Electron‐Rich Alcohol‐Soluble Neutral Conjugated Polymers as Highly Efficient Electron‐Injecting Materials for Polymer Light‐Emitting Diodes

We report the design and synthesis of three alcohol‐soluble neutral conjugated polymers, poly[9,9‐bis(2‐(2‐(2‐diethanolaminoethoxy) ethoxy)ethyl)fluorene] (PF‐OH), poly[9,9‐bis(2‐(2‐(2‐diethanol‐aminoethoxy)ethoxy)ethyl)fluorene‐alt‐4,4′‐phenylether] (PFPE‐OH) and poly[9,9‐bis(2‐(2‐(2‐diethanolaminoethoxy) ethoxy)ethyl)fluorene‐alt‐benzothiadizole] (PFBT‐OH) with different conjugation length and electron affinity as highly efficient electron injecting and transporting materials for polymer light‐emitting diodes (PLEDs). The unique solubility of these polymers in polar solvents renders them as good candidates for multilayer solution processed PLEDs. Both the fluorescent and phosphorescent PLEDs based on these polymers as electron injecting/transporting layer (ETL) were fabricated. It is interesting to find that electron‐deficient polymer (PFBT‐OH) shows very poor electron‐injecting ability compared to polymers with electron‐rich main chain (PF‐OH and PFPE‐OH). This phenomenon is quite different from that obtained from conventional electron‐injecting materials. Moreover, when these polymers were used in the phosphorescent PLEDs, the performance of the devices is highly dependent on the processing conditions of these polymers. The devices with ETL processed from water/methanol mixed solvent showed much better device performance than the devices processed with methanol as solvent. It was found that the erosion of the phosphorescent emission layer could be greatly suppressed by using water/methanol mixed solvent for processing the polymer ETL. The electronic properties of the ETL could also be influenced by the processing conditions. This offers a new avenue to improve the performance of phosphorescent PLEDs through manipulating the processing conditions of these conjugated polymer ETLs.     

Crystallographic anisotropy of growth and etch rates of CVD diamond

The investigation of orientation dependent crystal growth and etch processes can provide deep insights into the underlying mechanisms and thus helps to validate theoretical models. Here, we report on homoepitaxial diamond growth and oxygen etch experiments on polished, polycrystalline CVD diamond wafers by use of electron backscatter diffraction (EBSD) and white-light interferometry (WLI). Atomic force microscopy (AFM) was applied to provide additional atomic scale surface morphology information. The main advantage of using polycrystalline diamond substrates with almost random grain orientation is that it allows determining the orientation dependent growth (etch) rate for different orientations within one experiment. Specifically, we studied the effect of methane concentration on the diamond growth rate, using a microwave plasma CVD process. At 1% methane concentration a maximum of the growth rate near <100> and a minimum near <111> is detected. Increasing the methane concentration up to 5% shifts the maximum towards <110> while the minimum stays at <111>. Etch rate measurements in a microwave powered oxygen plasma reveal a pronounced maximum at <111>. We also made a first attempt to interpret our experimental data in terms of local micro-faceting of high-indexed planes.     

Coping and adaptation to facial pain in contrast to other stressful life events.

Investigates whether coping with chronic pain influences adaptation to other negative life events using data on Temporomandibular Pain and Dysfunction Syndrome (TMPDS) patients (N?=?99) and nonpatient controls (N?=?98). It is found that cases cope very differently with pain than with other stressful events and that cases and controls do not differ on coping with nonpain events, with 2 exceptions. Cases view nonfateful events as more outside their control and they have more negative changes in usual activities following negative events. This excess of negative change is associated with greater demoralization and physical exhaustion. It is concluded that coping with repeated pain episodes leaves cases vulnerable to stressful events. Alternative interpretations, especially those involving the role of preexisting personality differences, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Improved design methods for scarf repairs to highly strained composite aircraft structure

This paper presents an analytical method to optimise the profile of the scarf joint between dissimilar modulus adherends so that adhesive stresses are approximately uniform along the joint. The optimised scarf repair is expected to enhance joint strength and reduce the amount of material removal. Finite element analyses have been performed to both validate the optimal solution and to evaluate the use of low stiffness patch to repair carbon epoxy composites. In particular, the influence of patch lay-up on adhesive stresses has been investigated.     

Synergistic combustion of coal with natural gas

Using an improved coal-devolatilization model and a simple char-burnout model, we explore possible synergisms in the simultaneous combustion of coal and natural gas. After describing our own work briefly in the context of the conversion of oil boilers to coal burning, we consider the direct use of pulverized coal or of coal-water slurries with gas augmentation, and the two-stage use of pulverized coal or coal-water slurries with gas augmentation. In the first case, we identify advantageous interactions in cofiring which speeds up char-burnout. In the second case, the primary role of the first stage is the “methanogasification” of coal analogous to, and possibly more effective than, the hydrogasification of coal. In both cases, simultaneous coal-gas combustion appears to be synergistic.     

Caged Alumina Particles in Reticular Foam

A novel approach has been employed to suspend highly porous alumina particles within the reticular structure of silicon carbide foam. The particles are slightly smaller than the reticular cells that they occupy, thereby permitting them to "rattle" freely when subjected to a gas stream. Potential applications include low-pressure-drop catalyst supports.