The synthesis of some imides including bis-maleimides, bis-citraconimides, and bis-nadimides containing four phenylene rings, some of which are novel, is reported. These compounds were purified using preparative high performance liquid chromatography giving compounds of a high purity not commonly observed for monomers of this type. Chapter 2 describes the results of the synthesis and purification of the compounds. The unsaturated imides were heated under nitrogen to obtain polymers. Characterisation of both the monomers and polymers by a variety of techniques is described. The major impurity in the crude bis-citraconimides was isolated and characterised. It was found to be a structural isomer of the desired compounds, the citraconimide-itaconimide mixed imide. Chapter 3 describes the study of the bis-imides, both impure and pure samples, using differential scanning calorimetry. The purity of the compounds was shown to affect temperatures at which both liquifaction and polymerisation of these monomers occurred. Within the series of pure bis-maleimides and citraconimides studied it is noted that those bearing m-substituted rings liquified at much lower temperatures, and samples of these were apparently much less crystalline. Polymerisation rate was the same for m- and p-isomers, citraconimides were less reactive than maleimides. In very highly pure bis-maleimides a second exothermic reaction was observed. The DSC data obtained was analysed to obtain Arrhenius parameters useful in predicting the relative rates of thermal polymerisation of some pure and impure samples of the compounds. The overall order of reaction was found to vary during the course of the reaction. Chapter 4 describes the thermogravimetric analysis of polymer samples, and the bis-nadimide monomers. The results give some indication of thermal and thermo-oxidative stability of the polymers. Experimental details are given in Chapter 5.