Polyaromatic core

Approaches used to the development of LC materials with valuable luminescent properties include the synthesis of rod-like mesogens from fluorescent moieties, e.g. benzopyrans, " and discotic LCs with a fluorescent polyaromatic core. ... 

SCHEME 30.7 Photoreactivity of cyclic enediynes with polyaromatic core. 

The hydrocarbons present in oil can be classified into four main classes saturated (alkanes and cycloparaffins), aromatics (hydrocarbons, mono, di and polyaromatic), resins (fractions consist of polar molecules containing heteroatoms such as N, O or S) and asphaltenes (they are molecules similar to the resins, but with a higher molecular weight and polyaromatic core). This classification is known as SARA (Wang et al, 2002 Speight, 2001 Tissot and Welt, 1978). 

Aromatic compounds are present but do not constitute a predominant part of the molecule the polyphenollc and polyaromatic components are low in concentration and exhibit low degrees of substitution Aliphatic side chains are attached to the aromatic core, but due to the participation of lignin degradation products, aromatic moieties are more abundant... 

Lipophilic-hydrophilic character ICG is an amphiphilic molecule consisting of a lipophilic polyaromatic polyene core and a water-solubilizing sulfonate group (Fig. 7). 

Polyaromatic hydrocarbons (PAH) are low in concentration, and no human pollution effects were detected. Perylene data suggest active diagenesis down the sediment core. 

Solid polymer electrolytes, typically perfluorosulfonic acid (PFSA) membranes, are at the core of Polymer electrolyte membrane fuel cells (PEMFCs). These membranes electrically and mechanically isolate the anode and cathode while, when appropriately humidified, allowing for effective ion migration. Nafion, manufactured by DuPont, is one of the most thoroughly used and studied membranes in the PFSA family. Another family of membranes that holds some promise for use in PEMFCs is the group of sulfonated polyaromatic membranes, typically sulfonated polyetherketones. While research is being performed on other types of membranes, as well as hybrid membranes that might have been better-suited properties, information on these is searce [1-10]. 

Determinations of polyaromatic hydrocarbons (PAHs) in freeze-dried sediments (sample mass of the order 10-20 g) has been carried out where hexa-methylbenzene added as a standard to the sediment prior to extraction. The sediments were extracted sequentially with methanol followed by methylene chloride and substituted and unsubstituted were determined by GC-MS. The accuracy of the method was verified using the marine reference material HS6 (NRCC). The technique allowed the determination of 17 unsubstituted and 33 substituted PAHs with detection limits in the range 50-200ngperg. An example of the results from the sediment core from a Canadian fjord contaminated with PAHs derived from an almnimun smelter is shown in Figure 3. The PAH concentration illustrates the wide concentration range available to this analytical method and also show the variation of PAH concentrations with depth. Each PAH has an increase in concentrations... 

Diesel exhaust is a mixture of gases and particulates produced during the combustion of diesel fuel. The very small particles are known as diesel particulate matter (DPM), which consists primarily of solid elemental carbon (EC) cores with organic carbon (OC) compounds adhered to the surfaces. The organic carbon includes polyaromatic hydrocarbons (PAH), some of which cause cancer when tested in animals. Workers exposed to diesel exhaust face the risk of health effects ranging from irritation of the eyes and nose, headaches and nausea, to respiratory disease and lung cancer. 

Until 1977, it was believed that only rod-like molecules, having a considerably higher length than width, could show liquid crystalline properties (calamitic mesogens). However, in 1977, Chandrasekhar realized that not only rod-like molecules, but also compounds with a disc-like molecular shape are capable of forming mesophases (Chandrasekhar et al. 1977 Sabine et al. 2007) and these are referred to as discotic liquid crystals (DLCs). The first examples of this kind of mesomorphism were observed in hexa-alkanoyloxybenzenes, hexaalkoxy- and -aUcanoyloxy-triphenylenes (Fig. 16.2), and were established by X-ray studies (Kumar 2010). Generally, the disc shaped molecules have central core as benzene or polyaromatic, such as triphenylene or phthalocyanine. 

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