Layered polymers

Recent work with multi-layer polymer LEDs has achieved impressive results and highlights the importance of multi-layer structures [46]. Single-layer, two-layer and three-layer devices were fabricated using a soluble PPV-based polymer as the luminescent layer. The external quantum efficiencies of the single-layer, two-layer, and three-layer devices were 0.08%, 0.55%, and 1%, respectively, with luminous efficiencies of about 0.5 hn/W, 3 lm/W, and 6 lm/W. These results clearly demonstrate improvement in the recombination current because of the increase in quantum efficiency. The corresponding increase in luminous efficiency demonstrates that the improvement in recombination efficiency was achieved without a significant increase in the operating bias. 

MIM or SIM [82-84] diodes to the PPV/A1 interface provides a good qualitative understanding of the device operation in terms of Schottky diodes for high impurity densities (typically 2> 1017 cm-3) and rigid band diodes for low impurity densities (typically<1017 cm-3). Figure 15-14a and b schematically show the two models for the different impurity concentrations. However, these models do not allow a quantitative description of the open circuit voltage or the spectral resolved photocurrent spectrum. The transport properties of single-layer polymer diodes with asymmetric metal electrodes are well described by the double-carrier current flow equation (Eq. (15.4)) where the holes show a field dependent mobility and the electrons of the holes show a temperature-dependent trap distribution. 

A characteristic dependence of the efficiency on the thickness of the active layer has also been observed for single layer polymer LEDs. This effect has been attributed to reflection of the EL light at the mirror-like metal electrodes resulting in characteristic interference maxima and minima depending on the thickness of the active layer and its refractive index [116). 

This chapter is organized as follows in Section 11.2 the relevant properties of electroluminescent polymer Films are summarized in Section 11.3 the electronic properties of mctal/polymer junctions are described in Section 11.4 single layer polymer LEDs are discussed in Section 11.5 multi-layer polymer LEDs are considered and Section 11.6 summarizes the conclusions. 

As a final application of the profiling technique, the sensor for large depth measurements described in Section 2.4.2.5 was used to resolve multi-layer polymer coatings on concrete samples. Such coatings are used to protect concrete from degradation and corrosion. They are applied to the concrete surface to reduce the porosity in the upper first millimeters to prevent the penetration of water and... 

Fig. 2.4.14 Profile of a multi-layer polymer coating used to protect concrete surfaces from environmental corrosion. The profile is the signal amplitude resulting from the addition of the first 32 echoes acquired with a CPMG sequence with tE = 50 ps. It has an FOV of 8 mm and was measured with a spatial resolution of 100 pm. Using 256 scans per point and a repetition time of 100 ms, the total acquisition time per point was 25 s.

Fukushima, Y. and Tani M. (1995) An organic/inorganic hybrid layered polymer methacrylate-magnesium (nickel) phyllosilicate. Chemical Communications, 241—242. 

X Yang, D Neher, D Hertel, and TK Daubler, Highly efficient single-layer polymer electrophosphorescent devices, Adv. Mater., 16 161-166, 2004. 

S Kan, X Liu, F Shen, J Zhang, Y Ma, Y Wang, and J Shen, Improved efficiency of single-layer polymer light-emitting devices with poly(vinylcarbazole) doubly doped with phosphorescent and fluorescent dyes as the emitting layer, Adv. Funct. Mater., 13 603-608, 2003. 

The topochemical polymerization of 1,3-diene monomers based on polymer crystal engineering can be used not only for tacticity but also for the other chain structures such as molecular weight [ 102], ladder [84] or sheet [ 103] structures, and also polymer layer structures using intercalation reactions [ 104-107]. Some mechanical and structural properties have already been revealed with well-defined and highly or partly crystalline polymers [ 108-111 ]. A totally solvent-free system for the synthesis of layered polymer crystals was also reported [112]. 

AZ-1350 photoresist was used as a thick bottom layer polymer. AZ resist, thicker than 1.0 was spin-coated on silicon wafer (oxide coated) or substrate with topographic features. The resist was hard-baked for 1 hour at 200 C. SNR film was then spin-coated on a hard-baked AZ resist layer from 5 wt% solution in methylisobutylketone. 

The most current method of nitroglycerin application is a transdermal device or skin patch. A cross section of such a patch is illustrated in Figure 6. The patch is actually a multi-layered polymer stack. The semipermeable membrane which comes in contact with the skin is usually composed of an ethylene-vinyl acetate copolymer or polypropylene. The reservoir contains the drug in a hydrogel or polymer matrix or solvent (the material must be chosen to insure uniform delivery). Examples of some solvents used include dimethyl sulfoxide (DMSO), sodium lauryl sulfate (SDS - a detergent) and propylene glycol/oleic acid. 

Considerable potential exists to design surface modified electrodes which can mimic the behaviour of electronic components. For example, a rectifying interface can be produced by using two-layer polymer films on electrodes. The electroactive species in the layers have different redox potentials. Thus electron transfer between the electrode (e.g. platinum) and the outer electroactive layer is forced to occur catalytically by electron transfer mediation through the inner electroactive layer. 

Fig. 2 Normalized fluorescence lifetime distributions (ELDs) for (a) the cGMP-imprinted and (b) non-imprinted thin-layer polymer film obtained from the fluorescence microscopy measurements (adapted from [47, 66])...

Polymers on surface can change the surface properties drastically. Even physisorbed polymers are usually bound irreversibly due to the large number of binding sites. To produce dense and thick layers, polymers have to be grafted from the surface. 

More recently, Dai et al. demonstrated that an unique 2D double-layered polymer with composition [(Me2S)3 Cu4(g-I)4 ]ra 4 containing helical chains can be constructed according Scheme 2c under solvothermal conditions.124... 

Figure 5.4 (a) Schematic of a three-layer polymer laminate, (b) FTIR absorbance intensity gray scale at 2850, 2980 and 1730 cm-1 at spectral resolution of 16 cm 1. (c) FTIR absorbance spectra from a single pixel within each of the three layers. Reproduced from figure 1 of Ref. 18, with permission. 

It is worth noting that the coordination unit MNO is present in layer polymers containing fragments of deprotonated nitrylnitroxyl radicals, which have an imidazole or benzimidazole substituent in the position 2, as shown by structure 450 [790] ... 

Apparent mass change, assuming rigidity (equation [1]). Entries 2 - 4 refer to liquid modulation layer, liquid modulation layer+polymer and polymer, respectively. 

Wei, H., Ma, N., Shi, F., Wang, Z.Q., and Zhang, X. "Artificial nacre by alternating preparation of layer-by-layer polymer films and CaC03 strata". Chem. Mater. 19(8), 1974-1978 (2007). 

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