Poly styrene, synthetic applications

Sulfonated poly(arylene ether)s have shown promise for durability in fuel cell systems, while poly-(styrene)- and poly(imide)-based systems serve as model systems for studying structure-relationship properties in PEMs because their questionable oxidative or hydrolytic stability limits their potential application in real fuel cell systems. Sulfonated high performance polymer backbones, such as poly(phe-nylquinoxaline), poly(phthalazinone ether ketone)s, polybenzimidazole, and other aromatic or heteroaromatic systems, have many of the advantages of poly-(imides) and poly(arylene ether sulfone)s and may offer another route to advanced PEMs. These high performance backbones would increase the hydrated Tg of PEMs while not being as hydrolytically sensitive as poly(imides). The synthetic schemes for these more exotic macromolecules are not as well-known, but the interest in novel PEMs will surely spur developments in this area. 

Macroporous poly(styrene-divlnylbenzene) copolymer, FRF-1, columns were used as the stationary phase in the reverse-phase HFLC of the synthetic 3-lactam antihiotlc aztreonam [2S-[2a,33(Z)]]-3-[[(2-Amino-4-thiazolyl)[(1-carhoxy-l-methylethoxy)-imino]acetyl]amino]-2-methyl-4-oxo-l-azetidlnesulfonlc acid and related compounds. Aztreonam was separated better from its precursors and therefore could be assayed more accurately. In most cases, the elution order of compounds tested on a FKF-1 column followed that in conventional reverse-phase, suggesting a similar separation mechanism. For various separations Investigated, FRP-1 was found to be more suitable for our applications than the silica-based reversed-phase columns. 

Polymer-supported (diacetoxyiodo)arenes have found broad synthetic application. Poly[ (diacetoxyiodo)styrene] (4) has been used for the oxidation of alcohols catalyzed by TEMPO (2,2,6,6-tetramethylpiperidine-l-oxyl) [27-30], or in the presence of KBr [31]. In a specific example, primary alcohols are readily oxidized to methyl esters upon treatment with reagent 4 in the presence of KBr in the acidic aqueous methanol solution (Scheme 5.5) [31]. Likewise, organic sulfides are selectively oxidized to the respective sulfoxides by reagent 4 in water in the presence of KBr [32]. 

Caldarelli, M., Habermann, J., and Ley, S.V., Clean five-step synthesis of an array of 1,2,3,4-tetra-substituted pyrroles using polymer-supported reagents, J. Chem. Soc., Perkin Trans. 1, 107, 1999. Togo, H., Nogami, G., and Yokoyama, M., Synthetic application of poly[styrene(iodoso diacetate)],... 

The commercial utility of materials derived from natural sources and modified by controlled chemical reactions prompted the application of such methods to totally synthetic polymeric materials as they were discovered. The first chemical reaction on a totally synthetic pol3oner is probably the nitration of poly(styrene) in 1845. An approximate chronology of when reactions on the more common olefin polymers may have occurred may be constructed from a list of the dates these polymers were reported in the literature. An important step forward, both for pol3n[ner chemistry in general... 

Many interesting and important synthetic applications of 1,1-diphenylethylene and its derivatives in polymer chemistry are based on the addition reactions of polymeric organolithium compounds with 1,1-diphenylethylenes. Therefore, it is important to understand the scope and limitations of this chemistry. In contrast to the factors discussed with respect to the ability of 1,1-dipheny-lalkylcarbanions to initiate polymerization of styrenes and dienes, the additions of poly(styryl)lithium and poly(dienyl)lithium to 1,1-diphenylethylene should be very favorable reactions since it can be estimated that the corresponding 1,1-diphenylalkyllithium is approximately 64.5kJ/mol more stable than allylic and benzylic carbanions as discussed in Sect. 2.2 (see Table 2). Furthermore, the exothermicity of this addition reaction is also enhanced by the conversion of a tt-bond to a more stable a-bond [51]. However, the rate of an addition reaction cannot be deduced from thermodynamic (equilibrium) data an accessible kinetic pathway must also exist [3]. In the following sections, the importance of these kinetic considerations will be apparent. 

The antiviral properties of anionic polymers have recently received a lot of attention as agents to protect against infection with sexually transmitted diseases. Due to the cationic nature of most viruses, several anionic polymers are known to bind viruses. As early as the 1960s, researchers had studied the anti-viral properties of a variety of synthetic polymers [118]. However, not all anionic polymers inactivate viruses. Several classes of anionic polymers have been studied for their ability to inactivate the HIV virus. These polymers include poly(styrene-4-sulfonate), 2-naphthalenesulfonate-formaldehyde polymer, and acrylic acid-based polymers. Certain chemically modified natural polymers (i.e., semisynthetic) such as dextrin/dextran sulfates, cellulose sulfate, carrageenan sulfate, and cellulose acetate phthalate have also been investigated for this purpose. Of a number of such anionic polymers that have shown in-vitro and in vivo anti-HIV activity, a couple of polymeric drug candidates have proceeded to early stage human clinical trials for the evaluation of safety/tolerability [119]. While most of these have shown the desired tolerability and safety, further clinical trials are necessary to discern the therapeutic benefit and see if anionic polymers will be applicable as anti-HIV therapies. 

The most fruitful synthetic application of living polymers stemmed from their ability to produce tailor-made block polymers. For example, we showed in our first papershow the anionic polymerization of styrene followed by the addition of isoprene produced a block polymer (poly-isoprene) (poly-styrene) (poly-isoprene). 

More than 800 million pounds of EPM and EPDM polymers were produced in the United States in 2001. Their volume ranks these materials fourth behind styrene-1,3-butadiene copolymers, poly( 1,4-butadiene), and butyl rubber as synthetic rubbers. EPM and EPDM polymers have good chemical resistance, especially toward ozone. They are very cost-effective products since physical properties are retained when blended with large amounts of fillers and oil. Applications include automobile radiator hose, weather stripping, and roofing membrane. 

About half of the benzene produced as a chemical feedstock is for styrene production, followed by large fractions for phenol and cyclohexane-based products. As much as half of the toluene produced is converted to benzene, depending on the price and demand differential. The largest use of toluene itself is as a component of gasoline. Much smaller amounts are used as a solvent, or in the manufacture of dinitrotoluene and trinitrotoluene for military applications. Xylenes are also used in gasoline formulations and function as octane improvers like toluene. para-Xylene and o-xylene are the dominant isomers of value as chemical feedstocks, for the production of terephthalic acid (and dimethyl terephthalate) and phthalic anhydride, respectively. Polyester and the synthetic resin markets, in turn, are major consumers of these products. meto-Xylene is oxidized on a much smaller scale to produce isophthalic acid, of value in the polyurethane and Nomex aramid (poly(m-phenylene isophthalamide)) technologies. 

Emulsion polymerization is the basis of many industrial processes, and the production volume of latex technologies is continually expanding—a consequence of the many environmental, economic, health, and safety benefits the process has over solvent-based processes. A wide range of products are synthesized by emulsion polymerization, including commodity polymers, such as polystyrene, poly(acrylates), poly (methyl methacrylate), neoprene or poly(chloroprene), poly(tetrafluoroethylene), and styrene-butadiene rubber (SBR). The applications include manufacture of coatings, paints, adhesives, synthetic leather, paper coatings, wet suits, natural rubber substitutes, supports for latex-based antibody diagnostic kits, etc. ... 

Another important application of Py-GC/MS techniques is the evaluation of contamination caused by industrial wastes consisting of usual polymers such as PVC, PS, poly(vinyl acetate) (PVA), polybutadiene (PB), poly(acrylo-nitrile-co-styrene-co-butadiene) (ABS), styrene-butadiene random (SBR) and styrene-butadiene-styrene block (SBS) copolymers. The presence of synthetic polymers in environmental samples is indicated by anomalously high levels of styrene and benzene in the pyrograms, and by the detection of selected markers (e.g., chlorobenzene for PVC, acetic acid for PVA, benzenebutanenitrile for ABS, cyclohexenylben-zene for styrene-butadiene rubbers), which are useful for better identification of individual polymers. This method was applied to a particular case of contamination in an Italian lake near an industrial area. " " ... 

Emulsion polymerization is similar to suspension polymerization in the sense that the reaction also takes place in the presence of a water phase and the applied monomer forms a second liquid phase. However, in this case the added radical initiator is not soluble in the monomer droplets but in the water phase. To allow the monomer to come into contact with the initiator an emulsifier is added to the reaction mixture that creates micelles in the systems. By diffusion processes both monomer molecules and initiator molecules reach the micelle. Polymerization takes places and a polymer particle suspended in the water phase forms that is much smaller than the original monomer droplet (see Figure 5.3.12 for a graphical illustration of these steps). At the end of the overall emulsion polymerization process, all monomer droplets have been consumed by the polymerization reaction in the micelles. Typical emulsifiers for emulsion polymerization are natural or synthetic detergents, such as, for example, sodium palmitate or sodium alkyl sulfonates. Emulsion polymerization is very versatile and is applied for many polymers [e.g., PVC, styrene copolymers, poly(methacryl esters)] in batch, semi-continuous, and continuous processes. In some cases, the obtained polymer particles in water are directly applied as technical products for coatings, lacquer applications, or as adhesives. In other cases the formed product is further treated to obtain the dry polymer. Note that the aqueous phase in emulsion polymerization always contains some isolated emulsifier and also some monomer. Moreover, the formed polymer contains the emulsifier as impurity. 

With the development of synthetic elastomers during World War II, new types of adhesives appeared for application to a broader range of substrates and for use at higher temperatures. Styrene-butadiene and butadiene-acrylonitrile copolymers found application in new adhesives. There were also significant concurrent developments in adhesives based on chlorinated rubber, polychloroprene (neoprene), and poly sulfide rubber. Development of carboxylic elastomers, silicone rubbers, and polyurethanes followed. 

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