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dc.contributor.authorLiu, Ziwei
dc.description201 pages
dc.description.abstractMixed ionic/electronic conductors (MIECs) are materials that conduct both ions and electronic charge carriers simultaneously. Generally, they belong to two distinct families: ceramics and conducting polymers with the latter exhibiting advantages such as easy wet synthesis, low cost processability, biocompatibility and mechanical flexibility over its ceramic counterpart. Conducting polymers, either with single ionic or electronic conductivity, have been extensively studied for their potential applications in energy storage, sensors, and so on. New materials with combined functionalities within the same molecule are expected to form interesting structures and exhibit intriguing properties. Nano/micro-segregation between immiscible components will lead to spatially confined self-assembly with unanticipated synergies including the potential to improve ionic and electronic transport properties. Our goal has been to develop new materials with mixed ionic and electronic conductivity. A systematic study of design, synthesis and characterization of MIECs based on small dimension liquid crystals and large dimension block copolymers has been conducted. First, we synthesized linear structured coil-rod-coil liquid crystals with oligothiphene as a rigid building block for electronic conductivity and ion-doped ethylene oxide units as the flexible ionically-conducting phase. A variety of characterization methods were employed to study the structure and self-assembly behavior of our liquid crystal materials. Simultaneous ionic/electronic transport was for the first time characterized by electrochemical impedance spectroscopy (EIS) with LiTFSI and F4TCNQ as ionic and electronic dopant, respectively. Apart from experiments, molecular dynamic (MD) simulations were adopted to guide molecular design and material properties. Based on simulation results, a series of liquid crystals with ternary amphiphilic structures was synthesized and investigated, leading to complex structures and unique charge transport response. We also carried out the synthesis and study of P3HT-b-POEM rod-coil block copolymers. Without well-ordered phase separation between the two blocks, the incorporation of LiTFSI to the POEM phase resulted in enhanced molecular order as well as electronic doping of the P3HT block, leading to improved electronic conductivity with retained ionic conductivity. In order to achieve comparable mixed conductivity, a polymer with modified P3HT regioregularity and block ratio was investigated and showed a “crystallinity-conductivity” trade-off. The knowledge gained from those studies offers opportunities for further development of conducting polymers.
dc.rightsAttribution 4.0 International
dc.typedissertation or thesis Science and Engineering University of Philosophy D., Materials Science and Engineering
dc.contributor.chairOber, Christopher
dc.contributor.committeeMemberArcher, Lynden
dc.contributor.committeeMemberBaird, Barbara

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Except where otherwise noted, this item's license is described as Attribution 4.0 International