Single walled carbon nanotube (SWNT)-based polymer nanocomposites have generated a lot of interest as potential multifunctional materials due to the exceptional physical properties of SWNTs. To date, investigations into the electromechanical response of these materials are limited. Previous studies have shown marginal improvements in the electromechanical response of already electroactive polymers (EAPs) with addition of SWNTs. However, in general, disadvantages of EAPs such as high actuation electric field, low blocked stress and low work capacity remain unaddressed. This dissertation targets a comprehensive investigation of the electromechanical response of SWNT-based polymer nanocomposites. Specifically, the study focuses on incorporating SWNTs in three polymeric matrices: a non-polar amorphous polyimide (CP2), a polar amorphous polyimide ((-CN) APB-ODPA), and a highly polar semicrystalline polymer (PVDF). In the first step, emergence of an electrostrictive response is discovered in the non-polar polyimide CP2 in the presence of SWNTs. Transverse and longitudinal electrostrictive coefficients are measured to be six orders of magnitude higher than those of known electrostrictive polymers like polyurethane and P(VDF-TrFE) at less than 1/100th of the actuation electric fields. Next, the effect of the polymer matrix on the electrostrictive response is studied by focusing on the polar (-CN) APB-ODPA. A transverse electrostriction coefficient of 1.5 m2/MV2 is measured for 1 vol percent SWNT- (-CN) APB-ODPA, about twice the value found for 1 vol percent SWNT-CP2. The high value is attributed to higher dipole moment of the (-CN) APB-ODPA molecule and strong non-covalent interaction between the SWNTs and (-CN) APB-ODPA matrix. Finally, polyvinylidene fluoride (PVDF) matrix is selected as a means to optimize the electrostrictive response, since PVDF demonstrates both a high dipole moment and a strong non-covalent interaction with the SWNTs. SWNT-PVDF nanocomposites fared better than SWNT-CP2 nanocomposites but had comparable response to SWNT-(-CN) APB-ODPA nanocomposites. This was attributed to comparable polarization in both the polar nanocomposite systems. To maximize the SWNT-PVDF response, SWNT-PVDF samples were stretched leading to increase in the total polarization of the nanocomposite samples and decrease in the conductive losses. However, the dielectric constant also decreased after stretching due to disruption of the SWNT network, resulting in a decrease of the electrostrictive response.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed October 13, 2009). PDF text: 261 p. : ill. (some col.) ; 5 Mb. UMI publication number: AAT 3359063. Includes bibliographical references. Also available in microfilm and microfiche formats.

Includes bibliographical references (p. 193-206).

Thesis (Ph. D.)--University of North Texas, Dec., 2009. / Title from title page display. Includes bibliographical references.

Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2009. / "August, 2009." Title from electronic dissertation title page (viewed 9/23/2009) Advisor, Sadhan C. Jana; Committee members, Avraam I. Isayev, James L. White, George G. Chase, Shing-Chung Josh Wong; Department Chair, Sadhan C. Jana; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Nanohybrid materials have been prepared and examined for their electrocatalytic activity. The nanocomposites have been prepared from carbon nanomaterials (multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets), cadmium selenide quantum dots and metallophthalocyanines (MPcs). The MPcs used in this work are cobalt tetraamino-phthalocyanine (CoTAPc) and tetra (4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt (II)) (CoPyPc). Their activity has also been explored in different forms; polymeric MPcs, iodine doped MPcs and covalently linked MPcs. The premixed drop-dry, sequential drop-dry and electropolymerisation electrode modification techniques were used to prepare nanocomposite catalysts on the glassy carbon electrode (GCE) surface. The sequential drop dry technique for MPc and MWCNTs gave better catalytic responses in terms of limit of detection, catalytic and electron transfer rate constants relative to the premixed. MWCNTs and CdSe-QDs have been used as intercalating agents to reduce restacking of graphene nanosheets during nanocomposite preparation. Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for electrochemical characterization modified GCE. X-ray photoelectron spectroscopy, X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, infra-red spectroscopy, Raman spectroscopy were used to explore surface functionalities, morphology and topography of the nanocomposites. Electrocatalytic activity and possible applications of the modified electrodes were tested using oxygen reduction reaction, l-cysteine oxidation and paraquat reduction. Activity of nanocomposites was found superior over individual nanomaterials in these applications.

The modification of electrodes is always an important task in electrochemical detection of electroactive and biological molecules. Chemically modified electrodes can offer improved selectivity and sensitivity for the target analyte, which greatly enhance the electrode performance. Various materials such as conducting polymers, metal nanoparticles and carbon nanomaterials have been exploited and widely used for the modification of electrodes. Electrochemical or spontaneous deposition, electrostatic adsorption, layer-by-layer self assembly and covalent binding have also been developed for electrode modification and offer improved performance. Both Prussian blue (PB) and toluidine blue O (TBO) are excellent redox mediators and very popular in electrode modification. PB has shown strong catalytic property for the reduction of hydrogen peroxide, but the application in biosensor fabrication is limited for its instability at neutral pH. Graphene, as a single-atom-thick carbon material, is considered an ideal platform for designing composite nanomaterials for high-performance electrochemical or electrocatalytic devices. The combination of PB with reduced graphene oxide (RGO) and poly(toluidine blue O) (PTBO) will greatly improve the stability of PB. An amperometric biosensor based on glassy carbon (GC) electrode modified with reduced graphene oxide, PB and poly(toluidine blue O) was developed. Experimental results showed that the GC/RGO/PB/PTBO modified electrode offered an excellent electrocatalytic activity toward the reduction of hydrogen peroxide due to the possible synergistic effects of the PB-PTBO composite material. After codeposition of glucose oxidase (GOD) and chitosan (CHIT) coating, the resulting GC/RGO/PB/ PTBO/CHIT-GOD electrode exhibited excellent response to glucose with a sensitivity of 59 mA M1 cm2, a low detection limit of 8.4 μM and a linear range from 0.02 to 1.09 mM at a detection potential of +0.2 V vs. Ag.

Orientadores: Liliane Maria Ferrareso Lona, Fernando Wypych / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T11:49:48Z (GMT). No. of bitstreams: 1 Nogueira_TelmaRegina_D.pdf: 5921921 bytes, checksum: 94d41e3ad2e82662f94aff13bcfef289 (MD5) Previous issue date: 2012 / Resumo: Recentemente, nanocompósitos poliméricos reforçados com argilominerais têm atraído considerável interesse científico. A maioria dos trabalhos publicados sobre a produção de nanocompósitos poliméricos utiliza silicatos naturais lamelares da classe dos filosilicatos do tipo 2:1, como a montmorilonita e a hectorita, como agentes de reforço. Para permitir a compatibilização com polímeros hidrofóbicos, já que os filosilicatos são hidrofílicos, utiliza-se normalmente a montmorilonita modificada com surfactantes catiônicos (sais quaternários de amônio, por exemplo), como reforço. Outra classe de trocadores aniônicos é a dos hidróxidos duplos lamelares (HDLs), que raramente ocorrem na natureza, mas são muito simples e baratos de sintetizar. Neste trabalho de doutorado foi investigada a polimerização "in situ" de metacrilato de metila com hidróxidos duplos lamelares modificados com ânions orgânicos (dodecilsulfato, estearato e laurato). Há poucos estudos em literatura aberta sobre as propriedades mecânicas e térmicas dos nanocompósitos de PMMA reforçados com HDLs e até agora não foram encontrados estudos sobre nanocompósitos de PMMA reforçados com HDLs intercalados com ânions estearato. O laboratório iniciou o estudo nesta área de nanocompósitos recentemente, no entanto, já foram produzidos alguns resultados sobre as propriedades de nanocompósitos de poliestireno e hidróxidos duplos lamelares. No presente trabalho foram produzidos nanocompósitos com alta transparência na região espectral da radiação visível assim como nanocompósitos coloridos, sem a adição de pigmentos ou corantes. Através de resultados de análises termogravimétricas demonstrou-se que a adição de HDLs pode aumentar a temperatura de decomposição do PMMA em mais de 80°C. Os resultados de análise dinâmico-mecânica mostraram que a concentrações de HDLs de 1% em massa nos nanocompósitos foi possível obter módulos elásticos com valores mais do que o dobro daqueles obtidos para o PMMA na maior parte da faixa de temperatura estudada. Com o objetivo de avaliar como a concentração de HDL afetava as propriedades anteriormente avaliadas, foram sintetizados nanocompósitos poliméricos contendo seis diferentes HDLs pré-selecionados, em duas diferentes concentrações (3% e 5%). Estes resultados demonstraram que a maioria destes nanocompósitos apresentou valores de microdureza maiores do que os encontrados para o PMMA / Abstract: Recently, nanocomposites consisting of polymer and mineral clays have attracted considerable scientific interest. Most published works on the production of polymer nanocomposites use clay mineral fillers such as montmorillonite, modified with cationic surfactants. Another class of anionic exchanger is layered double hydroxides (LDH), which rarely occur in nature but are very simple and inexpensive to synthesize, allowing the production of highly defined composition material. In this study we have investigated "in situ" bulk polymerization of methyl methacrylate (MMA) in the presence of LDHs intercalated by organic anions (dodecyl sulfate, laurate, stearate). There are few studies in the open literature on the mechanical and thermal properties of PMMA nanocomposites reinforced with hydrophobic HDLs and so far it was not found in open literature studies about the mechanical and thermal properties of the PMMA nanocomposites reinforced with stearate intercalated LDHs. In our laboratory, the investigation in the nanocomposites area started recently, however, some results on the nanocomposites of polystyrene and layered double hydroxides have already been produced. In the present work were synthesized nanocomposites with high transparence in the visible region as well as nanocomposites with an uniform orange color, without the addition of dyes or pigments. By thermogravimetric analysis, the results showed that the addition of LDHs may increase PMMA decomposition temperature in more than 80°C. The results of dynamic mechanical analysis, for nanocomposites with 1wt% of LDHs, showed that elastic modulus more than 2 times higher than PMMA in the range of studied temperature. In order to verify how the LDH concentration could affect the previously evaluated properties, nanocomposites containing six different pre-selected LDHs, in two different concentrations (3% and 5%) were synthesized. These results demonstrated that most of these nanocomposites presented microhardness values higher than those found for PMMA / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

La surveillance de la santé humaine et le diagnostic anticipé des cancers (poumon et peau) en analysant le volatolome et en particulier les biomarqueurs présents dans l’haleine ou émis par une zone de peau affectée, est un domaine de recherche émergent. Il s'agit d'une technique non invasive, peu coûteuse, rapide et fiable qui peut être utilisée pour la détection des cancers à ses premiers stades au niveau clinique. Les capteurs de vapeur chémo-résistifs quantiques à base de nanomatériaux (vQRS) peuvent fournir une solution pour développer des nez électroniques (e- nose) à cet effet. La constitution d’une matrice de capteurs performante (e-nose) est nécessaire pour l'analyse de l’haleine ou des COV émis par la peau, car tous deux sont des mélanges complexes de COV incluant différents biomarqueurs. L'objectif de cette thèse était de développer un assortiment de capteurs hautement sensibles et sélectifs pour l'analyse de certains biomarqueurs du cancer du poumon et de la peau. Pour cela, une matrice de senseurs de haute performance a été fabriquée à partir de nanocomposites polymère conducteurs dont l’architecture conductrice construite à base de nanotubes de carbone a été fonctionnalisée par différentes matrices polymères pour en modifier la sélectivité vis-à-vis de différents COV. Dans un premier temps, des mélanges binaires de COV et d'eau ont été analysés avec une matrice de senseurs simple pour évaluer le comportement des capteurs en présence d'humidité. Ensuite, un e-nose plus complexe a été préparé avec neuf capteurs sensibles et sélectifs pour détecter une petite quantité de biomarqueurs du cancer présents dans une grande quantité d'autres COV. Les empreintes gazeuses obtenues à l'aide d'un outil statistique pour les divers mélanges de COV ont permis d'identifier la présence de biomarqueurs. Enfin, différents échantillons d’haleine ont été testés avec le même e-nose. Les échantillons d’haleine ont été recueillis dans différentes conditions et l’e-nose a pu les discriminer efficacement et les situer sur les cartes d’empreintes d’haleines obtenues par analyse statistique. / A Human health monitoring and anticipated diagnosis of cancers (lung and skin) by the analysis of the volatolome and in particular the biomarkers present in exhaled breath or emitted by affected skin area is an emerging area of research. This is a non-invasive, inexpensive, fast and reliable technique which can be used for cancers’ detection in their early stages at the clinical level. Nanomaterials based quantum resistive vapour sensors (vQRS) can provide solutions for developing electronic noses (e-nose) for this purpose. A complex sensors’ array is required for the analysis of exhaled breath or VOC emitted by skin as both of them are complex blend of various VOC biomarkers. The objective of this thesis was to develop highly sensitive and selective sensors for cancer biomarker analysis. Therefore, several high-performance sensors’ arrays have been fabricated based on conducting nanocomposites. The carbon nanotubes used to build the conducting architecture were functionalized with different polymer matrices for tuning their selectivity towards different VOC. Initially, binary blends of VOC and water were analysed with simple sensors’ array to evaluate the sensors behaviour in the presence of moisture. Later, a complex e-nose has been prepared with nine differently sensitive and selective sensors to detect subppm amounts of cancer biomarkers present in a large quantity of other VOC. Fingerprints were obtained using a statistical tool for various biomarkers blends which were able to identify the presence of biomarkers. Finally, exhaled breath samples were tested with the same e-nose. The breath samples were collected in different conditions and the e-nose was able to discriminate the different samples effectively by locating them on the breath maps obtained by a statistical analysis.

M.Tech. (Chemical Technology) / Please refer to full text to view abstract