<p>  </p> <p>Recently, there has been significant increase in research and development in the field of organic electronics. This is mainly because organic electronic devices can be flexible, lightweight, and processed from solution using low-cost manufacturing techniques. Typically, these devices have utilized conjugated polymers as their active layer components. This approach has been successful, but the use of conjugated polymers comes with limitations. To address these limitations and expand the field of organic electronics, this work studies a novel class of macromolecules, radical polymers. Unlike their conjugated polymer counterparts, radical polymers are comprised of a non-conjugated backbone with stable open-shell groups at their pendant sites. By studying the structure-property relationships of these radical polymers, this work developed novel polymer systems for a variety of organic electronic applications. Furthermore, these studies can be applied to future radical polymer systems yet to be discovered. Ultimately, this work served as a template for expanding the field of organic electronics. </p>

Polymerization reaction is carried out by the reaction of 2,4,6 trichlorophenol with sodium hydroxide, in the presence of small amount of water by microwave initiation. Synthesis of polymers were successfully performed under microwave enegy. The use of microwave energy was due to advantages of shorter processing time. The main focus of attention was the 90 to 600 watt microwave energy. Polymerizations were performed with different time intervals by keeping the microwave energy and water content constant / or with different energy levels by keeping the time interval and water content constant / or by varying the amount of water by keeping the time and energy level constant.Beside poly(dichlorophenylene oxide), conducting polymer, ion-radical polymer, crosslinked polymer were also be successfully synthesized and characterized. Characterizations of the products were performed by FTIR, 1H-NMR, 13C-NMR, DSC, TGA and elemental analysis. Molecular weight distribution was measured by PL-GPC 220 Polymer Laboratories Instrument. Conductivity measurements were performed by four probe technique.

<p>   Organic electronics has been a highly researched field owing to the low cost, biocompatibility, mechanical flexibility, and superior performance relative to their inorganic counterparts in some applications. Significant advancement has been achieved across various device platforms including organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic solar cells, for instance. Recently, soft materials that can conduct both charge and ions simultaneously (i.e., organic mixed conductors) have been a major catalyst in the fields of biosensors and energy storage. Extensive research efforts in the organic electronics field are being invested to establish the relevant structure-property relationships to design and develop higher performing organic mixed conductors. Simultaneously, these materials are utilized in developing prototype biosensors with the aim of superior performance, lower cost, and better patient comfort and outcomes than currently available technologies. Following suit, this dissertation is dedicated to furthering organic electronics on both fundamental and applied fronts. Specifically, this work examines a novel class of redox-active macromolecules, radical polymers, as the organic electrochemical transistor (OECT) active layer. In addition, wearable ocular biosensors utilizing soft materials to realize design innovation are presented.</p> <p>   For the first part of the present dissertation, radical polymer-based blends are evaluated for mixed electron and ion conduction in OECTs. Traditional macromolecular design motifs for OECT active layer materials have been a closed-shell macromolecular backbone for electron conduction with charge-neutral hydrophilic side chains (e.g., triethylene glycol) for ion conduction. When poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO) is blended with poly(3-hexylthiophene) (P3HT), 2,2,6,6-tetramethylpiperidin-N-oxy (TEMPO) radicals in PTEO act as an independent voltage regulator that modulates the ionic and hence electronic transport of the OECT devices. Electrochemical analysis of the blend films reveals that the ionic transport and hence electrochemical doping of the P3HT phase occur when the applied bias matches the onset oxidation potential of TEMPO radicals in PTEO even though that of P3HT is lower than that of TEMPO oxidation. By optimizing the blend ratio, figure-of-merit (i.e., μC*) values over 150 F V–1 cm–1 s–1 at loadings as low as 5% PTEO (by weight) are achieved, placing the performance on the same order as top-performing conjugated polymers despite the mediocre performance of pristine P3HT (<10 F V–1 cm–1 s–1). These findings suggest that introduction of open-shell moieties in the OECT active layer as a secondary redox-active species may significantly improve OECT performance metrics and offer a new paradigm for future macromolecular designs.</p> <p>   In the second part of the dissertation, novel design strategies for wearable ocular electroretinography (ERG) sensors are presented. Typically, wearable sensors are custom-made contact lenses fabricated in a bottom-up fashion where the pre-fabricated sensor component is either embedded in the contact lens body or sandwiched between two. The present work instead utilizes commercially available contact lenses, and the corneal electrode is integrated via electropolymerization of poly(3,4-ethylenedioxythiophene):iron(III) p-toluenesulfonate (PEDOT:Tos) on the lens surface. Electrochemical analysis of the PEDOT:Tos reveals that the measured impedance is several orders of magnitude lower than that of noble metals (e.g., Au) used as the working electrode in commercial electrodes. The mechanical and chemical stability along with the soft form factor of the present design strategy enables high-fidelity recording of ERG signals in human subjects without the need for topical anesthesia.</p> <p>   Following the similar strategy, a new seamless wearable ocular sensor integration strategy utilizing polydopamine (PDA) conformal coating is demonstrated. In this work, we utilize its strong adhesive property originating from the van der Waals interactions between catechol moieties of PDA and various hydrophilic functional groups (e.g., hydroxy, ether, etc.) already present in commercial contact lens materials. The facile integration demonstrates high peeling strength (> 55 J m-2), chemical and mechanical stability. A series of <em>in vivo</em> assessments demonstrates high accuracy, reliability, and user comfort of the fabricated wearable sensor in both animal and human subjects. The findings suggest that the PDA-assisted integration strategy may be applied in designing various future-generation wearable ocular electrophysiological sensors.</p>

<p> In an era of advancing printed electronics, solution-processable organic semiconductors continue to make significant strides in electronic and optoelectronic applications. Electrochromic (EC) technology, which encompass reversible optical modulation under electrochemical biasing, has progressed rapidly over the past half-century and developed into niche commercial-scale devices for auto-tinting glasses as well as low-power, non-emissive displays. To utilize the advantages of organic electrochromic materials in next-generation devices, it is imperative to understand their fundamental material properties, interactions with other device components, and the underlying electrochemistry that governs the overall optical and electrochemical response of the complete electrochromic device. This dissertation presents a discussion on the synergistic role of organic electrochromes, charge-balancing layers and electrolytes in determining two key performance metrics, namely the optical contrast and operational stability, of an electrochromic device (ECD). The absorption features of colored-to-transmissive switching conjugated polymers have been investigated by exploring material design strategies in conjunction with analytical approaches to optimize and enhance the optical contrast. In parallel, transmissive redox-active radical polymer counter electrodes have been developed as compatible charge-balancing layers and integrated into devices by pairing with electrochromic polymers (ECPs) to achieve stable and high-contrast optical modulation. Electrochemical activity of both conjugated and radical polymer electrodes in different ionic and solvent environments have been further examined to understand material-electrolyte interactions governing mixed ionic-electronic conduction. Finally, a small molecular approach to realizing transparent-to-colored electrochromism is discussed, where distinct substituent-induced degradation pathways of conjugated radical cations were revealed. Overall, this research aims to assist future development of robust, ultra-high contrast organic electrochromic platforms.  </p>