Abstract
The aim of this work is to study, by direct techniques, the vexed question of the need of water as co-catalyst in cationic polymerizations and its fate in such systems. Polymerization of isobutylene in n-heptane proceeded with AlBr 3 and with BF 3 alone under rigorously dry conditions. With TiCl 4, water was needed for starting the polymerization. Using tritiated water there was no conclusive evidence of proton incorporation in polymer through initiation in any of the above systems. The role of water, in subanalytical amounts in the cases of AlBr 3 and BF 3 and in measurable amounts in the case of TiCl 4, is to cleave (or solvate) an ion pair of the type TiCl 3 + + TiCl 5 −. However, protons from water are found in the polymer structure, to the extent of one or a few per 100 polymer chains in the cases of AlBr 3 and BF 3, and in the range of a fraction of one or one per polymer chain in the case of TiCl 4. Three possibilities are given for proton involvement in polymer structure by reactions other than proton initiation.
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