The thesis describes investigations into the preparation and magnetic properties of new conjugated polymers, with pendant free radical sites, produced from substituted acetylenes. The first two chapters involve reviews of the literature concerning organic ferromagnetism and the preparation and structure of the materials produced by polymerizing phenylacetylene. The syntheses of esters of propiolic acid and propargyl alcohol, and their polymerization using metathesis catalysts are described in chapter three. The preparation of new substituted triphenyhnethanes and triphenylmethanols, and the syntheses of new ethynyl-substituted arylacetylenes, are described in chapters four and five, together with their full characterization. The polymerizations of phenylacetylene and the new substituted arylacetylenes using well-defined tungsten, molybdenum and rhodium catalysts are reported in chapter six, together with electron spin resonance and magnetic susceptibility studies. All the polymers produced in this study were found to be paramagnetic, and the main target polymer, poly((4-ethynylphenyl)diphenylmethyl) was found to display a reversible increase in spin concentration with increasing temperature. The conclusions drawn from these studies were that conjugated polyradicals were prepared, but that subsequent spin-pairing took place
