Synthesis and characterization of conducting polymers with new architectural motifs

Abstract

Chapter one has a brief discussion of polythiophene and the important factors to consider with polythiophene synthesis and characterization. In chapter two, a variety of polythiophene derivatives that incorporated 2,2'-biphenyl units into the polymer main chain were synthesized. The potential utility of the 2,2'-biphenyl unit as a scaffold to facilitate the t-n interactions between thiophene oligomers was explored. The linkage of the thiophene to the biphenyl was varied between the a- or O-positions to assess how this variable affected the overall properties of the resulting polymers. The n-linked thiophene monomers produced highly cross-linked polymers and the electroactivity of these polymers depended on the length of the thiophene fragment in the corresponding monomer. The a-linked thiophene monomers produced segmented linear conjugated polymers and the polymers' segmentation dominated the resulting electroactivity. A model study demonstrated that through-space interactions between the oligothiopene fragments of the 2,2'-biphenyl monomers did occur. In chapter three, a synthetic scheme was developed to generate 2,2'-biphenyl monomers with long alkyl chains from which soluble polymers could be generated.

(cont.) The synthetic scheme was also utilized to produce a monomer that could be electrochemically cross-linked in a controlled fashion. In chapter four, a variety of polythiophene derivatives that incorporated azaferrocenes complexes into the main polymer chain were synthesized. These polymers were then used to ascertain the effect of a n-bound metal on the main chain of a conducting polymer. The oxidation of the metal centers in the polymer produced a significant change in the conductivity of the polymer film. Changing the length and oxidation potential of the polythiophene section of the monomer appeared to alter the charge delocalization of the polymers. In chapter five, a series of polythiophene derivatives containing cyclobutadiene cobalt cyclopentadiene complexes in the main polymer chain were synthesized. The viability of the electropolymerization of the complexes was determined by the relative position of organic section's oxidation potential versus the oxidation of the metal centers. The metal coordinated cyclobutadiene ring of the complex appeared to have a modest charge transport ability.