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International audience; This study aims to develop a concept of reactive compatibilizer-tracer, which allows one to study the evolution of the morphology and interfacial reaction of reactive polymer blends in a large-scale twin-screw extruder (TSE). A reactive compatibilizer-tracer is a compatibilizer precursor whose polymer chain bears reactive groups capable of reacting with at least one of the polymer components of a polymer blend. It also bears moieties capable of being analytically detected with great accuracy. This concept is shown for polystyrene (PS)/polyamide 6 (PA6) blends using a copolymer of styrene (St), 3-isopropenyl-alpha,alpha'-dimethylbenzene isocyanate (TMI), and 9-(methylaminomethyl)anthracene (MAMA) as a reactive compatibilizer-tracer (PS-TMI-MAMA). While its isocyanate groups are capable of reacting with the terminal group of the PA6 forming a graft copolymer of PS-g-PA6-MAMA, its anthracene moieties allow for measuring very small amounts of the reacted reactive compatibilizer-tracer or in situ formed graft copolymer by gel permeation chromatography (GPC) with an ultraviolet (UV) detector. The use of the reactive compatibilizer-tracer together with transit experiments provides a tool for studying reactive blending processes in a twin-screw extruder.

30th International Conference of the Polymer-Processing-Society (PPS), Cleveland, OH, JUN 06-12, 2014; International audience; A concept of reactive compatibilizer-tracer is developed to study reactive polymer blending processes in a twin screw extruder. It is summarized as follows. Fluorescent moieties such as anthracene are attached to a reactive compatibilizer so that the latter can be served both as a compatibilizer and a tracer. When evaluating its compatibilizing efficiency for a polymer blending system, unlike the polymer components of the blend which are continuously fed to the extruder, the reactive compatibilizer-tracer is added as a pulse. The concentration of the reactive compatibilizer-tracer in the polymer blend at the die exit is measured, in-line and in real time, using probes capable of detecting the signal of the emission of fluorescent moieties of the reactive compatibilizer-tracer. In the meantime, the corresponding size of the dispersed phase domains of the blend is determined off-line. These two pieces of information allow assessing the compatibilizing efficiency of a reactive compatibilizer in a much easier manner and using a much smaller amount of compatibilizer. Consequently, the concept of reactive compatibilizer-tracer can help select most appropriate compatibilizers under real industrial polymer blending conditions as well as scaling up and/or optimizing them.

p-di(p-N,N-diphenyl-amino-styryl)benzene (DSA-Ph)-based blue top-emitting organic light-emitting devices (TOLEDs) with low bias and single-mode resonant emission were fabricated. Microcavity optimization was demonstrated by altering the hole-transport-layer thickness. C60 was demonstrated to be an effective capping layer and improved the luminance by a factor of 1.6 in between the maximum and minimum transmittance of top contact. For sky-blue TOLED, the luminance was enhanced by 50% by using a dual emission layer composed of DSA-Ph doped 2-(t-butyl)-9,10-di(2-naphthyl)anthracene and DSA-Ph doped tris(8-hydroquinoline) aluminium (Alq3). The improvement was attributed to the energy transfer from Alq3 to DSA-Ph and DSA-Ph directly harvesting carriers in the emission layer of Alq3 : DSA-Ph.

A dual electron-transport layer (d-ETL) with hole-blocking function was successfully applied to a 2-(t-butyl)-9,10-di(2-naphthyl)anthracene (TBADN)-based blue organic light-emitting device (OLED) for improving chromaticity and electron injection. The d-ETL was constructed by sandwiching a 1,3-bis[2-(2,2'-bipyridin-6-yl)-1,3,4-oxadiazol-5-yl]benzene (Bpy-OXD) layer between the emission layer (EML) and the most common ETLs of tris(8-hydroquinoline) aluminum (Alq3) and 4,7-diphyenyl-1,10-phenanthroline (BPhen). Due to the hole-blocking function of Bpy-OXD and thereby the better confinement of carriers within the EML, d-ETL devices showed much better chromaticity and less current-induced color shift as compared to the corresponding single ETL ones. Moreover, the d-ETL devices revealed higher power efficiency (increased by ~30%) and lower driving voltage, indicating an enhanced electron injection. This could be explained by the fact that an interlayer of Bpy-OXD provided a stepped energy level which greatly facilitated electron injection and hence enhanced injection current.