The polymerisation behaviour of p-quinodimethane systems: Verification of radical and anionic mechanisms in the Sulfinyl and the Gilch route

The aim of this research was to elucidate the polymerisation mechanism of p-quinodimethane-based routes towards PPV derivatives. A first mechanistic study was performed on the Sulfinyl route towards PPV precursors in dipolar aprotic solvents (DAS). The presence of p-quinodimethane systems is confirmed by UV-vis and NMR. Addition of TEMPO and water indicate that in DAS, two distinct polymerisation mechanisms can occur simultaneously, giving rise to a bimodal molecular weight distribution. Apart from a radical mechanism that is responsible for the formation of a higher molecular weight polymer, also an anionic polymerisation mechanism can take place, which results in oligomer formation (Mw < 10 000 g/mol). Results from temperature and concentration variation experiments confirm the mechanism proposals and help to gain insight in the competition between both mechanisms, at the same time offering ways to control each of them. Extension to other monomers and solvents resulted in the general conclusion that the competition between the anionic and radical mechanism strongly depends on the reaction conditions, more specific on the solvent and monomer ring substituents. In standard conditions, the main polymerisation mechanism of the Sulfinyl route is radical of nature yielding high(er) molecular weight polymer. In a second mechanistic study on OC1C10-PPV the polymerisation mechanism of the Sulfinyl and the Gilch route---both p-quinodimethane-based polymerisations were linked. Multiple polymerisations were performed in apolar, aprotic solvents in the presence of different types of additives, chosen to anticipate upon recent publications, and the effects were evaluated by means of size exclusion chromatography (SEC). In contrast with the Sulfinyl route, the Gilch route proved to give irreproducible results when performed in the solvent THF. Therefore, a reproducible Gilch procedure was developed in dioxane at room temperature. For the Sulfinyl as well as the Gilch route all observed additive effects point at a radical nature of the polymerisation mechanism responsible for the formation of high molecular weight polymer. Hence, the results lie in the line of expectation elaborated in the first mechanistic study, and are inconsistent with an anionic polymerisation mechanism, questioning some conclusions of others. During this mechanistic study also some new features of gelation behaviour were observed and found to be originating from chemical as well as physical network formations. The last chapter concerns the use of the LS-SEC characterisation technique in a study of the structural conformation and differences in branching degree of various Sulfinyl and Gilch polymers.