Date of Award
Master of Science in Mechanical Engineering (MSME)
Dr . Saud Al-Dajah
Dr. Nayef Ghasem
The aim of this project is to synthesize and characterize conductive polymers made out of blending nonconductive polymers with ionic liquids. An application to demonstrate the use of these novel conductive polymers is to create an organic memory device.
Attempts to synthesize conductive polymers have been reported in the literature; several of these approaches include doping a polymer with arsenic or iodine based dopant. In this work, ionic liquids, known as plasticizer, are sued as the dopant for non-conductive polymers. There are several advantages of employing the ionic liquids over other dopants, including the maintenance of organic based blends (both the polymers and ionic liquids are organic) and maintaining biocompatibility of the blends for bio-related applications.
In this work, conductive polymers were synthesized by blending non-conductive mixture of poly vinyl alcohol (PVA) and Poly-acrylamide-co-acrylic acid (PAA) with different weight percentages of glycerol, sorbitol and imidazolium bromide). The percentage of the dopant plasticizers were varied from 0-5% by wt ratio. The solution casting method was used to form thin films, which were examined with nanoindentation, differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), Fourier Transform Infrared spectroscopy (FT-IR) and ac impedance spectroscopy. It was found that the thermal properties (glass transition, Tg, melting point, Tm, and decomposition temperature, Td) for the blended PVA/PAA showed a decrease proportional to the percentages of the three plasticizers used in this project. The hardness and elastic modulus obtained from the nanoindentation test were also found to decrease with increase in plasticizer concentration. FT-IR confirmed the reduction in hydrogen bonding between combined polymer chains in favor of formation new bonding between the plasticizers and the polymer blend chains.
The novelty of doping nonconductive polymers with ionic liquid stems from the ability to modulate the degree of electrical conductivity, mechanical and thermal properties of the blends by controlling the percentage of the ionic liquid introduced into the polymer will open a new field of polymer studies; hence, organic polymer blends.
Once blends with favorable properties were identified; they were then utilized in producing an organic storage memory device. A hysteresis loop approximately ±20V wide was observed as a charge element based under ± 20V sweep range when CNT was blended, but ±5 to ±10 when gold (Au) and zinc oxide (ZnO) were blended along with the mixture of the polymers and the glycerol. The impedance measurements showed that the ionic conductivity of PVA/PAA polymer membrane can be controlled by addition of plasticizer. Hence, the novel conductive polymer presented in this thesis formed a solution to overcome challenges associated with a total organic memory device. The doped polymers were substituted for the silicon base semiconductor in a conventional memory device, however with enhanced performance compared to the silicon based device.
Yousef Al-Haik, Mohammad, "Conductive Polymer Blends and Their Use in Memory Devices" (2013). Theses. 295.