Electrochemical Impedance Spectroscopy (EIS) was used to develop a novel methodology for studying ionic interaction with lipids arranged in a lipid cubic phase (LCP). Studying different types of ions, both cations and anions, validated the method. A free-standing LCP membrane was formed between two cell compartments and impedance experiments were carried out in a 2-electrode setup to estimate dielectric properties of the membrane, exposed to the following electrolyte solutions at different concentrations: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptophan. Two different LCP were used in this setup, i.e: Monoloein/water and the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/H2O). SAXRD measurements were performed to determine the space group of the cubic phase and confirm the stability of the LCP during measurements. Membrane resistances and capacitances were found from equivalent circuit fitting to the impedance data. The membrane resistance was shown to be related to ionic interaction with the lipid head group in the water channels of the LCP. Membrane capacitance were correlating to condensing and swelling effect of LCP due to the exposure of ions. The results correlated well with the SAXRD results and earlier published data. The results also indicate that these membranes become less permeable to ions as they increase in size as well as in charge or polarity.  Cyclic voltammetry was used to study the applications of a LCP for modification of the bioanode in a biofuel cell. The monoolein cubic phase was used to host Glucose oxidase (GOx) and a freely diffusing ferrocene carboxylate was used as mediator. The supported cubic phase had an intrinsic resistance in the same order of magnitude as the freestanding MO-LCP membrane as measured with EIS. / Elektrokemisk impedans spektroskopi har använts för att utveckla en ny metod för att studera joners växelverkan med lipider som bildat en kubisk fas. Olika typer av joner, både positiva och negativa, användes för att validera metoden. Ett fristående membran uppbyggt av en kubisk fas separerade två avdelningar i en elektrokemisk cell. Cellen fylldes med elektrolyt-lösningar och impedansmätningar kunde utföras mellan två platina elektroder placerade i vardera avdelning. Membranet exponerades för följande elektrolytlösningar av olika koncentration: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptofan. Två olika kubiska faser användes i denna uppställning, dvs: Monoloein/vatten och det ternära systemet monoolein/dioleoylfosfatidylkolin/vatten(MO/DOPC/H2O). Med hjälp av SAXRD kunde den kubiska fasens kristallstruktur bestämmas och dess stabilitet under mätningarna bekräftas. De dielektriska egenskaperna hos membranet bestämdes genom att anpassa impedansspektrat till en ekvivalent krets bestående av resistanser, kapacitanser och konstant-faselement. Membranresistansen visade sig vara relaterad till jonernas växelverkan med lipidhuvudgruppen i vattenkanalerna i kubiska fasen. Ju starkare växelverkan desto högre var resistansen. Membrankapacitansen kunde korreleras med kondenserande och uppsvällande effekter på kubiska fasen förorsakade av exponeringen till joner. Resultaten bekräftades av SAXRD mätningar och även tidigare publicerade data. Resultaten indikerar också tydligt att permeabiliteten hos membranet minskar med ökad jonstorlek, jonladdningoch polaritet hos jonen. Cyklisk voltammetri användes för att studera en tillämpning av kubiska fasen i en tänkt applikation som bioanod i en biobränslecell. Elektroden modifierades med en kubisk fas innehållande GOx och tillsammans med en fritt diffunderande ferrocen karboxylat som mediator, där oxidation av glukos studeras. Det visade sig att den kubiska fasen hade en resistans av samma storleksordning som det fristående membranet uppmätt med impedansspektroskopi.

No description available.

Bio-inspired monomers functionalized with nucleobase or ionic group allowed synthesis of supramolecular polymers using free radical polymerization and controlled radical polymerization techniques. Comprehensive investigations for the structure-property-morphology relationships of these supramolecular polymers elucidated the effect of noncovalent interactions on polymer physical properties and self-assembly behaviors. Reverse addition-fragmentation chain transfer (RAFT) polymerization afforded acrylic ABC and ABA triblock copolymers with nucleobase-functionalized external blocks and a low-Tg central block. The hard-soft-hard triblock polymer architecture drove microphase-separation into a physically crosslinked hard phase in a low Tg matrix. Hydrogen bonding in the hard phase enhanced the mechanical strength and maintained processability of microphase-separated copolymers for thermoplastics and elastomers. A thermodynamically favored one-to-one stoichiometry of adenine and thymine yielded the optimal thermomechanical performance. Intermolecular hydrogen bonding of two thymine units and one adenine unit allowed the formation of base triplets and directed self-assembly of ABC triblock copolymers into remarkably well-defined lamellae with long-range ordering. Acetyl protected cytosine and guanine-containing random copolymers exhibited tunable cohesive strength and peel strength as pressure sensitive adhesives. Post-functionalization converted unprotected cytosine pendent groups in acrylic random copolymers to ureido-cytosine units that formed quadruple self-hydrogen bonding. Ureido-cytosine containing random copolymers self-assembled into nano-fibrillar hard domains in a soft acrylic matrix, and exhibited enhanced cohesive strength, wide service temperature window, and low moisture uptake as soft adhesives. A library of styrenic DABCO salt-containing monomers allowed the synthesis of random ionomers with two quaternized nitrogen cations on each ionic pendant group. Thermomechanical, morphological, and rheological analyses revealed that doubly-charged DABCO salts formed stronger ionic association and promoted more well-defined microphase-separation compared to singly-charged analogs with the same charge density. Bulkier counterions led to enhanced thermal stability, increased phase-mixing, and reduced water uptake for DABCO salt-containing copolymers, while alkyl substituent lengths only significantly affected water uptake of DABCO salt-containing copolymers. Step growth polymerization of plant oil-based AB monomer and diamines enabled the synthesis of unprecedented isocyanate-free poly(amide hydroxyurethane)s, the first examples of film-forming, linear isocyanate-free polyurethanes with mechanical integrity and processability. Successful electrospinning of segmented PAHUs afforded randomly orientated, semicrystalline fibers that formed stretchable, free-standing fiber mats with superior cell adhesion and biocompatibility. / Ph. D.

The dynamic characteristics of hydrogen and ionic bonding contributes to the reversible properties of acrylic polymers, opening new avenues for designing materials with mechanical strength and processability. These non-covalent interactions function as physical crosslinks, which provide enhanced structural and mechanical integrity to acrylic block copolymers. The strong hydrogen bonding or ionic interaction also directs self-assembly to hierarchical microstructures, which enables many applications including thermoplastic elastomers and energy storage devices. Inspired by complementary hydrogen bonding interactions between nucleobase pairs in DNA, a series of bioinspired nucleobase-acrylate monomers such as adenine acrylate (AdA), thymine acrylate (ThA), cytosine acrylate (CyA) were designed, whose synthesis were afforded by aza-Michael addition. Among those nucleobases, cytosine arises as a unique category. It is not only able to self-associate via weak hydrogen bonds, but also forms quadruple hydrogen-bond bearing units (ureido-cytosine) when functionalized with isocyanates. Reversible addition-fragmentation chain transfer polymerization (RAFT) yielded acrylic ABA triblock copolymers with CyA external hard blocks. A subsequent post-functionalization using hexyl-isocyanate generated the corresponding ureido-cytosine acrylate(UCyA)-containing triblock copolymers. The self-complementary quadruple hydrogen bonding in the UCyA polymers achieved a broader service temperature window, while the alkyl chain ends of UCyA units allowed tunability of the mechanical strength to apply as thermoplastic elastomers. In addition, quadruple hydrogen bonding induced stronger propensity of self-assembly and denser packing of the polymers, which contributed to a well-defined ordered morphology and enhanced resistance to moisture uptake. A facile 2-step synthesis provided doubly-charged styrenic DABCO salt monomer(VBDC₁₈BrCl) containing an octadecyl tail. RAFT polymerization allowed the preparation of DABCO ABA block copolymers with defined molecular weights and low polydispersity. Thermal analysis revealed a melting transition of the VBDC₁₈BrCl block copolymer resulting from the side-chain crystallization of the long alkyl tail. Systematic mechanical comparisons between DABCO salt-containing copolymers and the corresponding singly-charged polymer controls demonstrated superior mechanical properties attributable to a stronger ionic interaction between the doubly-charged groups. Morphological characterizations revealed a well-ordered lamellar microstructure and a unique three-phase morphology of the DABCO block copolymers, which involve a soft phase, a hard phase, and an ionic aggregates domain dispersed within the hard domain. / Master of Science

Supramolecular polymers represent a family of polymeric materials that are held together with dynamic, noncovalent interactions. In contrast to conventional functional polymers that usually have high melt-viscosity due to their covalent nature and chain entanglement, supramolecular polymers combine excellent physical properties with low melt-viscosity, allowing for less energy-intensive processability and recyclability. Dynamic bonding with multiple binding sites, such as multiple hydrogen bonding or multiple ionic bonding, exhibits much stronger binding strength compared to the counterparts containing only a single binding site, thereby allowing for enhanced mechanical integrity to the polymers and facilitate self-assembly. This dissertation focuses on the design of novel supramolecular polymers building from the doubly-charged or quadruple hydrogen bonding (QHB) scaffolds utilizing chain-growth polymerization or step-growth polymerization, as well as elucidate the structure-property-morphology relationships of the polymers. A 2-step nucleophilic substitution reaction afforded a series of 1,4-diazabicyclo[2.2.2]octane (DABCO)-based styrenic monomers with two pairs of charged groups. An optimized 2-step reversible-addition-fragmentation chain-transfer (RAFT) polymerization synthesized ABA triblock thermoplastic elastomers (TPEs) with a low Tg poly (n-butyl acrylate) central block and a high Tg external charged blocks. Strong ionic interactions between doubly-charged units drove molecular self-assembly to form densely packed, hierarchical microstructures, which contributed to a robust, crosslinked physical network that allows the polymer to retain thermomechanical integrity until degradation. High-resolution single-crystal X-ray diffraction (SCXRD) coupled with powder X-ray diffraction (PXRD) further disclosed a detailed 3-D structural information of molecular arrangement and ion distribution within the charged phase through comparing DABCO-salt monomer single-crystal structure and the corresponding homopolymer XRD pattern. It was found that the physical properties of the DABCO-salt copolymers not only relied on their charge content and architectures but also dependent on their electrostatically-bonded counterions. The size and structure of the counterion determined the strength of dipole-dipole interaction, which significantly impact on thermal property, (thermo)mechanical performance, water affinity, and microstructure. A cytosine-functionalized monomer, cytosine acrylate (CyA), allowed the synthesis of acrylic ABA triblock TPEs with pendant nucleobase moieties in the external blocks and a low Tg central polymer matrix through RAFT polymerization. Post-functionalization of cytosine (Cyt) bidentate hydrogen bonding sites with alkyl isocyanate, allowed the formation of ureido-cytosine (UCyt) groups in the external block that were readily dimerized through QHB interactions. The UCyt units in the external block enhanced mechanical strength and induced stronger phase-separation of the block copolymers compared to the corresponding Cyt-containing TPE analogs. Facile conventional free-radical polymerization using CyA and subsequent post-functionalization enabled accessibility to random copolymers containing pendant UCyt QHB moieties in the soft polymer matrix. The synergy of the flexible polymer matrix and the dynamic character of QHB groups contributed to the ultra-high elasticity of the polymer and rapid self-healing properties. QHB interactions enabled efficient mechanical recovery upon deformation by facilitating elastic chain retraction to regenerate the original physical network. Finally, one-pot step-growth polymerization through chain extending a novel bis-Cyt monomer and a commercially available polyether diamine using a di-isocyanate extender afforded segmented polyurea series for extrusion additive manufacturing. The molecular design of the polyureas featured soft segments containing flexible polyether chain and a relatively weak urea hydrogen bonding sites in the soft segment and rigid UCyt hydrogen bonding groups in the hard segment. The reversible characteristics of QHB enabled low viscosity at the processing temperature while providing mechanical integrity after processing and reinforced bonding between the interlayers, which contributed to the remarkable strength, elasticity, toughness, and interlayer adhesion of the printed parts. / Doctor of Philosophy / This dissertation focuses on designing supramolecular thermoplastic elastomers containing strong noncovalent interactions, i.e., quadruple hydrogen bonds or double ionic bonds. Inspired from noncovalent interactions in our mother nature, a series of bio-inspired monomers functionalized with nucleobase or ionic units were synthesized through scalable reactions with minimal purification steps. Polymerization of the functional monomers through step-growth or chain-growth polymerization techniques affords a variety of supramolecular thermoplastic elastomers with well-defined structures and architectures. These thermoplastic elastomers comprise soft and hard constituents; the former contains low glass transition polymer chains that provide elasticity while the latter contains strong noncovalent units to impart mechanical strength. Varying the soft/hard component ratios enables polymers with tunable physical properties to address different needs. Systematic characterizations of these supramolecular polymers revealed their distinct properties from the polymers containing the covalent or weak noncovalent interactions and facilitate molecular-level understanding of the polymers. Generally, incorporating strong noncovalent interactions increases the temperature for polymer segmental motion and extends thermomechanical plateau windows. Additionally, the strong association strength of those non-covalent interactions promotes microphase separation and self-assembly, contributing to a high degree of structural ordering of the polymers. Moreover, the dynamic characteristics of the noncovalent interactions offer the polymers with reversible properties, which not only enables melt-processability and recyclability of the polymer but also contributes to a series of smart properties, including self-healing, shape-memory, and recoverability. Thus, the molecular design using supramolecular chemistry provides promising avenues to developing functional materials with enhanced mechanical properties, processability, and stimuli-responsiveness for emerging applications.

Chloride-induced corrosion of reinforcing steel in concrete is a worldwide problem. In order to predict how chlorides penetrate in concrete and how other ionic species in con-crete pore solution affect the penetration of chlorides, this thesis presents a numerical study on multi-phase modelling of ionic transport in concrete dominated by migration process. There are many advantages in rapid chloride migration test (RCM) method and numeri-cal approach. However, most of models in the literature predicting chloride diffusivity in concrete are diffusion models, which not consider the action of externally applied electric field. In view of this, the specific aim of this thesis is to develop a rational nu-merical migration model to simulate chloride migration tests. By using this model, the diffusion coefficient of chlorides in concrete will be efficiently predicted. Furthermore, other mechanisms of ionic transportation in composite materials can be scientifically in-vestigated in the meantime. In most existing work, researchers tend to use the assumption of electro-neutrality con-dition, which ensures that no external charge can be imported (Bockris and Reddy, 1998), to determine the electrostatic potential within concrete as well as considering a 1-D problem with only one phase structure and single species (i.e. the chlorides) for pre-dicting the ionic migration. In contrast, this thesis presents a number of sets of multi-phase migration models in more than one dimension and uses the Poisson’s equation for controlling the multi-species interactions. By solving both mass conservation and Pois-son’s equations, the distribution profiles of each ionic species and electrostatic potential at any required time are successfully obtained. Some significant factors, i.e. the influ-ence of dimensions, aggregates, interfacial transition zones (ITZs), cracks and binding effect have also been discussed in detail. The results reveal a series of important features which may not be seen from existing numerical models. For quantitative study, this thesis also provides the prediction method of chloride diffu-sivity not only by the traditional stationary diffusion models but also by the migration models presented in the thesis. The obtained results are compared with three proven analytical models, i.e., Maxwell’s model (Dormieux and Lemarchand, 2000), Brug-geman’s equation (Bruggeman’s, 1935) and the lower bound of the effective diffusion coefficient proposed by Li et al. (2012) as well as validated against experimental data sets of an accelerated chloride migration test (ACMT) brought by Yang and Su (2002).

Made available in DSpace on 2016-06-02T19:55:23Z (GMT). No. of bitstreams: 1 2455.pdf: 1413452 bytes, checksum: 0d85e80e19b01ab27cd6e9dd30beb3b9 (MD5) Previous issue date: 2009-04-02 / Financiadora de Estudos e Projetos / The industrial production of 6-APA includes: (1) cultivation of Penicillium chrysogenum; (2) extraction with organic solvents, (3) crystallization; (4) penicillin hydrolysis by immobilized penicillin acylase; (5) extraction of phenyl acetic acid (AFA); (6) precipitation of 6-APA at its isoelectric point ( pH ~ 3,6). The scientific community and industry have interest in reducing the number of process steps required for 6-APA production. In this thesis a new method for 6-APA production is presented. In this process, the simultaneous production and hydrolysis of penicillin was carried out. The 6-APA was extracted from culture broth using ionic adsorbent. To demonstrate the technical viability of the process a suitable biocatalysts to perform the hydrolysis of penicillin in the complex media has been developed. The enzymatic extract, containing PGA was partially purified by affinity adsorption on agarose-tryptophan, it was necessary to prepare the biocatalyst. The apparent purification factor obtained was 4,5 and purified PGA was immobilized on agaroseglyoxil by multipoint covalent attachment. The biocatalysts obtained show stability under conditions of sterilization and application in bioreactor. However, their mechanical stability under vigorous conditions of agitation used in stirred tank bioreactors was not satisfactory. Three strategies were used to avoid fragmentation of the biocatalyst. The first strategy was to involve the impellers with a helicoidal structure. In this system the biocatalyst was maintained under agitation in external bulk of the apparatus. In the second strategy, the biocatalyst was introduced into the bioreactor as the biomass density reached a maximum, in this case, the cultivation was carried out under constant agitation speed (300 rpm). An airlift bioreactor was used as third strategy to maintain the pellet structure. These systems were efficient in increasing medium agitation without destroying the pellets. Complete hydrolysis of penicillin (30 g / L) was obtained after five days of cultivation and extraction of 6-APA on ionic exchanger was investigated. The extraction of 6-APA by ionic interaction using chitosan modified with glutaraldehyde and arginine is a good method for recovery it. However, optimization in this method is necessary to achieve the recovery of 6-APA at satisfactory levels for the pharmaceutical industry. The new method for production of 6-APA shows that is possible to eliminate the use of organic solvents and to reduce the number of process steps. / A produção industrial de ácido 6-aminopenicilânico (6-APA) inclui etapas de cultivo de Penicillium chrysogenum, extração com solvente orgânico, cristalização, hidrólise enzimática e precipitação. O interesse industrial e científico em reduzir o número de etapas deste processo tem motivado pesquisadores a buscar processos alternativos para obtenção de 6-APA. Neste trabalho, um novo processo é apresentado para a produção de 6-APA, cujas inovações envolvem a hidrólise de penicilina durante o cultivo de P. chrysogenum, a recirculação de ácido fenilacético (AFA) e extração de 6-APA ao final do cultivo utilizando adsorvente iônico. Para atender aos requerimentos do novo processo, foi desenvolvido um biocatalisador para atuar no complexo meio de cultivo. O preparo deste biocatalisador exigiu o uso de extrato enzimático purificado e uma metodologia para purificação de penicilina G acilase (PGA) foi investigada. Um fator de purificação aparente de 4,5 vezes foi obtido e a enzima foi ligada a agarose utilizando a técnica de imobilização covalente multipontual. O biocatalisador obtido apresentou boa estabilidade química em condições de esterilização e aplicação em biorreator. Entretanto, sua estabilidade mecânica sob condições rigorosas de agitação em biorreatores tipo tanque agitado e aerado não foram satisfatórias. Para solucionar este problema três estratégias foram avaliadas: (1) utilizando-se uma peça em forma de hélice envolvendo os impelidores, (2) adicionando-se o biocatalisador ao biorreator após a concentração de células atingir seu valor máximo e utilizando velocidade de agitação constante de 300 rpm, (3) usando um biorreator tipo air lift . As três estratégias permitiram manter a integridade do biocatallisador. Hidrólise completa de penicilina (30 g/L) foi obtida em 120 h de cultivo e a extração de 6-APA em coluna de troca iônica foi estudada. O método de extração de 6-APA através de interação iônica utilizando quitosana-arginina apresentou resultados promissores, entretanto, um aperfeiçoamento do método ainda faz-se necessário para atingir a recuperação de 6-APA em níveis satisfatórios para a indústria farmacêutica. Os resultados obtidos indicam que é possível eliminar o uso de solventes orgânicos na produção de 6-APA, além disso, a redução no número de etapas torna este processo mais simples e conseqüentemente reduz o tempo de produção e custo do produto final. Portanto, o processo desenvolvido neste trabalho é promissor para a aplicação na indústria farmacêutica.

L’objectif de ce travail a été d’introduire des groupements fonctionnels au sein de chaînes polymère silicone pour former des assemblages supramoléculaires, dans le but de former de nouveaux matériaux. Tout d’abord, une étude approfondie de la bibliographie a permis de cerner les avantages et limitations de la réaction d’aza-Michael appliquée aux silicones. Cette étude a aussi permis d’acquérir de solides connaissances générales sur la réaction d’aza-Michael appliquée à des composés organiques aminé et de soulever des points peu ou pas traités tels que la sélectivité et la réversibilité de la réaction. Afin de comprendre et contrôler cette réaction, une étude modèle impliquant un PDMS aminé simple et l’acrylate de butyle a été réalisée. Plusieurs paramètres tels que la présence de solvants polaires protiques, de catalyseurs, ou une température élevée permettent de promouvoir la réaction. Des données cinétiques ont également mis en relief la possibilité de contrôler la sélectivité de la réaction sur un groupement amine primaire (mono- ou di-addition). Un composé 100% mono-adduit et un composé 100% di-adduit ont ainsi été synthétisé en choisissant soigneusement les paramètres expérimentaux. La réaction d’aza-Michael a ensuité été appliquée à un accepteur de Michael moins réactif, l’acide acrylique. Ce composé a la particularité de réagir instantanément et exothermiquement avec les amines par réaction acido-basique. Un déplacement de l’équilibre chimique de la réaction acido-basique vers la formation d’adduits de Michael a été rendu possible, générant ainsi des groupements zwitterioniques. Une étude approfondie de la réaction avec des amines organiques et des oligomères/polymères siliciés et aminés a été réalisée afin de déterminer la structure exacte des groupements fonctionnels obtenus et d’évaluer les propriétés visco-élastiques de tels produits. La dernière partie de ce projet a été focalisée sur l’étude et la caractérisation de ces matériaux silicones supramoléculaires s’échelonnant du liquide visco-élastique à l’élastomère silicone thermoplastique. / This PhD thesis was focused on the incorporation of functional groups onto the siloxane polymer backbone such that supramolecular assemblies are formed, in order to prepare new supramolecular silicone materials. First, an in-depth review of the aza-Michael reaction applied to silicon-containing compounds was realized, highlighting the whole potential of this addition reaction. The aza-Michael reaction applied to organic amines was thoroughly analyzed in order to emphasize some open issues such as selectivity or retro-aza-Michael reaction. In order to understand and master the aza-Michael reaction, a model reaction involving a bis-(3-aminopropyl)-terminated PDMS and butylacrylate was then fully investigated. Operating parameters such as protic polar solvents, catalysts or temperature allow promoting the reaction rate. Kinetic data showed that the selectivity towards the main formation of mono- or di-adduct can be controlled by carefully selecting the solvent nature and content. The syntheses of 100% mono- and 100% di-adduct compounds was succesfully achieved. The aza-Michael reaction was then applied to a less reactive Michael acceptor, i.e. acrylic acid. This unsaturated organic acid reacts instantaneously with amines by acid-base reaction leading to the formation of ionic pairs. This acid-base equilibrium is then shifted in the forward direction allowing the synthesis of zwitterionic groups by aza-Michael. The aza-Michael reaction of this peculiar Michael acceptor was thoroughly investigated both with simple organic amines and aminosilicone oligomers and polymers in order to elucidate the structures and to evaluate the rheological properties. Finally, supramolecular silicone materials bearing zwitterionic-like groups were prepared leading to supramolecular materials with properties ranging from visco-elastic liquids to thermoplastic silicone elastomers.