A NEW, GENERAL-APPROACH TO TUNING THE PROPERTIES OF FUNCTIONALIZED POLYTHIOPHENES - THE OXIDATIVE POLYMERIZATION OF MONOSUBSTITUTED BITHIOPHENES

A new synthetic approach to functionalized polythiophenes utilizing 4- substituted 2,2'-bithiophenes is described. The general utility of thi s approach is illustrated by the preparation of the representative pol y(4-substituted 2,2'-bithiophenes) (where substituent = octyl, hydroxy methyl, carboxy, carbomethoxy, or acetoxyethyl), The use of monofuncti onalized bithiophenes as monomers has a number of advantages over trad itional S-substituted thiophene precursors. These advantages include d irect oxidative polymerization of electron-poor monomers, selective ox idative polymerization in the presence of oxidatively sensitive side c hains, polymerization without oxidative degradation of the backbone, a nd production of polymers with decreased side-chain density. The combi nation of these advantages allows the facile oxidative polymerization of monomers containing a large variety of functional groups. The reduc tion in side-chain density results in polymers with increased effectiv e conjugation lengths as evidenced by their improved electrical and op tical properties.