ABSTRACT

I. INTRODUCTION Conjugated polymers are polymers with conjugated double bonds in the main chains, which result in an extensively conjugated system with strong delocalization of electrons along the polymer chains. The more extended the conjugated system becomes, the smaller the energy difference between the ground and excited states. This highly polarizable electronic cloud responds nonlinearly to an applied external field and contributes to charge carrier mobility. Furthermore, such high polarizability is accompanied by a capability for ultrafast responses originating in the electron mobility. Accordingly, in addition to their inherent mechanical strength and processibility, conjugated polymers are characterized by large third-order nonlinear susceptibilities and optimal electrical activities, as compared with inorganic or organic crystal materials. Therefore, it is not surprising that conjugated polymers have attracted increasing interest in their great potential for high-technology applications, especially ultrahigh density memory and information storage materials. In recent years, a number of monographs on nonlinear optically and electrically active polymers, particularly conjugated polymers, have been published [1-14].