Monomers phenylene sulfide

Figure 5.2 Monomers Used for Poly(phenylene sulfide)...

In the same way, poly(phenylene sulfide-phenyleneamine-phenylene-amine) (PPSAA) has been synthesized via a soluble precursor polymer through an acid-induced polycondensation reaction of A-(4-methylsulfin-yl)phenylene-A -phenyl-hd-phenylenediamine." The polymerization is performed by treating the monomer with methanesulfonic acid for 24 h at room temperature. The demethylation is performed in refluxing pyridine. Precipitation in methanol yields the PPSAA as a light purple solid in 91% yield. 

Perhaps the first indication of chain-growth polymerization was realized in the synthesis of poly(phenylene sulfide) using p-halothiophenol salts. For certain monomers, it was realized that the pol5mier chain end groups were more reactive than the monomers. Later, in the polycondensation of chlorophenylsulfonyl phenoxide, an increased reactivity of the polymer end group was detected. The reaction scheme is shown in Figure 7.2. The polymeric end group reacts ca. 20 times faster than the monomer. 

Crosslinked sulfonated poly(phenylene sulfide sulfone nitrile) has been prepared for its potential use for direct methanol fuel cell membrane applications [91]. The monomers and the synthesis are shown in Figure 5.9. 

Poly(ether sulfide)s were also prepared by a precursor route, 4,4 -Difluorodiphe-nylsulfoxide (234) was used as electrophilic monomer in combination with hydroquinone or 4,4 -dihydroxybiphenyl. The resulting poly(ether sulfoxide)s were then reduced in tetrachloroethane by means of oxalylchloride and tetrabutylammonium fluoride (235) [357]. Furthermore, the preparation of sulfonated poly(phenylene-sulfide) should be mentioned. SO3 served as sulfonating agent and the sulfonated polysulfide was treated with SOCI2, whereby a poly sulfide with SO2CI and Cl substituents was obtained [358]. 

Early work performed by Lenz et al. in the 1960s demonstrated this approach by using electrophilic aromatic substitution to produce poly(phenylene sulfide) [91] (Scheme 1.10). In this case, an aryl halide is the electrophile, which is substituted by the metal thiophenoxide nucleophile. In the monomer, the metal sulfide is a strong electron-donating group, which deactivates the para position where electrophilic substitution must take place. Conversely, the polymer chain end is only weakly deactivated by the sulfide bond, rendering the polymeric aryl halide more reactive than the monomeric aryl halide. Unfortunately, Lenz was unable to characterize molecular weight distribution due to the insolubility of the resultant polymers. 

Mellace et al. [206] reported the preparation and characterization of hb poly (phenylene sulfide) (hb-PPS) utilizing 3,4-dichlorobenzenethiol as the AB2 monomer. Furthermore, polymerization of 3,4-dichlorobenzenethiol as AB2 monomer with 1,3,5-trichlorobenzene as a multifunctional core (B3 monomer) was utilized to prepare hb-PPS by the AB2-fB3 approach. Polymerization of commercially available 3,4-dichlorobenzenethiol was accomplished utilizing anhydrous K2CO3 as a base in the presence of DMF or NMP as solvent. The monomer combination is presented in Scheme 19. When DMF was used as solvent, the reaction was carried out at 100°C for 24 h and in NMP the reaction was carried out at 150°C for 8.5 h. 

A different structural modification, which is mainly based on lowering the chain stiffness and as a result also on reducing the intermolecular interactions, is the incorporation of kinked and double kinked comonomers (Fig. 2b and c). Typical monomers with kinks are meta-substituted phenylene derivatives or 4,4 -functionalized biphenyl-ethers and 4,4 -functionalized biphenyl-sulfides. Monomers with double kinks are,... 

Researchers at DnPont used hydroquinone as5mimetrically substituted with chloro, methyl, or phenyl substituents and swivel or nonlinear bent substituted phenyl molecnles such as 3,4- or 4,4 -disubstituted diphenyl ether, sulfide, or ketone monomers. For example, poly(chloro-l,4-phenylene- ra/ s-hexahydroterephthalate) and related copolymers were prepared in a melt-polymerization process involving the reaction of molar equivalents of the diacetoxy derivatives of diphenols and hexahydroterephthalic acid (19). During polymerization, a phase transition from isotropic to anisotropic occurred soon after the rapid melting of the intermediates to form a clear, colorless liquid. 

A fast atom bombardment spectrum of silver doped poly(m-phenylene hexamethyl sulfide) is shown in Figure 2.7. Peaks due to cyclic monomers are seen at m/z 225 (MH" ), miz 331 (MAg ) and the dimer miz 555 (M Ag ) can be noted indicating in this case a negative interaction between the macrocycles and the silver nitrate. 

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