Les surfaces de polymères électro-stimulables font partie de la catégorie des surfacesintelligentes. Elles sont capables de modifier leurs propriétés lorsqu’elles sont stimulées par unchamp électrique. Au cours de cette thèse nous avons fabriqué des surfaces de chaines depolyélectrolytes faibles greffées (PAA, P2VP, PDMAEMA), soit par auto-assemblage, soit partransfert via la balance de Langmuir. Nous avons ensuite étudié l’organisation des chaines depolyélectrolytes à la surface en fonction des conditions de pH et de sel de la sous-phase dans labalance de Langmuir. Avant de stimuler ces chaines de polyélectrolytes greffées à l’aide d’unchamp électrique, nous avons étudié leur sensibilité à la variation de pH et à la variation de laconcentration en sel. Pour cela des mesures d’épaisseurs de films de polyélectrolytes et desmesures d’angle de contact ont été effectuées. Ces études préliminaires nous ont permis desélectionner des valeurs de densité de greffage des chaines de polyélectrolytes ainsi que le pH etla concentration en sel de la solution adaptés pour la stimulation des surfaces par un champélectrique. Nous avons alors montré que les chaines greffées de PAA et de PDMAEMA étaienttrès sensibles à la variation de la tension électrique lorsque le pH est proche du pKa ou du pKb dela surface : pour une charge de la surface identique aux charges des chaines de polyélectrolytes,ces dernières vont adopter une conformation de brosse tandis qu’elles seront collapsées lorsque lacharge de la surface est de signe opposé aux charges des chaines. Cette transition réversible deschaines en fonction de la valeur de la tension appliquée permet de contrôler les propriétés demouillage et d’adhésion de ces surfaces. En revanche, pour un pH proche du pKb, les chainesgreffées de P2VP sont peu sensibles à l’application d’un champ électrique. Nous avons supposéque cela était dû à une variation de pH local au sein des chaines lorsque le champ électrique estappliqué. / Electro-responsive polymer surfaces are able to change their properties when they are stimulatedby an electric field. In this work, we grafted weak polyelectrolyte on surfaces by self-assembly orby transferring the molecules using the Langmuir-Schaefer method. First we studied theorganization of the polyelectrolyte chains at the surface for different pH and salt concentration ofthe subphase used in the Langmuir trough. Then we explored the response of the surfaces to pHand salt concentration changes by measuring the thickness variation of the polyelectrolyte filmsand the changes in contact angle. These preliminary studies allowed us to select the graftingdensity of polyelectrolyte chains and the pH and salt concentrations of the aqueous solutionadapted for the stimulation of the surfaces by an electric field. We then demonstrated that PAAand PDMAEMA grafted chains were very sensitive to the variation of the applied voltage whenthe pH is close to the pKa or from the pKb of the surface. If the charge of the surface has the samesign as the charges on the polyelectrolyte chains, the latter would adopt a brush conformation,whereas if the charge of the surface has the opposite sign compared to the sign of the charges onthe polyelectrolyte chains, the chains would collapse. This reversible transition of the chainsconformation with the sign of the applied voltage allowed us to control the wetting and theadhesion properties of these surfaces. Nevertheless, for a pH close to the pKb, the P2VP graftedchains are almost unresponsive to the application of an electric field. We supposed that this is theconsequence of a local pH variation inside the grafted chains when the electric field is applied.

No description available.

Oral delivery of insulin used for the management of Type 1 Diabetes could be referred to as one of the major long term goals of diabetes research. However, the bioavailability of orally administered insulin is significantly compromised by enzymatic degradation in the GI tract and poor enteral absorption of the protein due to its macromolecular size and hydrophilicity. Nano-sized polymer-protein polyelectrolyte complexes (PECS) formed by electrostatic interactions between insulin and Polyallylamine-based polymers at pH 7.4 have been adapted to facilitate oral insulin delivery. Polyallylamine (15kDa) was quaternised by methylation of its primary amines using methyl iodide to yield quaternised Paa (QPaa). Average level of polymer quaternisation was determined by elemental analysis and was found to be 72 ± 2mol%. Subsequent thiolation of Paa and QPaa using two different thiolation procedures involving carbodiimide mediated conjugation to N-acetylcysteine (NAC) and modification of the polymers using 2-iminothiolane hydrochloride yielded their respective NAC and 4-thiobutylamidine (TBA) conjugates: Paa-NAC/QPaa-NAC and Paa-TBA/QPaa-TBA. Estimation of the free thiol content of these thiomers by iodometric titration showed that both Paa-NAC and QPaa-NAC displayed 60 ± 1.2 and 60 ± 4.3ìmol free thiol groups per gram polymer, while Paa-TBA and QPaa-TBA conjugates displayed 490 ± 18 and 440 ± 21ìmol free thiol groups per gram polymer respectively. Mixing optimal mass ratios of each polymer and insulin in Tris buffer at pH 7.4 resulted in the formation of soluble nanocomplexes. Complexes were characterised by transmittance measurements, particle size analysis, zeta potential, complexation efficiency, and transmission electron microscopy (TEM). Stable polymer-insulin complexes were observed to have hydrodynamic sizes between 50-200nm, positively charged zeta potential values ranging between 20-40mV and high insulin complexation efficiency (> 90%). Complexation of insulin with TBA conjugates however appeared to alter insulin conformation affecting the detection of complexed insulin by HPLC. TEM analysis revealed the formation of bilayered nanovessicles as well as conventional single-layered nanoparticles on complexation of insulin with QPaa and thiolated Paa/QPaa derivatives. In-vitro assessments of enzyme-protective effect of QPaa, Paa-NAC and QPaa-NAC insulin complexes showed that when compared to a free insulin control, all the aforementioned complexes could protect insulin from degradation by trypsin and á-chymotrypsin, but not from pepsin. In-vitro mucin adsorption assays showed that all polymers exhibited a similar mucoadhesive profile with their corresponding insulin PEC, with thiolated Paa derivatives adsorbing >20% more mucin than Paa. Thiolation of QPaa did not result in a noticeable improvement in its mucoadhesive capacity indicating that polymer-mucin thiol-disulphide interactions may be hindered by the presence of quaternary groups. The IC50 of each polymer was determined by MTT assays carried out on Caco-2 cells with or without the inclusion of a 24-hour cell recovery period. An MTT assay conducted without a recovery period indicated that quaternisation of Paa was associated with a 6-fold improvement in its IC50; also cells subjected to a 24-hour recovery period following treatment with QPaa (0.001-4mgml-1) showed no signs of toxicity. Thiolation of Paa resulted in slight (≤ 2 fold) improvements in IC50, while thiolation of QPaa resulted in a decrease in IC50 values obtained both with and without a cell recovery period. Each polymer was subsequently labelled with rhodamine B isothiocyanate (RBITC) and complexed with fluorescein isothiocyanate (FITC)-insulin. Monitoring uptake of these complexes by Caco-2 cells using fluorescence microscopy with DAPI staining indicated that uptake of QPaa and QPaa-TBA complexes was mainly intracellular being localised within the perinuclear area of cells highlighted by DAPI. Hence, intracellular uptake of PECS by Caco-2 cells was enhanced by Paa quaternisation and TBA-based thiolation of QPaa.

Active Pharmaceutical Ingredients with poor solubility have presented significant difficulties in drug product design and development including slow and ineffective absorption leading to inadequate and variable bioavailability. Therefore it has become increasingly desirable to overcome the low aqueous solubility of drug candidates and develop more novel and innovative formulation approaches to increase the dissolution rate of the poorly soluble drugs. This work focuses on the formulation of novel amorphous ibuprofen-polymer nanoconjugates based on the polymer-drug complexation in order to improve its physical and dissolution characteristics without the use of toxic organic solvents. Plain and ibuprofen-loaded binary and ternary nanoconjugates were prepared using four modified co-precipitation techniques including melt solubilization; alkaline solubilization; surfactant solubilization and hydrotropic complexation techniques. A remarkably high loading capacity was achieved ranging from 89.05 to 99.49% across the four techniques and polymer-polymer ratio of 50:50 was found to be most efficient. All the four techniques reduced the size of ibuprofen (2.87 μm) significantly in the presence of 2.0 x10-3 mM of Diethylaminoethyl Dextran (DEAE-Dextran) in the order melt solubilization (203.25 nm) > alkaline solubilization (185.68 nm) > surfactant (Tween 80) solubilization (122.17 nm) > hydrotropic complexation (77.92 nm). 5.0 x 10-4 mM of chitosan also reduced the size of ibuprofen from 2872.12 to 10.70 nm (268-fold reduction). The FTIR spectroscopic analysis revealed electrostatic, hydrophobic and hydrogen bonding interaction between solubilized ibuprofen and the cationic polymers (DEAE-Dextran and chitosan) to form a new product (an amide). Polymer-polymer complexation also occurred between DEAE-Dextran and gellan as well as chitosan and gellan to a different extent depending on the mixing ratios. 1H and 13C NMR analysis confirmed the conjugation between ibuprofen and each of the cationic polymers as well as the formation of a new amide product. DSC thermal analysis showed that the nanoconjugates exhibited new broad and diffuse peaks confirming that they did exist in amorphous state as multiple complexes. The TGA thermograms of the binary nanoconjugates exhibited one step degradation profile compared with the physical mixture which exhibited two steps. However the ternary nanoconjugates exhibited two steps degradation profile confirming the formation of multiple complexes. Marked enhancement of drug release was achieved by the four techniques compared with the ibuprofen control. All the DG (DEAE-Dextran - Gellan) complexes exhibited a higher release profile than ibuprofen control. Fickian and non-Fickian anomalous mechanisms were deduced for the drug release of ibuprofen from the binary conjugates. The ternary nanoconjugates exhibited non-Fickian (anomalous) diffusion, Fickian diffusion and Super Case II transport release mechanisms. The ternary nanoconjugate hydrogels exhibited complete release (100%) within 48 h. The lowest concentration of DEAE-Dextran, Gellan - Ibuprofen - DEAE-Dextran (GIbDD) 2:0.125, increased the release of ibuprofen by 13.4% however higher concentrations of DEAE-Dextran decreased the release profile steadily. It was concluded that DEAE-Dextran has potentials in the formulation of modified (extended) release of ibuprofen. The most prominent mechanism of release of ibuprofen from the nanoconjugate hydrogel was Super Case II transport. SEM and AFM micrographs of the drug loaded composite pharmaceutical films exhibited concentric spheres with two and three layers for the binary and ternary films respectively. This supports the evidence of internalization of ibuprofen by the polyelectrolyte complex. The FTIR and DSC results confirmed electrostatic and hydrophobic interactions between ibuprofen and DEAE-Dextran as well as between gellan and DEAE-Dextran. Thermal analysis revealed that plain bilayer films were thermally more stable than composite films. The addition of ibuprofen significantly increased (p < 0.05, n = 4) the swelling ratio of the films compared with films without the drug. The drug loaded bilayer films exhibited Fickian diffusion mechanism while the dominating mechanism for composite films was anomalous (Non-Fickian) transport. From the foregoing, it was evident that ibuprofen-polymer nanoconjugate present a novel tool for the delivery of ibuprofen with potential application for transdermal delivery.

There has been a remarkable progress in the development of organic electronic materials since the discovery of conducting polymers more than three decades ago. Many of these materials can be processed from solution, in the form as inks. This allows for using traditional high-volume printing techniques for manufacturing of organic electronic devices on various flexible surfaces at low cost. Many of the envisioned applications will use printed batteries, organic solar cells or electromagnetic coupling for powering. This requires that the included devices are power efficient and can operate at low voltages. This thesis is focused on organic thin-film transistors that employ electrolytes as gate insulators. The high capacitance of the electrolyte layers allows the transistors to operate at very low voltages, at only 1 V. Polyanion-gated p-channel transistors and polycation-gated n-channel transistors are demonstrated. The mobile ions in the respective polyelectrolyte are attracted towards the gate electrode during transistor operation, while the polymer ions create a stable interface with the charged semiconductor channel. This suppresses electrochemical doping of the semiconductor bulk, which enables the transistors to fully operate in the field-effect mode. As a result, the transistors display relatively fast switching (≤ 100 µs). Interestingly, the switching speed of the transistors saturates as the channel length is reduced. This deviation from the downscaling rule is explained by that the ionic relaxation in the electrolyte limits the channel formation rather than the electronic transport in the semiconductor. Moreover, both unipolar and complementary integrated circuits based on polyelectrolyte-gated transistors are demonstrated. The complementary circuits operate at supply voltages down to 0.2 V, have a static power consumption of less than 2.5 nW per gate and display signal propagation delays down to 0.26 ms per stage. Hence, polyelectrolyte-gated circuits hold great promise for printed electronics applications driven by low-voltage and low-capacity power sources.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Cette thèse porte pour l'essentiel sur la synthèse de copolymères à blocs bien définis composés au moins d'un bloc polymère semi-conducteur et d'un segment hydrosoluble pour être utilisés comme agents dispersants de nanotubes de carbone (NTCs) dans des milieux aqueux. Des copolymères de différentes masses molaires ont été synthétisés en suivant des procédés de polymérisation sans métaux et l’influence de la fraction volumique de la partie hydrosoluble a été étudiée au regard de leur solubilité en milieux aqueux. La capacité de ces copolymères à s'organiser ou s'auto-assembler tant en solution qu'en film a été examinée. Enfin, des dispersions de NTCs avec ces copolymères ainsi que leurs films obtenus par différents types de dépôts ont été réalisés et caractérisés pour déterminer notamment leurs caractéristiques électro-optiques. / Our work focused on the synthesis of well-defined copolymers constituted with at least a conductive polymer segment along with hydrophilic moieties in order to disperse CNTs in aqueous media. Using metal free polymerizations, copolymers with different molecular weights were synthesized in order to study the influence of the hydrophilic part on these materials. Besides the self-assembly behavior of these copolymers, both in bulk and in solution, were addressed. This type of copolymers were successfully used to disperse both single and multi wall carbon nanotubes. Electrical and optical characteristics of the dispersions together with their films will also be discussed.

"Polyelectrolyte multilayer (PEM) thin films prepared via the Layer-by-Layer (LbL) deposition technique are of special interest in this research. The purpose of this study is to replace current mechanical closure systems, based on hook-and-loop type fasteners (i.e. Velcro), with PEM thin film systems. The technique is simple, cheap, versatile and environmental friendly; as a consequence a variety of thin films can be easily fabricated. By proposing PEMs as non-mechanical and nanoscopic molecular closures, we aim to obtain hermetic sealing, good adhesive strength, and peel off ease. Atomic force microscopy (AFM) and colloidal probe techniques were used to characterize the morphology, roughness and adhesive properties of PEMs. AFM measurements were conducted in air, necessarily requiring careful control of ambient humidity. PEMs were formed by consecutive deposition of polyanions and polycations on a charged polyethylene terephthalate (PET) solid surface, the result of which was stable nanostructured films. By systemically varying the parameters of PEM build-up process: different combinations of polyelectrolytes, different numbers of bilayers (polyanion/polycation pairs), and miscellaneous types and concentrations of salts (NaCl, NaBr and NaF salts at 0.5 M and 1.0 M concentrations), the adhesion and morphology of PEMs were thoroughly investigated. The PEM thin films specifically investigated include poly(ethyleneimine) (PEI), poly(styrene sulfonate) (PSS), poly(allylamine hydrochloride) (PAH), poly(acrylic acid) (PAA), and poly(diallydimethylammonium chloride) (PDADMAC). Silica colloidal probes were utilized in the investigation, some of which were functionalized with COOH and/or coated with PEI-PSS. Silica colloidal probes were used in order to quantify interaction forces on the PEMs. A functionalized silica colloidal probe (a probe with COOH surface chemistry) and a silica colloidal probe coated with PEI-PSS were used to simulate PEM-PEM interactions. The results suggest that adhesion in the PEMs depend on the number of layers, the salt concentration and the salt type used during the build-up process, the environmental conditions where the adhesion force measurements were made, and the choice of probe. "

Polyelectrolytes are conductive polymers because of their ionic side group and PEDOT-S is one of those conductive polyelectrolytes. Previously, recombinant silk fibre has been dyed with PEDOT-S. PEDOT-S showed that it can be dyed with recombinant silk fibre over a very wide range of pH from 11 to 1.7. Previous experiments of dyeing recombinant silk fibre with PEDOT-S has shown that it is a very versatile process and can also be applied on other types of protein-based fibres, and that prompted me to dye wool and silk fibre from Bombyx Mori and make these fibres functionalized. So in this thesis dyeing of wool and silk fibres with PEDOT-S has been carried out. By this bottom-up approach of making an organic polymer electrically conductive and utilising the flexibility of organic polymer, one can integrate it in OLEDs and in smart textiles. In this thesis dyeing of silk and wool fibres with different dyeing pH has been carried out to maximise the exhaustion of dyes on to the fibres to acquire maximum conductance. Then the wool and silk fibres’ conductance and mechanical properties after dyeing were compared. Wool showed better conductance and mechanical properties as compare to silk after being dyed with PEDOT-S. These results helped to propose a model that tells about the interaction between protein-based fibres and polyelectrolytes and gives us better understanding of how these protein-based fibres show certain conductivity at different pH. Results also showed that these conductive fibres can be used further in special purposes and applications. / Program: Magisterutbildning i textilteknologi

Among the great breakthroughs in nanoscience and nanotechnology is the emergence of synthetic polymers that demonstrate biological activity and thus can be exploited for biomedical applications, extending from agents in therapeutics to drug delivery and tissue engineering. A key factor in the fabrication of such polymeric materials is the ability to tune and control their properties. To this end, an insight into the mode of interactions with biological systems is imperative. Computer simulations have proved to be a valuable tool that can compliment experiments and provide -otherwise inaccessible- information. In the context of this thesis, different aspects of the polymeric biological activity were investigated by studying two polymeric materials suitable for different types of applications, aiming to clarify yet undisclosed mechanisms that govern the polymers' behaviour either in solution or in conjunction with model lipid membranes. The first part of the thesis is dedicated to a nonionic amphiphilic copolymer known as Pluronic L64 that is considered as a candidate for the design of novel hybrid polymer-lipid vesicles that will act as carriers for drugs or genes. The hybrid bilayers are subjected to mechanical stress and their properties are compared to those of pure lipid bilayers. The simulations showed that the hybrid membranes can sustain increased surface tension prior to rupture, are stiffer, thicker and the polymers can induce higher lipid tail packing and also reduce the lipid mobility, rendering the membranes more ordered and less fluid. At high values of lateral pressure, which leads to pore formation, the copolymer chains decelerate the pore growth. The examination of the defect formation mechanism reveals that the hydrophilic PEO segment plays the most vital role. The same systems were also observed in varying temperatures and the impact of the inserted polymers on the phase behaviour was investigated. The data suggested that the polymers change the nature of the phase transition from a discontinuous to a continuous one. The hybrid membranes transform between the ordered and the disordered phase in a continuous manner and not at a critical melting temperature. Interestingly, the effect of polymers is different at the low and high temperature regions, as proved by the analysis of the mechanical, structural and dynamic membrane properties. The second part is focused on the study of polyhexamethylene biguanide (PHMB), a biguanide-based polyelectrolyte, that possesses remarkable biocidal properties. Even though PHMB's activity is known, the specific mode of action against bacterial membranes is still puzzling. Our work revealed that the polyelectrolyte assumes a counterintuitive behaviour in aqueous solution tending to self-organise into ordered compact structures, despite the repulsive electrostatic interactions of its positively charged segments. The formed nano-objects are thermodynamically stable, as was confirmed by free energy calculations and could be linked to PHMB's antibacterial mechanism. These findings pave the way for further computational and experimental exploration of these fascinating and promising materials that could lead to the design of novel smart biologically active nanoparticles.