Ionic sulfonate monomers, copolymerization

In contrast, the other simple ionic sulfonate monomer, NaSS, copolymerizes with NVP with preferential incorporation of NaSS (rNvp = 0.084, Nass = 7.19) (Table I and Figure 2). Furthermore, there is significant drift in copolymer composition with conversion for this polymer (Figure 4). 

This chapter describes the synthesis, kinetics, and solution properties for copolymers ofN-vinylpyrrolidone (NVP) with sulfonate ionic and zwitterionic monomers. Examples of the sulfonate ionic monomers are sodium styrenesulfonate (NaSS) and sodium acrylamido-2-meth-ylpropanesulfonate (NaAMPS) an example of the zwitterionic sulfonate monomer is 2-hydroxyethyt)dimethyl(3-sulfopropyt)-ammonium inner salt, methacrylate (SPE). The NVP-NaAMPS monomer pair was exceptional, showing evidence for donor-acceptor character and an alternating tendency in copolymerization. The NVP copolymers containing simple sulfonate ionic monomers e.g., NaAMPS) showed polyelectrolyte solution properties. On the other hand, the NVP copolymers with zwitterionic sulfonate monomers showed antipoly electrolyte solution behavior. 

The rates of polymerization (R ) for the copolymerization of NVP and the various sulfonate monomers (simple ionic and zwitterionic) as a function of sulfonate content are shown in Figure 1. The for the copolymerization of NVP with the sulfonate monomers is... 

Another way to improve the solubility characteristics of hydrophobically associating polymers is through incorporation of water-soluble, ionic monomers into the polymer. Carboxylate functionality has been introduced into RAM polymers by either copolymerization with acrylic acid salt or by a postpolymerization partial hydrolysis of the acrylamide groups. Incorporating about 20 mol% sodium acrylate functionality, significantly improves solubility of these HRAM polymers. Sulfonate groups can be introduced by copolymerizing with a sulfonate monomer such as vinyl sulphonate or 2-acrylamido-2-methylpropane sulfonate, AMPS. We call these polymers SRAM. 

Ionomers have been prepared by two general routes (1) copolymerization of a low level of functionalized monomer with an oleflnlcally unsaturated comonomer or (2) direct functionalization of a preformed polymer. Almost all ionomers of practical Interest have contained either carboxylate or sulfonate groups as the ionic species. Other salts, such as phosphonates, sulfates, thloglycolates, ammonium, and pyridinium salts have been studied, but nowhere to the extent of the carboxylate and sulfonate anlonomers. (An anlomer is defined as an lonomer In which the anion is bonded to the polymer. Conversely, ionomers that have the cation bonded to the polymer are termed cationomers). Relatively little information is available on the structure and properties of these types of ionomers. 

Copolymerization with other water-soluble monomers is also carried out in a similar manner. Cationic polyacrylamides are obtained by copolymerizing with ionic monomers such as dimethylami-noethyl methacrylate, dialkyldimethylammonium chloride, and vinylbenzyltrimethylammonium chloride. These impart a positive charge to the molecule. Anionic character can be imparted by copolymerizing with monomers such as acrylic acid, methacrylic acid, 2-acrylamido-2-methyl-propanesulfonic acid, and sodium styrene sulfonate. Partial hydrolysis of polyacrylamide, which converts some of the amide groups to carboxylate ion, also results in anionic polyacrylamides. 

Special post-functionalizable copolymers have also been used to derive acid ionomers by hydrolysis, thus avoiding the difficulties of copolymerizing ionic and nonionic monomers. To this end there are many examples where carboxylic acid polymers are formed by hydrolyzing copolymers containing acrylate esters, acrylonitrile, or maleic anhydride. As described later, a sulfonic acid ionomer, Nafion, is formed by hydrolysis of tetrafluoroethylene copolymerized with a sulfonyl fluoride. 

Another possibility for producing stable PAN emulsions is to incorporate ionic or hydrophilic groups such as sulfonate or carboxylate groups into the polymer. This can be done by copolymerizing AN with monomers with adequate functions [885,886]. 

Many methods such as incorporation of hydrophilic nanoparticles or mesoporous materials into SPI membranes, block copolymerization, and structural modihcation of sulfonated diamine monomers have been attempted to enhance the proton conductivity of SPI membranes at low RHs. Among them, block copolymerization seems to be a promising method. Another strategy is to develop anhydrous proton-conducting membranes such as ionic liquids, which is a hot topic of current researches. 

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