Sulfonation of polystyrene

Materials. Four samples of sodium poly(styrenesulfonate) (NaPSS) prepared by sulfonation of polystyrenes with narrow molecular weight distribution were purchased from Pressure Chemical Co. The characteristics of the samples, according to the manufacturer, are listed in Table I. The intrinsic viscosities of NaPSS in aqueous NaCl solution were measured using an Ubbelhode viscometer at 25 °C. 

Sulfonation of polystyrene occurs by an electrophilic aromatic substitution... 

The melt behavior of sulfonated polystyrene ionomers was studied by Lundberg and coworkers41. As was shown in the case of a sulfonated elastomer30, sulfonation of polystyrene leads to an increase in the melt viscosity (measured at 250 °C) of the SPS upon neutralization, indicating increased association of the sodium poly-(salt). A sudden jump of the melt viscosity occurs at the point of complete neutralization, where a critical concentration of Na polystyrenesulfonate is reached, apparently resulting in a sharp phase separation between the ionic and hydrophobic domains (Figure 5). 

Table 16.1 Ion exchange capacity (meq/g) of the macronet isoporous hypercrosslinked, and conventional sulfonates of polystyrene [369]...

The preparation of ionomers involves either the copolymerization of a functionalized monomer with an olefinic unsaturated monomer or direct functionalization of a preformed polymer. Typically, free-radical copolymerization of ethylene, styrene, or other a-olefins with acrylic acid or methacrylic acid results in carboxyl-containing ionomers. The copolymer, available as a free acid, is then neutralized partially to a desired degree with metal hydroxides, acetates, or similar salts. The second route for the preparation of ionomers involves modification of a preformed polymer. For example, sulfonated polystyrene is obtained by direct sulfonation of polystyrene in a homogeneous solution followed by neutralization of the acid to the desired level. Some commercially available ionomers are listed in Table 15.17. 

Direct synthesis is used for polyelectrolytes such as carboxy polymers, e.g., poly(acryiic acid) and poly(methacrylic acid), which are probably the most common ionic polymers of all. Post-fimctionaliza-tion of pre-formed polymers is a frequently used synthetic method, provided that the polymer is sufficiently reactive. Common examples are the sulfonation of polystyrene and the grafting of thioglycollic acid on to polybutadiene using free radicals. 

Sulfonation reactions of polystyrene and its copolymers with divinyl benzene are carried out commercially to prepare ion exchange resins. Partial sulfonations of polystyrenes are achieved in the presence of ethers. When more than 50% of the aromatic rings are sulfonated, the polymers become water soluble. At lesser amounts of sulfonation (25-50%), the polymers are solvent soluble. ... 

PROBLEM 14.2 Explain why sulfonation of polystyrene occurs in the positions shown in the ion-exchange resin formula. Hint Review Sec. 4.11.)... 

A polymer is synthesized, and then anions are introduced into the polymer, for example, by sulfonation of polystyrene to introduce sulfonate anions. 

The sulfonation of polystyrene and styrene divinyl benzene copolymers has been extensively studied as their products are ion exchangers for the recovery of metals and have many other uses. " Some of the sulfonalkylation reactions of polystyrene have been summarized by Cameron (see Scheme 26). 

Synthetic polymers can be equally useful as bases for the preparation of polymeric amphiphilc materials. A common example of the functionalization of a water-insoluble material is the sulfonation of polystyrene... 

Ion-exchange resins have also served as catalysts [32-35]. However, the resin gets completely deactivated at around 200°C, and the safe working temperature is around 125°C. Strongly acidic resins are prepared by sulfonation of polystyrene gels. Strongly basic resins are obtained by the amination of chloromethylated resins by tertiary amines such as trimethyl amine ... 

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