The properties of polymer networks composed of flexible monomer units are well understood, however only limited investigations into the properties of networks composed of rigid rodlike monomer units linked by flexible netpoints have been carried out to date. The aim of this work was to develop a method of synthesising processable difunctional rigid rodlike molecules which could be incorporated into polymer networks; the physical properties of the polymer networks would then be investigated. The following thesis describes the background to both processable rigid rod polymers and to rigid rod polymer networks. The route utilised in an attempt to synthesise processable, difunctional rigid rodlike materials is described and details of the characterisation and properties of those difunctional rods successfully synthesised are given. Attempts to incorporate the difunctional rods into polymer networks are discussed. A series of rigid rod polymers, in the class of either poly(arylene diynylene)s or poly(arylene ynylene)s, were synthesised. The materials were either unsubstituted linear polymers, linear polymers substituted with alkyl side chains, or polymers containing a bend via an ether or a ketone link. The synthesis and molecular structural characterisation of the polymers is described and investigations of their solubilities, thermal properties and, in some cases, bulk and LB film ordering behaviour are discussed.