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Electroactive polymers (EAP) are an emerging branch of smart materials that possess the capability to change shape in the presence of an electric field. Opportunities for the advancement of knowledge were identified in the branch of EAP consisting of inherently electrically conductive polymers. This dissertation explores methods by which the unique properties of composite materials having conductive polymers as a constituent may be exploited. Chapter 3 describes the blending of polyaniline with conventional thermoplastics. Processing these polyblends into foams yielded a porous conductive material. The effect of blend composition and processing parameters on the resulting porous morphology and electrical conductivity was investigated. These findings represent the first systematic study of porous conductive polymer blends. In Chapter 4, multilayer electroactive polymer actuators consisting of polypyrrole films electropolymerized on a passive polymer membrane core were harnessed as actuators. The membrane is vital in the transport of ionic species and largely dictates the stiffness of the layered configuration. The impact of the mechanical properties of the membrane on the actuation response of polypyrrole-based trilayer bending actuators was investigated. Candidate materials with distinct morphologies were identified and their mechanical properties were evaluated. These results indicated that polyvinylidene difluoride membranes were superior to the other candidates. An electrochemical synthesis procedure was proposed, and the design of a novel polymerization vessel was reported. These facilities were utilized to prepare actuators under a variety of synthesis conditions to investigate the impact of conductive polymer morphology on the electromechanical response. Characterization techniques were implemented to quantitatively assess physical and electrochemical properties of the layered composite. Chapter 5 proposes a new unified multiphysics model that captures the electroactive actuation response inherent to conductive polymer trilayer actuators. The main contribution of this investigation was the proposal and development of a new hybrid model that unifies concepts from charge transport and electrochemomechanical models. The output of the proposed model was compared with published data and shown to be accurate to within 10%. Finally, Chapter 6 demonstrated the application of these materials for use as precision mirror positioners in adaptive optical systems.

Esta tese aborda quatro tópicos fundamentais para o desenvolvimento e aplicação de membranas eletroativas nanoestruturadas (MENs): (i) síntese e caracterização de nanopartículas (Nps) de prata, ouro e platina encapsuladas em moléculas de dendrímero poliamidoamina geração 4 (PAMAM); (ii) preparação de filmes automontados contendo PAMAM e Nps de ouro (PAMAM-Au); (iii) preparação de MENs utilizando sistema core-shell PAMAM-Au@Me, onde Me é um mediador redox; (iv) imobilização enzimática em MENs e estudos biocatalíticos associados a processos eletroquímicos. As Nps foram caracterizadas observando-se a banda plasmônica em espectros na região do UV-Vis. Imagens de microscopia eletrônica de transmissão revelaram que PAMAM-Au e PAMAM-Pt possuem morfologias esféricas, enquanto o PAMAM-Ag forma grandes cristais com estruturas fractais. Estruturas cúbicas de face centrada caracterizaram os cristais formados de Au e Pt, sendo possível estimar os diâmetros (3,0 nm) das Nps pela equação de Scherrer em difratogramas de raios X, confirmados posteriormente por microscopia eletrônica por transmissão (TEM). Um indício de estabilização por encapsulamento do híbrido PAMAM-Au foi obtido de espectros de infravermelho (FTIR), a partir de modificações nas bandas das amidas. A cinética de reação para formação de PAMAM-Au também foi estudada. Filmes de PVS/PAMAM-Au (onde PVS é o poli(ácidovinilssulfônico)) foram preparados com 5 minutos de imersão, com a mesma quantidade de material sendo adsorvida em cada camada, segundo medidas de espectroscopia UV-Vis e voltametria cíclica (CV). No caso do eletrodo ITO-(PVS/PAMAM-Au), saltos de elétrons foram considerados o mecanismo de transporte de carga ao longo do filme. Um novo sistema core-shell Au@PB foi preparado, formando um sistema ITO-(PVS/PAMAM-Au)6@PB, em que a eletrodeposição de PB (azul da Prússia) foi monitorada medindo-se as correntes faradaicas durante os ciclos potenciodinâmicos. Outros mediadores de hexacianoferratos de metais de transição (Fe, Ni, Co e Cu) foram obtidos sobre eletrodos de ITO-(PVS/PAMAM-Au). De resultados de espectroscopia de impedância eletroquímica (EIS), verificou-se que a resistência de transporte de carga decresce na sequência CuHCF > FeHCF > NiHCF > CoHCF e todos os eletrodos apresentaram atividade catalítica para o peróxido de hidrogênio. Uma nova configuração de eletrodo, ITO-(PVS/PAMAM-Au)3@CoHCF-GOx, pôde ser aplicada como dispositivo enzimático, com a glicose oxidase (GOx) sendo imobilizada por drop-coating na superfície do eletrodo e aplicada em experimentos de biocatálise. A glicose pôde ser detectada a 0,0 V (Ag/AgCl), com resposta linear até 100 µmol L-1 de glicose, sensibilidade de 115 nA mmol L-1, limite de detecção de 5,5 µmol L-1 e KMapp de 0,24 mmol L-1, mostrando que o sistema aqui proposto cria um ambiente propício para a enzima operar com alta atividade catalítica. / This thesis addresses four fundamental topics for producing and applying electroactive nanostructured membranes (ENMs): (i) synthesis of Au, Pt and Ag nanoparticles (Nps) using polyamidoamine (PAMAM generation 4) dendrimers as template/stabilizers; (ii) fabrication of layer-by-layer (LbL) films comprising PAMAM with AuNps (PAMAM-Au) and poly(vinylsulfonic acid) (PVS); (iii) preparation of a new core-shell system with Prussian blue (PB) around the Au nanoparticles (PAMAM-Au@PB); (iv) enzyme immobilization on ENMs and bioelectrochemistry studies. The formation of the Nps inside PAMAM was monitored by measuring the plasmonic band of NPs via UV-Vis spectroscopy. Images from transmission electron microscopy (TEM) showed well-organized Au and Pt spherical particles, with average diameter of 3 nm and narrow size distribution. In addition, X-ray diffraction of Nps enabled easy identification of the Nps atomic planes (face-centered cubic arrangements). However, PAMAMAg growth showed fractals structures. In order to confirm Au NPs encapsulation inside the PAMAM dendrimer, FTIR spectra in the transmission mode for neat PAMAM and PAMAM-Au were compared. The kinetics of formation of PAMAM-Au was studied by UV-Vis spectroscopy. The deposition of individual PAMAM-Au layers was examined in detail: the adsorption kinetics was determined by CV to be first-order and that 5 min of adsorption was sufficient for maximum coverage. Formation of PVS/PAMAM-Au multilayers showed a linear increase in anodic and cathodic peak currents, indicating that the same amount of material was adsorbed in each deposition step. Electron-hopping was inferred as the charge transport mechanism between PAMAM-Au layers. Using hexacyanoferrate (III) to probe the electrochemical reaction at the electrode surface, the charge transport in the PAMAM-Au layers was shown to be faster than for non-modified electrodes. A new system based on PAMAM-Au@PB was prepared by simple potential cycling electrodeposition after ITO-PVS/PAMAM-Au LbL film preparation. New systems are described based on ENM membranes of ITOPVS/ PAMAM-Au LbL electrodes, with a redox mediator (Me) electrodeposited around Au nanoparticles. The resulting ITO-PVS/PAMAM-Au@Me system was then characterised electrochemically using cyclic voltammetry and electrochemical impedance spectroscopy. We demonstrated that the concept of ENM can be generalized to a wider variety of redox mediators. All electrodes modified with hexacyanoferrates showed electrocatalytic activity towards hydrogen peroxide, which is promising for the preparation of nanodevices requiring redox mediators. An electrochemical enzyme device with glucose oxidase (GOx) immobilized at ITO-(PVS/PAMAM-Au)3@CoHCF ENM was developed. Using CoHCF as redox mediator, hydrogen peroxide (the enzymatic reaction product) was determined at 0.0 V (vs. SCE), with linear range up to 100 Zmol L-1 of glucose, sensitivity of 115 nA mmol L-1, detection limit of 5.5 Zmol L-1 and KM app of 0.24 mmol L-1. Such a performance indicates that this system promotes a friendly environment for enzyme immobilization.

Abstract: Poly (vinylidene fluoride) (PVDF), thanks to its versatile properties, finds many applications ranging from water purification membranes (thermal and chemical stability) to electronic devices (piezoelectric, pyroelectric and ferroelectric properties). Block copolymers of PVDF with other polymers further expand its properties and, consequently, its applications. Toward this line, my thesis investigates the synthesis, molecular characterization and properties of novel PVDF-based copolymers mainly with poly(tert-butyl acrylate) (PtBuA), poly(methyl methacrylate) (PMMA) and polystyrene (PSt). To prepare the block copolymers a living polymerization is needed, which is compatible with the VDF and the comonomer (tBuA, MMA, St). For this purpose, we used iodine transfer polymerization (ITP) with the difunctional chain transfer agent (CTA) C4F8I2. Difunctional macroinitiator (I-PVDF-I) was first obtained by ITP of VDF monomer with C4F8I2, followed by addition of the comonomer tBuA, MMA or St to afford the triblock copolymers poly(tert-butyl acrylate)-block-poly(vinylidene fluoride)-block-poly(tert-butyl acrylate) (PtBuA-b-PVDF-b-PtBuA), poly(methyl methacrylate)-block-poly(vinylidene fluoride)-block-poly(methyl methacrylate) (PMMA-b-PVDF-b-PMMA) and polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PSt-b-PVDF-b-PSt). The structure of all intermediates and final products were characterized by Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC). The microstructure and polymorphism of all triblock copolymers, characterized by XRD, shown that the PVDF in the first two copolymers exhibits the electroactive β-phase, while in the third copolymer there is the coexistence of α- and γ-phases. Linear PVDF homopolymers, using the free radical and IT polymerizations, were prepared for comparison purposes. All linear polymers possess the α-phase. The thesis is divided into the following five chapters: 1. Introduction, where the scope of this thesis is given with a brief background on PVDF; 2. Literature Review, where a summary of previously published works on PVDF synthesis and polymorphism is presented; 3. Experimental Section, where detailed procedures and characterization methods are given; 4. Results and Discussion, where outcomes of successful experiments are discussed; and 5. Conclusion and Perspective, where the outcomes of this work are summarized and perspective are discussed.

Microbial electrolysis cell (MEC) system is a potential technology that could treat wastewater while simultaneously generating H2 (green energy). MEC's electroactive bacteria (EAB) are essential microbes responsible for oxidizing organic pollutants (such as acetate) in wastewater using an electrogenesis process. Since EABs comprise the core of MECs, they are essential for maintaining functional stability (Coulombic efficiency (CE), current density, and pollutant removal) of MECs. The cause of EAB becoming dominant at the anode of MECs fed with wastewater is still unclear. Furthermore, efficient EAB are typically not detected in wastewater, and when they are present their abundance is low, which affects their early colonization on the anode and subsequent growth into a mature biofilm. This study investigated bioaugmentation as a strategy to drive the assembly of functionally redundant anode EAB biofilms to improve MEC performance. Two bioaugmentation strategies (Conditions 2 and 3) with known EABs (G. sulfurreducens and D. acetexigens) were tested during the startup of MECs. Meanwhile, control MEC reactors (Condition 1) were operated with only wastewater as the sole source of inoculum to compare the anodic biofilm assembly and system performance with the bioaugmented reactors. Equal number of G. sulfurreducens and D. acetexigens cells were added to the wastewater-fed MEC (10% inoculum at 2.1E+07 live cells/mL). In Condition 3, anodic-biofilm colonized G. sulfurreducens and D. acetexigens was used as anode in wastewater fed MECs. Using single-chambered MEC reactors, the bioaugmented MECs (Condition 2 and 3) performed more efficiently than the non-bioaugmented (Condition 1) MECs. Current generation, CE and gas production were different between the three conditions tested (Condition 3 > Condition 2 > Condition 1). Analysis of 16S rRNA gene sequencing of anodic biofilm indicates revealed that the bacterial communities was not affected between the tested conditions. However, the relative abundance of EABs, mainly G. sulfurreducens and D. acetexigens, was markedly influenced by bioaugmentation compared to the control reactor. The highest peak current generation (~ 1500 mA/m2), CE (70.3 ± 9%), and gas production (0.04 m3/m3/day) was observed in Condition 3. Collectively, these results provide a framework for engineering the anode microbial communities in MECs for wastewater treatment.

Les hydrogels de Polyacrylamide (PAAM) hydrolysés sont des matériaux électroactifs biocompatibles non biodégradables. Ils possèdent des propriétés très proches de celles du muscle naturel et leur mode opérationnel basé sur la diffusion d’ions est similaire à celui existant dans les tissus musculaires naturels. Compte tenu de ces caractéristiques, ces hydrogels sont de bons candidats pour la conception de nouveaux muscles artificiels. Le problème qui limite leur utilisation réside dans leur temps de réponse qui reste encore inférieur à celui du système de fibres musculaires naturelles. Leur fonction actuatrice est limitée par le phénomène de diffusion en raison de leur structure massique qui est à l’origine de cycles de fonctionnement relativement lents. Dans le but de développer un nouveau système artificiel mimant le comportement du muscle squelettique naturel cette étude se divise en deux grandes étapes. La première étape vise le développement d’une étude de la synthèse de l’hydrogel de PAAM et de son mode de fonctionnement. Dans cette étude les effets des paramètres gouvernant la polymérisation sur les propriétés des hydrogels sont évalués. Les propriétés électrochimiques et le mécanisme d’activation des actuateurs soumis à une excitation électrique sont étudiés et le mode de fonctionnement des actuateurs est caractérisé et expliqué. La seconde étape est la proposition et le développement d’une nouvelle architecture de muscle artificiel à base de PAAM. Cette architecture consiste en une structure fibreuse du gel encapsulée par une couche en gel conducteur jouant le rôle d’électrodes. La structure fibreuse permet au système d’exhiber une réponse rapide et la couche en gel améliore ses propriétés mécaniques. Comme un premier pas dans la réalisation du modèle nous avons mis en place un nouveau procédé basé sur la technique d’électrofilage qui permet la génération de fibres linéairement disposées. En utilisant ce processus nous avons réussi à fabriquer des microfibres de PAAM réticulées, électroactives montrant des réponses rapides. / Hydrolyzed Polyacrylamide (PAAM) hydrogels are electroactive, biocompatible and non-biodegradable materials. Their main attractive characteristic is their operative similarity with biological muscles and particularly their life-like movement. They suit better the artificial muscle fabrication despite their response time which stays low compared to natural human muscle due to their bulky structure and due to the kinetics of the size dependence of their volume change. In order to copy the natural skeletal muscle design into a new artificial muscle system this study is divided into two steps. The first step is the development of a comprehensive study of the hydrogel itself in order to obtain the elementary background needed for the design of actuating devices based on this material. The effect of polymerization parameter on the hydrogel properties is investigated. The electrochemical properties and actuation mechanisms of the hydrogel is studied, the bending of PAAM actuators induced by electric field is discussed and a mechanism for the bending phenomenon is proposed. The second step is the proposition of a new artificial muscle architecture based on PAAM hydrogel. The model consists on a fiber like elements of hydrolyzed PAAM, working in parallel, embedded in a thin conducting gel layer which plays the role of electrodes. The fiber-like elements enable the system to exhibit relatively rapid response and the gel layers enhance their mechanical properties. Aiming to realize the model we have put in place a new electrospinning setup which is a modified process for the production of micro to nanofibers via electrostatic fiber spinning of polymer solutions. The main advantage of this technology is to produce aligned electrospun fibers over large areas by simple and a low cost process making it possible to produce fiberbased devices efficiently and economically. Using this setup, we succeeded in the fabrication of electroactive crosslinked hydrogel microfibers that can achieve fast electroactive response

Ionic electroactive polymer (IEAP) actuators are a class of electroactive polymer devices that exhibit electromechanical coupling through ion transport in the device. They consist of an ionomeric membrane coated with conductive network composites (CNCs) and conductive electrodes on both sides. A series of experiments on IEAP actuators with various types of CNCs has demonstrated the existence of a direct correlation between the performance of actuators and physical and structural properties of the CNCs. Nanostructure of CNC is especially important in hosting electrolyte and boosting ion mobility. This dissertation presents a series of systematic experiments and studies on IEAP actuators with two primary focuses: 1) CNC nanostructure, and 2) ionic interactions. A novel approach for fabrication of CNC thin-films enabled us to control physical and structural properties of the CNC thin-films. We, for the first time, facilitated use of layer-by-layer ionic self-assembly technique in fabrication of porous and conductive CNCs based on polymer and metal nanoparticles. Results were porous-conductive CNCs. We have studied the performance dependence of IEAP actuators on nano-composition and structure of CNCs by systematically varying the thickness, nanoparticle size and nanoparticle concentration of CNCs. We have also studied influence of the waveform frequency, free-ions and counterions of the ionomeric membrane on the performance and behavior of IEAP actuators. Using the LbL technique, we systematically changed the thickness of CNC layers consisting of gold nanoparticles (AuNPs) and poly(allylamine hydrochloride). It was observed that actuators consisting of thicker CNCs exhibit larger actuation curvature, which is evidently due to uptake of larger volume of electrolyte. Actuation response-time exhibited a direct correlation to the sheet-resistance of CNC, which was controlled by varying the AuNP concentration. It was observed that size and type of free-ions and counterion of ionomeric membrane are also influential on the actuation behavior or IEAP actuators and that the counterion of ionomeric membrane participates in the actuation process. / Ph. D.

Ionic electroactive polymers have been developed as mechanical sensors or actuators, taking advantage of the electromechanical coupling of the materials. This research attempts to take advantage of the chemomechanical and chemoelectrical coupling by characterizing the transient response as the polymer undergoes an ion exchange, thus using the polymer for ionic sensing. Nafion™ is a biocompatible material, and an implantable polymeric ion sensor which has applications in the biomedical field for bone healing research. An ion sensor and a strain gauge could determine the effects of motion allowed at the fracture site, thus improving rehabilitation procedures for bone fractures. The charge sensitivity of the material and the capacitance of the material were analyzed to determine the transient response. Both measures indicate a change when immersed in ionic salt solutions. It is demonstrated that measuring the capacitance is the best indicator of an ion exchange. Relative to a flat response in deionized water (±2%), the capacitance of the polymer exhibits an exponential decay of ~25% of its peak when placed in a salt solution. A linear correlation between the time constant of the decay and the ionic size of the exchanging ion was developed that could reasonably predict a diffusing ion. Tests using an energy dispersive spectrometer (EDS) indicate that 90% of the exchange occurs in the first 20 minutes, shown by both capacitance decay and an atomic level scan. The diffusion rate time constant was found to within 0.3% of the capacitance time constant, confirming the ability of capacitance to measure ion exchange. / Master of Science

Ionic polymer materials are a class of electroactive polymers that have been used in recent applications that take advantage of their large bending deflection. Although these materials have been around since the 1960s, it has only been in the last decade that their electromechanical coupling has been discovered. Because their life as a transducer has been relatively short, the underlying mechanisms for their mechanical motion have not yet been fully characterized. Modeling has been performed with ionic polymers, but there is no existing model, to date, that explains all the physical phenomena associated them. The work presented in this document will contribute to the characterization of these materials. To better understand the dehydration effect of ionic polymers operating in an open air environment, research was performed to help characterize this effect. Through the use of frequency response analysis, trends were established showing how the material's response characteristics varied with time, as the polymer dehydrated. These tests were also run at different humidity levels to assess the impact environmental conditions had on the response. It was shown that lower humidity levels cause the system parameters to shift at a higher rate. The two configurations tested were clamped-free and clamped-clamped, in an effort to bound the performance of the actuators for engineering applications. The clamped-clamped condition also facilitated applying tension to the polymers for evaluation of the dehydrating effects. Several comparisons to beam theory were made throughout the analysis, using it as a baseline condition illustrator. Though qualitative results were obtained with the polymers, there was much discrepancy in quantitative measures. This was to be expected though, because ionic polymers are composite actuators that exhibit nonlinear behavior, while uniform beams are linear. Environmental testing was not all that was done, however. Control techniques were applied to improve the closed-loop performance of the actuators. Using proportional-integral control, it was demonstrated that ionic polymers are capable of tracking reference inputs better than it was previously thought. This result will validate future experimentation with ionic polymers for micro-manipulation applications. The simplicity of integral control also eliminated the need for cumbersome model derivations and control system designs, reducing the time necessary to implement and test an actuator. Through the use of this control algorithm, the closed-loop bandwidth was also characterized for the cantilever and clamped-clamped polymers. / Master of Science

Metal ion contamination in surface and ground water is a major threat as it has a direct implication on the health of terrestrial and aquatic flora and fauna. Lead (Pb2+), mercury (Hg2+), cadmium (Cd2+), nickel (Ni2+), copper (Cu2+) and cobalt (Co2+) are few of these metal ions which are classified under the high risk category. Of these, lead and mercury are of greater concern, as even nanomolar concentrations can be lethal, as they can be bio-accumulated and result in physiological as well as neurological disorders. In Asian countries like India and China, heavy metal pollution is more prevalent, as a consequence of poor governmental policies or ineffective or inadequate measures to combat this problem. In recent times, the monitoring and assessment of water pollution is a critical area of study, as it has a direct implication for its prevention and control. The major techniques used for metal ion detection are atomic absorption spectroscopy (AAS), X-ray fluorescence, ion chromatography, neutron activation, etc. Alternatively, the electrochemical, optical and electrical methods provide a platform for the fabrication of portable devices, which can facilitate the on-site analysis of samples in a rapid and cost-effective manner. This has led to a new field of research called chemical sensors or chemo sensory devices. The main aim of this study is to develop various chemosensory materials and test their response towards metal ion sensing. In this study, electroactive polymers have been synthesized for various sensor applications. The focus has been to design synthesize and test various functionalized electroactive polymers (FEAP) for the development of electrochemical, optical and chemoresistive sensors. Electroactive polymers like polyaniline, polypyrrole, polypyrrole grafted to exfoliated graphite oxide and dipyrromethene conjugated with p-(phenylene vinylene) have been synthesized and evaluated after functionalizing with metal coordinating ligands. These metal coordinating ligands were selected, in order to enhance their metal uptake capacity. Various metal ligands like imidazole, tertiary amine group, iminodiacetic acid, and dipyrromethene incorporated either in the polymer backbone or as a part of the backbone have been chosen for the metal binding. These functionalized electroactive polymers (FEAP) served as active material for metal ion sensing. The present investigation is subdivided into three sections. The first part includes design and chemical synthesis of the functionalized polymers by a series of organic reactions. The synthesis has been followed up by characterization using spectroscopic methods including NMR, FTIR, GCMS and Mass spectrometry. In the second part of the investigation, the synthesized polymer has been characterized for the changes in electronic, electric and optical properties after interaction with the selected metal ions. For this, the FEAP is allowed to interact with various metal ions and the changes in the relevant properties have been measured. This includes the study of changes in the conductivity, electronic properties like absorption or emission of the polymer, changes in the redox properties, etc. The third phase of investigation deals with the fabrication of the devices using the active FEAP. The sensor devices comprised of either films, or electrode modified with FEAP or solution of the FEAP, in combination with an appropriate technique has been used for the sensing. The major objectives are enumerated below 1. Functionalzation of polyaniline with imidazole functional group to get imidazole functionalized polyaniline (IMPANI) and study of the electronic, electrical and optical properties of the same. 2. Preparation of films of IMPANI and study of the change in conductivity of the film upon interaction with various metal ions, namely Cu2+, Co2+ and Ni2+ in their chloride form. 3. Synthesis of amine functionalized aniline monomer and chemical graft polymerization onto exfoliated graphite oxide as a substrate to synthesise the amine funtionalised polyaniline grafted to exfoliated graphite oxide (EGAMPANI). Modification of the carbon paste electrode (CPE) with EGAMPANI and study of the electrode characteristic. 4. Study of the electrode properties of EGAMPANI modified carbon paste electrode. 5. Evaluation of the EGAMPANI modified carbon paste electrode as a multi-elemental voltammetric sensor for Pb2+, Hg2+ and Cd2+ in aqueous system. 6. Functionalization of polypyrrole with iminodiacetic acid and characterization of the polymer to synthesis iminodiacetic acid functionalized polypyrrole (IDA-PPy). 7. Modification of the CPE with IDA-PPy by drop casting method and evaluation of the Pb2+ sensing properties. 8. Study of the effect of other metal ions say Hg2+, Co2+, Ni2+, Zn2+, Cu2+ and Cd2+ on the anodic stripping current of Pb2+ using EGAMPANI modified CPE. 9. Synthesis of dipyrromethene-p-(phenylene vinylene) conjugated polymer for heavy metal ion sensing. 10. Study of the changes in the optical absorption and emission properties of the polymer in THF and evaluation of the change in these optical properties upon interaction with the metal ions as analyte. The salient findings of the research work are highlighted as follows, In the first synthesis, aniline has been functionalized with imidazole group and this monomer has been chemical oxidatively polymerized to obtain imidazole functionalized polyaniline (IMPANI). The synthesized polymer possesses a nano-spherical structure, as confirmed from the morphological characterisation using scanning electron microscopy. The IMPANI has been interacted with a representative metal ion, copper (II) chloride, and the copper complexed polymer (Cu-IMPANI) has been subjected to various studies. The coordination of copper with IMPANI results in an increase of molecular weight of the polymer as a result of aggregation, as observed from dynamic light scattering measurements. Apart from this, a significant finding is the decrease of the pH of the system after copper ion coordination attesting to the generation of a secondary hydrochloride ion during the coordination of the copper to the imidazole side chain. This is further confirmed by an increase in conductivity of the Cu-IMPANI compared to IMPANI, measured using the four-probe technique. The increase of conductivity due to copper coordination is one order of magnitude higher. The films which have been prepared from IMPANI and Cu-IMPANI exhibit different morphology. The Cu-IMPANI film prepared by prior co-ordination of Cu ion with IMPANI powder shows a flaky structure, which is not preferable for the conductivity measurements, as a consequence of discontinuity in the medium. To overcome this problem, IMPANI films were initially prepared and then interacted with copper ions for a desired duration, before measurement of the conductivity. This latter procedure enabled the preparation of smooth films for the development of chemoresistive sensors. In continuation of the initial study highlighted above, IMPANI films of thickness 0.02 ± 0.001 mm have been prepared using IMPANI and PANI in DMPU in the ratio of 7:3 by mass. After exposure of the films with respective metal chlorides, such as Ni2+, Co2+ and Cu2+, a change in conductivity is observed in the concentration range of 10-2 to 1 M of metal chlorides. The sensor response may be arranged in the sequence: Ni2+ > Cu2+ > Co2+ at 1M concentration. On the contrary, films prepared from PANI-EB under identical conditions do not exhibit any appreciable change in conductivity. The optimum exposure time is determined to be 10 min for a maximum change in conductivity, after exposure to the chosen metal ions. In the second system taken up for investigation, a tertiary amine containing polyaniline (AMPANI) has been grafted to exfoliated graphite oxide. The amine containing polyaniline grafted to exfoliated graphite oxide (EGAMPANI) has been characterised for structural, morphological and elemental composition. The grafting percentage has been determined to be 7 % by weight of AMPANI on the EGO surface. The synthesized EGAMPANI (5 weight %) has been used to modify carbon paste electrode (CPE) for electrochemical sensor studies. Based on the differential pulse anodic stripping voltammetric studies, the electrochemical response may be arranged in the following sequence: Pb 2+>Cd 2+>Hg 2+ The minimum detection levels obtained are 5×10-6, 5×10-7, and 1.0×10-7 M for Hg2+, Cd2+ and Pb2+ ions respectively. In the next study, an iminodiacetic acid functionalized polypyrrole (IDA-PPy) has been synthesized and characterised for its elemental and structural properties. This has been further used to modify the CPE by drop casting method and used for the specific detection of Pb2+ in acetate buffer. Various parameters governing the electrode performance such as concentration of depositing solution, pH of depositing solution, deposition potential, deposition time, and scan rate, have been optimized to achieve maximum performance and found to be 20 μl, 4.5, -1.3 V, 11 min, 8 mV s-1 respectively for the chosen parameters. Additionally, the influence of other heavy metal ions on the lead response has been studied and it is observed that Co, Cu and Cd ions are found to be interfering. Further, the response of Cd, Co, Cu, Hg, Ni and Zn on IDA-PPy functionalized electrode has been evaluated. The selectivity of IDA-PPy modified electrode for Pb2+ is observed in the concentration range of 1 × 10-7 M and below. The IDA-PPy modified CPE shows a linear correlation for Pb2+ concentration in the range from 1×10-6 to 5×10-9 M and with a lowest limit of detection (LLOD) of 9.6×10-9 M concentration. The efficacy of the electrode for lead sensing has also been evaluated with an industrial effluent sample obtained from a lead battery manufacturing unit. The fourth synthesis pertained to the development of an optical sensor for Fe2+, and Co2+ ions. For this, dipyrromethene as a metal coordinating ligand in conjugation with p-phenylenevinylene has been synthesized and tested for its structural as well as optical properties. It is observed that the polymer shows three absorptions, namely at 294 nm, 357 nm and a major absorption observed as a broad band ranging from 484 to 670 nm. The emission spectrum of the polymer excited at 357 nm shows a characteristic blue emission with a maximum intensity centered at 425 nm. The emission quenching in the presence of various metal ions have been tested and are found to be quenched in presence of Fe2+ and Co2+ ions. All the other metal ions tested namely, Cr3+, Cu2+, and Zn2+ are not found to exhibit any change in the emission spectra below the concentration of 1 × 10-4 M. The linear correlation of the emission intensity with the concentration of the Co2+ and Fe2+ ions has been determined using Stern-Volmer plot. For Co2+ the Stern-Volmer regime is observed from 1×10-4 to 9×10-4 M concentration and the quenching constant Ksv is determined to be 8.67 ×103 M-1. For Fe2+, the linearity is found to be in the regime of 1×10-5 to 9×10-5 M and the quenching constant Ksv is determined to be 7.90 × 103 M-1. In conclusion, different electroactive polymers functionalized with metal coordinating ligands have been synthesized, characterised and evaluated for metal sensing applications. Techniques like electrochemical, optical and conductivity have been used to characterise the response of these FEAP towards metal sensing. It is can be concluded that the electrochemical sensors are more reliable for sensing especially at very low concentrations of metal ions such as Pb, Cd and other techniques like optical and conductimetric are good for detecting metal ions namely Fe, Co, Ni, Cu. The selectivity towards the metal ions is a function of the metal chelating ligand and the extent of sensitivity is dependent upon the technique employed.