Keele Research Repository

The work described in this Thesis is concerned with the identification of the chain carriers in polymerisation systems involving acid and Lewis-acid catalysts.

In a preliminary study of the spectroscopic and conductimetric properties of carbonium ions derived from carbinols and olefins it was found that the phenylethanols are dehydrated by strong mineral acids to the corresponding olefins before protonation takes place (Chapter Two). The protonation of triphenylethylene gives a classical carbonium ion which can react with excess of olefin to produce a radical ion (Chapter Three).

The protonation of tetraphenylethylene gives a highly conjugated carbonium ion in which the proton is attached to one of the phenyl groups and not to the ethylenic double bond (Chapter Three).

The kinetics of the protonation of styrene by excess anhydrous perchlorio acid and the spectroscopic properties of the 1-phenylethyl carbonium ion obtained in this reaction have been studied (Chapter Four).

Styrene is polymerised by perchloric acid and other acidic catalysts without formation of carbonium ions, and it has been shown that, in the case of HCl04, the intermediate responsible for the polymerisation is the 1-phenylethyl perchlorate ester. The polymerisation kinetics have been investigated and the results agree with those of other authors where they overlap. Other monomers, acenaphthylene and N-vinylcarbazole, behave similarly to styrene (Chapter Four).

These ester-catalysed polymerisations have been called
pseudocationic. The pseudocationic polymerisation of styrene by perchlorio acid is followed by formation of styryl ions, a complicated reaction which has been studied in some detail.

True cationic polymerisation has also been observed during this work, and it was found that carbonium ions are very powerful chain carriers giving reaction rates at least 100 times greater than the corresponding esters (Chapter Four).

In the course of this work the spectra of many carbonium ions have been fully characterised.