Poly aromatic polymer

An alternative approach utilizes polymeric analogs of PBD. The oxadiazole unit may be in the polymer main chain or attached as a side chain. A reasonable device performance has been demonstrated in poly(aromatic oxadia/ole)s [71—74. ... 

The formation ofC—C bonds between aromatic rings is an important step in many organic syntheses and can be accomplished by chemical, photochemical, or electrochemical means. As was noted earlier, fundamental considerations of the parameters for a dielectric which must be dealt with in designing a thermally stable, low-dielectric-constant polymer naturally lead one to consider rigid-rod, nonconjugated aromatic polymers containing no lossy functional groups. A structure such as poly(naphthalene) is a likely candidate. 

A substantial intramolecular protective effect by phenyl groups in polymers is shown by the low G values for Hz and crosslinking in polystyrene (substituent phenyl) and in polyarylene sulfones (backbone phenyl), as well as many other aromatic polymers. The relative radiation resistance of different aromatic groups in polymers has not been extensively studied, but appears to be similar, except that biphenyl provides increased protection. Studies on various poly(amino acid)s indicate that the phenol group is particularly radiation resistant. 

To date, much effort has been undertaken to develop new alternatives. For example, sulfonated aromatic polymers, i.e., polymers with the sulfonic acid groups directly attached to the main chain or carrying short pendant side chains with terminal sulfonic acid units, attract increasing interest because of their chemical and thermal stability, and the ease of the sulfonation procedure. Some of the proposed polymers are sulfonated polysulfone (SPSU) [134] sulfonated poly(phenylene oxide) (SPPO) [135] sulfonated poly-(ether ether ketone) (SPEEK) [136] poly(phenylquinoxaline) (PPQ) [137] and poly(benzeneimidazole) (PBI) [138],... 

Wholly aromatic polymers are thought to be one of the more promising routes to high performance PEMs because of their availability, processability, wide variety of chemical compositions, and anticipated stability in the fuel cell environment. Specifically, poly(arylene ether) materials such as poly-(arylene ether ether ketone) (PEEK), poly(arylene ether sulfone), and their derivatives are the focus of many investigations, and the synthesis of these materials has been widely reported.This family of copolymers is attractive for use in PEMs because of their well-known oxidative and hydrolytic stability under harsh conditions and because many different chemical structures, including partially fluorinated materials, are possible, as shown in Figure 8. Introduction of active proton exchange sites to poly-(arylene ether) s has been accomplished by both a polymer postmodification approach and direct co-... 

The most common way to modify aromatic polymers for application as a PEM is to employ electrophilic aromatic sulfonation. Aromatic polymers are easily sulfonated using concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or sulfur trioxide (or complexs thereof). Postmodification reactions are usually restricted due to their lack of precise control over the degree and location of functionalization, the possibility of side reactions, or degradation of the polymer backbone. Regardless, this area of PEM synthesis has received much attention and may be the source of emerging products such as sulfonated Victrex poly (ether ether ketone). 

A related approach has been used for the synthesis of poly(thiaacene)s, which are novel helical aromatic polymers comprised of fused benzothiophene rings, poly(thiaheterohelicene) <20050L755>. 

Reissert chemistry has been employed for polymeric attachment of the isoquinoline heterocycle. Reissert compound (227) reacted with poly(vinylbenzyl chloride) (192) yielding the substitution product (228) in quantitative yield (Scheme 110) (76MI11111). Alkaline hydrolysis of (228) afforded the fully aromatized, polymer-bound isoquinoline derivative (229), again in quantitative yield. In a variation of this reaction (76MI11112), the Reissert... 

Ballard et al. 250) have described synthesis of poly(p-phenylene) via the polymerization of esters of 5,6-m-dihydroxycyclohexadiene. The polymer, produced by free-radical initiation, is soluble in common solvents and smoothly eliminates in the temperature range 140 to 240 °C to give the aromatic polymer. 

Since many of the aromatic polymers studied [e.g., poly(n-hexylphenylsilane)] are also quite rigid in solution and optical microscopy studies on concentrated solutions often show signs of long range order, a partially oriented sample of this material was prepared by shear flow extension. Third harmonic measurements at 1.064 /im on partially oriented films prepared in this... 

Poly Aromatic Hydrocarbons as Luminescent Probes for Polymer-Based PSP... 

Stiff rod-like helical polymers are expected to spontaneously form a thermotropic cholesteric liquid crystalline (TChLC) phase under specific conditions as well as a lyotropic liquid crystal phase. A certain rod-like poly(f-glutamate) with long alkyl side chains was recently reported to form a TChLC phase in addition to hexagonal columnar and/or smectic phases [97,98]. These properties have already been observed in other organic polymers such as cellulose and aromatic polymers. 

Gilmer TC et al. (1996) Synthesis, characterization, and mechanical properties of PMMA/poly(aromatic/aliphatic siloxane) semi-interpenetrating polymer networks. J Poly Sci Part A Poly Chem 34(6) 1025—1037... 

Many computational studies of the permeation of small gas molecules through polymers have appeared, which were designed to analyze, on an atomic scale, diffusion mechanisms or to calculate the diffusion coefficient and the solubility parameters. Most of these studies have dealt with flexible polymer chains of relatively simple structure such as polyethylene, polypropylene, and poly-(isobutylene) [49,50,51,52,53], There are, however, a few reports on polymers consisting of stiff chains. For example, Mooney and MacElroy [54] studied the diffusion of small molecules in semicrystalline aromatic polymers and Cuthbert et al. [55] have calculated the Henry s law constant for a number of small molecules in polystyrene and studied the effect of box size on the calculated Henry s law constants. Most of these reports are limited to the calculation of solubility coefficients at a single temperature and in the zero-pressure limit. However, there are few reports on the calculation of solubilities at higher pressures, for example the reports by de Pablo et al. [56] on the calculation of solubilities of alkanes in polyethylene, by Abu-Shargh [53] on the calculation of solubility of propene in polypropylene, and by Lim et al. [47] on the sorption of methane and carbon dioxide in amorphous polyetherimide. In the former two cases, the authors have used Gibbs ensemble Monte Carlo method [41,57] to do the calculations, and in the latter case, the authors have used an equation-of-state method to describe the gas phase. 

For flexible aliphatic polymers, e.g. poly(oxy methylene), sm has a value of 0.175 K MPa-1 for semi-rigid aromatic polymers (such as PEEK) the value of sm is much larger, viz. 0.5 K MPa-1. 

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