract The compatibilizing effect of the symmetric narrowly distributed block copolymer poly(styrene- b -methyl methacrylate) (P(S- b -MMA)) in blends of high-molecular-weight poly(styrene- co -acrylonitrile) containing 20 wt% (PSAN20) or 43 wt% acrylonitrile (PSAN43) with poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was investigated by dynamic mechanical spectroscopy and transmission electron microscopy. In blends with the PSAN43, P(S- b -MMA) forms spherical micelles in the PPE phase with no dispersing efficiency. In contrast to this, for blends with PSAN20, the block copolymer is located at the phase boundary, causing an extremely fine dispersion of the components. Depending on the loc…
Poly(styrene-b-methyl methacrylate) block copolymers as compatibilizing agents in blends of poly(styrene-co-acrylonitrile) and poly(2,6-dimethyl-1,4-…
1993
Abstract The influence of the molecular weight of the symmetric block copolymer poly(styrene-b-methyl methacrylate) (P(S-b-MMA)) in blends with high-molecular-weight poly(styrene-co-acrylonitrile) (PSAN) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is investigated by dynamic mechanical analysis and transmission electron microscopy. Total molecular weights of the block copolymers vary from 16 up to 275 kg mol−1. Independent of molecular weight, all block copolymers locate to the interface with strong dispersing efficiency. The different block copolymers also showed approximately the same emulsifying efficiency. The degree of segmental mixing of the blocks with the respective phases is ev…
Electronic structure of poly(p-(disilanylene)phenylene)
1996
Abstract We present the geometrical and electronic structures of several isomers of poly(p-(disilanylene)phenylene), The structural analysis, performed at the 3-21G* level, shows that the isomers with the phenylene group perpendicular to the silicon backbone are the more stable conformations, displaying almost the same energy. The electronic properties, as obtained from the valence-effective Hamiltonian (VEH) band structure calculations, strongly depend on the disposition of the phenylene group into the polymeric backbone. The VEH predicts a wide and asymmetric absorption band in excellent agreement with UV experimental data.
Rigid Rod Polymers Having Flexible Side Chains. 3. Structural Investigations on a Novel Layered Mesophase Formed by Thermotropic Poly(1,4-phenylene-2…
1987
A series of thermotropic poly(1,4-phenylene-2,5-di-n-alkoxy terephthalate)s with the length of the n-alkoxy side chains being varied between n = 2 and n = 18 carbon atoms has been examined by optic...
Star-Shaped Conjugated Systems
2010
The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.
Cobalt(IV) corroles as catalysts for the electroreduction of O2: reactions of heterobimetallic dyads containing a face-to-face linked Fe(III) or Mn(I…
2006
Abstract A series of heterobinuclear cofacial porphyrin–corrole dyads containing a Co(IV) corrole linked by one of four different spacers in a face-to-face arrangement with an Fe(III) or Mn(III) porphyrin have been examined as catalysts for the electroreduction of O 2 to H 2 O and/or H 2 O 2 when adsorbed on the surface of a graphite electrode in air-saturated aqueous solutions containing 1 M HClO 4 . The examined compounds are represented as (PCY)M III ClCo IV Cl where P is a porphyrin dianion, C is a corrole trianion and Y is a biphenylene (B), 9,9-dimethylxanthene (X), dibenzofuran (O) or anthracene (A) spacer. The catalytic behavior of the seven investigated dyads in the two heterobimet…
Synyhesis, structure, spectroscopy and redox chemistry of square-planar nickel(II) complexes with tetradentate o-phenylenedioxamidates and related li…
2005
[EN] A series of four-coordinate square-planar nickel(II) complexes of o-phenylenebis(N¿-methyloxamidate) (L1) and related o-phenylene(N¿-methyloxamidate)oxamate (L2) and o-phenylenebis(oxamate) (L3) tetradentate ligands have been synthesized and characterized structurally, spectroscopically and electrochemically. The parent nickel(II)¿L1 complex presents an intense MLCT band in the UV region (¿max = 357 nm) and a distinctive 1 s ¿ 4p CT satellite in the Ni K-edge XANES spectrum (E = 8339.2 eV). These features together with the short Ni¿N(amidate) bond lengths (1.85¿1.93 Å) as revealed by the analysis of the Ni K-edge EXAFS spectrum and confirmed by single-crystal X-ray diffraction are typi…
Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical
2013
The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H4N2O2) are reported. A formally molybdenum(VI) complex [Mo(N2O2)Cl2(dmf)] (1) was synthesized by the reaction between [MoO2Cl2(dmf)2] and H4N2O2, whereas the other molybdenum(VI) complex [Mo(N2O2)(HN2O2)] (2) was formed when [MoO2(acac)2] was used as a molybdenum source. Both complexes represent a rare case of the MoVI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations ind…