Organically modified layered silicates (OLS) with high thermal stability are critical for synthesis and processing of polymer layered silicate nanocomposites (PLSN). In the current study, the non-oxidative thermal degradation chemistry of alkyl and aryl quaternary phosphonium-modified montmorillonites (P-MMT) was examined using TGA combined with pyrolysis/GC-MS. The morphology evolution at elevated temperature was investigated using in-situ high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The onset decomposition temperature via TGA of these P-MMTs ranged from 190 to 230 °C. The initial degradation of the alkyl P-MMTs follows potentially two reaction pathways − β-elimination [Eβ] and nucleophilic displacement at phosphorus [SN(P)] − reflecting the multiple environments of the surfactant in the silicate. Aryl P-MMT decomposition proceeds via either a reductive elimination through a five-coordinate intermediate or radical generation through homologous cleavage of the P−phenyl bond. Overall, the interlayer environment of the montmorillonite has a more severe effect on stability of the phosphonium surfactant than previously reported for ammonium-modified montmorillonite (N-MMT). Nonetheless, the overall thermal stability of P-MMT is higher than that of N-MMT. These observations indicate that, in addition to their conventional purpose as stabilizers, phosphonium salts offer unique opportunities for melting processing polymer layered silicate nanocomposites.

The synthesis of a series of asymmetric triaryldiamines has provided a number of materials with a wide range of thermal, electrochemical, and spectroscopic properties. The asymmetric materials described herein have two different diarylamine groups bound to a 1,4-phenylene or 4,4‘-biphenylene core, i.e., Ar1Ar2N−C6H4−NAr1‘Ar3 or Ar1Ar2N-biphenyl-NAr1‘Ar3, respectively. The diarylamines studied include diphenylamine, phenyl-m-tolylamine, naphthylphenylamine, iminostilbene, iminodibenzyl, and carbazole. These materials were prepared by copper- and palladium-catalyzed coupling of aryl halides and diarylamines. The asymmetry inherent in these compounds prevents these low molecular mass compounds from crystallizing, thus yielding higher thermal stability over that of the symmetric derivatives. In all cases, the asymmetric diamines form stable glasses, with glass transition temperatures up to 125 °C. HOMO levels for these materials, estimated by cyclic voltammetry, show a broad range of values, with oxidation potentials both lower and higher than those of common hole transport materials used in organic light emitting devices.

ExperimentalThe polyelectrolytes used for the fabrication of the self-assembled films were D-PPV, the polycation PAH, and the polyanion SPS. The detail synthesis of D-PPV and the fabrication of multilayer films can be found in previous papers [6,7]. We note here that PEI was used to charge the substrate positively. The film thickness is controlled by the addition of salt to the polyelectrolyte solutions. Thus, we added 0.2 M CaCl 2 to the PEI solution, as well as CaCl 2 (4 g/250 mL) to all the polymer solutions (such as the SPS, PAH, and the pre-D-PPV solutions). The pH value of all these solutions is around 7.The multilayer (SPS/PAH) n can easily be reached, where the uppermost layer of PAH provides a positively charged surface for subsequent selfassembly of SPS and D-PPV. This assembly procedure was repeated to obtain the required layer structure. The films were converted to conjugated polymers by heating the assembly at 200 C for 12 h under a vacuum of 10 ±6 torr.The neutron reflectivity studies were conducted at the Neutron Scattering Center at the Hahn-Meitner-Institut, Berlin (BENSC). We used the V6 neutron reflectometer, which has a vertical scattering plane and is operated at a neutron wavelength of l = 4.66 [17] The resolution of this spectrometer is of the order of 10 ±3 ±1 .

We report a new class of diamine hole‐transporting materials (HTMs) based upon a fluorene core. Using a fluorene core, rather than a biphenyl group, leads to enhanced thermal stability, as evidenced by glass‐transition (Tg) temperatures as high as 161 °C for N,N′‐iminostilbenyl‐4,4′‐fluorene (ISF). The fluorene‐based HTMs have lower ionization potentials (Ip) than their biphenyl analogs, which leads to more efficient injection of holes from the indium tin oxide (ITO) anode, and higher quantum efficiencies. Devices prepared with fluorene‐based HTMs were operated under thermal stress. The failure of an organic light‐emitting diode (OLED) under thermal stress has a direct correlation with the thermal stability of the HTM that is in contact with the ITO anode. OLEDs based on ISF are stable to over 140 °C.

A nanocomposite comprised of conductive poly(aniline) chains interleaved between the layers of sol‐gel derived V2O5 displays desirable properties as a positive electrode in a Li battery. The reversible capacity of false[PANI]yV2O5 (after mild oxygen treatment) is higher than the V2O5 xerogel at intermediate discharge/charge rates at constant current. Li insertion is completely reversible in this modified hybrid material even after deep reduction to 3Li per formula unit, whereas the increased cell polarization exhibited for the xerogel in the same discharge state leads to partial irreversibility. Relaxation studies (GITT) demonstrate that Li diffusion is more rapid in the polymer nanocomposite for x(Li) < 2.0. The effect of the conductive polymer is to facilitate the insertion/deinsertion of the lithium ions between the layers.

The first hydrothermal synthesis and crystal structure of a novel organically templated layered vanadium oxide is described; the structural units of (C6H14N2)V6O14 are comprised of a unique arrangement of VO5 square pyramids and VO4 tetrahedra that are interconnected to form highly puckered sheets that are separated by diazabicyclooctane cations which act as the template in the synthesis.

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) consisting of a film of aluminum tris-(8 hydroxyquinoline) (Alq3) grown on the surface of a film of N′-diphenyl-N,N′-bis(3-methylphenyl)1-1′biphenyl-4-4′diamine. The resulting heterojunction OLED was found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown device has an external quantum efficiency of 0.40±0.05% and a turn-on voltage of approximately 6 V. The rapid throughput demonstrated with LP-OVPD has the potential to facilitate low cost mass production of conventional small molecule based OLEDs, and its use of low vacuum in a horizontal reactor lends itself to roll-to-roll deposition of organic films for many photonic device applications.

Two distinct V(9)O(23) building blocks having different vanadium coordination environments are intergrown in the unusual layered vanadate [N(CH(3))(4)](5)V(18)O(46) (see picture). Lattice strain is relieved by alternation of the vanadate strips formed from the blocks in both directions (akin to a three-dimensional tire tread). The formation of this lattice has implications for the assembly mechanism of this compound and related materials in hydrothermal synthesis.