Polyaryl hydrocarbons

A large family of new dendrimers has been synthesized following this divergent method. Hawker and Frechet developed polyaryl(-benzyl)ether dendrimers [27], Miller andNeenan [28], and also Moore and Xu [29] prepared hydrocarbon dendrimers. The latter have reported the largest monodisperse organic hydrocarbon dendrimer with a molecular mass of 18 kDa and a diameter of 12.5 nm [30]. 

If solutions of CgQ in aromatic hydrocarbons are treated with Lewis acids, such as AICI3, AlBrj, FeBrj, FeClj, GaClj or SbClj, then a fullerylation of aromatics takes place (Scheme 8.11) [66, 88, 90, 91], In this case, the Lewis acid serves as a catalyst and increases the electrophilicity of the fullerene. Mixtures of polyarylated fullerenes are obtained. Depending on the reaction conditions and the aromatic used for the fullerylation, up to 16 aryl groups are covalently bound to the fullerene core [66, 88,... 

One of the side reactions is the formation of linear polyaryls, which may be considered to be formed by further reaction of the biaryl initially produced. From the high-boiling residue remaining after the removal of the biphenyl, formed from diazotized aniline, benzene, and alkali, p-terphenyl and quaterphenyl16 have been isolated and in the mixture formed in the preparation of 4-methylbiphenyl a hydrocarbon was found... 

Investigation of a wide range of block copolymers, consisting of various flexible (polydimethylsiloxane, polybutadiene) and rigid (polycarbonate, polysulphone, polyarylate) phases [44], shows that irrespective of the chemical nature of copolymer, content and molecular weight of blocks as well as pressure and composition of the hydrocarbon mixture, sorption, and mass transfer of alkanes take place primarily in the rubbery phase. The phenomenon of plasticization of polymers by hydrocarbons was demonstrated by baromechanical methods [7,45 8]. Figure 9.13 shows baromechanical curves for the block copolymer... 

Aromatic nitriles can be thermally selectively polymerized in pyrrolidin-2-one at temperatures above 200 C. Between 200 and 350 °C trimerization to 2,4,6-triaryl-l,3,5-triazines occurs, while at temperatures above 300 °C imidization occurs resulting in nonmelting, linear polyaryl-carbimine. Mixtures of trimers and polymeric imines are separable by sublimation or extraction with aromatic hydrocarbons.180 Since aryltriazines and polymeric aryltriazines have various industrial applications, several catalytic systems have been developed for the trimerization of aromatic nitriles and dinitriles, e.g. metal chlorides,181 iron(II) or iron(lll) cyanide,182 cop-per(II) carbonate,183 and molten zinc(II) chloride.184... 

The temperature resistance of the polyarylates lies between polysulfone and polycarbonate. The polymer is flame retardant and shows good toughness and UV resistance. Polyarylates are transparent and have good electrical properties. The abrasion resistance of polyarylates is superior to polycarbonate. In addition, the polymer shows a very high recovery from deformation. However, the material is subject to environmental stress cracking, particularly in the presence of aromatic and aliphatic hydrocarbons. 

In most cases, routine problems can be solved with a polyaryl-etheretherketone (PEEK) capillary. However, PEEK is susceptible to attack by halogens and strong Brpnsted and Lewis acids as well as some halogenated compounds and aromatic hydrocarbons. A stainless steel capillary with additional protection of turbomo-lecular pump (admission of shielding gas) should be used in corrosive media (NH3, CI2, F2 etc.). Glass-lined plastic is the optimal choice when any undesirable reagent adsorption should be diminished. 

The amorphous character of polyarylates renders this class of polymer susceptible to stress-cracking tendencies in solvents such as ketones, aromatic hydrocarbons, esters, and chlorinated hydrocarbons. In applications where chemical resistance is critical, alloying polyarylate with other high performance materials can often meet the requirement. 

The chemical resistance of polyarylates (polyester carbonate) is largely similar to that of polycarbonate, but their ester content causes a more favorable behavior in hydrocarbons and boiling water. Figure 5.342. They are resistant to dilute mineral acids and acidic and neutral aqueous salt solutions. Bases, aqueous solutions of ammonia, amines, and alkaline salt solutions destroy polyarylates by hydrolytic degradation. Polyarylates are not attacked by aliphatic hydrocarbons and alcohols with the exception of methyl alcohol they are swelled and often dissolved by aromatics, ketones, esters, and halogenated hydrocarbons [723]. 

Details of the manufacture of polyarylates have not been disclosed but the polymers may be made by interfacial polymerization of the diacid chlorides (dissolved in a chlorinated hydrocarbon) and bisphenol A (in aqueous alkali). 

Polyaryl and polycyclic aromatic compounds. The behavior of higher aromatic hydrocarbons can be viewed as an extrapolation of that of alkylbenzenes described above. The molecular and doubly charged ions are of higher abundance. Similar characteristic alkyl side-chain cleavages occur decomposition in the unsaturated system is subject to severe hydrogen and skeletal scrambUng. 

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