Oxidative polymerization of diphenyl disulfide under molten conditions at moderately elevated temperatures gave poly(1,4-phenylene sulfide) (PPS), using a vanadyl complex–strong acid catalyst with oxygen as the ultimate oxidant. Origin of the selectivity of the sulfonium electrophile for the formation of the 1,4-thiophenylene chain, characterized by the presence of a disulfide bond at the chain end, was determined by the behavior of polymerization and structural analysis of the product together with a computational calculation, which revealed a unique chain growth-type polycondensation process.

The first VO(salen) catalyzed oxidative polymerization of PhSSPh and bromanil-assisted acceleration of the polymerization were reported.

In the presence of diphenyl sulfide, oxygen-oxidative polymerization of diphenyl disulfide gave highly crystalized poly(1,4-phenylene sulfide) (PPS) using a vanadyl-strong acid catalytic system. Effect of the sulfide, which was inactive to the vanadyl catalyst, was ascribed to the enhancement of the electrophilic substitution with a sulfonium cation onto a thiophenyl end. The finally purified PPS showed high crystallinity (Xc = 44%), which was even higher than that of the reagent grade PPS produced by the conventional polycondensation process.

Front Cover: The first protic‐acid‐free oxygen‐oxidative polymerization of diphenyl disulfide to yield poly(1,4‐phenylene sulfide), catalyzed by a vanadyl complex and a borate compound, is accomplished. Triphenylmethylium tetrakis(pentafluorophenyl)borate, having a non‐coordinating anion, is especially effective for the polymerization. Catalysis by the tetrafluoroborate salt is established at elevated temperatures where the anion is found to be less coordinative. Further details can be found in the article by F. Aida, S. Yamaguchi, Y. Takatori, K. Nagamatsu, D. Kiyokawa, K. Oyaizu,* and H. Nishide,* on page 1850.

A newly established catalyst system for oxygen-oxidative polymerization of diphenyl disulfi de is reported. Combination of vanadyl compounds (e.g., VO(acac) 2 ) and triphenylmethylium tetrakis(pentafl uorophenyl)borate (TrB(C 6 F 5 ) 4 ) proceeds the polymerization to give poly(1,4-phenylene sulfi de) (PPS) at 100 °C. When triphenylmethylium tetrafl uoroborate (TrBF 4 ) is applied with vanadyl tetraphenylporphyrin (VO(TPP)) or N,N′ -(ethylenebis(salicylid eneaminato))oxovanadium (VO(salen)), PPS is also given via polymerization under conditions near 160 °C. Combination of the vanadyl complex and the borate affords the fi rst protic-acid-free catalytic system for the polymerization of the disulfi de, suggesting the overall reaction to produce PPS and H 2 O from O 2 and protons that are eliminated from the monomer.