Gas-free initiators for high-temperature free-radical polymerization

Quaternary ammonium persulfates as free-radical initiators for high-tempera ture polymerization are synthesized and their shelf-life stability investig ated. These initiators do not have gaseous byproducts and are therefore ide al for frontal polymerization, a process in which polymeric materials are p roduced via a thermal front that propagates through the unreacted monomer/i nitiator solution. Quaternary ammonium persulfate initiators offer addition al qualities such as high solubility in organic media and low volatility, w hich are desirable for frontal polymerization. The initiators are synthesiz ed using two procedures, and the initiating efficacy of the respective prod ucts is compared to a peroxide initiator in the frontal polymerization of 1 ,6-hexanediol diacrylate. Of all the quartenary ammonium persulfates synthe sized, tricaprylmethylammonium (Aliquat) persulfate (APSO) is the best init iator for frontal polymerization because it is soluble in organic media, is very reactive, and does not produce volatile byproducts under decompositio n. A study of the decomposition kinetics of APSO is performed, and frontal polymerization is proposed as a quicker analytical technique to assay the p urity. (C) 2000 John Wiley & Sons, Inc.