Thermal and crystallization behaviors of polyethylene blends synthesized by binary late transition metal catalysts combinations

A series of reactor blends of linear and branched polyethylenes have been prepared, in the presence of modified methylaluminoxane, using a combination of 2,6-bis[1(2,6-dimethyphenylimino) pyridyl]-cobalt(II) dichloride (1), known as an active catalyst for producing linear polyethylene, and [1,4-bis(2,6-diidopropylphenyl)] acenaphthene diimine nickel(II) dibromide (2), which is active for the production of branched polyethylene. The polymerizations were performed at various levels of catalyst feed ratio at 10 bar. The linear correlation between catalyst activity and concentration of catalyst 2 suggested that the catalysts performed independently from each other. The weight-average molecular weights ((M) over bar (w)), crystalline structures, and phase structures of the blends were investigated, using a combination of gel permeation chromatography, differential scanning calorimetry, wide-angle X-ray diffraction, and small angle X-ray scattering techniques. It was found that the polymerization activities and MWs and crystallization rate of the polymers took decreasing tendency with the increase of the catalyst 2 ratios, while melting temperatures (T-m), crystalline temperatures (T,), and crystalline degrees took decreasing tendency. Long period was distinctly influenced by the amorphous component concentration.

Self-assembly of a polymer pair through poly(lactide) stereocomplexation

A polymer pair composed of poly( N-isopropylacrylamide-co-2-hydroxyethyl methacrylate terminated oligo( L-lactide)) ( poly( NIPAAm-co-HEMAOLLA)) graft random copolymer and poly( D-lactide) ( PDLA) homopolymer was self-assembled into micelles with a diameter around 100 nm through the stereocomplexation between the OLLA branches of the graft copolymer and the PDLA homopolymer. The specific intermolecular stereocomplexation was considered as the powerful ordered aggregation force in the micelle cores. The shell's component of poly( NIPAAm-co-HEMA) and its thermosensitivity were proved by H-1 nuclear magnetic resonance ( NMR) and dynamic light scattering ( DLS), respectively. The incorporation of PDLA homopolymer into the graft copolymer affected the micelle size and the critical micelle concentration ( CMC). The incorporation of even a small quantity ( 11 wt%) of PDLA into the graft copolymer micelles resulted in a great decrease of the micelle size. For the graft copolymer with low per cent grafting of 18%, the size of the corresponding micelles decreased slightly even if the PDLA content increased up to 33 wt%. For the graft copolymer with high per cent grafting of 58%, with the further increase of PDLA content, the size of the corresponding micelles at first decreased further and then began to increase. The molecular weight of the PDLA did not significantly affect the micelle size.

Molecular design on highly efficient white electroluminescence from a single-polymer system with simultaneous blue, green, and red emission

A highly efficient white electroluminescent polymer with simultaneous blue, green, and red emission is reported, developed using a dopant/host strategy by covalently attaching both a green- and a red-light-emitting dopant to the side chain of a blue-light-emitting polymer host (see figure). In a single-layer device a maximum luminance efficiency of 7.3 cd A(-1) with CIE coordinates of (0.31,0.32) is achieved.

White electroluminescence from a single polymer system: Improved performance by means of enhanced efficiency and red-shifted luminescence of the blue-light-emitting species

High-efficiency white electrolurninescence from a single polymer is achieved by enhancing the electroluminescence efficiency and effecting a red-shift in the emission spectrum of the blue emissive species. A single-layer device of the resultant polymer exhibits a higher luminous efficiency than the nonmodified species (12.8 cd A(-1), see figure) and an external quantum efficiency of 5.4 % with CIE coordinates of (0.31,0.36), exemplifying the success of the reported methodology.

Three-color white electroluminescence from a single polymer system with blue, green and red dopant units as individual emissive species and polyfluorene as individual polymer host

A white electroluminescent single polymer system with both high electroluminescence efficiency and excellent color rendering index (CRI) value is developed by covalently attaching blue, green, and red dopant units as individual light-emitting species to the side chain of polyfluorene as individual polymer host. A luminous efficiency of 8.6 cd A(-1), CIE coordinates of (0.33, 0.36) and CRI value of 88 was demonstrated with their single-layer devices.

White electroluminescence from a single-polymer system with simultaneous two-color emission: Polyfluorene as blue host and 2,1,3-benzothiadiazole derivatives as orange dopants on the side chain

Four single polymers with two kinds of attachment of orange chromophore to blue polymer host for white electroluminescence (EL) were designed. The effect of the side-chain attachment and main-chain attachment on the EL efficiencies of the resulting polymers was compared. The side-chain-type single polymers are found to exhibit more efficient white EL than that of the main-chain-type single polymers. Based on the side-chain-type white single polymer with 4-(4-alkyloxy-phenyl)-7-(4-diphenylamino-phenyl)-2,1,3-benzothiadiazoles as the orange-dopant unit and polyfluorene as the blue polymer host, white EL with simultaneous orange (lambda(max) = 545 nm) and blue emission (lambda(max) = 432 nm/460 nm) is realised. A single-layer device (indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Ca/Al) made of these polymers emits white light with the Commission Internationale de l'Eclairage coordinates of (0.30,0.40), possesses a turn-on voltage of 3.5 V, luminous efficiency of 10.66 cd A(-1), power efficiency of 6.68 lm W-1, and a maximum brightness of 21240 cd m(-2).

The first polyoxometalate polymer constructed by assembly of the heptamolybdic anion and copper coordination groups

The first example of one-dimensional organic-inorganic polymetallic coordination polymer based on heptamolybdate anions, formulated (NH4)[Cu(en)(2)][Na(en)Cu(en)(2)(H2O)(Mo7O24)].4H(2)O (en = ethylenediamine) (1) has been hydrothermally synthesized and characterized by element analysis, IR, EPR, CV and single crystal X-ray diffraction. The structure of 1 is fabricated by self-assembly of integrated heptamolybdic anions without collapse of primary structure and copper-ethylenediamine(en) coordination groups into one-dimensional zigzag-shaped chains.

A Monte Carlo simulation of morphology and structure for thin films of symmetric triblock copolymer after quenching and annealing

Self-assembly thin films of symmetric triblock copolymer after annealing and quenching were examined by an effective Monte Carlo simulation method. The defects in the ordered lamellae of the thin films after quenching, which were dependent on the initialization of copolymer melts, are removed in the thin films after annealing. The mean-square gyration radius and end-to-end distance of copolymer chains in the thin films after annealing are smaller than those in the thin films after quenching because of the complete relaxation of polymer during annealing. We also find that the density of A block in the region near to the surface is higher than that in the interior of the thin films. As a result, it is different from the thin films of symmetric A(n)B(n) diblock copolymer, in which surface ordering forms before the interior, that ordering phenomena occurs first in the interior region in the thin films of symmetric A(n)B(m)A(n). triblocl copolymer.

Zirconocene catalyst well spaced inside modified montmorillonite for ethylene polymerization: role of pretreatment and modification of montmorillonite in tailoring polymer properties

Zirconocene catalyst was heterogenized inside an organosilane-modified montmorillonite (MMT) pretreated by calcination and acidization, for supported catalyst systems with well-spaced alpha-olefin polymerization active centers. The varied pretreatment and modification conditions of montmorillonite are efficient for supported zirconocene catalysts in control of polyethylene microstructures, in particular, molecular weight distribution. In contrast to other supported catalyst systems, Cp2ZrCl2/modified montmorillonite(MMT-7)-supported catalysts with a distinct interlayer structure catalyzed ethylene homopolymerization and copolymerization with I-octene activated by methylaluminoxane (MAO), resulting in polymers with a bimodal molecular weight distribution (MWD).

A single ionic conductor based on Nafion and its electrochemical properties used as lithium polymer electrolyte

In an attempt to raise the transport number of Li+ to nearly unity in solid polymer electrolytes, commercial perfluorinated sulfonate acid membrane Nafion 117 was lithiated and codissolved with copolymer poly(vinylidene fluoride)hexafluoropropylene. The effect of fumed silica on the physical and electrochemical properties of the single ion conduction polymer electrolyte was studied with atom force microscopy, fourier transform infrared spectroscopy, differential scanning calorimetry, and electrochemical impedance spectroscopy. It was confirmed that the fumed silica has an obvious effect on the morphology of polymer electrolyte membranes and ionic conductivity. The resulting materials exhibit good film formation, solvent-maintaining capability, and dimensional stability. The lithium polymer electrolyte after gelling with a plasticizer shows a high ionic conductivity of 3.18 x 10(-4) S/cm.

Poly(vinylidene fluoride-hexafluoropropylene)/organo-montmorillonite clays nanocomposite lithium polymer electrolytes

Polymer-clay nanocomposite (PCN) materials were prepared by intercalation of an alkyl-ammonium ion spacing/coupling agent and a polymer between the planar layers of a swellable-layered material, such as montmorillonite (MMT). The nanocomposite lithium polymer electrolytes comprising such PCN materials and/or a dielectric solution (propylene carbonate) were prepared and discussed. The chemical composition of the nanocomposite materials was determined with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, which revealed that the alkyl-ammonium ion successfully intercalated the layer of MMT clay, and thus copolymer poly(vinylidene fluoride-hexafluoropropylene) entered the galleries of montmorillonite clay. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of the lithium polymer electrolyte. Equivalent circuits were proposed to fit the EIS data successfully, and the significant contribution from MMT was thus identified. The resulting polymer electrolytes show high ionic conductivity up to 10(-3) S cm(-1) after felling with propylene carbonate.

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles

Three fully amorphous comb-branch polymers based on poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO2 nanoparticles of various contents and the salt LiCF3SO3 were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been characterized. The maximum conductivity of 2.8x10(-4) S cm(-1) is obtained at 28 degreesC. In the system the longer side chain of the comb-branch polymer electrolyte increases in ionic conductivity after the addition of nanoparticles. To account for the role of the ceramic fillers in the nanocomposite polymer electrolyte, a model based on a fully amorphous comb-branch polymer matrix in enhancing transport properties of Li+ ions is proposed.

A new 1D metal-organic coordination polymer with blue fluorescent emission: [Cd-2(1,10 '-phen)(2)(betc)(H2O)](n)

A new coordination polymer [Cd-2(1,10'-phen)(2)(betc)(H2O)](n) (1) (betc = benzene-1,2,4,5-tetracarboxylate, 1,10'-phen = 1,10'-phenanthroline) was hydrothermally synthesized from CdCl2.2.5H(2)O, H(4)betc and 1,10'-phen at 160 degreesC. It was characterized by IR, XPS, TG and single-crystal X-ray diffraction. Compound 1 possesses infinite chair-like chains which construct 3D framework through pi-pi interactions and the hydrogen bond interactions. The fluorescent spectrum study shows that compound 1 exhibits blue fluorescent emission in the solid at room temperature.

Hydrothermal synthesis and crystal structure of a sulfur-bridged binuclear copper(II) coordination polymer generated by a spontaneous reduction

A simultaneous reduction SO42- to S2- by 2,5-pyridinedicarboxylate under hydrothermal conditions produced a new binuclear copper(II) coordination polymer [CuS(4,4'-bipy)](n) (4,4-bipy = 4,4'-bipyridine) (1). Single crystal X-ray analysis revealed that compound I consisted of sulfur-bridged binuclear copper(II) units with Cu-Cu bonding which were combined with 4,4-bipy to generate a three-dimensional network constructed from mutual interpenetration of two-dimensional (6,3) nets. Crystal data for 1:C10H8CuN2S, tetragonal 14(1)/acd, a = 14.0686(5) Angstrom, b = 14.0686(5) Angstrom, c = 38.759(2) Angstrom, Z = 32. Other characterizations by elemental analysis, IR, EPR and TGA analysis were also described in this paper.