Organic halides as cationic initiators

The reaction of organohalides with silver hexafluorophosphate or silver perchlorate in THF to generate cationic initiators has been examined. Reactivities in the order fluoride < chloride < bromide < iodide and alkyl « allyl ≈ benzyl were found. Selected halides were examined in more detail, and it was shown that under controlled conditions living poly THF could be obtained. This was difunctional if p-xylylene dibromide or 1,4-dibromobut-2-ene was used, or monofunctional with conventional monohalides. Molecular weight distributions of MwMn ⩽ 1.2 were obtained. Experiments demonstrated that allyl bromide and p-methylbenzyl bromide initiated THF polymerization entirely additively but, with isopropyl iodide at room temperature, up to 10% proton transfer occurred.