THERMALLY INDUCED CATIONIC POLYMERIZATION OF DIVINYL ETHERS USING IODONIUM AND SULFONIUM SALTS

Cationic polymerization of diethyleneglycoldivinyl ether was thermally induced by diphenyliodonium, alkylbenzylsulfonium, and phenacyltetramethylenesulfonium salts. The reactivity was enhanced by using free radical sources in combination with diphenyliodonium or phenacyltetramethylenesulfonium salts. Even at low onium salt concentrations extremely reactive formulations could be obtained, e.g., the polymerization was complete within 1 minute at 100-degrees-C when using the most reactive salts. Polymerizations were induced at temperatures ranging from 50 to 180-degrees-C. The counterion, supplied by the onium salt, strongly influenced the appearance of the resulting crosslinked polymer: salts containing SbF6- usually gave highly discolored samples due to the large heat evolution during polymerization whereas polymerization with PF6- proceeded smoother resulting in transparent, uncolored polymers. The purity of the monomer greatly affected the initiation by the diphenyliodonium and phenacyltetramethylenesulfonium salts. Adventitious radical sources, e.g., hydroperoxides on oxidized monomer, lowered the activation temperature but also led to poor storage stability of these formulations.