Designing conjugated polymer-based functional materials via the incorporation of supramolecular complexities

Abstract

One of the major goals in molecule engineering is the creation of molecule- or polymer- based devices that mimic the integrated functions of their macroscopic (and often inorganic) counterparts. Because of their unique photophysical and/or redox properties, supramolecular systems and conjugated polymers (CPs) have emerged as the ideal candidates for such applications. This dissertation details the design and synthesis of various CPs with pendant supramolecular complexes. The marriage of these two materials should yield complex and unique properties that are not accessible from single-molecule systems. Chapter One is an introduction on conjugated polymers and their properties. The ease of synthetic modifications, coupled with their unique transport properties make CPs very desirable for the design of sensitive chemosensors. The incorporation of rotaxane moieties to poly(p-phenyleneethynylene)s will be described in Chapter Two. By design, the rotaxane groups behave as molecular recognition elements for the detection of small molecules. In addition, these bulky scaffolds prevent polymer aggregation. We turn our focus to the rotaxane monomers in Chapter Three. We investigate the photoinduced charge transfer interactions between donor and acceptor pairs within the rotaxane scaffold and examine the parameters that facilitate these interactions. Chapter Four describes our effort to encapsulate electroactive polymers using these bulky groups. As expected, insulation of conducting polymer severely limits the polymer's charge transport and leads to a dramatic decrease in the polymer's bulk conductivity. The tetrahedral binding site in the rotaxane group allows complexation of redox active metal ions.

(cont.) These ions provide critical interconnects and mediate interchain charge hopping. Chapter Five describes another conducting organic-metal hybrid system, wherein two distinct conducting polymers are configured in a cross-linked network held together by a rotaxane architecture. Anion interactions with the redox active metal ions modulate the redox properties of the metal centers, thereby affecting the polymer's conductivity.