Thienylenevinylene derived polymers have been extensively investigated for use in electrooptical devices. A precursor route and direct polymerisation methods to soluble thienylenevinylene homopolymers have been developed. These synthetic routes routinely yield little control of the polymer molar mass distribution and require further purification to remove the impurities and small oligomers. In this thesis, a new route to produce soluble polythienylenevinylenes is described via a ring-opening metathesis polymerisation (ROMP) it is extended to the preparation of PPV-PTV copolymers and block copolymers with a well-defined chain structure. Chapter 1 introduces the fundamentals of conjugated polymers and the general principle of the applications in organic light-emitting diodes and organic photovoltaic devices. The synthetic methods used to prepare poly(para-phenylenevinylene)s and poly(thienylenevinylene)s are introduced. Alkene metathesis is described and its use in ROMP examined. Chapter 2 focuses on the preparation and characterisation of poly(3,4-dialkylthienylenevinylene)s. Chapter 3 describes the preparation and characterisation of poly(para-phenylenevinylene-co-3,4-dioctylthienylenevinylene) copolymer. In Chapter 4, the preparation and characterisation of poly(para-phenylenevinylene)-block-poly(thienylenevinylene) copolymer are discussed. An overview of the work in this thesis and the potential for future work are presented in Chapter 5. All the experimental procedures are described in Chapter 6.