Du fait de leurs propriétés intrinsèques exceptionnelles, les nanotubes de carbone (CNTs) sont des matériaux bien adaptés pour renforcer les polymères thermodurcissables. Le nanocomposite multifonctionnel ainsi obtenu possède des propriétés électriques, thermiques et mécaniques sensiblement meilleures que le polymère seul, ce qui lui procure de nombreuses applications potentielles, et tout particulièrement dans le domaine de l’électronique ou de l’aéronautique. Le but de cette thèse de doctorat est orienté suivant deux axes. Il s’agit dans un premier temps de mettre au point un matériau nanocomposite avec des propriétés multifonctionnelles à partir de techniques d’élaborations efficaces. Puis dans un second temps, l’objectif consiste à proposer des alternatives permettant d’améliorer ces propriétés. Le premier chapitre de cette thèse établit une revue de l’état de l’art au sujet des matériaux qui ont été étudiés au cours de ce travail de recherche. Parmi ces matériaux, nous pouvons citer tout particulièrement les CNTs, les renforts hybrides nano/micrométriques constitués de CNTs et d’alumine, les polymères conducteurs électroniques et les polymères thermodurcissables. Il s’agit plus précisément de présenter pour chaque matériau les techniques d’élaboration, leurs structures et finalement leurs propriétés. Dans la seconde partie du manuscrit, nous décrivons en premier lieu les procédés d’élaboration permettant d’obtenir des nanocomposites conformes aux normes internationales. Ensuite, nous présentons les différentes techniques de caractérisation de ces nanomatériaux. Il s’agit notamment de déterminer les phénomènes de transports électriques et thermiques. Des techniques d’analyses supplémentaires permettent de mieux comprendre la structure des matériaux obtenus dans une gamme d’échelle allant de l’état macroscopique à l’atomique. Ainsi, nous avons eu recours à l’utilisation de la microscopie électronique à balayage et en transmission, et aussi la microscopie à force atomique (AFM). Différentes études spectroscopiques de types : Raman, perte d’énergie des électrons (EELS), photoélectrons X (XPS) fournissent des informations additionnelles sur ces matériaux. Les résultats obtenus sur ces nanocomposites en matière de transports électronique et thermique montrent que certaines améliorations sont nécessaires pour optimiser les propriétés multifonctionnelles de ces nanomatériaux. Nous avons concentré nos efforts sur les phénomènes physicochimiques à l’interface matrice/renfort. Par conséquent, nous avons décidé de modifier la surface des CNTs afin de favoriser la cohésion matrice/renfort, mais aussi et surtout, pour diminuer les résistances de contacts entre les CNTs lorsqu’ils sont distribués aléatoirement dans une matrice polymère. Le dernier chapitre de la thèse s’articule autour de la fonctionnalisation des CNTs par un polymère conducteur électronique (ECP). Dans un premier temps, nous avons mis au point des techniques électrochimiques permettant de déposer une couche homogène d’épaisseur nanométrique d’ECP à la surface des CNTs. Ce polymère conducteur et en même temps biocompatible est le polypyrrole (Ppy). La précision et l’efficacité de notre démarche sont démontrées par les différents outils de caractérisation, et tout particulièrement grâce à la microscopie électronique en transmission à haute résolution. Des études supplémentaires par AFM couplé à un résiscope ont montré l’évolution de la résistance électrique d’hybrides CNT-Ppy plus ou moins isolés. Dans une seconde partie, nous avons mis au point une méthode permettant de contrôler finement l’épaisseur de Ppy déposé à la surface des CNTs. / Carbon nanotubes (CNTs) are ideal candidates to reinforce thermoset polymers due to their exceptional intrinsic properties. The resulting multifunctional nanocomposite has electrical, thermal and mechanical properties sensitively higher than pristine polymer. Therefore, this new material possesses various potential applications, and particularly in the domain of electronics and aerospace. The aim of this PhD thesis is oriented towards two directions. In the first one, we establish efficient techniques to produce composite materials with multifunctional properties. Then, the objective consists in the enhancement of these properties by proposing valuable alternatives to previous results cited in the litterature. In the first chapter, we present the state of the art research concerning the materials studied during this work. Among these, there are in particular: CNTs, hybrids constituted of CNTs and alumina microparticles, electronically conducting and thermoset polymers. Moreover, this chapter deals with the characteristics of each material, i.e. elaboration techniques, structures and properties. The second chapter of the manuscript contains first, the elaboration techniques allowing the synthesis of high quality nanocomposites according to international standards. Then, we analyze the properties of these nanomaterials, and particularly in terms of electrical and thermal transports. Further characterization procedures allow better understanding of the obtained structures in a domain ranging from macroscopic to atomic scales. This is realized using scanning/transmission electron microscopy, Raman spectroscopy, EELS, XPS, and AFM. Electrical and thermal conductivity measurements obtained on these new materials give prominence to the necessity of some improvements. Thereby, we have focused our research on the physico-chemical phenomena at the matrix/filler interface. We have proposed to modify the surface of CNTs, in order to favour the matrix/filler cohesion, but also and mainly to decrease contact resistances between the randomly distributed CNTs within the polymer matrix. Finally, the last chapter deals with the surface functionalization of CNTs using electrochemistry. First, we have implemented an accurate technique to deposit a nanometric layer of electronically conducting polymer on the surface of CNTs. This conducting polymer, namely polypyrrole (Ppy) is in the meantime biocompatible. The accuracy and efficiency of our approach are demonstrated through various characterization techniques, and particularly using transmission electron microscopy. Further studies using AFM coupled with a resiscope indicate the electrical resistance distribution performed on CNT-Ppy hybrids. In the second part of this chapter, we present our method to control precisely the thickness of the Ppy layer around the CNTs.

No description available.

Conjugated polymers are organic polymers that can conduct electricity. They undergo a volume change upon redox reaction and can be used as an active material in some micro- actuator system. Micro-actuators are useful in biomedical and electronic application. We have fabricated a patterned Polypyrrole (PPy) trilayer microactuator device that has individually addressable microactuators (a micro walker) which can operate in air. Furthermore, the PPy trilayer microactuator device is fabricated using standard microfabrication method called photolithography to pattern PPy on PVDF membrane material. An etching process was used to achieve the patterning process. We presented the result of characterization of speed as a function of voltage and thickness of PPy film. Secondly, distance as a function of applied voltage and thirdly, the work density as a function of applied voltage. The procedures for fabrication of PPy microactuator device, using clean room facility is detailed in this thesis.

Microbial  Cellulose  (MC)  is  a highly  porous  macromolecule  with  intrinsic  properties  that  make  it  a  useful  substrate  for  conductive  materials  within  ultracapacitors.  MC  has  the  potential  to  increase  capacitance  by  serving  as  a  high  surface  area  substrate  for  conductive  polymers  and  carbonaceous  materials.  Electrode  surface  area  is  a  critical  parameter  in  ultracapacitors  because  capacitance  depends  on  the  available  active  sites  that  are  accessible  to  counter  ions.  Commercial  ultracapacitors  increase  electrode  surface  area  by  adding  micro­size  carbonaceous  materials.  Most  commercial  devices  also  require  adhesive  compounds  to  bind  the  conductive  material  to  the  substrate.  Adhesive  compounds  increase  sheet  resistance  and  hinder  overall  capacitance.  MC  membranes  possess  highly­ordered  surface  hydroxyl  groups  that  readily  bind  to  different  types  conductive  materials  and  reduce  the  need  for  additive  adhesive  compounds.  This  thesis  investigates  three  unique  methods  for  converting  a  MC  membrane  into  a  working  ultracapacitor electrode. In  the  first  method,  polypyrrole  and  carbon  nanotubes  (CNTs)  are  added  to  a  medium  of  Acetobacter  that  incorporates  the  material  into  a  homogeneous  crystalline  matrix of beta­1,4 glucan chains. The resulting MC is a fully integrated membrane  with a  homogeneous  embedded  layer  of  conductive  material.  SEM  imaging  shows  the  conductive  material  is  incorporated  primarily  at  the  core  of  the  membrane.  As  a  result,  this  electrode  suffered  from  high  sheet  resistance  and  did  not  generate  any  significant  capacitance.  In  the  second  method,  a  conductive  ink  consisting  of  CNTs,  carboxymethyl  cellulose  (CMC),  polypyrrole,  and  DI  water  was  used  to  coat  the  surface  of  a  dried  cellulose  membrane.  After  1­2  hours,  the  ink  dries  and  leaves  a  shiny  black  conductive  layer  on  the  membrane’s  surface.  CMC’s  role  in  the  ink  is  to  increase  viscosity  and  help  bind  the  conductive  material  to  the  membrane  surface.  CMC  is  also  a  dielectric  material  that  acts  as  an  insulator  to  the  polypyrrole  and  CNTs,  and  ultimately  impedes  electrical  energy  storage.  In  the  final  method,  a  MC  membrane  was  soaked  in  aqueous  and  non­ aqueous  pyrrole  solutions,  and  polymerized  with  FeCl3  and  Fe2(SO4)3.  Single  and  double  membrane  device  configurations  were  also  investigated.  Surface  polymerization  of  pyrrole  monomers  proved  to  be  the  best  method  for  converting  microbial  cellulose  into  a  working electrode with good capacitance and cyclability. / text

The objective of my thesis is to explore the use of the conducting polymer, polypyrrole, in neural applications. In addition a supplementary aspect of dissertation will involves understanding the effects of external stimuli on nervous system cells, with the ultimate goal of designing therapeutic systems for nerve regeneration. In normal development and peripheral nervous system repair, nerves encounter naturally occurring chemical, physical, and electrical stimuli. Polypyrrole (PPy) has attracted much attention for use in numerous biomedical applications as it presents chemical, physical and electrical stimuli. In addition, PPy is particularly exciting because the extent by which chemical, physical, and electrical cues are presented to the injured nerve can be easily tailored. Thus, conducting polymers are excellent scaffolds for the exploration of how the cellular components of the nervous system (i.e., Schwann cells and neurons) interact with chemical, topographical, and electrical stimuli. This dissertation covers three main objectives and is supplemented by two additional topics. The two additional topics explore the effect stimuli present on the conducting polymer PPy have on neural interfaces. These fundamental studies use computational modeling to gain a better understanding of cellular motility on substrates containing different stimuli. Both topics are covered in the appendices of this dissertation. With regards to the three main objectives, I first characterized and optimized the electrochemical synthesis of the conducting polymer, PPy, for Schwann cell biocompatibility. Next, I investigated the effect the application of electrical cues through PPy has on Schwann cell migration. In addition to investigating the effect of the direct electrical current on Schwann cells I also considered the effect that electrical stimulation provided by PPy has on protein adsorption. Finally, I developed a hybrid PPy material that will provide advantageous properties for neural interfaces. Specifically, I describe the development of a polypyrrole:poly-(lactic-co-glycolic) acid blend for neural applications. In summary the three specific objectives covered in my thesis are: Specific Aim 1: Characterize and optimize the electrochemical synthesis of the conducting polymer, polypyrrole, for Schwann cell biocompatibility Specific Aim 2: Determine the effect of electrical stimulation on Schwann cell migration Specific Aim 3: Develop polypyrrole:poly-(lactic-co-glyolic) acid blends for neural engineering applications. / text

For many years, electrochemically deposited polypyrrole has found application in a host of technologically significant areas. Popular applications include use in rechargeable batteries, electrochromic displays and artificial muscles. However, perhaps the most significant application of polypyrrole is as a gas sensing material. The relatively low selectivity of polypyrrole has led to it seldom being used as a 'stand alone' sensor; the ease by which the properties of polypyrrole may be subtly modified during electrochemical deposition (resulting in subtly different sensor responses) makes it ideally suited for incorporation into sensing 'arrays'. The level of understanding concerning the growth dynamics and structural characteristics of electrochemically deposited polypyrrole was poor prior to the commencement of the work presented; this thesis describes research undertaken in order to elucidate the properties of this material. As variation of the dopant group used during electrochemical deposition has been shown to result in significant structural and operational variations, the work presented focuses on polypyrrole doped with sodium benzene sulfonate (benzene sulfonic acid, sodium salt). The effects of deposition parameter variation have been studied (such as deposition potential and dopant concentration); repeatable relationships were found between deposition parameters and [a] sensor electrical conductivity, and [b] the surface morphology of the films formed. The influence of sensor substrate design is also considered; dissimilarities were found between the consistency and resistance temporal stability of elements deposited on simple 'boot' electrodes and interdigital microelectrodes. A significant proportion of the work presented concerns the study of the macrostructure of electrochemically deposited polypyrrole films. Several novel structural features have been presented, all of which have been documented in the scientific press. These include: The formation of 'tendrillar' morphology (as opposed to the commonly observed polypyrrole 'nodular' morphology) during electrochemical deposition from aqueous electrolyte. Tendril formation has been shown to be the result of the accumulation of impurities at the advancing growth face; a model has been presented which relates impurity accumulation to tendrillar polymer morphology; Demonstration of the evolution of gas at the polymer/substrate interface during aqueous electrolytic deposition. It is suggested that gas evolution is the result of the catalysed disassociation of the (aqueous) supporting electrolyte, and shown that the production of gas at the substrate/polymer interface results in the formation of discrete pockets, the positions of which relate strongly to the positions of nodules on the upper film surface. Demonstration of the recrystallisation of ionic dopant trapped within the polymer films during maturation. Dopant recrystallisation has been verified by SEM and ED AX; crystal growth has been demonstrated by XRD.Finally, the microstructures of a range of subtly different polypyrrole films have been considered. Repeatable relationships were observed between deposition potential, electrolyte solution concentration and microstructure. Characteristic features of X-Ray diffractograms have been related to the theoretical spacing between adjacent pyrrole rings (=3.6A), we believe for the first time.

Electrochemical Supercapacitors (ES), also known as Supercapacitor or Ultracapacitor, has been regarded as an advanced electrical energy storage device for decades. Fabrication of advanced electrode materials is of critical importance for advanced ES. Among various materials used for ES electrode, polypyrrole (PPy) is found to be a promising material due to high specific capacitance, good electrical conductivity, low cost and ease of processing. The use of advanced anionic dopants and addition of multiwall carbon nanotube (MWCNT) have been proved an .effective approach towards advanced PPy based ES with improved electrochemical behaviors. In this research, chemical polymerization of PPy powders and PPy/MWCNT composite materials have been successfully accomplished in presence of advanced anionic dopants, including chromotrope families, amaranth, pyrocatechol violet, eriochrome cyanine R and acid fuchsin. The influence of polyaromatic dopants with different molecular size, charges and charge to mass ratios on the microstructure and electrochemical characteristics has been discussed. PPy coated MWCNT with uniform microstructures was successfully achieved in simple chemical methods. The results showed PPy powders with enhanced microstructures and electrochemical behaviors can be obtained by using such advanced anionic dopants. Multi-charged polyaromatic dopants with larger molecular size benefitted PPy powders with smaller particle size, improved specific capacitance, and enhanced cycling stability, at high electrode mass loadings. Moreover, advanced aromatic dispersant and chemical synthesis was proved a simple and effective method for fabrication of PPy/MWCNT composite materials at different PPy/MWCNT mass ratio, among which the powder with PPy/MWCNT mass ratio of 7:3 showed optimum electrochemical performance. Last but not the least, the use of advanced high porosity current collector (Ni foam) allowed high electrode mass loading and good electric conductivity. As a result, advanced PPy/MWCNT composite materials which allows improved electrochemical behaviors, especially at high mass loading, are promising electrode materials for ES. / Thesis / Master of Applied Science (MASc)

No description available.

La stimulation électrique (SE) semble favoriser la cicatrisation des plaies par ses effets sur les fibroblastes. Cependant, son interaction avec les kératinocytes n'a pas été bien établie. Le polypyrrole (PPy) en tant que biomatériau conducteur est un excellent candidat pour délivrer les SE aux cellules, ce qui devient plus évident avec le développement de la nouvelle membrane souple à base de PPy. Cependant, les faibles propriétés mécaniques limitent l'utilisation de cette membrane. La présente étude visait à améliorer la résistance mécanique de la membrane à base de PPy et étudier les comportements cellulaires et moléculaires des kératinocytes après exposition à des SE via cette nouvelle membrane PPy. Premièrement, la membrane souple à base de PPy a été renforcée par électrofilage, de manière synergique, avec des fibres de polyuréthane (PU) et de polylactide (PLLA). Des tests mécaniques ont confirmé que la résistance à la traction de la membrane a été considérablement augmentée. Ensuite, les kératinocytes ont été cultivés sur la membrane PPy renforcée, puis stimulés par des intensités électriques de 100 ou 200 mV mm⁻¹ pendant 6 ou 24 heures. Les cellules stimulées présentaient une capacité proliférative considérablement accrue. Les sécrétions d'IL-6, IL-1α, IL-8, GROα, FGF2 et VEGF-A ont également augmenté. Fait intéressant, l'SE de 24 heures a induit une « mémoire de stimulation » car les cellules stimulées ont montré une augmentation significative de formation de colonies (CFE) après 6 jours après l'exposition à la stimulation électrique. De plus, l'expression des kératines 5, 14 et 10/13 était significativement augmentée par la SE. La SE a augmenté l'expression de la phosphorylation des kinases ERK1/2. L'expression des protéines des kératinocytes de la peau humaine peut être activée par des stimulations électriques appropriées pour favoriser la cicatrisation des plaies cutanées. La membrane PPy souple renforcée peut servir de pansement conducteur pour faciliter l'exposition de la plaie à une stimulation électrique pour favoriser sa cicatrisation. / Keratinocytes as the principal skin cell type play a major role in wound closure. In the meantime, electrical stimulation (ES) has been found effective in promoting wound healing. However, the role of ES on keratinocytes has not been well established. Polypyrrole (PPy), especially the recently developed soft PPy membrane, is an electrically conductive biomaterial and a good candidate to deliver ES to cells. However, the weak mechanical strength of the soft PPy membrane has limited its practical use. The present work was to enhance the mechanical strength of this soft PPy membrane and to investigate the cellular and molecular behaviors of the keratinocytes underwent ES via this novel PPy membrane. Firstly, the soft PPy membrane was synergically reinforced with polyurethane (PU) and poly (L-lactic acid) (PLLA) fibers through electrospinning technology. Mechanical tests confirmed the significantly increased tensile strength, which rendered the originally fragile PPy membrane strong enough to stand ordinary manipulations without compromising its electrical properties. Afterwards, HaCaT keratinocytes were cultured on the PU/PLLA reinforced PPy membranes under electrical intensities of 100 and 200 mV mm⁻¹ for 6 or 24 hr. The electrically stimulated cells exhibited a considerably increased proliferative ability. Meanwhile, secretions of the IL-6, IL-1α, IL-8, GROα, FGF2 and VEGF-A increased as well. Interestingly, the 24 hr ES induced a "stimulus memory" by showing a significant rise in colony forming efficiency (CFE) 6 days post-ES. Additionally, the expressions of keratin 5, keratin 14, keratin 10 and keratin 13 were significantly modulated by ES. Finally, the phosphorylation of ERK1/2 kinases was regulated by ES. The overall results demonstrated that the proliferation, differentiation, and protein expression of human skin keratinocytes can be activated through appropriate ES to benefit skin wound healing. Moreover, the PU/PLLA reinforced soft PPy membrane may server as a conductive wound dressing to facilitate ES to wound.

Parmi tous les polymères conducteurs, le polypyrrole est l’un des plus utilisés notamment à cause de ses propriétés telles que la facilité de préparation, la stabilité environnementale et la biocompatibilité qui permettent son utilisation dans de très nombreuses applications. Le polypyrrole peut être préparé par polymérisation chimique ou électrochimique, cette dernière méthode étant la plus appropriée si on souhaite entre autre contrôler l’épaisseur du film de polypyrrole déposé. Les nanostructures de polypyrrole sont généralement synthétisées en présence de gabarits (« soft-template » ou « hard-template »).Le but de cette thèse est orienté suivant deux axes. Il s’agit dans un premier temps de synthétiser des (nano)structures de polymère conducteur par voie électrochimique et sans emploi d’une matrice support. Puis dans un second temps, d’utiliser ces (nano)structures dans des applications de type (bio)capteurs.Le premier chapitre de cette thèse établit une revue de l’état de l’art concernant la synthèse, les propriétés et les applications des polymères conducteurs. Dans le deuxième chapitre de ce manuscrit, nous décrivons le matériel et les différentes techniques de caractérisation utilisées au cours de ce travail. Le troisième chapitre s’articule autour de la synthèse par voie électrochimique de films de polypyrrole suroxydé et de nanostructures de polypyrrole, alors que le quatrième chapitre présente les résultats de l’étude de l’influence de différents paramètres expérimentaux à savoir le potentiel appliqué, la durée de polarisation, le pH de la solution de pyrrole et la concentration en pyrrole et en anions d’acide faible. Dans le cinquième chapitre nous discutons les différents mécanismes de formation de (nano)structures de polypyrrole décrits dans la littérature en nous basant notamment sur les expériences de suivi du pH interfacial au cours de la polymérisation. Nous proposons également un mécanisme en accord avec les résultats obtenus avec des monomères de pyrrole ou d’EDOT. Le sixième et dernier chapitre est consacré aux applications étudiées à savoir les (bio)capteurs de glucose et de pH et la synthèse de polypyrrole sur des électrodes de titane et sur des fibres de carbone. / Polypyrrole is one of the most widely investigated conducting polymer notably due to its high conductivity under its doped oxidized form, its biocompatibility and good stability in air and aqueous media allowing its use for various applications. Polypyrrole can be synthesized either by a chemical oxidation (powder) or electrochemical oxidation (film coating). To control over the location and the thickness of the deposit, the electropolymerization can be considered as the main method. Polypyrrole nanostructures are usually synthesized in the presence of templates (hard-templates or soft-templates).The aim of this PhD thesis is oriented towards two directions. In the first one, we synthesized polypyrrole nanostructures by electropolymerization and without using a template. Then we used these nanostructures as a material for various applications including (bio)chemical sensors.The first chapter of this thesis establishes a review of the state of the art concerning the synthesis, properties and applications of conducting polymers. In the second chapter of this manuscript, we describe the equipment and various characterization techniques used in this work. The third chapter focuses on the electrochemical synthesis of overoxydized polypyrrole and polypyrrole (nano)structures, while the fourth chapter presents the results of the study of the influence of various experimental parameters. In the fifth chapter we discuss the different formation mechanisms of polypyrrole (nano)structures described in the literature based in particular on the experiences of interfacial pH monitoring during the polymerization. We also propose a mechanism in accordance with the results obtained with pyrrole or EDOT monomers. The sixth and final chapter is devoted to the applications studied namely the glucose and pH (bio)sensors and synthesis of polypyrrole on titanium electrodes and carbon nanofibers.