Photoinitiated cationic polymerization with triarylsulfonium salts

Triarylsulfonium salts Ar3S+MXn− with complex metal halide anions such as BF4−, AsF6−, PF6−, and SbF6− are a new class of highly efficient photoinitiators for cationic polymerization. In this article we describe several synthetic routes to the preparation of these compounds along with their physical and spectroscopic properties. Mechanistic studies have shown that when these compounds are irradiated at wavelengths of 190–365 nm carbon-sulfur bond cleavage occurs to form radical fragments. At the same time the strong Brϕnsted acid HMXn, which is the active initiator of cationic polymerization that takes place in subsequent “dark” steps, is also produced. A study of the parameters that affect the photolysis of triarylsulfonium salts is reported with a measurement of the absolute quantum yields. The cationic polymerizations of four typical monomers—styrene oxide, cyclohexene oxide, tetrahydrofuran, and 2-chloroethyl vinyl ether—with triarylsulfonium salt photoinitiators are described.

[1]  James V. Crivello,et al.  Diaryliodonium Salts. A New Class of Photoinitiators for Cationic Polymerization , 1977 .

[2]  S. Ōae,et al.  Sulfilimine. I. Synthesis and Formation Mechanism , 1969 .

[3]  N. Turro,et al.  Molecular photochemistry. XXIV. Photocycloaddition of acetone to 1,2-dicyanoethylene , 1970 .

[4]  P. Reilly,et al.  Chain propagation constants in the cationic polymerization of styrene , 1962 .

[5]  W. E. Mcewen,et al.  Syntheses and reactions of triarylsulfonium halides , 1968 .

[6]  W. E. Mcewen,et al.  Photolysis of triarylsulfonium salts in alcohol , 1970 .

[7]  S. Okamura,et al.  Rate constant of propagation reaction in stationary state of cationic polymerization. Part VI.1 Theoretical consideration about the propagation reaction of the cationic polymerization , 1963 .

[8]  T. Saegusa,et al.  Determination of concentration of propagating species in cationic polymerization of tetrahydrofuran , 1968 .

[9]  B. Wildi,et al.  The Preparation of Triarylsulfonium Halides by the Action of Aryl Grignard Reagents on Diphenyl Sulfoxide , 1951 .

[10]  A. Nesmeyanov,et al.  Heterolytic decomposition of onium compounds (diphenyl halogenonium and triphenyloxonium salts) , 1957 .

[11]  T. Ōishi,et al.  Activation of Weak Organic Bases. III. The Reactions of Divalent Sulfides with Acid Chlorides in the Presence of Friedel-Crafts Catalysts , 1971 .

[12]  James V. Crivello,et al.  A new preparation of triarylsulfonium and -selenonium salts via the copper(II)-catalyzed arylation of sulfides and selenides with diaryliodonium salts , 1978 .

[13]  N. Turro,et al.  The Photocycloaddition of Acetone to 1-Methoxy-1-butene. A Comparison of Singlet and Triplet Mechanism and Singlet and Triplet Biradical Intermediates , 1970 .

[14]  H. Heine,et al.  Aromatic Keto Compounds as Initiators in Photopolymerizations , 1972 .

[15]  G. A. Berchtold,et al.  Photochemical reactions of phenacyl- and benzylsulfonium salts , 1970 .

[16]  J. C. Brosheer,et al.  Fertilizer Technology, Ammoniation of Nitric Acid Extracts of Rock Phosphate , 1958 .

[17]  M. Asai,et al.  Photoreactions of N-Vinylcarbazole Induced by Metal Salts. III. Photocationic Polymerization Senitized by Tetra-n-butylammonium Tetrachloro- and Tetrabromoaurate(III) in Aprotic Solvents. On the Mechanism of Initiation , 1973 .