Novel thiophene-containing semiconducting polymers for organic electronic applications

The pi-conjugated polymers such as polythiophenes (PT's) represent a class of organic-based materials that possess unique optical and electronic properties. The electronic properties of such conjugated macromolecules are primarily governed by the chemical structure of the polymer backbone itself. Synthesizing new conjugated polymers by further functionalizing precursor monomers is an attractive route to enhance optical and electronic properties of these materials. The introduction of an unsaturated side chain will encourage solid-state pi-pi stacking and allow for facile post polymerization chemical modification. Additionally, a number of other tools can be employed in order to adjust the electronic properties of conjugated polymers. Tuning the band gap of conjugated polymers and introduction of liquid crystalline segments are two important strategies to tune the opto-electronic and physical properties of these materials. The research efforts of this thesis have been directed towards the design, synthesis, and electronic characterization of well-defined novel semiconducting thiophene-based polymers.;Chapter 1 focuses on the synthesis and characterization of novel poly (3-alkenylthiophene) derivatives. The copolymers have been investigated as the active layer in organic field-effect transistors. The surface morphology of polymer films has been analyzed by AFM microscopy. Chapter 2 describes the synthesis of novel semiconducting polymers with extended electron delocalization. Semiconducting polymers containing a fused benzodithiophene core with phenylethynyl substituents were prepared and characterized. The electronic properties and morphologies of the synthesized homopolymers and copolymers containing benzodithiophene with phenylethynyl substituents were correlated with their molecular structures. The synthesized polymers have a lower band gap due to the extended electron delocalization.;Chapter 3 describes the synthesis of a novel rod-rod di-block copolymer containing a liquid crystalline segment and semiconducting poly(3-hexylthiophene). Poly(3-hexylthiophene)-b-poly(gamma-benzyl-L-glutamate) di-block copolymer was synthesized and characterized. This polymer is capable of participating in secondary interactions through hydrogen bonding with specific analytes that can alter the morphology. The conformation is tunable between rod-rod and rod-coil depending on the polarity of the solvent medium, which would allow more control over the structure formation.