The use of cyanine dyes in bioanalytical applications has become a widely explored topic of interest in chemistry. Their ability to absorb and fluoresce in the UV-visible and near-infrared region of the electromagnetic spectrum benefits their use as imaging probes and fluorescent labels due to the reduced auto-fluorescence from biological molecules. The behavior of these dyes lies in their structure which consists of two nitrogen containing heterocycles joined by an electron deficient polymethine bridge that allows specific energy transitions to occur. The first portion of this work aims to explore dye functionality for analytical applications regarding the non-covalent labeling of bovine serum albumin. The second portion of the work explores dye interactions with human serum albumin in biological membrane mimetic environments using the ternary system of sodium dioctyl sulfosuccinate (AOT) in water and n-heptane.

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Polyferrocenylsilane (PFS) diblock copolymers self-assemble in selective solvents to form one-dimensional micelles for a broad range of polymer compositions and experimental conditions, driven by the crystallization of the PFS block that forms the micelle core. The most striking feature of these micelles is that they remain active for further growth. They can be extended in length when additional polymer, dissolved in a good solvent, is added to a solution of the pre-existing micelles. This thesis describes several studies investigating the factors that affect the growth and fragmentation of PFS diblock copolymer micelles in solution, with a particular emphasis on polyisoprene-PFS (PI-PFS) diblock copolymers. The goal of my research was trying to provide deeper understanding of this crystallization-driven self-assembly (CDSA) process. In an attempt to understand the growth kinetics of the PI-PFS cylindrical micelles, I added tiny amount of short micelle seeds into supersaturated solution of the same polymer, and followed the micelle growth by light scattering. The data analysis showed that the increase of micelle length could be described by an expression with two exponential decay terms. In another attempt to examine the factors that may affect the growth behavior of the PI-PFS micelles, I found that PI-PFS long micelles underwent fragmentation when they were subjected to external stimuli, e.g. addition of polar solvent, or heating. During the course of studying the effect of heating on the micelles, I developed a new approach to generate cylindrical micelles with controllable and uniform length, a one-dimensional analogue of self-seeding of crystalline polymers. I carried out a systematic study to investigate the self-seeding behavior of PFS block copolymers.

Polyferrocenylsilane (PFS) diblock copolymers self-assemble in selective solvents to form one-dimensional micelles for a broad range of polymer compositions and experimental conditions, driven by the crystallization of the PFS block that forms the micelle core. The most striking feature of these micelles is that they remain active for further growth. They can be extended in length when additional polymer, dissolved in a good solvent, is added to a solution of the pre-existing micelles. This thesis describes several studies investigating the factors that affect the growth and fragmentation of PFS diblock copolymer micelles in solution, with a particular emphasis on polyisoprene-PFS (PI-PFS) diblock copolymers. The goal of my research was trying to provide deeper understanding of this crystallization-driven self-assembly (CDSA) process. In an attempt to understand the growth kinetics of the PI-PFS cylindrical micelles, I added tiny amount of short micelle seeds into supersaturated solution of the same polymer, and followed the micelle growth by light scattering. The data analysis showed that the increase of micelle length could be described by an expression with two exponential decay terms. In another attempt to examine the factors that may affect the growth behavior of the PI-PFS micelles, I found that PI-PFS long micelles underwent fragmentation when they were subjected to external stimuli, e.g. addition of polar solvent, or heating. During the course of studying the effect of heating on the micelles, I developed a new approach to generate cylindrical micelles with controllable and uniform length, a one-dimensional analogue of self-seeding of crystalline polymers. I carried out a systematic study to investigate the self-seeding behavior of PFS block copolymers.

Thesis (Ph. D.)--University of Wisconsin--Madison, 2006. / Includes bibliographical references. Also available on the Internet.

O interesse por sistemas formados por misturas de surfatantes se deve ao fato destas misturas apresentarem propriedades diferentes, e algumas vezes superiores, às dos surfatantes puros. Neste trabalho foram realizadas, em água e em soluções aquosas de sal, medidas de CMC, constantes de dissociação iônica, concentrações superficiais de contra-íons e entalpias de micelização para misturas de surfatantes zwiteriônicos e catiônicos. Os surfactantes catiônicos utilizados foram: brometo e cloreto de N- hexadecil - N,N,N - trimetil amônio, CTAB(C), e brometo de N- dodecil N,N,N - trimetil amônio, DTAB. Os zwiteriônicos foram: N-hexadecil- N,N-dimetil-3-amônio-1-propanosulfonato, HPS, e N-dodecil- N,N-dimetil-3amônio-1-propanosulfonato, DPS, e n-hexadecil- fosforil colina, HFC. Medidas de tensão superficial, condutividade e entalpia molar de diluição em função da concentração da mistura mostraram que, em água, ocorre primeiro a formação de micelas zwiteriônicas, seguida, com o aumento da concentração total de detergente, da incorporação do surfatante catiônico na fase micelar. A adição de sal facilita a formação de micelas mistas, principalmente nas misturas formadas por surfatantes de maior cadeia hidrocarbônica. Em micelas mistas medidas da concentração superficial de contra-íons por captura química mostraram que a concentração superficial de contra-íons aumenta com a fração molar do detergente catiônico. A concentração superficial de ânions é maior para misturas HPS/CT AB do que para misturas H FC/CTAB, quando a fração molar do detergente zwiteriônico é alta, denotando importância da composição da mistura e do sentido do momento de dipolo da cabeça polar do surfatante zwiteriônico, na capacidade da interface micelar em ligar ânions. Com o objetivo de verificar a extensão na qual a catálise de uma reação unimolecular pode ser controlada por propriedades interfaciais de micelas, foi estudada a reação de descarboxilação do íon 6-nitro benzisoxazol-3- carboxilato que é favorecida em micro-ambientes menos hidratados. Os resultados obtidos nos diferentes sistemas mostraram que misturas HFC/CTAB favorecem mais a reação do que micelas constituídas pelos anfifílicos puros, enquanto que nas misturas HPS/CTAB e DPS/DTAB, a velocidade de descarboxilação aumenta linearmente com a fração molar do surfatante zwiteriônico. A variação das constantes de velocidade com a concentração de detergente para misturas com menos de 30% de surfatante catiônico foi analisada usando o formalismo da pseudo fase, enquanto que as demais foram analisadas usando o formalismo da troca-iônica, levando em conta a dependência de a com a concentração. Este estudo representa a primeira análise integrada de propriedades físico-químicas e cinéticas para um sistema de misturas de detergentes zwiteriônicos e catiônicos. Os dados estruturais, junto com os efeitos cinéticos, fornecem uma descrição detalhada tanto do efeito de interfaces sobre reatividade como da estrutura das micelas mistas. / The interest for systems formed by surfactant mixtures is related to the fact that these mixtures exhibit properties that are more interesting, or useful, than those of the isolated components. Some mixtures can, for example, have a lower critical micelle concentration (CMC) or a higher efficiency on the reduction of the surface tension than the components. In this work we determined CMC\'s, ionic dissociation constants, surface counter-ion concentrations and micellization enthalpies for pure zwiterionic and cationic surfactants and their mixtures, in water and in aqueous salt. For this purpose, we used different alkyl chain sizes and varying structures of the polar head groups of zwiterionic detergents thereby changing the dipole moment orientation. In addition the nature of the cationic surfactant counter-ion was varied. Ammonium quaternary detergents (cationic) and sulphobetaines and phosphocholines derivatives (zwiterionic) were used as surfactants. Surface tension, conductivity and isothermal titration calorimetry were used as the main analytical methods. The judicious use of these methods allowed a better understanding of mixed micelle formation. The formation of mixed micelles depended upon several conditions such as: salt concentration, molar fraction of the components and hydrocarbon chain length. Measurements of the surface counter-ion concentrations by chemical trapping demonstrated the importance of mixture composition and of dipole moment orientation on the ability of micellar interface to bind anions. In water, zwitterionic micelles form first and, as the total detergent concentration rises, the positively charged detergent increasingly incorporates into the micellar pseudophase. Salt addition assists mixed micelle formation, especially with longer chain surfactants. Determination of interfacial anion concentration by chemical capture showed that, as expected, the interfacial counterion concentration increases with the molar fraction of the positively charged detergent. Interfacial anion concentration was larger for mixtures of HPS/CTAB when compared with HFC/CTAB mixtures at high molar ratio of the zwitterionic detergent. These results evidence the importance of mixture composition and dipole orientation on the interfacial properties of mixed micelles. The kinetic study of the effects of surfactant mixtures on the rate of a unimolecular decarboxylation reaction using 6-nitro benzisoxazole-3-carboxylate (NBOC) also showed important features of the mixed micellar surface. The rate of the unimolecular NBOC decomposition is extremely sensitive to the hydrogen donating capacity of the solvent at the reaction site. HFC/CTAB mixtures increase the reaction rate more than the single detergent micelles. For HPS/CTAB and DPS/DTAB mixtures the reaction rate increases linearly with the mole fraction of the zwitterionic component. Quantitative kinetic analysis was done using the ion exchange formalism above 30 mole % CTAB and the simple pseudophase model at lower positively charged detergent. This study represents the first integrated analysis of both physicochemical and kinetic properties of zwitterionic/positively charged micelles. The structural data, together with the kinetic effects furnish a detailed description of both micellar interfacial effects on reactivity and mixed micelle formation and properties.

The ability of surfactants to form micelles and solubilise hydrophobic substances in aqueous environments has been widely exploited in formulation science. In spite of extensive studies over the past few decades by both experimental and theoretical methods, however, it remains difficult to predict key micellar parameters such as their size, shape and nanostructure which is essential for their successful implementation in the solubilisation of active ingredients. This is partly due to the vast number of surfactants commercially available but, in addition, the fragmentation of the field of surfactant science, over recent years, has made it more difficult to identify general trends and properties of surfactant systems. A further challenge is in characterising systems of heavily mixed surfactants since our knowledge on pure surfactant systems may not allow us to predict the behaviour of these systems. The broad aim of this thesis was to contribute to these aspects of surfactant science. The first part of the thesis reports a systematic study of the surfactant structure-micellar structure relationship of pure alkyl ethoxylate (CmEn) surfactants. This was done by independently varying the lengths of the alkyl chain and ethoxylate group and measuring the micellar structural properties. The next part of the thesis reports the effects of solubilisation of two model pesticides, Cyprodinil and Diuron, on the size, shape and internal structure of these surfactant micelles. These pesticides were chosen because they were structurally representative of different features of those widely used in agrochemicals. The final part of the thesis reports the work on binary surfactant mixtures that rationalise the general structural features of mixed micelles and their impact on pesticide solubilisation. Various experimental techniques were used including small angle neutron scattering (SANS), nuclear magnetic resonance (NMR), nuclear Overhauser effect spectroscopy (NOESY NMR), dynamic light scattering (DLS) and UV spectroscopy. The key findings of the thesis were that the micellar core volumes could be predicted with reasonable accuracy using the hydrophilic-lipophilic balance (HLB) of the surfactants in pure micelles. NOESY results revealed protrusions of the terminal methylene groups into the ethoxylate shell, thus providing evidence for the theoretically predicted phenomenon referred to as the-shell interface. SANS revealed that solubilisation of both pesticides caused micellar growth, with the long axial lengths of the micelles growing much longer. These structural changes were associated with the dehydration of the ethoxylate shells. Although a partitioning experiment predicted that the pesticides would be solubilised in the hydrated ethoxylate micellar shell, NOESY measurements revealed that the solubilisation occurred predominantly in the micellar cores. The discrepancy was caused by alkyl chain-ethoxylate mixing leading to the formation of dehydrated palisade regions that entrapped the pesticides towards the cores. The results from the binary mixed micelles showed some signs of synergistic behaviour but no enhancement of pesticide solubilisation.

Orientador: Edvaldo Sabadini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T18:09:34Z (GMT). No. of bitstreams: 1 Creatto_EduardoJose_M.pdf: 2495128 bytes, checksum: 6912961c15614521a8e45f4e9139f99f (MD5) Previous issue date: 2015 / Resumo: A química supramolecular envolve estruturas mantidas por interações intermoleculares. Neste contexto, sistemas que apresentam estruturas auto organizadas são de interesse devido importância como ciência de base bem como aplicabilidade. Neste trabalho foram utilizadas micelas de brometo de hexadeciltrimetilamônio (CTAB) como reticulantes de hidroxietilceluloses hidrofobicamente modificadas. Como as micelas estão em constante quebra e recombinação, reticulações transientes são obtidas. Tais sistemas apresentam comportamento reológico característico, dependente da concentração do surfactante. Obervou-se que a celulose que apresenta maior ramificação hidrofóbica resulta em aumento mais efetivo da viscosidade como consequência do maior grau de reticulação. A Técnica de calorimetria de titulação isotérmica (ITC) foi utilizada de modo a compreender os processos energéticos envolvidos na agregação. Com esta pôde-se obter parâmetros do sistema como cmc, cac e ?H°mic . Elucidou-se também que as interações polímero-surfactante são de origem hidrofóbica. A adição de salicilato de sódio (NaSal) em solução de CTAB leva a formação de micelas gigantes. Determinou-se por ITC a razão, [CTAB]/[NaSal], em que ocorre a formação de micelas gigantes, bem como a variação de entalpia deste processo. Sistemas contendo micelas gigantes e na presença de celulose hidrofóbicamente modificada foram estudados por reologia. Variações em seu comportamento foram claramente observadas / Abstract: Supramolecular chemistry involves structures maintained by the intermolecular interactions. In this context, systems that have self-assembled structures are of interest because of importance as basic science as well as applicability. In this study, we used micelles formed by hexadecyltrimethylammonium bromide (CTAB) as crosslinking agents of hydrophobically modified hydroxyethylcelluloses. As the micelles are constantly breaking and recombination, transient crosslinks are obtained. Such systems have characteristic rheological behavior, dependent on the surfactant concentration. It was observed that the cellulose which is more hydrophobic branching results in more effective increase in viscosity as a result of the higher degree of crosslinking. Isothermal titration Calorimetry (ITC) technique was used to understand the energy involved in the aggregation process. With this it was possible to obtain system parameters such as cmc, cac and ?H°mic. It is also elucidated that the interaction polymer-surfactant are of hydrophobic origin. The addition of sodium salicylate (NaSal) into CTAB solutions leads to formation of giant micelles. It was determined by ITC the ratio [CTAB]/[NaSal] in what occurs the formation of giant micelle, and the enthalpy change of the process. Systems containing giant micelles in the presence of hydrophobically modified cellulose were studied by rheology. Variations in their behavior were clearly observed / Mestrado / Físico-Química / Doutor em Ciências

Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find the optimal conditions, leading to a considerable demand of resources. Experimental insights demonstrate that the self-assembly of the block copolymers in solution has an effect on the final membrane structure. Nevertheless, the complete understanding of these multi-scale phenomena is elusive. Herein we use the coarse-grained method Dissipative Particle Dynamics to study the self-assembly of block copolymers that are used for the preparation of the membranes. To simulate representative time and length scales, we introduce a framework for model reduction of polymer chain representations for dissipative particle dynamics, which preserves the properties governing the phase equilibria. We reduce the number of degrees of freedom by accounting for the correlation between beads in fine-grained models via power laws and the consistent scaling of the simulation parameters. The coarse-graining models are consistent with the experimental evidence, showing a morphological transition of the aggregates as the polymer concentration and solvent affinity change. We show that hexagonal packing of the micelles can occur in solution within different windows of polymer concentration depending on the solvent affinity. However, the shape and size dispersion of the micelles determine the characteristic arrangement. We describe the order of crew-cut micelles using a rigid-sphere approximation and propose different phase parameters that characterize the emergence of monodisperse-spherical micelles in solution. Additionally, we investigate the effect of blending asymmetric diblock copolymers (AB/AC) over the properties of the membranes. We observe that the co-assembly mechanism localizes the AC molecules at the interface of A and B domains, and induces the swelling of the B-rich domains. The B-C interactions control the curvature of the assemblies in these blends. Finally, we study the self-assembly triblock copolymers used for membranes fabrication. We show that the polymer concentration, the block-copolymer composition, and the swelling of the micelle are responsible for the formation of elongated micelles in the casting solution. The formation of nanoporous membranes arises from the network-like packing of those micelles.