Optically transparent, water processable intrinsically conductive polymers

Date of Completion

January 2006

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

The first part of this dissertation has been focused on the preparation of stable dispersion of low band gap conducting polymer consisting of thieno[3,4- b]thiophene (T34bT) in water. We studied the oxidative chemical dispersion polymerization of T34bT in water using three different chemical oxidant systems in the presence of the polyelectrolyte poly(styrenesulfonic acid). The resulting polymer (PT34bT-PSS) is rendered a colloidal dispersion in water with a particle size diameter ranging between 180 and 220 nm depending on the oxidant used for polymerization. PT34bT-PSS films have band gaps of ca. 1 eV (1260 nm) with absorption maxima ranging from 1.4 eV (912 nm) to 1.7 eV (724 nm). PT34bT-PSS films showed ca. 100% cation dominant ion transport behavior and the doping level of the polymer was calculated to be 26%. Electrical conductivities for these polymers were found to be dependent on chemical oxidants used and varied from 10-2 to 10-4 S/cm. ^ In the second part of the thesis, we report an example wherein ring sulfonation of insoluble poly(thieno[3,4-b]thiophene) (PT34bT) was carried out to produce a low bandgap, water processable sulfonated poly(thienothiophene) (SPoT). We demonstrated the ability to control the sulfonation level and thereby alter spectral properties. Furthermore, we report processing of this polymer via the layer-by-layer (LBL) technique to give ultra thin films that are stable in their neutral form. The band gaps of SPoT is ca. 1.1 eV. SPoT goes into water and other solvents such as DMSO and DMF. The resulting composition of SPoT in water is very stable in that it shows no sign of precipitation after 8 months of storage under normal laboratory conditions. ^ Initial coupling of T34bT through alpha coupling results in six different dimers, three of which exhibit symmetry. In an attempt to further understand the oxidative polymerization of T34bT, we report the synthesis of the three symmetrical T34bT dimers and their electrochemical polymerizations in the final part. The properties of these three dimers are compared with respect to oxidation potential, and the resulting PT34bTs prepared from them are compared with respect to their optical, electro-optical, and electrical properties. ^

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