Amorphous molecule

In contrast to the solid state concepts presented above, Ioannidis et al. [90] describe the organic materials as amorphous molecules. This model is suitable to fit 1/V characteristics of LEDs based on Alq3 and PPVs with a low mobility (j.ik 1CT, h cm2 V 1 s l). Essentially, they found that the current flow through these materials can be attributed to the increase in the mobility (sec Eq. (9.18)) with the applied voltage, which has been observed for many conjugated polymers [91 ]. In the case that the mobility exponentially increases with the electric field, the current flow raids ... 

Nonpolymeric amorphous dyes for electron transport, some of them containing an oxadiazole ring, were prepared and theoretically studied. It was concluded that reversible electron injections and ejection properties without impurity effects could be obtained for the symmetric and globular amorphous molecules <1997PCA2350>. Amplified spontaneous emission laser spikes were observed for some simple 2,5-diaryl oxadiazoles <1997PCA3260>. 

The dihydrogen molecule (s1 + s1) is formed through the interaction of s-electrons only. There is no angular momentum to impart structure to the diatomic molecule, which hence cannot be described in classical geometrical terms other than a spherically symmetrical distribution of electron and proton densities. It has no shape, no bond and, unless it interacts with external fields, no geometrical features. Compounds such as LiH, Li2, etc. belong to the same class of amorphous molecules. 

Hole-transporting materials (HTM) have relatively low ionization potentials (1P). 2 The IP is defined as the energy required to remove an electron from the highest occupied molecular orbital (HOMO) of a substance. It can be measured, for instance, by photoelectron spectroscopy or obtained from electrochemical oxidation potentials in solution. It is also preferable that the HTM have sufficiently high hole drift mobilities. Various classes of materials have been used in the HTL, for example, starburst amorphous molecules, spirocompounds, triarylamines, and tetraarylbenzidines are representative classes of well-known HTMs. The structure of the most commonly used HTM, 4,4 -bis[N-(l-naphthyl)-N-phenylamino]biphenyl (NPB), is shown in Figure 14.2. 

An in-depth smdy shows that spider silks are made of two-phase semicrystalline proteins with hydrogen bonded crystalline moleeules as the hard domain and amorphous molecules as... 

Figure 5.31 Schematic of the alignment change of amorphous molecules during free shape recovery and fiiUy constrained stress recovery.

Copolymers of ethylene and propylene (EPM) and terpolymers of ethylene, propylene, and a diene (EPDM) as manufactured today are rubbers based on the early work of Natta and co-workers (1). A generic formula for EPM and EPDM may be given as follows, where m = 1500 ( 60 mol%), n = 975 ( 39 mol%), o = 25 for EPDM ( 1 mol%) and 0 for EPM in an average amorphous molecule, and the comonomers are preferably statistically distributed along the molecular chain. 

Mesoporous silica was recently investigated as an excipient for formulations of molecules with low water solubility. These materials have very high specific surface area and small pore size. The customized template synthesis produces highly porous silica materials which can enhance the drug dissolution of hydrophobic molecules. Due to the porous nature and the controlled pore size volume of these materials, surface adsorption of the molecules to the mesoporous silica not only enhances the dissolution but also prevents the recrystallization of the amorphous materials. Due to the relatively finite space available to the amorphous molecules, the probability to align with their crystalline counterparts is low to negligible, resulting in amorphous... 

Figure 1 CPU time (seconds) for the numerical integration of the overlap matrix (3-21G basis set) versus the number of atoms (N) in an amorphous molecule. Grid size 2000 grid points per atom...

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