This project aims to discover a new means of overcoming the drawbacks of traditional layer-by-layer dip coating through the use of polyelectrolyte complexes (PECs) and electrophoretic deposition. The layer-by-layer process, by which oppositely charged polyelectrolytes or other charged particle are alternately adsorbed onto a substrate to produce a thin film of precisely controllable thickness, is versatile and simple to implement but suffers from requiring numerous, long deposition steps to produce uniform micron thick films. PECs are small associations of oppositely charged polyelectrolytes that, when mixed in non-stoichiometric ratios, can form charged water- soluble particles. There is much still to be determined about the phase behavior of PECs. However, it has been shown that they can exist over a range of conditions. Electrophoretic deposition is a technique used in many commercial applications for the deposition of charged particles onto a conducting substrate. It has even been shown to enhance the deposition of polyelectrolyte single layers and multilayers. This study examines the phase behavior of PECs made of linear poly(ethyleneimine) (LPEI) and poly(acrylic acid) (PAA). PEC behavior is studied over a pH range of 4.0 to 6.0, with no salt added to the system. This study also reports the results of tests examining how soluble PECs responded to changes in pH and whether solid PECs could be made to dissolve through the addition of different salts. Light scattering is used to examine the particle size distribution and effective diameter of PECs in solution. This information is then used to electrophoretically deposit PECs with 10%, 30%, 70%, and 90% excess LPEI. Stylus profilometry is used to assess the thickness of deposited films. The results showing that PEC layers deposited under an applied voltage were 40% to 400% thicker than PECs deposited with no applied potential.

A variety of functional thin films can be produced using the layer-by-layer assembly technique. In this work, assemblies of anionic clay and cationic polymer were studied with regard to film growth and gas barrier properties. A simple, yet flexible robotic dipping system, for the preparation of these thin films, was built. The robot alternately dips a substrate into aqueous mixtures with rinsing and drying in between. Thin films of sodium montmorillonite clay and cationic polymer were grown and studied on poly(ethylene terephthalate) film or a silicon wafer. After 30 clay polymer bilayers were deposited, the resulting transparent film had an oxygen transmission rate (OTR) below 0.005 cm3/m2/day/atm. This low OTR, which is unprecedented for a clay-filled polymer composite, is believed to be due to a ?brick wall? nanostructure comprised of completely exfoliated clay bricks in polymeric ?mortar?. The growth of polymer and clay assemblies is then shown to be controlled by altering the pH of polyethylenimine (PEI). Growth, oxygen permeability, and mechanical behavior of clay-PEI assemblies were studied as a function of pH in an effort to tailor the behavior of these thin films. Thicker deposition at high pH resulted in reduced oxygen permeability and lower modulus, which highlights the tailorability of this system.

A variety of materials were used to fabricate nanocoatings using layer-by-layer (LbL) assembly to reduce the flammability of cotton fabric. The most effective brominated flame retardants have raised concerns related to their toxicity and environmental impact, which has created a need for alternative flame retardant chemistries and approaches. Polymer nanocomposites typically exhibit reduced mass loss and heat release rates, along with anti-dripping behavior, all of which are believed to be due to the formation of a barrier surface layer. Despite these benefits, the viscosity and modulus of the final polymeric material is often altered, making industrial processing difficult. These challenges inspired the use of LbL assembly to create densely layered nanocomposites in an effort to produce more flame-retardant coatings. Laponite and montmorillonite (MMT) clay were paired with branched poly(ethylenimine) to create thin film assemblies that can be tailored by changing pH and concentration of aqueous deposition mixtures. Both films can be grown linearly as a function of layers deposited, and they contained at least 70 wt percent of clay. When applying these films to cotton fabric, the individual fibers are uniformly coated and the fabric has significant char left after burning. MMT-coated fabric exhibits reduced total heat release, suggesting a protective ceramic surface layer is created. Small molecule, POSS-based LbL thin films were also successfully deposited on cotton fabric. With less than 8 wt percent added to the total fabric weight, more than 12 wt percent char remained after microscale combustion calorimetry. Furthermore, afterglow time was reduced and the fabric weave structure and shape of the individual fibers were highly preserved following vertical flame testing. A silica-like sheath was formed after burning that protected the fibers. Finally, the first intumescent LbL assembly was deposited on cotton fabric. SEM images show significant bubble formation on fibers, coated with a 0.5 wt percent PAAm/1 wt percent PSP coating after burning. In several instances, a direct flame on the fabric was extinguished. The peak HRR and THR of coated fabric has 30 percent and 65 percent reduction, respectively, compared to the uncoated control fabric. These anti-flammable nanocoatings provide a relatively environmentally-friendly alternative for protecting fabrics, such as cotton, and lay the groundwork for rendering many other complex substrates (e.g., foam) flame-retardant without altering their processing and desirable mechanical behavior.

Layer-by-layer (LbL) assembly was used to produce highly conductive thin films with carbon black (CB) and polyelectrolytes. The effects of sonication and pHadjustment of the deposition mixtures on the conductivity and transparency of deposited films were studied. Drying temperature was also evaluated with regard to thin film resistance. Sonication and oven drying at 70oC produced films with the lowest sheet resistance (~ 1500 Ω/sq), which corresponds to a bulk resistivity of 0.2 Ω⋠cm for a 14- bilayer film that is 1.3 μm thick. Increasing the pH of the PAA-stabilized mixture and decreasing the pH of the PEI-stabilized mixture resulted in films with 70% transparency due to thinner deposition from increased polymer charge density. Varying the number of bilayers allows both sheet resistance and optical transparency to be tailored over a broad range. Variation of deposition mixture composition led to further reduction of sheet resistance per bilayer. A 14 bilayer film, made from mixtures of 0.25wt% carbon black in 0.05wt% PAA and plain 0.1wt% PEI, was found to have a sheet resistance of approximately 325 Ω/sq. Bulk resistivity was not improved due to the film being 8 μm thick, but this combination of small thickness and low resistance is an order of magnitude better than carbon black filled composites made via traditional melt or solution processing. Applications for this technology lie in the areas of flexible electronics, electrostatic charge dissipation, and electromagnetic interference shielding.

Submitted by DANIELA BRANCO TAVARES MASCAGNI null (danibtmascagni@gmail.com) on 2017-07-19T19:56:50Z No. of bitstreams: 1 TESE final.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-19T20:03:40Z (GMT) No. of bitstreams: 1 mascagni_dbt_dr_bauru.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) / Made available in DSpace on 2017-07-19T20:03:41Z (GMT). No. of bitstreams: 1 mascagni_dbt_dr_bauru.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) Previous issue date: 2017-04-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho, foram desenvolvidos biossensores eletroquímicos enzimáticos fabricados com óxido de grafeno reduzido (rGO) e funcionalizado depositados pelas técnicas LbL (Layer-by-Layer) e Langmuir-Blodgett (LB) para a detecção de glicose. Para isso, primeiramente foi sintetizado quimicamente o óxido de grafeno (GO) pela oxidação do grafite, em seguida, o GO foi reduzido para aumentar a sua condutividade elétrica e foi funcionalizado em meio estabilizante contendo cloridrato de poli(dialildimetilamônio), formando o GPDDA, ou poli(4-estireno sulfônico) PSS, formando GPSS. Com isso, foi possível formar dispersões aquosas estáveis das nanofolhas de grafeno, essencial para a fabricação de filmes LbL. Em um primeiro momento, foram fabricados biossensores com filmes LbL contendo GPDDA, GPSS e a enzima glucose oxidase (Gox). O desempenho desses biossensores na detecção de glicose foi avaliado em função do número de bicamadas contendo Gox. O melhor desempenho na detecção de glicose foi apresentado pelo biossensor com o filme LbL com a arquitetura (GPDDA/GPSS)/(GPDDA/GPSS)2. Este biossensor apresentou limite de detecção de 13,4 µmol.L-1, sensibilidade 2,47 μA.cm-2.mmol-1.L e faixa analítica entre 0,04 e 0,95 mmol.L-1. Este biossensor foi eficiente na detecção de glicose na presença de interferentes comumente encontrados em fluidos corporais, alimentos e fármacos. Quando avaliado na detecção de glicose em amostras reais, recuperou 100,8% para uma solução eletrolítica comercial e 88,8% para leite sem lactose. Em um segundo momento, foram fabricados biossensores a partir de filmes LB contendo os mesmos materiais utilizados para fabricar os biossensores com filmes LbL (GPDDA, GPSS e Gox), com a finalidade de comparar os dois métodos de fabricação de filmes no desempenho dos biossensores. O desempenho dos biossensores fabricados com filmes LB foi avaliado em relação à quantidade de monocamadas (GPDDA/GPSS/Gox) depositadas. O melhor desempenho na detecção de glicose entre os biossensores com filme LB foi apresentado pelo biossensor de arquitetura (GPDDA/GPSS/Gox)3. Este biossensor apresentou limite de detecção 0,54 µmol.L-1, sensibilidade de 8,69 μA.cm-2.mmol-1.L e faixa analítica entre 0,0018 e 1,5 mmol.L-1. Também se mostrou eficiente na detecção de glicose na presença de interferentes e na detecção de glicose em amostra real, com recuperação de 101,2 % para o leite sem lactose. A partir dos resultados de desempenho dos biossensores com filme LbL e LB foi possível concluir que a técnica LB promoveu uma maior sinergia entre os nanomateriais, atribuída ao maior ordenamento dos nanomateriais proporcionado pela técnica LB. / In this work, enzymatic electrochemical biosensors fabricated with reduced graphene oxide (rGO) and functionalized deposited by the LbL (Layer-by-Layer) and LangmuirBlodgett (LB) techniques were developed for the detection of glucose. Firstly, to get this, graphene oxide (GO) was chemically synthesized by the oxidation of graphite and after GO was reduced to increase its electrical conductivity and it was functionalized in stabilizing medium containing the poly (diallyl dimethyl ammonium chloride) PDDA, forming the GPDDA, or poly (4-styrene sulphonic) PSS, forming GPSS. Hence, stable aqueous dispersions of graphene nanosheets were formed, essential for the fabrication of LbL films. In a first moment, biosensors with LbL films containing GPDDA, GPSS and the enzyme glucose oxidase (Gox) were fabricated. The performance of these biosensors in the detection of glucose was evaluated as a function of the number of bilayers containing Gox. The best performance in the detection of glucose was presented by the biosensor with the LbL film with the architecture (GPDDA/GPSS)/(GPDDA/GPSS)2. It presented a detection limit of 13.4 μmol.L-1 , sensitivity 2.47 μA.cm-2 .mmol-1 .L and analytical range between 0.04 and 0.95 mmol.L-1 . This biosensor was efficient in detecting glucose in the presence of interferents commonly found in body fluids, foods and drugs. When evaluated in the detection of glucose in real samples, it recovered 100.8% for a commercial electrolytic solution and 88.8% for lactose-free milk. In a second moment, biosensors were fabricated from LB films containing the same materials used to fabricate the biosensors with LbL films (GPDDA, GPSS and Gox), in order to compare the two methods of films deposition in the performance of the biosensors. The performance of biosensors fabricated with LB films was evaluated in relation to the amount of deposited monolayers (GPDDA/GPSS/Gox). The best performance on the detection of glucose among LB film biosensors was presented by the architecture biosensor (GPDDA/GPSS/Gox)3. The detection limit was 0.54 μmol.L-1 , sensitivity of 8.69 μA.cm- 2 .mmol-1 .L and analytical range between 0.0018 and 1.5 mmol.L-1 . This biosensor was also efficient in the detection of glucose in the presence of interferents and in the detection of glucose in a real sample, with a recovery of 101.2% for lactose-free milk A conclusion derived from the performance results of the biosensors with LbL and LB films, may support that LB technique promoted a greater synergy among the nanomaterials, attributed to the best arrangement of nanomaterials provided by LB technique.

No description available.

Surface chemistry of wood is based on the exposed cut surface that is the combination of intact (lumen wall) and cut cell wall material. It is inherently complex and changes with history of processing. Modification of wood surface through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Furthermore, modification of the surface can be performed using layer-by-layer (LbL) assembly, where the adsorption of polyelectrolytes or nanoparticles in sequential steps yields a multilayer film with a defined layer sequence on a given substrate. The objective of this study was to quantify adsorption of polyelectrolytes onto wood surface and use these polyelectrolytes as adhesives. In this study, optimal pH conditions for modifying wood surfaces, by anchoring adsorbing polyelectrolytes, were detected using zeta- ( )-potential measurements. Positively charged wood surfaces were also detected by the same technique after a layer of poly(diallyldimethylammonium chloride) (PDDA) or poly (ethylenimine) (PEI) was adsorbed. Both X-ray photoelectron spectroscopy (XPS) and Carbon-Nitrogen-Sulfur analyzer (CNS) were used to quantify the amount of charged polymer on wood surfaces to elucidate optimal pH and ionic strength for polyelectrolyte adsorption. Confocal laser scanning microscopy (CLSM) and Environmental Scanning Electron Microscope (ESEM) were used to characterize adsorbed LbL multilayers of poly(acrylic) acid (PAA) and poly(allylamine hydrochloride) (PAH). Cross-linking between PAA and PAH at various temperatures was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the evaluation of multilayer as bonding agents was carried out by compression shear test following ASTM D905 standard. / Master of Science

Made available in DSpace on 2016-06-02T19:19:58Z (GMT). No. of bitstreams: 1 CAMPOS_Paula_2014.pdf: 1924698 bytes, checksum: d5134f8bff1512ce41535c0a1f61d175 (MD5) Previous issue date: 2014-02-28 / Financiadora de Estudos e Projetos / In this work the immobilization of enzyme β-Galactosidase has been investigated with use of assembly technique of nanostructured films denominated LbL (Layer-by-Layer) for employment in an amperometric biosensor of lactose. Therefore, spectroscopy measured has made for UV-vis (Ultraviolet-visible) and fluorescence, in order to monitor the bands of absorption and emission of each bilayer deposited and to confirm the presence of enzyme in the films. It has made too FTIR (Fourier Transform Infrared Spectroscopy) and SFG (Sum Frequency Generation) for the purpose to understand the films structure, the interactions present and the efficiency of technique in the immobilization process. For the lactose detection amperometric measured have carried and that way the performance of modified electrode have evaluated in relation to enzyme immobilization, the polyelectrolytes performance Poly (allylamine hydrochloride) (PAH) and Poli (etileno imina) (PEI) and poly(ethyleneimine) and the operations conditions of biosensor which sensibility, limit of detection, interferences and stability. The evaluation of enzyme deposition by UV-vis and fluorescence showed that the films growth has been satisfactory presenting the characteristics bands of da β-Gal regarding to amino acid residues tryptophan, tyrosine and phenylalanine, among others, in λ = 280 nm for absorption and λ = 344 nm for emission and the deposition of material has been growing. The spectrum of FTIR and SFG indicated bands of chemical groups characteristics of polymers and enzyme and proved that the bonds, probably secondary of the elements are sufficiently strong for to keep the films in substrate during the sensory evaluation. In lactose detection it has made electrode of (PEI/β-Gal)n e (PAH/β-Gal)n both of ten and third bilayers. The sensibility of film (PEI/β-Gal)10 was 0.061 μA mmol-1 cm-2, while the (PAH/β-Gal)10 was 0.079 μA mmol-1 cm-2. In order to increase the efficiency of the biosensors, electrodes compounds for third bilayers were tested, this way the film (PEI/β-Gal)30 has achieved a sensibility higher than the previous electrodes of 0.31 μA mmol-1 cm-2, is likely that a great amount of enzyme has been immobilized. However, the film ITO/PB/(PAH/β-Gal)30 has not get the same efficiency despite de number of bilayer have been increase. Have been identified two interferences, the glucose and the ascorbic acid, but both can be avoided, the first with use of a biosensor for glucose coupled with lactose biosensor and the second causes an elevation on current, being naturally differentiated. The stability of the biosensor was twelve days, being measured in days alternate. All experiments performed to converge to prove that the LbL technique were adequate to assembly the biosensor and that lactose detection can be done and in levels nearby to real samples, but is possible to improve the system still with studies more expanders about the films structure and to test news biosensors configurations. / Neste trabalho investigou-se a imobilização da enzima β-Galactosidase utilizando a técnica de automontagem de filmes nanoestruturados, denominada LbL (Layer-by-Layer do inglês) para o emprego em um biossensor amperométrico de lactose. Foram feitas medidas espectroscópicas por Ultravioleta e visível (UV-vis) e fluorescência, a fim de monitorar as bandas de absorção e emissão de cada bicamada depositada e confirmar a presença da enzima nos filmes. Fez-se também espectroscopia por transformada de Fourier (FTIR) e Geração de Soma de Frequências (SFG) para compreender a estrutura dos filmes, as interações presentes e a eficiência da técnica no processo de imobilização. Para a detecção de lactose realizou-se medidas amperométricas e dessa forma avaliou-se o desempenho do eletrodo modificado em relação à imobilização da enzima, a eficiência dos polieletrólitos Poli (alilaminahidroclorada) (PAH) e Poli (etileno imina) (PEI) e as condições de operação do biossensor tais como sensibilidade, limite de detecção, interferentes e estabilidade. A avaliação da deposição da enzima pelo UV-vis e fluorescência mostrou que o crescimento dos filmes foi satisfatório, apresentando as bandas características da β-Gal atribuídas aos resíduos de aminoácidos triptofano, tirosina e fenilalanina, entre outros, em λ = 280 nm por absorção e sendo os mesmo responsáveis pela emissão em λ = 344 nm sendo que a deposição de material foi crescente. Os espectros de FTIR e SFG indicaram bandas de grupamentos químicos característicos dos polímeros e da enzima e comprovaram que as interações, provavelmente secundárias, entre os elementos são fortes o suficiente para manter o filme no substrato durante as avaliações sensoriais. Na detecção de lactose foram feitos eletrodos de ITO/PB/(PEI/PVS)1/(PEI/β-Gal)n e ITO/PB/(PAH/PVS)1/(PAH/β-Gal)n ambos com dez e trinta bicamadas. A sensibilidade do filme ITO/PB/(PEI/PVS)1/(PEI/β-Gal)10 foi 0,061 μA.mmol-1.cm-2, enquanto o ITO/PB/(PAH/PVS)1/(PAH/β-Gal)10 foi 0,079 μA.mmol-1.cm-2. A fim de aumentar a eficiência do biossensor eletrodos compostos por 30 bicamadas foram testados, dessa forma o filme ITO/PB/(PEI/PVS)1/(PEI/β-Gal)30 alcançou uma sensibilidade superior aos eletrodos anteriores de 0,31 μA.mmol-1.cm-2, pois é possível que uma maior quantidade de enzimas tenha sido imobilizada. Entretanto o filme ITO/PB/(PAH/PVS)1/ (PAH/β-Gal)30 não obteve a mesma eficiência mesmo tendo o número de bicamadas aumentado, o que pode ser atribuído à estrutura do polieletrólito. Foram identificados dois interferentes, a glicose e o ácido ascórbico, mas ambos podem ser evitados, o primeiro com o uso de um biossensor para glicose acoplado ao da lactose e o segundo causa uma elevação na corrente, sendo naturalmente diferenciado. A estabilidade do biossensor foi de 12 dias, com medida em dias alternados. Todos os experimentos realizados convergem para provar que a técnica LbL foi adequada para a construção do biossensor e que a detecção da lactose pode ser feita em níveis de concentração próximos à de amostras reais, mas ainda é possível aprimorar o sistema com estudos mais aprofundados sobre a estrutura dos filmes e testar novas configurações de biossensores.

CHARLES UNIVERSITY FACULTY OF PHARMACY IN HRADEC KRÁLOVÉ Department of Pharmaceutical Chemistry and Pharmaceutical Analysis Candidate: Aneta Ptáčková Supervisor: PharmDr. Lukáš Lochman, Ph.D. Title of thesis: Modification of capillary wall by graphene for separation applications Capillary electrophoresis (CE) is a highly efficient separation method. Substances are separated due to their different mobility in an electric field. The CE modes of operation can be modified in different ways, e.g. capillary electrochromatography or micellar electrokinetic capillary chromatography. Modification of the inner wall of the capillary is believed to help improve separation efficiency and selectivity. Graphene is carbon with a hexagonal structure in form of two-dimensional sp2 single-atom-thick sheets. Graphene seems to be a suitable material for separation application due to its excellent properties such as large surface area and affinity to aromatic ring through π-π interactions. Our work is focused on the modification of the capillary wall by graphene. One of the methods of capillary wall modification is the Layer-by-Layer method via layering of differently charged substances bounded by electrostatic forces. Another method is chemical coating employing covalent interactions. Different combinations of polymers...

A técnica de automontagem [Self-Assembly (SA)] tem sido largamente empregada na fabricação de estruturas supramoleculares de polímeros condutores que requerem controle molecular. O paradigma implícito no método de automontagem é a adsorção espontânea de camadas carregadas com cargas opostas, conduzindo assim a um filme de multicamadas formado pela alternância de policátions e poliânions. Nesta dissertação, são empregados dois tipos de polímeros conjugados e seus derivados que são identificados por suas famílias, que são a da polianilina (PAn) e a do poli(pfenileno vinileno) (PPV). São enfatizados os processos de adsorção para as polianilinas e precursores do PPV, propondo-se um mecanismo de adsorção não autolimitada sustentado por condições de não equilíbrio. O processo não autolimitado comprova que a adsorção pode ser controlada por outras interações que não a eletrostática, como as pontes de hidrogênio que são comuns nas polianilinas, e/ou por interações típicas de dispersões coloidais, visto que os polímeros se agregam em solução. Este novo método pode ter grande impacto na fabricação de estruturas supramoleculares porque podem ser obtidos filmes espessos de uma única camada com controle em nível molecular. A desvantagem deste método está na obtenção de filmes não uniformes, propriedade que ainda não é adequadamente controlada. A investigação da formação de filmes de múltiplas camadas e dos processos de fluorescência para filmes de bicamadas e não autolimitados é apresentada e discutida em função dos trabalhos da literatura. Finalmente, são correlacionados os processos de adsorção e a fluorescência / The self-assembly (SA) technique has been widely used for producing supramolecular structures fi-om conducting polymers, in which molecular control may be achieved. The paradigm implicit in the SA method is the spontaneous adsorption of oppositely charged layers, thus leading to a multilayer film containing polycations alternated with polyanions. In this dissertation, two types of polymer are employed in the fabrication of SA films, namely polyanilines and poly(p-phenylene vinylenes) (PPVs). For the polyanilines, emphasis was placed in the adsorption processes, where it is proposed that a non-self-limiting process may be achieved if adsorption is carried out under non-equilibrium conditions. A non-self-limiting process is proof that adsorption is not entirely controlled by electrostatic interactions, but may also depend on H-bonding which is very efficient in polyanilines and on interactions typical of colloid dispersions as the polymers aggregate while in solution. This nove1 method may have a large impact in the fabrication of supramolecular structures because much thicker films may be obtained in a single layer. The disadvantage of this method, however, lies in the fabrication of non-uniform films which cannot be controlled adequately. The investigation of the fabrication of multilayers and of fluorescence processes in films built with bilayers and via non-self-limiting adsorption is presented and discussed in terms of work published in the literature. Finally, the processes of adsorption and fluorescence are correlated