Improvement of emission efficiency in polymer light-emitting devices based on phosphorescent polymers

We report improvement of emission efficiency in polymer light-emitting devices (PLEDs) employing phosphorescent polymers. A hole-blocking layer was inserted between the emissive layer and the cathode to enhance recombination efficiency for the injected holes and electrons. Aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolato (BAlq) was used for the hole-blocking layer. The resultant PLEDs exhibited significant improvement of emission efficiency. The respective external quantum efficiencies for red, green and blue PLEDs were 6.6, 11 and 6.9%. These values are very high compared with those based on conventional fluorescent polymers.     

XPS studies of directly fluorinated HDPE: problems and solutions

X-ray photoelectron spectroscopy (XPS) applied to the study of fluorinated polymer surfaces presents several problems related both to peak assignment and to degradation. In this work, we analyse extensively the question of XPS peak assignments in this kind of surfaces. We conclude that in this kind of surfaces using binding energy differences between fluorine and carbon is better than using absolute binding energies. Also a useful relation between fluorine photoelectron energy vs. polymer composition expressed through the atomic ratio fluorine/carbon (F/C) was found. A protocol for data treatment is proposed and applied to a XPS study of the degradation induced by X-ray on high-density polyethylene surfaces modified by direct fluorination. Results obtained for the degradation, namely the atomic ratio F/C obtained by two different methods, combined with angle resolved X-ray photoelectron spectroscopy (ARXPS) were used to study the fluorine concentration profile in depth, producing self-consistent results.     

膨润土凝胶调剖剂XJF的研制及应用

介绍了调剖剂XJF的配方,讨论了影响调剖剂性能的配方因素(膨润土含量、HPAM溶液浓度、XJ用量及添加剂Fc的浓度),考察了封堵能力和应用范围,简介了在火烧山油田现场试验的结果。     

塑料合金用反应型相容剂

反应型相容剂含有反应基团,可与含相应基团的聚合物起化学反应,因而在混炼过程中增容。本文系统地介绍各种反应型相容剂的设计、合成、品种和应用。     

Phase equilibria of quasi-binary systems consisting of multicomponent polymers 1 and 2. IV: Poly(ethylene oxide)/poly(propylene oxide) systems

To confirm the reliability of the theory of phase equibria of multicomponent polymer 1/multicomponent polymer 2 systems (i.e. quasi-binary systems) and the method of computer experiment based on this theory (Brit. Polym. J., 23 (1990)285; 23 (1990)299; Polym. Int., 29 (1992)219), could point curves (CPC), two-phase volume ratios ( R ) and critical solution points (CSP) have been determined experimentally for the quasi-binary mixtures of poly(ethylene oxide) (M¯_w = 647, M¯_w/M¯_n = 1.15; M¯_w and M¯_n, the weight-average and numberaverage molecular weights, respectively) and poly(propylene oxide) (M¯_w = 2028, M¯_w/M¯_n = 1.08; and M_w = 2987, M_w/M_n = 1.13). The hydroxyl end groups of both polymers were methoxylated in advance by the Cooper & Booth method (Polymer, 18 (1977)164). The thermodynamic interaction parameter between both polymers, χ₁₂, and the concentration dependence parameters for the above quasi-binary systems were determined by the method proposed in a previous paper (Brit. Polym. J., 23 (1990)299). CPC, R and CSP values calculated on the basis of the theory are in good agreement with the values determined experimentally.     

Flow of solutions of hydroxypropyl guar-poly(ethylene oxide) mixtures through a porous medium

Summary In flow through porous media, solutions of poly(ethylene oxide) (PEO) exhibit extension thickening, whereas hydroxypropyl guar (HPG) solutions are shear-thinning at high concentrations. The results show that the extension-thickening exhibited by PEO solutions becomes less critical with increasing flow rate as the concentration of HPG in the solution is increased. At high concentrations of HPG, the presence of PEO inhibits the shear-thinning behaviour, without increasing the apparent viscosity of the solution. The presence of HPG reduces the rate and extent of degradation of PEO in the flowing solution.     

Preparation and characterization of metal-complex imprinted PVDF hollow fiber membranes

Using nickel-2,2′-dipyridyl complex as a template, N-vinyl-2-pyrrolidone as the metal coordination functional monomer, and ethylene glycol dimethacrylate as the crosslinker, polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membrane as the supported membrane, metal complex imprinted polymeric membranes were prepared. The association constant of template-monomer interaction in the prepolymerization solution was estimated to be 4.38 × 10⁴ (L/mol)² by spectrophotometric titration analysis. The attenuated total reflection Fourier transform infrared spectroscopy and scanning electron micrograph characterization indicated that the surface of the support PVDF membrane was completely coated by the imprinted polymer layer after modification. The imprinted membranes exhibited the selective permeability for the template in certain nickel acetate solution. The molecularly imprinted membranes gave higher permeation separation factors at about pH 6, whereas increasing pressure would lower the separation ability. The effects of ion concentration, cations and counterions, ligand selectivity, pH, and trans-membrane pressure were investigated and the permeation performances of the imprinted membranes could be regarded as facilitated transport mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gas transport in poly(n-alkyl acrylate)/poly(m-alkyl acrylate) blends

Poly(n-alkyl acrylate)s can have side chains that crystallize independently of the main chain; side-chain length can thus be used as a tunable parameter to control the gas permeability of membranes. The gas permeation response of poly(n-alkyl acrylate) and poly(m-alkyl acrylate) blends as a function of temperature is reported for varying side-chain lengths, n and m, and blend composition in the semi-crystalline and molten states. Macroscopic homogeneity is observed for a small range of n and m where |n − m| ≤ 2-4 methylene units. Thermal analysis indicates that the blend components crystallize independently of one another; however, crystallization is hindered by the presence of the other component. Permeation responses of the blends investigated in some cases exhibited two distinct permeation jumps or increases at the melting temperature of each component. Blends with continuous permeation responses but higher effective activation energies of permeation (i.e., more thermally responsive) were observed for some blends over the temperature of interest for membranes to be used for modified atmosphere packaging.