Energy transfer in phase-separated luminescent polymer films

The energy transfer in a blend film of poly 3-(2-(5-chlorobenzotriazolo) ethyl) thiophene (PCSET) and polyvinylcarzole (PVK) was investigated. The UV-VIS and photoluminescence (PL) results suggest that the energy transfer from PVK to PCBET leads to the enhancement of PL emission of PCBET. The AFM and LMF results indicated that the domains of blend polymer film are of micro-meter size. (C) 2001 Elsevier Science B.V. All rights reserved.

聚β-羟基丁酸酯接枝顺丁烯二酸酐的研究

采用自由基引发聚合方法研究了聚 β-羟基丁酸酯 ( PHB)与顺丁烯二酸酐 ( MA)的接枝反应 .讨论了各种因素 ,如溶剂种类、单体浓度、引发剂浓度、反应时间和温度等对接枝反应的影响 ,确定了合成 PHB接枝 MA的最佳反应条件 .采用对酸酐基团进行化学滴定和 1 3C NMR检测等方法对产物的接枝率和结构进行了表征 .结果表明 ,MA成功的接枝到 PHB大分子链上 ,接枝率可以控制在 0 .3%～ 0 .85%范围内.

Preparation and characterization of poly(piperazineamide) composite nanofiltration membrane by interfacial polymerization of 3,3 ',5,5 '-biphenyl tetraacyl chloride and piperazine

Most nanofiltration (NF) membranes are composite and have a polyamide thin film prepared by interfacial polymerization. Their performances mainly correlate the structure of the thin film and monomers used for its preparation. In this work, a novel thin-film composite (TFC) nanofiltration membrane was successfully prepared from 3,3',5,5'-biphenyl tetraacyl chloride (mm-BTEC) and piperazine (PIP) through interfacial polymerization. Attenuated reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS) were used to characterize the chemical composition of the membrane surface. The membrane performance was optimized by studying preparation parameters including monomer concentration, reaction time, and pH of aqueous phase.

catena-Poly[diammonium [diaquabis(pyridine-2,4-dicarboxylato-kappa N-2,O-2)cuprate(II)] [[diaquacopper(II)]-mu-pyridine-2,4-dicarboxylato-kappa N-3,O-2:O-2 '-[tetraaquacadmium(II)]-mu-pyridine-2,4-dicarboxylato-kappa O-3(2):N,O-2 '] hexahydrate]

The title mixed-metal complex, {(NH4)(2)[Cu(C7H3NO4)(2)(H2O)(2)][CdCu(C7H3NO4)(2)(H2O)(6)]center dot 6H(2)O}(n), contains one octahedrally coordinated Cd-II center and two octahedrally coordinated Cu-II centers, each lying on an inversion center. The two Cu-II atoms are each coordinated by two O atoms and two N atoms from two 2,4-pydc (2,4-H(2)pydc = pyridine-2,4-dicarboxylic acid) ligands in the equatorial plane and two water molecules at the axial sites, thus producing two crystallographically independent [Cu(2,4-pydc)(2)(H2O)(2)](2-) metalloligands. One metalloligand exists as a discrete anion and the other connects the Cd(H2O)(4) units, forming a neutral chain.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Poly[di-mu(3)-chloro-mu(2)-trans-1,2-di-4-pyridylethylene-dicopper(I)]: a two-dimensional organic-inorganic hybrid constructed from linear CuCl clusters and bridging ligands

The structure of the title compound, [Cu2Cl2(C12H10N2)](n), contains infinite CuCl staircase-like chains, which lie about inversion centres. The trans-1,2-di-4-pyrid-ylethyl-ene mol-ecules also lie about inversion centres and connect the CuCl chains through Cu-N coordination bonds into a two-dimensional organic-inorganic hybrid network. The planar sheets are stacked along the c axis and associated through weak C-H center dot center dot center dot Cl inter-actions. The results show a reliable structural motif with controllable separation of the CuCl chains by variation of the length of the ligand.

聚3-羟基丁酸酯(PHB)生物降解过程的研究

利用DS970 1菌株对聚 3 羟基丁酸酯 (PHB)膜进行降解 ,对降解到不同程度的PHB膜采用扫描电子显微镜观察其表面形态结构的变化 ,并对其降解产物进行分析测定 .结果表明 ,PHB的生物降解首先发生在PHB表面的非晶部分 ,随后结晶部分开始降解 ,并且降解首先发生在球晶的中心部分 .DS970 1菌株所产生的PHB解聚酶主要降解PHB的第二个酯键 ,降解产物为二聚体.

Phase transition and transition kinetics of a thermotropic poly(amide-imide) derived from 70% pyromellitic dianhydride, 30% terephthaloyl chloride, and 1,3-bis[4-(4 '-aminophenoxy)cumyl]benzene

The phase transition and transition kinetics of a liquid crystalline copoly(amide-imide) (PAI37), which was synthesized from 70 mol% pyromellitic dianhydride, 30 mol% terephthaloyl chloride, and 1,3-bis[4-(4'-aminophenoxy)cumyl]benzene, was characterized by differential scanning calorimetry, polarized light microscopy, X-ray diffraction, and rheology. PAI37 exhibits a glass transition temperature at 182 degreesC followed by multiple phase transitions. The crystalline phase starts to melt at similar to 220 degreesC and forms smectic C (S-C) phase. The Sc phase transforms into smectic A (S-A) phase when the temperature is above 237 degreesC. The S-C to S-A transition spans a broad temperature range in which the S-A phase vanishes and forms isotropic melt. The WARD fiber pattern of PAI37 pulled from the anisotropic melt revealed an anomalous chain orientation, which was characterized by its layer normal perpendicular to the fiber direction. The transition kinetics for the mesophase and crystalline phase formation was also studied.

Soluble 2,5-dimercapto-1,3,4-thiadiazole/poly(o-toluidine) electroactive composite

A poly(o-toluidine) (POT)/2,5-dimercapto-1,3,4-thiadiazole (DMcT) composite was prepared. When POT and DMcT are mixed in a proper solvent, POT in a medium-oxidation state is reduced, and DMcT in turn is oxidized to its soluble dimer when the molar ratio of DMcT to POT is higher than 0.5. Therefore, the composite was soluble in organic solvents such as tetrahydrofuran (THF), dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) and exhibited very high electroactivity, two orders of magnitude higher than that of pure POT and three orders of magnitude higher than that of pure DMcT. Molecular-level contact between POT and DMcT is the reason for the improved catalytic effect of POT on DMcT, compared to that of polyaniline on DMcT. (C) 1999 The Electrochemical Society. S0013-4651(98)08-059-8. All rights reserved.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .3. Determination of the time of pressure application

The curing temperature, pressure, and curing time have significant influence on finished thermosetting composite products. The time of pressure application is one of the most important processing parameters in the manufacture of a thermosetting composite. The determination of the time of pressure application relies on analysis of the viscosity variation of the polymer, associated with curing temperature and curing time. To determine it, the influence of the time of pressure application on the physical properties of epoxy-terminated poly(phenylene ether ketone) (E-PEK)-based continuous carbon fiber composite was studied. It was found that a stepwise temperature cure cycle is more suitable for manufacture of this composite. There are two viscosity valleys, in the case of the E-PEK system, associated with temperature during a stepwise cure cycle. The analysis on the effects of reinforcement fraction and defect content on the composite sheet quality indicates that the width-adjustable second viscosity valley provides a suitable pressing window. The viscosity, ranging from 400 to 1200 Pa . s at the second viscosity valley, is the optimal viscosity range for applying pressure to ensure appropriate resin flow during curing process, which enables one to get a finished composite with optimal fiber volume fraction and low void content. (C) 1997 John Wiley & Sons, Inc.

Interfacial characteristics of the self-assembly system of poly-L-lysine 3-mercaptopropionic acid gold electrode

The interfacial characteristics of poly-L-lysine (PL) attached on self-assembled monolayers (SAMs) of 3-mercaptopropionic acid (MPA) were studied by an electrochemical method. The results indicated that PL\MPA layer inhibited partly the diffusion process of redox species in solution, and the electrode surface behaved like a microelectrode array. Its permeation effect was also strongly affected by Mg2+. The more Mg2+ ions were added into the electrolyte solution, the greater the difficulty with which the electron transfer of potassium ferricyanide took place. The three different conformations of PL on the electrode surface had different influences on the electron transfer processes of ferricyanide. PL in random coil state hindered most strongly the electron transfer behavior of ferricyanide,while the alpha-helical PL had nearly no effect and the effect of the beta-sheet state PL was intermediate of these. (C) 1997 Elsevier Science S.A.

The crystal structure and drawing induced polymorphism in poly(aryl ether ketone)s .3. Crystallization during hot-drawing of poly(ether ether ketone ketone)

The evolution of crystallinity and polymorphism during hot-drawing of amorphous poly(ether ether ketone ketone) (PEEKK) as a function of strain rate, draw ratio, and temperature was investigated. In modification I, the competition of chain extension and molecular alignment is responsible for the strain rate and temperature dependence. Modification II crystallization is basically controlled by chain extension during stretching. The former can be transformed into the latter via relaxation during stretching or annealing at elevated temperature.

The crystal structure and drawing-induced polymorphism in poly(aryl ether ketone)s .1. Poly(oxybiphenyl-4-4'-diyloxy-1,4-phenylenecarbonyl-1,3-phenylenecarbonyl-1,4-phenylene)

Crystal structure and polymorphism induced by uniaxial drawing of a poly(aryl ether ketone) [PEDEKmK] prepared from 1,3-bis(4-fluorobenzoyl)benzene and biphenyl-4,4'-diol have been investigated by means of transmission electron microscopy (TEM), electron diffraction (ED), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) techniques. The melting and recrystallization process in the temperature range of 250-260 degrees C, far below the next melting temperature (306 degrees C), was identified and found to be responsible for the remarkable changes in lamellar morphology. Based on WAXD and ED patterns, it was found that crystal structure of isotropic-crystalline PEDEKmK obtained under different crystallization conditions (melt-crystallization, cold-crystallization, solvent-induced crystallization, melting-recrystallization, and crystallization from solution) keeps the same mode of packing, i.e., a two-chain orthorhombic unit cell with the dimensions a = 0.784 nm, b = 0.600 nm, and c = 4.745 nm (form I). A second crystal modification (form II) can be induced by uniaxial drawing above the glass transition temperature, and always coexists with form I. This form also possesses an orthorhombic unit cell but with different dimensions, i.e., a = 0.470 nm, b = 1.054 nm, c = 5.064 nm. The 0.32 nm longer c-axis of form II as compared with form I is attributed to an overextended chain conformation due to the expansion of ether and ketone bridge bond angles during uniaxial drawing. The temperature dependence of WAXD patterns for the drawn PEDEKmK suggests that form II can be transformed into the more stable form I by relaxation of overextended chains and relief of internal stress at elevated temperature in absence of external tension.

STUDIES ON THE SULFONATION OF POLY(PHENYLENE OXIDE) (PPO) AND PERMEATION BEHAVIOR OF GASES AND WATER-VAPOR THROUGH SULFONATED PPO MEMBRANES .3. SORPTION BEHAVIOR OF WATER-VAPOR IN PPO AND SULFONATED PPO MEMBRANES

Water vapor absorption and desorption by poly (phenylene oxide) (PPO) and sulfonated PPO (SPPO) membranes were studied at a constant temperature of 30-degrees-C and over a broad range of water activity (0.05 less-than-or-equal-to a < 0.8) by the weighing