Synthesis and Characterization of Soluble Conducting Polymers and Conducting Adhesives
Abstract (Summary)With the demanding nature of the technology today, scientists are looking for new materials in order to decrease the cost, increase the efficiency of the use of the materials, and decrease time-consuming steps in order to increase the speed of production. New materials are being studied to decrease the weight of cars, planes and space vehicles; surface properties are being modified to decrease the drag coefficient; new technologies are being introduced for speeding up applications in production and assembly lines. In this research we address the needs of different technological applications from a conductivity perspective. In the first part of the thesis, the synthesis of soluble conducting polymers in order to make them more processable for potential electronic and photovoltaic applications is presented. Soluble conducting polymers of 3-hexylthiophene, 3-octylthiophene, 3-decylthiophene and 3-dodecylthiophene were synthesized electrochemically and thus, doped during synthesis. It was found that the conductivities; molecular weights and degrees of polymerization of the polymers strongly depend on the side chain's length. The substitution of alkyl side chains decreases the reactivity of the growing chain, and with an increasing side-chain length, all of these properties show a decrease. The hexyl substituent, being the shortest of the four side chains, causes the least distortion in the background, has the highest conjugation, and has the highest shift in the UV spectrum when it polymerizes. As the length of the side chain increases, the shift in the UV spectrum decreases, too. Decrease in the ?-stacking, conjugation and delocalization decreases the conductivity. This gives the material an opportunity to be used in photovoltaic applications. In the second part of the thesis, a conducting adhesive formulation that eliminates the need for heat or other expensive and rather bothersome application methods to activate the adhesive is investigated. Using the quick setting feature of the cyanoacrylates, a fast and serviceable conducting adhesive is formulated. Environmentally stable and electrically conducting cyanoacrylate formulations have been successfully prepared by introducing silver particles into a stabilized cyanoacrylate formulation. Silver particles have been observed to increase the viscosity and decrease the thixotropicity of the formulations. The stability of the formulations was achieved by using excess amounts of anionic stabilizers. This excess amount of inhibitor increases the set time by delaying the start of the reaction. This inhibition problem was solved by introducing functional amine groups and accelerating the reaction. Addition of the amine groups created more nucleation sites on the surface, which competed with the stabilizer to start the reaction. The use of accelerators did not affect the adhesive strength of the bond, however, it did change the resistivity of the adhesive joint.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2008