Phenacyltriphenyl phosphonium, phenacyltriphenyl arsonium and acyltriphenyl phosphonium salts containing the anion, SbF6, are useful photoinitiators for cationic polymerization of cyclohexene oxide at 25 Β°. Thermal polymerization using these salts was examined in dichloromethane at 50 and 70. It was found that increases from 50 to 70 Β° almost doubled the polymer yield. Experimental data are presented comparing the efficiency of these salts as photoinitiators or thermal initiators, the effects of photolysis duration, and initiator concentration. Irradiation of the reaction mixture was shown to be the most efficient means of polymerization using these initiators. INTRODUCTIONcyclohexene ~ O _ Cationic polymerization of oxide has Ph3-PΓ· CH Xx~._~ H2P+-Ph 3 2X"
been demonstrated using triphenylmethyl hexafluoroarsinate [1] and organozinc compounds such as diethyl zinc at 0 Β° in dichloromethane [2]. The polymer-X" = at--, PF 6-, SbF'~, BF4, AsF~ization of cyclohexene oxide using aluminium aikyl catalysts at -78 Β°, where high molecular polymer was 1 obtained, was studied by Bacskai . Ultraviolet irradiation of cyclohexene oxide in the presence of 1-iodocyclohexene gives polycyclohexene oxide and mechanism of polymerization; it was found that an initiation mechanism has been proposed by photosensitization with pyrene or phenothiazine in-Kinstle and Tufts .
creases the polymerization rate. Photoinitiated cationic polymerization of cyclo-This paper reports that phenacyl triphenyl arsonhexene oxide using thermally stable onium initiators, ium and acyltriphenyl phosphonium salts containing such as diaryliodonium and triarylsulfonium salts the anion, SbF6, are useful photoinitiators for the having complex metal halide anions was reported by cationic polymerization of cyclohexene oxide at Crivello and Lam [5].
25 Β°. Comparative studies are also reported between Hayase et al. reported on the photopolymeriz-the thermal and photochemical efficiency of these ation of cyclohexene oxide with a triarylsilyl ether initiators having the same anion. (Ph3SiCOPh)-aluminum complex-alcohol catalyst system, and also a catalyst consisting of alkyl aluminum, alkyl aluminum modified by active hydrogen EXPERIMENTAL PROCEDURES compounds [7] and o-nitrobenzyltriphenylsilyl ether which photochemically decomposes to give triphenyl-Materials and procedures silanol, that initiate the polymerization of the epoxide Phenacylbromide, acyltriphenyl phosphonium salts, triupon reaction with an aluminum compound as phenylarsine, triphenylphosphine, benzene, potassium hexashown in Scheme 1 [8]. These studies showed that fluorophosphate (KPF6) and potassium hexafluoroantiphotopolymerization was influenced by the wave-monate (KSbF6) were all of reagent grade quality (Fluka) length of light used and the structures of the alumi-and used without further purification. num compound and the triarylsilyl ether.
Cyciohexene oxide (Fluka) and dichloromethane (Fluka)
were dried over calcium hydride and distilled before use.