Interfacial materials functions

Highly branched polymers play an increasingly important role in interface and surface sciences, since their distinctive chemical and physical properties can be used advantageously as functional surfaces and as interfacial materials. Due to their highly compact and globular shape, as well as their monodispersity, for... 

Due to the relatively high mobility of holes compared with the mobility of electrons in organic materials, holes are often the major charge carriers in OLED devices. To better balance holes and electrons, one approach is to use low WF metals, such as Ca or Ba, protected by a stable metal, such as Al or Ag, overcoated to increase the electron injection efficiency. The problem with such an approach is that the long-term stability of the device is poor due to its tendency to create detrimental quenching sites at areas near the EML-cathode interface. Another approach is to lower the electron injection barrier by introducing a cathode interfacial material (CIM) layer between the cathode material and the organic layer. The optimized thickness of the CIM layer is usually about 0.3-1.0 nm. The function of the CIM is to lower... 

The surface properties of CNTs are paramount for their hybridization with other components. The formation of large bundles due to van der Waals interactions between hydrophobic CNT walls further limits the accessibility of individual tubes. Functionalization of CNTs can enhance their dispersion in aqueous solvent mixtures and provide a means for tailoring the interfacial interactions in hybrid and composite materials. Functionalization techniques can be divided in covalent and non-covalent routes, which will be described in greater detail in Chapter 3. 

Although the emphasis here will, by necessity, be placed on more recent data, several key reviews of transport in nanocrystalline ionic materials have been presented, the details of which will be outlined first. An international workshop on interfacially controlled functional materials was conducted in 2000, the proceedings of which were published in the journal Solid State Ionics (Volume 131), focusing on the topic of atomic transport. In this issue, Maier [29] considered point defect thermodynamics and particle size, and Tuller [239] critically reviewed the available transport data for three oxides, namely cubic zirconia, ceria, and titania. Subsequently, in 2003, Heitjans and Indris [210] reviewed the diffusion and ionic conductivity data in nanoionics, and included some useful tabulations of data. A review of nanocrystalline ceria and zirconia electrolytes was recently published [240], as have extensive reviews of the mechanical behavior (hardness and plasticity) of both metals and ceramics [13, 234]. 

The interfacial resistance between the coating and the lower thermocouple plate is different from the interfacial resistance between the substrate-measurement plate due to light oxidation of the steel substrate, which is not observed for the coating. We have observed that the interfacial resistance of ceramics depends primarily on the surface finish of the ceramic material, since ceramics are chemically stable. Therefore, we use an interfacial resistance that was previously measured between Pyroceram 9606, of the same surface finish as the FGM coating, and the upper thermocouple plate as our interfacial resistance function for the coating-measurement plate interface [6]. Thermal conductivity of the FGM coating can then be extracted from the total conductance data by using these interfacial resistances and the thermal conductivity data for 410 stainless steel. The estimated uncertainty of the measurement system is 5%. 

In 1990, Honerkamp and Weese published a seminal paper on the use of Tikhonov s regularization for the determination of material functions. The developed method of data treatment was found particularly useful for the computation of the relaxation and retardation spectra [Elster et al, 1991 Honerkamp and Weese, 1993]. It has also been used to compute the sphere-size distribution of the dispersed phase in binary blends [Gleinser et al, 1994a], as well as the ratio of the dispersed drop diameter divided by the interfacial tension coefficient, d/Vj [Gleinser et al, 1994b]. 

Compared with their inorganic counterparts, organic interfacial materials, especially water/alcohol soluble conjugated polymers (WSCPs) and water/alcohol soluble small molecular (WSSMs), have attracted growing attention and exhibited more potential owing to their solution processibility from environmentally friendly solvents, excellent ECE modification ability and their tunable functions through facile modification in molecular structures. The chemical structures of some organic ECL materials are shown in Scheme 6.4. 

In the JKR experiments, a macroscopic spherical cap of a soft, elastic material is in contact with a planar surface. In these experiments, the contact radius is measured as a function of the applied load (a versus P) using an optical microscope, and the interfacial adhesion (W) is determined using Eqs. 11 and 16. In their original work, Johnson et al. [6] measured a versus P between a rubber-rubber interface, and the interface between crosslinked silicone rubber sphere and poly(methyl methacrylate) flat. The apparatus used for these measurements was fairly simple. The contact radius was measured using a simple optical microscope. This type of measurement is particularly suitable for soft elastic materials. 

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