Synthesis of poly(arylene sulfide)s by cationic oxidative polymerization of diaryl disulfides

Alkyl-substituted poly(arylene sulfide)s (PASs) are prepared by the oxidative polymerization of diaryl disulfides with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The structures of the formed poly(arylene sulfide)s are confirmed by spectroscopic measurements. The linear structure of poly(2-methyl-1,4-phenylene sulfide) is confirmed by comparing its spectroscopic data with those of the polymer prepared from bis(2-methylphenyl) disulfide, bis(3-methylphenyl) disulfide and (4-bromo-2-methylthiophenoxy) copper salt. Bis(2,5-dimethylphenyl) disulfide is easily polymerized to poly(2,5-dimethyl-1,4-phenylene sulfide) with high yield and high melting point in comparison with the other methyl-substituted poly(arylene sulfide)s, due to the symmetry of the polymer structure. The polymerization reaction, with the exception of bis(3,5-dimethylphenyl) disulfide, produces low molecular weight polymers because of the solvent insolubility of PASs and the low reactivity of diaryl disulfides. Soluble poly(2,6-dimethylphenylene sulfide) is isolated by the polymerization of bis(3,5-dimethylphenyl) disulfide as a white powder with ca. 3 × 10⁴ weight-average molecular weight.