Doctor of Philosophy, University of Akron, 2023, Polymer Engineering

Reliable and sustainable energy is a cornerstone of the modern human's life prosperity. Lately, advancements in portable electronics and smart technologies, along with conventional energy sources rising environmental concerns and shortage threats, had highlighted the cruciality of attaining more sustainable, innovative, and efficient energy harvesting and storage systems. Current overwhelming demand for such energy generating/storing devices is forecasted to boost in the coming years, according to several reports, credited to the projected growth in the utilization of high power and high energy storage systems within modern inventions such as electric vehicles (EV) and autonomous aircrafts. These elements encouraged the exploration of alternative solutions that are derived from clean and renewable natural sources like wind power and solar energy to generate electricity. The enhancement of the current storage systems to achieve great efficiency and high energy storage capacity is another route that enables the development of new technologies. The first part of the dissertation is focused on investigating the electricity generation in multifunctional polymer electrolytes membranes (PEMs) when mechanically deformed, i.e., flexoelectricity originated from the ionic polarization/depolarization principle. Flexural bending of the flexoionic laminates was applied in different modes, intermittent and oscillatory, to study the impact of several parameters on the flexoelectric response and the mechanoelectrical energy conversion efficiency. One of the parameters investigated was the effect of the copolymer network functionality on the mechanoelectric transduction. The impact of the molecular weight of the precursor on the flexoelectric response was also studied. The role of the ionic concentration, i.e., lithium salt loading and multivalent cations salt, on the current and voltage response was systematically explored. The influence of operating temperature on the flexoelect (open full item for complete abstract)

Committee: Thein Kyu (Advisor); Xiong Gong (Committee Chair); Siamak Farhad (Committee Member); Steven S.C. Chuang (Committee Member); Weinan Xu (Committee Member) Subjects: Energy; Engineering; Materials Science; Physical Chemistry; Plastics

Doctor of Philosophy, University of Akron, 2021, Polymer Engineering

A crucial objective in the study of polymers is to comprehend how the interactions of atoms and molecules govern the molecular structure and the macroscopic properties of the materials. When those molecular characteristics are determined by the interactions of ions and polymer chains, the material is broadly classified as an ion-containing polymer. This classification contains an enormous number of materials, and it encompasses work from the first half of the last century to the most contemporary research in material development. Such long history has enriched the field with a broad spectrum of applications, such as mechanical and solubility modifiers, self-healing agents, or ionic conductivity boosters. In particular, this research investigates the effect of some ion-polymer interactions over the flexoelectric effect, and the rubbery behavior of a polymer matrix. To that purpose, a polymer membrane was designed targeting specific molecular characteristics. The flexoelectric response of the system was quantified, and the effect of the molecular structure over the electrochemical response was analyzed. The mechanism of polarization and the flexoelectric properties of the aforementioned membranes were studied. These membranes exhibited remarkably high flexoelectric coefficients (>1000 uC/m) that were at least three times larger than those reported in the literature to date. In addition, a rubbery film was developed based on a renewable monomer and ion-pair comonomers synthesized in-house. The viscoelastic response and chemical characterization were analyzed as a function of the molecular features. The effect of the ion-pair comonomers over the transient response of the rubbery films was well understood as a function of the molecular structure. The results established that the ion-pair comonomers imparted stretchability and additional stress relaxation mechanisms to the films. The molecular characteristics of the sol-fraction of the films were also analyzed. The af (open full item for complete abstract)

Committee: Kevin Cavicchi (Advisor); Weinan Xu (Committee Chair); Fardin Khabaz (Committee Member); Toshikazu Miyoshi (Committee Member); Yi Pang (Committee Member) Subjects: Chemistry; Energy; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

Sustainable energy is becoming a crucial enabler to today's activities. Due to the increasing demand of electronics, smart technologies, and high-power requirements in applications such as electrical vehicles (EV), the development of consistent energy systems capable of generating, and/or storing energy is becoming more attractive. According to recent reports, the increase of shortage in conventional energy sources, such as fossil fuel, and the associated environmental concerns have motivated the energy industry to scout for energy alternatives from untapped resources, such as intermittent renewable wind, and solar energy. Another solution to mitigate the present challenge of energy scarcity manifest with the development of efficient energy supply via integrated energy storages “batteries”. The first part of this dissertation is dedicated to investigate the understudied mechanoelectrical phenomenon of ion polarization-based flexoelectricity in ion-containing polymers, viz. polymer electrolyte membranes (PEMs). Such materials operate under the principles of ion polarization/depolarization to derive electrical current and voltage in response to stress/deformation stimuli, best understood as the converse effect of electromechanical phenomenon reported for soft actuators based on ionic electroactive polymers. Under different bending modes (i.e. square-intermittent and sinusoidal-oscillatory bending), several factors influencing the mechanoelectrical response of PEMs were systematically studied including (1) the effect of side chain branching of host polymer matrix (i.e. employing various branching degrees of poly(ethylene glycol) networks), (2) role of ion characteristics, viz. cationic size and valency/charge, (3) dual effects of side-chain branching and multivalent counter ions, and (4) the impact polymer constituent functionality (i.e. ether vs. amine containing polymers). The measured flexoelectric coefficient based on ionic polarization was found to be as high as (open full item for complete abstract)

Committee: Thein Kyu PhD (Advisor); Xiong Gong PhD (Committee Chair); Steven Chuang PhD (Committee Member); Ruel McKenzie PhD (Committee Member); Celal Batur PhD (Committee Member) Subjects: Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Some living cells are known to generate bioelectricity by manipulating the ion concentration gradient across the cell membrane via passive and active ion transports, which are controlled by ion gates and pumps. This process involves polarization and depolarization of the cell membrane, resulting in electrical potential often called membrane potential. Neuron cells utilize such ionic polarization process to send electrical signals for communication and control of body parts. On the other hand, electroplaques in electric eels can store sizable electrical energy and release it on demand for defending and hunting. A similar ionic polarization potential can be generated via bending deformation (as a means of exerting a pressure (stress) gradient) of polymer electrolyte membrane (PEM), which was originally developed as ion conducting solid medium for solid-state Li-ion batteries. This is the motivation of the present dissertation to explore the novel flexoelectric effect in the aforementioned solid-state PEM by subjecting it to mechanical deformation. A plausible mechanism has been proposed to explain the mechano-electrical transduction in the above solid PEMs, wherein ionic polarization occurred as a result of ion diffusion under pressure (stress) gradient. The flexoelectric coefficient has been measured to be as high as ~300 µC/m, which is several orders of magnitude higher relative to those of other flexoelectric materials hitherto reported in literature. These new and fascinating features found in the present solid PEM system open up a new avenue of polymeric energy materials for diverse applications such as flexible sensor and energy harvesting devices.

Committee: Thein Kyu (Advisor) Subjects: Energy; Engineering; Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Present dissertation outlines a study of the basic important physicochemical properties of photo-cured polymer electrolyte membranes (PEM) that can be enhanced and optimized in order to be implemented as electrolyte in solid-state Li-ion batteries. The studied properties include mechanical integrity, ionic conductivity, thermal and electrochemical stability, etc. This dissertation also introduces and characterizes a novel application of PEMs as energy harvesting materials, due to their capability to transform mechanical stimuli into an electrical signal and vice versa. Chapter I provides a brief overview of the general content of the dissertation. Chapter II presents the material that was taken as the basis for the study. It contains essential information related to the battery principles, operation, development and applications. In addition, it encompasses the description of electroactive polymers, which are in principle, equivalent to the discovered flexoelectric PEMs that are as well introduced in this work. Chapter III illustrates the materials, methods and calculations utilized to perform and analyze the data collected for the purpose of the study. Chapter IV describes an incorporation of mercaptopropyl methyl siloxane homopolymer (thiosiloxane) as a co-component to the matrix of the PEM, which in result enables enhancement of the polymer segmental motion and hence, the ionic conductivity. UV irradiation was applied to various thiosiloxane and poly(ethylene glycol) diacrylate (PEGDA) mixtures to get the `thio-ene' reaction between the thiol functionality and the double bonds of the PEGDA precursor, which formed a complete amorphous self-standing PEM. The thiosiloxane modified PEM film exhibits higher extension-at-break in comparison to the PEM containing only PEGDA such as PEGDA700/SCN/LiTFSI 20/40/40, FTIR and Raman spectroscopy techniques were employed to detect the thiol (SH) groups consumed after performing the so-called thiol-ene reaction. It was fou (open full item for complete abstract)

Committee: Thein Kyu Dr (Advisor); Mark Soucek Dr (Committee Member); Younjin Min Dr (Committee Chair); Steven Chuang Dr (Committee Member); Siamak Farhad Dr (Committee Member) Subjects: Chemistry; Energy; Plastics; Polymer Chemistry; Polymers; Solid State Physics

PHD, Kent State University, 2011, College of Arts and Sciences / Department of Physics

In part because of its anticipated application for faster and lower power-consuming electro-optic devices, small energy generator in industry and low operating voltage in multicolor LC display, which could revolutionize display technology, the bent-core nematic (BCN) liquid crystals has long been sought after. Due to their bow like shape, BCN gives rise to some interesting features including flexoelectricity (a coupling between electric polarization and elastic flexure) and viscoelastic properties. The viscoelastic parameters are relevant to performance of LC devices and to the understanding of the connection between unusual properties (like “giant flexoelectricity”) and structure (molecular organization) that gives rise to them. We have investigated basic properties- particularly the absolute elastic constants (K11 for splay, K22 for twist, and K33 for bend distortion of the uniaxial director, or optic axis) and the corresponding viscosities, ηsplay, ηtwist, ηbend, at a characteristic temperature in the nematic phases of three bent-core nematic liquid crystals, CIPbis10BB, DT6PY6E6 and 2832, using two techniques, dynamic light scattering (i.e., through the detection and characterization of the symmetry breaking fluctuation mode associated with the director) and magnetic field induced orientational distortion (Fredericksz transition) on well aligned samples. At certain fixed temperatures below the isotropic-nematic transitions, we have explored different experimental geometries and optical selection rules to optimize and probe the quantitative measurements of these parameters and our result shows that the orientational elastic constants of the BCN studied are significantly lower (particularly K22) than those of typical calamitics (5CB) [1] and that K11>K33≫K22 (for CIPbis10BB and 2832). A dramatic enhancement of orientational viscosities (4 to 100 times larger than calamitics) was also confirmed in BCNs. The unusual anisotropies of these parameters are discussed in (open full item for complete abstract)

Committee: Samuel Sprunt PhD (Committee Chair); James Gleeson PhD (Committee Member); Jakli Antal PhD (Committee Member); David Allender PhD (Committee Member); Mietek Jaroniec PhD (Committee Member) Subjects: Condensed Matter Physics; Physics

PHD, Kent State University, 2009, College of Arts and Sciences / Chemical Physics

With the energy demands of today, exploration for new sources is of the utmost importance. This work explores possible roles in which liquid crystals can produce electrical signals (electricity) via mechanical distortions. For example, bent core molecules have been found to have high flexoelectric coefficients when directly flexed.Typical Giant Flexoelectric coefficients are 10nC/m order. This is verified by measuring the current produced from a oscillatory bend of the sample and by measure the bending produced by application of an applied electric field. These materials may be used to produce small scale power generators. Naturally these materials need to be studied and their flexoelectric coefficients measured. Also, phospholipids, which make up a large percentage of the cell membrane, are not well studied for their liquid crystalline properties. This work found that shearing these cell membranes can produce a piezoelectric signal. The cell membrane is basically a chiral smectic A (SmA*) liquid crystal. However, a shear will produce tilt which would make it a chiral smectic C (SmC*). This symmetry breaking induces a piezoelectric signal within the cell membrane. In essence, the cell membrane is itself a generator of electricity. This newly discovered membrane piezoelectricity may play important roles in cellular processes such as ion channels, mechano-reception and magneto-reception.

Committee: Antal Jakli PhD (Advisor); Jonathan Selinger PhD (Committee Chair); James Gleeson PhD (Committee Chair); Chanjoong Kim PhD (Committee Chair); Scott Bunge PhD (Committee Chair) Subjects: Physics