Polymers, phenylated aromatic

An elegant synthesis method which is specific to sulfone polymers containing phenyl—phenyl linkages (such as PPSF) is the nickel-catalysed coupling of aryl dihahdes. The scheme for this synthesis involves a two-step process. First, an aromatic dihaUde intermediate is formed which carries the backbone features of the desired polymer. This aromatic dihahde intermediate is then self-coupled in the presence of sero-valent nickel, triphenylphosphine, and excess sine to form the biphenyl- or terphenyl-containing polymer. AppHcation of this two-step scheme to PPSF can be depicted as follows ... 

Polymers containing pendant carbamate functional groups can be prepared by the reaction of phenyl isocyanate with poly(vinyl alcohol) in homogeneous dimethylsulfoxide solutions using a tri-ethylamine catalyst. These modified polymers are soluble in dimethyl sulfoxide, dimethylacetamide, dimethylformamide and formic acid but are insoluble in water, methanol and xylene. Above about 50% degree of substitution, the polymers are also soluble in acetic acid and butyrolactone. The modified polymers contain aromatic, C = 0, NH and CN bands in the infrared and show a diminished OH absorption. Similar results were noted in the NMR spectroscopy. These modified polymers show a lower specific and intrinsic viscosity in DMSO solutions than does the unmodified poly(vinyl alcohol) and this viscosity decreases as the degree of substitution increases. 

Examination of the absorption spectra of the new polysilane materials reveals a number of interesting features (14). As shown in Table III, simple alkyl substituted polymers show absorption maxima around 300-310 nm. Aryl substitution directly on the silicon backbone, however, results in a strong bathochromic shift to 335-345 nm. It is noteworthy that 4, which has a pendant aromatic side group that is buffered from the backbone by a saturated spacer atom, absorbs in the same region as the peralkyl derivatives. This red shift for the silane polymers with aromatic substituents directly bonded to the backbone is reminiscent of a similar observation for phenyl substituted and terminate silicon catenates relative to the corresponding permethyl derivatives... 

The MW of polymers of aliphatic disubstituted acetylenes such as 2-octyne remarkably reduces, when such polymers are irradiated with y-rays in airll7) (Fig. 10). In contrast, polymers of aromatic disubstituted acetylenes like 1-phenyl-1-propyne hardly degrade by y-rays irradiation in air. Thus the degradation behavior of substituted poly acetylenes is greatly dependent on the kind of substituent. The mechanism is essentially the same as that for thermal degradation. 

Intramolecular Excimer Fluorescence Studies in Polymers Carrying Aromatic Side Chains. Some years ago, it was shown that certain excited aromatic molecules may form a complex with a similar molecule in the ground state, which is characterized by a structureless emission band red-shifted relative to the emission spectrum of the monomer. The formation of such complexes, called "exclmers", requires the two chromophores to lie almost parallel to one another at a distance not exceeding about 3.5A° (11). Later, it was found that Intramolecular excimer formation is also possible. In a series of compounds of the type C5H (CH2)jiC H5, excimer fluorescence, with a maximum at 340nm, was observed only for n 3 -all the other compounds had emission spectra similar to toluene, with a maximum at about 280nm (12). Similar behavior was observed in polystyrene solutions, where the phenyl groups are also separated from one another by three carbon atoms (13). 

Apparently, there will not be exhaustive results either with the chemical structure of the polymer on the preferential adsorption," or the influence of the tacticity on the preferential adsorption. In the last years, investigations regarding the effect of ortho-substituents in polymers with aromatic bulky side groups on the preferential adsorption and viscometric behavior have been reported for poly(phenyl methacrylate) and its dimethyl and diisopropyl ortho derivatives in tetrahydrofiiran/water. " Figure 5.4.5 from ref " shows the Xvalues for three polymers in THF/water. 

Another modified PC, In this case with a phenyl side-group in the bisphenol moiety, was made available by Bayer (see Figure 6). Molecular mechanics calculations predicted that for this polymer the aromatic side-group in its lowest-energy conformation is in the desired perpendicular position. And indeed the stress optical coefficient resulting from the flow birefringence measurement for this polymer has a value of 1.8 x 10- Pa (at 253°C), considerably lower than that of unmodified PC (11). 

Polymer phenyl radicals (4.8) may react with oxygen giving polymeric aromatic hydroperoxides (4.16), which are further photodecomposed into... 

H. S. Ndwa. T. Wataoabc. A. Kakuta. A. Mukoh. and S. Miyata. N-phenylated aromatic polyurca A new nonlinear optical material with large second harmonic generatkm and UV trattspnrency, Polymer 34 637 (1993V... 

S. Iksaka, K. Ohisbi. H. S. Nalwa, T. Watanabe, and S. Miyata. Ferroelectric polarization reversal stabilized by hydrogen bonding in N-phenylated aromatic polyurea. Polymer J.. 26 505 (1994V... 

In a wide definition, PBI refers to a large family of aromatic heterocyclic polymers containing benzimidazole units. PBI with different structures can be synthesized from hundreds of combinations of tetraamines and diacids. In a specific way, PBI refers to the commercial product under the trademark Celazole , poly(2,2 -m-(phenylene)-5,5 -bibenzimidazole) (Fig. 4.1). In the context of PBI with different structures, this specific PBI is also named as meia-PBI because phenylene ring is meto-coordinated. As an amorphous thermoplastic polymer, the aromatic nuclei of PBI provide the polymer high thermal stabihty (glass transition temperature, Fg = 425-436 °C), excellent chemical resistance, retention of stiffness and toughness, but poor process-abihty [56-58]. Primarily used in textile fibers, the selection of poly(2,2 -m-(phenyl-ene)-5,5 -bibenzimidazole) as the commercial product was made on the basis of its... 

Polyquinoxalines (PQ) have proven to be one of the better heat-resistant polymers with regard to both stabiUty and potential appHcation. The aromatic backbones are derived from the condensation of a tetramine with a bis-glyoxal, reactions first done in 1964 (61,62). In 1967, a soluble, phenylated version of this polymer was produced (63). The chemistry and technology of polyquinoxalines has been reviewed (64). 

The pyromellitic dianhydride is itself obtained by vapour phase oxidation of durene (1,2,4,5-tetramethylbenzene), using a supported vanadium oxide catalyst. A number of amines have been investigated and it has been found that certain aromatic amines give polymers with a high degree of oxidative and thermal stability. Such amines include m-phenylenediamine, benzidine and di-(4-amino-phenyl) ether, the last of these being employed in the manufacture of Kapton (Du Pont). The structure of this material is shown in Figure 18.36. 

Crystallisable polymers have also been prepared from diphenylol compounds containing sulphur or oxygen atoms or both between the aromatic rings. Of these the polycarbonates from di-(4-hydroxyphenyl)ether and from di-(4-hydroxy-phenyl)sulphide crystallise sufficiently to form opaque products. Both materials are insoluble in the usual solvents. The diphenyl sulphide polymer also has excellent resistance to hydrolysing agents and very low water absorption. Schnell" quotes a water absorption of only 0.09% for a sample at 90% relative humidity and 250°C. Both the sulphide and ether polymers have melting ranges of about 220-240°C. The di-(4-hydroxyphenyl)sulphoxide and the di-(4-hydroxy-phenyl)sulphone yield hydrolysable polymers but whereas the polymer from the former is soluble in common solvents the latter is insoluble. 

A large part of organic and macromolecular chemistry starts with the chemical functionalization of benzene, and benzene units serve us building blocks for important polymers. Naturally, benzene-based aromatic materials also represent an important subclass of jt-conjugaled architectures. Despite some synthetic difficulties related to the generation of structurally well-defined oligo- and poly(phenyl-... 

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