Synthesis of pi conjugated polymers for use in photovoltaic and electrochromic applications

Abstract

Conjugated polymers are currently being used for a wide range of electronic applications. In this thesis, we studied two different synthetic approaches that lead to novel monomers and polymers that can be potentially used in electrochromic, or photovoltaic devices. The first approach described in this thesis is the utilization of olefin cross metathesis to create a family of dithienogermole (DTG) monomer derivatives in which synthetic control of the solubilizing side chains is achieved through an alkenyl building block. This alkenyl intermediate allows one to functionalize the DTG moiety though olefin cross metathesis to obtain a wide range of alkyl chain lengths and pendant functionalities on the polymer backbone. This work lead to the first example in the literature in which the synthesis of DTG moieties was not limited by the chain length of the solubilizing alkyl units. It provides a route that avoids the use of distillation for the purification the DTG monomer, allowing for the synthesis of a wide range of DTG derivatives that were previously unobtainable though the conventional synthetic methods. Finally, in this thesis we also describe the work of the use of direct (hetero)arylation polymerizations (DHAP) as a means of obtaining 3,4-propylenedioxythiophene-based conjugated polymers for use in electrochromic applications. This synthetic method offers a rapid route to achieving polymers in high yields with simplified purification procedures and low residual metal content, as determined by inductive coupled plasma-mass spectrometry (ICP-MS). The studied polymers possess comparable electrochromic properties to those previously reported by the Reynolds group, implying that their switching ability from a colored to a transmissive state is independent of the residual metallic impurities.