Polystyrene hydrocarbon backbone

The earliest commercial membranes tested for use in chlor-alkali cells were composed of ionomeric polymers having hydrocarbon backbones with attached carboxyl and sulfonate functional groups such as the polystyrene sulfonic or carboxylate materials, (46), (47), (48), (49). 

To be informative, it is desirable that the comparisons of these two different technologies be based on identical polymer backbones, having identical molecular weights, and having comparable levels of ionic functionality present. In addition, it is the purpose of these studies to make such comparisons with the same metal cation and thereby quantify, insofar as possible, the nature of the ionic interactions that exist. To do this, ionomers were prepared based on a polystyrene (PS) hydrocarbon backbone into which the ionic functionality was incorporated. PS was selected as the backbone because of the relative ease of functionalization and the relative freedom of side reactions during the sulfonation or carboxylation reactions. The polymers prepared were designed to come as close as possible in terms of ionic functionality for both sulfonate and carboxylate ionomers over a range of ionic contents. 

A type of angle-dependent x-ray photoemission spectroscopy was used to investigate the molecular orientation at the surface of sulfonated polystyrene as a function of reaction depth. A model based on these measurements indicates that at a critical sulfonation depth the aliphatic hydrocarbon backbone becomes exposed preferentially at the surface. These results are consistent with surface energy and tribo-electric charging measurements, which also reveal the effects of associative interactions in the form of conversion dependencies. 

In general, the preparation of ionomers is a straightforward procedure. The particular acid group of interest can be introduced onto the hydrocarbon backbone either by direct copolymerization or post-synthesis reaction. The following five important groups of ionomers illustrate the various methods of preparation. These ionomer families are ethylene-based materials, ionic elastomers, modified polystyrenes, perfluorinated resins and halato-telechelic polymers. 

Thus, in the non-polar medium, due to the collapse of the otherwise partially extended peptide chain within itself, one can rationalize the steric hindrance in the polar medium, due to the collapse of the otherwise extended polystyrene backbone, some of the peptide chains can be visualized as buried and hence hindered to the approach of reagents and solvents. Thus, based on these models of polystyrene-bound peptides in different environments (Fig. 1), an ideal situation would be that where both the polymer and the peptide chains are extended. This is likely to be attained most easily if the polymer and peptide are of comparable polarities and are placed in a good solvating medium. This is in contrast to the polystyrene case where the macromolecular support is a pure hydrocarbon physicochemically quite dissimilar to the peptide chain being synthesized 44). 

The majority of packaging plastic materials consists of polyolefins and vinyl polymers, namely polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly(vinyl chloride) (PVC). Obviously, these polymers have many other applications not only as packaging materials. Chemically they are all composed of saturated hydrocarbon chains of macro-molecular size their typical thermal decomposition pathway is free radical one initiated by the homolytic scission of a backbone carbon-carbon bond. In spite of the basic similarity of the initial cleavage, the decomposition of the hydrocarbon macroradicals is strongly influenced by fhe nafure of the side groups of the main chain. 

According to the backbone structures, sulfonated hydrocarbon PEMs can be classified as sulfonated polystyrene copolymers... 

SAN copolymers are linear, amorphous materials with improved heat resistance over pure polystyrene. The polymer is transparent but may have a yellow color as the acrylonitrile content increases. The addition of a polar monomer, acrylonitrile, to tbe backbone gives these polymers better resistance to oils, greases, and hydrocarbons when compared to polystyrene. Glass-reinforced grades of SAN are available for applications requiring higher modulus combined with lower mold shrinkage and lower coefficient of thermal expansion. ... 

Secondary spectral features such as shake up satellites are frequently observed for polymeric materials containing unsaturated hydrocarbons. Theoretical studies have shown that these are associated with ti-ti transitions in aromatic materials. The shake up peak is clearly visible in the spectra of an oligomeric polyalkylthiophene that is being subjected to attack by and polystyrene (Figure 9.15). It should be noted that the difference between the binding energy for aliphatic carbons in the backbone of polystyrene and the... 

During this early period, Bailey developed a very clever free radical route to polyesters which he used to introduce weak linkages into the backbones of hydrocarbon polymers and render them susceptible to biodegradability (Bailey 1975, 1979, 1985, 1991). Copolymerization of ketene acetals with vinyl monomers incorporates an ester linkage into the pohmier backbone by rearrangement of the ketene acetal radical as illustrated below. The ester is a potential site for biological attack. The chemistr) has been demonstrated with polyethylene (Bailey), poly (acrylic acid) (Bailey, 1990), and polystyrene (Tokiwa). 

A basic chemical hydrocarbon such as ethylene, containing one or more pairs of carbon atoms linked by a double bond. Olefins, which might be considered an archaic synonym that is widely used in the petrochemical industry, are also referred to as alkenes. The two most important alkenes/ olefins are ethylene and propylene, as they form the backbone of the petrochemicals market. The highly reactive double bond makes the olefin molecule ideal for conversion to many useful end products. The majority of olefins capacity is consumed in the production of polymers used for plastics (i.e., polyethylene and polypropylene). Ethylene dichloride, ethylene oxide, propylene oxide, oxo alcohol, polystyrene, and acrylonitrile are other important olefins-based petrochemicals. 

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