Poly sulfonated monomers

Directly copolymerized sulfonated poly(arylene ether ketone) PEMs are also possible by employing a sulfonated dihalide ketone monomer (sodium 5,5 -carbonylbis(2-fluorobenzenesulfonate)), as first reported by Wang. ° The sulfonated monomer chemical structure is shown in Figure 20. 

Direct copolymerization of sulfonated monomers has been used to synthesize sulfonated poly (benzimidazoles), poly(benzoxazole)s, and poly(benzothia-zole)s. As an example, Kim et al. synthesized poly-(benzthiazole)s from 2,5-diamino-1,4-benzenedithiol dihydrochloride and either 2-sulfoterethphthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, or 2,4-disulfoisophthalic acid potassium salt in poly-phosphoric acid (PPA), as shown in Figure 34. Similar sulfonated poly(benzimidazole) and sulfonated poly(benzoxazole) ° structures have also been synthesized. A general synthetic scheme for each is shown in Figure 35. The stability of these polymers in aqueous acidic environments appears... 

Postsulfonation of polymers to form PEMs can lead to undesirable side reactions and may be hard to control on a repeatable basis. Synthesis of sulfonated macromolecules for use in PEMs by the direct reaction of sulfonated comonomers has gained attention as a rigorous method of controlling the chemical structure, acid content, and even molecular weight of these materials. While more challenging synthetically than postsulfonation, the control of the chemical nature of the polymer afforded by direct copolymerization of sulfonated monomers and the repeatability of the reactions allows researchers to gain a more systematic understanding of these materials properties. Sulfonated poly(arylene ether)s, sulfonated poly-(imide)s, and sulfonated poly(styrene) derivatives have been the most prevalent of the directly copolymerized materials. 

The sodium salts and the acids of poly-3(2-ethanesul-fonate) thiophene and poly-3-(4-butanesulfonate) thiophene are the first known examples of water soluble CPs many other examples of water-soluble, self-doped CPs are given in recent reviews. Indeed, it is well known that the incorporation of highly soluble sulfonate groups on the CP backbone is a common method of achieving water solubility in a doped CP. The two most popular routes are the use of sulfonated polymeric dopants and the polymerization of sulfonated monomers. 

Poly(N-vinylpyrrolidone), P(NVP), is a nonionic, water-soluble polymer with high thermal and hydrolytic stability (7-9). Copolymers of N-vinylpyr-rolidone (NVP) with various carboxylate and carboxylate-precursor monomers (e.g., acrylic acid, sodium acrylate, crotonic acid, itaconic acid, and maleic anhydride) are also well-known (10). In addition, the homo- and copolymerization kinetics of these monomers are well-established. On the other hand, reports of copolymerizations of NVP with sulfonate monomers are sparse 11, 12). This chapter describes the synthesis, kinetics, and reactivity ratios for the copolymerization of NVP and some of the newer sulfonate monomers. A comparison of some of the solution properties for such copolymers is also included. 

In blends of PPESK and sulfonated poly (ether ether ketone) (PEEK), both methanol permeability and proton conductivity increase nonlinearly with increasing content of PEEK. Sulfonated PAES copolymers obtained from sulfonated 4,4 -dichlorodiphenyl sulfone, 4,4 -dichlorodiphenyl sulf-one and phenolphthalein have been tested with respect to their use for direct methanol fuel cell application. The proton conductivity increases linearly with the degree of sulfonation, but the methanol permeability increases linearly up to 20 mol-% sulfonated monomer content. Above this level, a sudden increase in permeability is observed. This effect is referred to as percolation threshold. 

The desirable properties of Pis and poly(sulfone)s can be combined into a single resin, such as in a poly(etherimide sulfone)." These resins have low levels of residual volatile species and low levels of reactive groups. Thus articles may be prepared from these resins, which are essentially free of voids, bubbles, splay, silver streaks or other imperfections. Monomers that introduce the sulfone group into the polymer are shown in Table 15.4. 

Void-free fibers have been produced by incorporating hydrophilic comonomers, such as sulfonated monomers, acrylamide derivatives, and hydroxyalkyl acrylates [451]. Polymer blends are also effective in reducing macrovoids. Examples include blends of hydrophilic polymers such as polyvinyl methyl formamide [452], poly Ai-vinylpyrrolidone, and acryloni-trile-dimethylacrylamide copolymer [453,454]. Dense fibers can be produced by incorporating comonomers, such as vinylidene chloride, with small molar volumes relative to acrylonitrile. 

Sulfonated monomers were also used for the synthesis of sulfonated poly-imides [123,124]. hi particular, sodium salt of the sulfonated bis-4-[(3-aminophenoxy)phenyl]phenylphosphine oxide was used for the preparation of sulfonated polyimides [123]. 

Recently conjugated polyelectrolytes containing alkylsulphonic and alkyl-phosphonic groups have received considerable interest [176-180]. Sulfonate-substituted poly(p-phenylene) was prepared [ 176] using Suzuki co-polymerisation of 1,4-benzenediboronic acid with sulfonate monomer in three steps starting from 1,4-dimethoxybenzene ... 

Sulfonated polysulfones (sPSf) can be prepared by sulfonation of commercial polysulfones, such as Udel 1700 (Solvay), or poly(arylene ether sulfones) (PAES), leading to structures like that shown in Fig. 6.9a [7, 186]. Also, they can be synthesized by direct copolymerization of sulfonated monomers available commercially [7, 187, 188], to produce polymers with the structure shown in Fig 6.9b. 

The development of polyaryls, in particular polyetherketones (PEEK), as a substitute of perfluorinated polymers was mainly based on cost and stability considerations [1]. Sulfonated polyetherketones has been found to be durable under fuel cell operation conditions over several thousand hours [185]. Victrex Company is the main producer of PEEK polymer and its sulfonation can be performed directly on the polymer backbone or by polymerization of sulfonated monomers [7]. Hoechst-Aventis and Eumatech commercialize sulfonated PEEK (sPEEK) and sulfonated poly(phtalazinone ether ketone) (sPPEK) membranes for fuel cell applications [3]. 

Reynolds et al. [54] reported the electrochemical synthesis of self-doped, water-soluble, N-propanesulfonated poly(3,4-propylenedioxypy-rrole). The sulfonated monomer, N-propanesulfonate-substituted 3,4-propylenedioxypyrrole (N-PrS PProDOP) was prepared by treating 3,4-propylenedioxypyrrole with NaH in dry tetrahydrofuran and 1-propanesulfonate as shown in Figure 5.10. The poly(N-PrS PProDOP) films were synthesized in a mixture of propylene carbonate and water (94 6) with supporting electrolyte LiC104 in the potential range —0.4 to... 

Zhang et al. [151] used Ni(0)-catalyzed coupling copolymerization to synthesize a series of sulfonated fluorinated poly(p-phenylene-co-aryl ether ketone)s (SPP-co-PAEKs). Copolymerization with the sulfonated monomer 2,5-dichloro-3 -sulfobenzophenone (DCSB) and 2,2 - w[4-(4-chlorobenzoyl)]phenoxyl perfluoropropane (BCPPF) was carried out by varying the molar ratio of DCSBrBCPPF. The structure of SPP-co-PAEKs is shown in Scheme 2.35. 

Furthermore, Banerjee and group prepared sulfonated fluorinated poly(arylene ether sulfone) (IBQSH-XX) copolymers (where XX=20, 30, 40, 50, and 60 and DS=0.16, 0.26, 0.39, 0.47, 0.56, respectively) based on imidoaryl biphenol, namely, 3,8-few(4-hydroxyphenyl)-A -phenyl-l,2-naph-thaUmide (IB), by direct copolymerization with SDCDPS as the sulfonated monomer and QBF as the fluorinated monomer [160]. Sulfonated copolymers were obtained with M values in the range 41,200-60,200g/mol with D values in the range 0.96-1.89 the trend increased with an increase in the DS (0.16-0.56 as per H-NMR spectra). Scheme 2.36 shows a representative structure of sulfonated fluorinated poly(arylene ether sulfone) containing IB... 

Z. Qiu, S. Wu, Z. Li, S. Zhang, W. Xing, C. Liu, Sulfonated poly (arylene-co-naphthalimide) s synthesized by copolymerization of primarily sulfonated monomer and fluorinated naphthalimide dichlorides as novel polymers for proton exchange membranes. Macromolecules 39 (19)(2006) 6425-6432. 

Zhao et al. synthesized a series of sulfonated poly(benzoxazole thioether sulfone)s (SPTESBO-XX) by varying the molar concentration of sulfonated monomer, disodium 3,3 -disulfonated-4,4 -difluorodiphenyl sulfone (SDCDPS) with 2,2 -bis[2-(4-fluorophenyl) benzoxazol-6-yl] hexa-fluoropropane (6BO) and 4,4 -thiobisbenzenethiol (TBBT) (Figure 5.68) [108]. They also prepared another series (SPTESBO-HFB-XX) by incorporating... 

The methanol permeability through the proton exchange membranes was proportional to the proton conductivities, as shown in Fig. 4.16. That is, the proton conductivity has a trade-off in its relationship with the methanol permeability. Target membrane would be located in the upper left-hand comer, of which the fluorenyl copolymers show the same tendency. Series of sulfonated poly(aryl ether ketone)s membranes obtained by direct copolymerization using various sulfonated monomers are listed in Table 4.2. The water content and proton conductivities of these membranes are shown in Fig. 4.17. 

Poly(ether ether) ketone (PEEK) and poly(ether ether ketone ketone) (PEEKK) are highly stable polymers with good potential for application in DMFCs [10,17,18]. They are semicrystalline and display excellent chemical and thermal stability. They may be sulfonated through direct polymerization of sulfonated monomers or by postsulfonation, the latter again leading to materials with less tightly controlled degree and location of sulfonation, but with the attraction that it is a simple and low-cost approach [19]. 

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