Hole-transporting property of a chemically hybridized poly(vinylcarbazole)-fullerene

We synthesized a star copolymer of poly(vinylcarbazole) (PVK) branched from a fullerene (C₆₀) center, and investigated its optical absorption and photoluminescence properties. The chemically hybridized PVK-C₆₀ was then employed as a hole-transporting layer of the electroluminescent device with a poly(9,9^′-dihexylfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) (CPDHFPV) emitting layer. The ITO/PVK-C₆₀/CPDHFPV/LiF/Al device showed a strong electroluminescence quenching due to a direct contact of the PVK-C₆₀ and the CPDHFPV layers. In contrast, when an additional PVK layer was introduced between the two layers, the electroluminescence was largely enhanced. The emitted light power of the ITO/PVK-C₆₀/PVK/CPDHFPV/LiF/Al device was improved by 3 times compared with the device without the PVK-C₆₀ layer.     

Physicochemical properties of Mg-phthalocyanine molecules covalently bonded to the surface of nanopores in a silicate gel matrix

Molecules of Mg-tetracarboxyphthalocyanine, chemically modified with 3-aminopropyltrimethoxysilane, were immobilized on the surface of the nanopores in a silicate gel matrix by copolymerizing them with tetraethoxysilane monomer. Formation of covalent bonds between the Mg-phthalocyanine molecules and the surface of the nanopores in the silicate xerogel was confirmed by the absence of leaching of the “grafted” pigment from the interior volume of the xerogel to the liquid extraction agent, and also by IR Fourier spectroscopy data. The observed bleaching of the activated silicate xerogel under normal atmospheric conditions is reversible: subsequent heat treatment restores the original absorption spectrum. We hypothesize that two mechanisms are responsible for the observed effect: formation of high order associates of the Mg-phthalocyanine molecules involving water molecules adsorbed from the atmosphere, and/or oxidation of the phthalocyanine macrocycle with disruption of the conjugation chain. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 591–597, September–October, 2007.     

Monomer reactivity ratios for acrylonitrile–methyl acrylate free‐radical copolymerization

Nonlinear monomer reactivity ratios for the homogeneous free‐radical copolymerization of acrylonitrile and methyl acrylate were determined from ¹H NMR and real‐time Fourier transform infrared (FTIR) analyses. All ¹H NMR data were obtained on polymers isolated at low conversions (<10%), whereas the FTIR data were collected in situ. The copolymerizations were conducted in N,N‐dimethylformamide at 62 °C and were initiated with azobisisobutyronitrile. The real‐time FTIR technique allowed for many data points to be collected for each feed composition, which enabled the calculation of copolymer compositions (dM₁/dM₂) with better accuracy. Monomer reactivity ratios were estimated with the Mayo–Lewis method and then were refined via a nonlinear least‐squares analysis first suggested by Mortimer and Tidwell. Thus, monomer reactivity ratios at the 95% confidence level were determined to be 1.29 ± 0.2 and 0.96 ± 0.2 for acrylonitrile and methyl acrylate, respectively, which were valid under the specific system conditions (i.e., solvent and temperature) studied. The results are useful for the development of acrylonitrile (<90%) and methyl acrylate, melt‐processable copolymer fibers and films, including precursors for carbon fibers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2994–3001, 2004     

A nanocomposite based on a styrene-acrylate copolymer and organically modified montmorillonite 2. Barrier and thermal properties

The results of an investigation into the barrier and thermal properties of polymer nanocomposites prepared by blending a styrene-acrylate copolymer solution with a suspension of organically modified montmorillonite are presented. The influence of organomontmorillonite content on the barrier properties of the nanocomposite is investigated with the example of water vapor permeability. The experimental values of the permeability coefficient are compared with those calculated by using a model taking into account the increased path of diffusing water molecules caused by the shielding effect of plate like particles. The thermograms of differential scanning calorimetry in the temperature range from −40 to 130°C are presented. The results of a thermogravimetric analysis for specimens heated in air to 800°C are also reported. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 503–516, July–August, 2006.     

Adsorption and electrically stimulated desorption of the triblock copolymer poly(propylene sulfide-bl-ethylene glycol) (PPS-PEG) from indium tin oxide (ITO) surfaces

Protein-resistant triblock copolymers, poly(propylene sulfide-bl-ethylene glycol) (PPS-PEG) have been previously demonstrated to chemisorb onto gold surfaces forming monolayers that resist non-specific protein adsorption and are stable against oxidation. In this paper, we report on the adsorption of PPS-PEG onto a transparent and electrically conductive substrate, indium tin oxide (ITO). In addition, we demonstrate the controlled desorption of PPS-PEG by applying an electrical stimulus. We have used three complementary surface characterization techniques: variable angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze the adsorption and electro-desorption of PPS-PEG from an ITO surface. All three methods confirmed the formation of PPS-PEG adlayers on the ITO surfaces. Based on our experimental XPS and ToF-SIMS results as well as former publications, we postulate that the chemisorption of the PPS-PEG on ITO involves direct sulfide-indium (or tin) interactions. When an ascending anodic electrical stimulus was applied to the surface of the modified samples, a gradual and steady polymer removal was observed, with complete loss of the polymeric monolayer at a potential of 2000 mV (referenced to Ag electrode). Anodic polarization did not result in oxidation of the thioether function of the PPS-PEG adlayers, indicating excellent oxidation resistance of PPS-PEG on ITO surfaces. This work is focused on exploiting electrical stimuli for the in situ surface modification under dynamic control.     

(μ-RS)(μ-XMgS)Fe_2(CO)_6与取代丙烯酸酯的加成反应——甲基取代的酯乙基铁硫络合物的合成

通过硫镁络合物(μ-RS)(μ-XMgS)Fe_2(CO)_6分别与反式-巴豆酸乙酯,α-甲基丙烯酸甲酯的加成-醇解反应,合成了十三个甲基取代的酯乙基铁硫络合物(μ-Rs)(?)Fe_2(CO)_6,(μ-RS)(?)Fe_2(CO)_6。这些新络合物的结构均经元素分析、IR及~1H NMR谱确证。     

EFFECT OF AMPHIPHILIC POLY (STYRENE-B-ETHYLENE OXIDE) DIBLOCK COPOLYMER INTERCALATED LAYERED SILICATE AS FILLER ON ACRYLONITRILE-BUTADIENE-STYRENE RESIN

1.INTRODUCTION[()-227.3()]Polymer/layeredsilicatenanocompositeshavereceivedgreatattentioninrecentyearssincethesematerialsexhibitunexpectedimprovementinstiffness,strengthandbarrierpropertiesbyaddingonlyafewweightpercentagesoforganicsmodifiedlayeredsilicatesdispersedinthenanometerscaleinthepolymermatrix[1~10].Montmorilloniteinnatureconsistsmainlyoflayeredsilicatecarryingnegativechargesthatformionicbondswithmetalcationsintheintergalleryofthelayeredsilicates.Thesesilicatesalsocontaindanglinghy…     

丙烯酸十六酯与丙烯酸共聚物凝胶的合成及其性能

合成了丙烯酸十六酯(HA)与丙烯酸(AA)的共聚物凝胶，研究了共聚组成对共聚物凝胶性能的影响。结果表明：经二甲亚砜(DMSO)平衡溶胀后的凝胶，在HA与AA的物质的量比为1：1时，具有较高的规整性。溶剂的极性对聚合物凝胶的规整性有较大的影响。DSC及X射线衍射表明共聚物凝胶具有液晶性能。     

Fluorescence Depolarization Due to Excitation Energy Migration in Polymeric Micelles: A Monte Carlo Study

Cores of block copolymer micelles have been studied by Monte Carlo simulation. Core-forming chains have been modeled as self-avoiding chains enclosed in a spherical cavity and tethered to its surface. A fraction of the untethered end segments of chains (18–53%) has been treated as fluorescent probes. The time-dependent solution of the Pauli master equation that describes excitation energy migration among probes has been averaged in an ensemble of 10⁴ simulated cores. We have studied the dependence of the depolarization function G ^S(t), i.e., the probability that the originally excited probe is still excited at time t, on the chain length and on the energy migration critical radius of the probe. Cores with randomly solubilized probes and with clusters of probes have been also studied for comparison.