This thesis is mainly concerned with the preparation of a range of novel poly(thiophene)s incorporating fused redox active substituents. Confirmation of the structure of the monomer units was carried out by NMR ([1]H and [13]C), mass spectral analysis, C,H,N analysis and where applicable, single crystal X-ray structural determination. Electrochemical studies on a number of the systems synthesised was also investigated, and voltammetric measurements were made using cyclic voltammetry. The novel fused TTF-thiophene monomer 2,5-dibromothieno[3,4-d]-1,3-dithiole-2-ylidine-4,5-bis(hexylsulfanyl)-1,3-dithiole has been prepared and polymerised using Yamamoto methodology. The resulting polymer exhibits significant electrical conductivity in the neutral state and is the first example of an annelated TTF-thiophene polymer. The development of terthiophene and bithienyl furan derivatives bearing the synthetically versatile 1,3-dithiole-2-thione functionality is also described, and conversion to a tetrathiafulvalene derivative via a phosphite mediated coupling reaction has been investigated. However, electropolymerisation of this system was unsuccessful which highlights unfavourable interactions arising between the two redox units. Synthesis of analogous terthiophene derivatives bearing a fused dithiino spacer group between the polythiophene chain and the 1,3-dithiole-2-thione moiety is also discussed. A series of bis-substituted alkylsulfanyl terthiophene derivatives have been synthesised which can be electrochemically polymerised; a hexylsulfanyl derivative can also be polymerised chemically. Preliminary photoinduced absorption studies show that an ethylene bridged derivative exhibits interesting properties, which has been studied in collaboration with the Johannes Keppler University, Linz, Austria. A polythiophene bearing a fused quinoxaline moiety has been prepared and electropolymerised to form polymer films which are capable of molecular recognition of transition metal cations. This is the first example of a conducting polymer which is able to detect selectively and reversibly Hg[2+] and Ag[+] ions in aqueous and organic media.