Nach den Ergebnissen der zweiten Nationalen Verzehrsstudie sind in Deutschland bereits 66 % der Männer und 51 % der Frauen übergewichtig (BMI > 25) oder adipös (BMI > 30) [BMELV, 2008]. Bisher auf dem Markt befindliche „Light-Lebensmittel“ mit Fettaustausch- bzw. Fettersatzstoffen weisen jedoch häufig sensorische Mängel auf. Im Kooperationsprojekt „Pflanzliche Fettaustauschstoffe aus sphärischen Proteinmizellen“ (Universität Leipzig: Institut für Lebensmittelhygiene; Freising: Fraunhofer IVV) wurde ein Lupinenproteinisolat entwickelt, welches micellare Strukturen mit hydrophober Oberfläche ausbilden kann und sich aufgrund seiner fettähnlichen Eigenschaften als neuer proteinbasierter Fettaustauschstoff in Lebensmitteln eignet. Aufgrund der geringen mikrobiologischen Stabilität und einer hohen Belastung mit sporenbildenden Bakterien, z. T. Bacillus cereus, waren jedoch Maßnahmen zur Entkeimung der Rohstoffe sowie des Proteinisolats notwendig. Die Arbeit stellt diese Maßnahmen und deren Einfluss auf die mikrobiologische Beschaffenheit sowie sensorische, technofunktionelle und ausgewählte ernährungsphysiologische Eigenschaften dar. In der vorliegenden Arbeit wurde eine physikalische Methode der Saatgutentkeimung etabliert (130 °C/60 min), welche die mikrobielle Stabilisierung des lupinenproteinbasierten Fettaustauschstoffes sicherstellte, wobei die sensorische Qualität (Geschmack, Cremigkeit, Farbe) nur minimal, die ernährungsphysiologische (in-vitro-Verdaubarkeit, Maillard-Produkte, Polyphenolgehalt) jedoch nicht beeinflusst wurde. Starke Veränderungen der technofunktionellen Eigenschaften (z. B. Gelbildung, Wasserbindung, Emulgierbarkeit, Schaumbildung etc.) konnten sowohl im positiven als auch im negativen Sinne nicht beschrieben werden. Lichtmikroskopische Aufnahmen und Untersuchungen der Proteine mittels SDS-PAGE und DSC bestätigten eine nur geringfügige Beeinflussung der micellaren Struktur und Proteinzusammensetzung. Die Anwendung als Fettaustauschstoff in Lebensmitteln würde somit nicht beeinträchtigt. Der Einfluss der Saatgutbehandlung auf das Protein war wesentlich geringer als eine direkte thermische Behandlung des Proteinisolats. Im Hinblick auf den Gesamtprozess sollte eine Pasteurisierung der feuchten Proteinisolate im nichtproteinschädigenden Temperaturbereich (75 °C/5 min) dennoch durchgeführt werden, um während des Prozesses eingetragene Mikroorganismen zu inaktivieren.

Statistical physics in soft matter systems, physical properties of bio-inspired systems and the mechanical manipulations of nano-systems have been studied using optical tweezers to form the basis of this doctoral Thesis. The first two chapters are on a general introduction about optical tweezers and detailed description of the setup used along with its calibrations. The next three chapters describe studies of statistical properties in soft matter systems, namely, out-of-equilibrium microrheology in a worm-like micellar system, irreversibility to reversibility crossover in the non-equilibrium trajectories of an optically trapped particle with the verification of fluctuation theorems even for non-ergodic descriptions of the system and high velocity Brownian vortexes at the liquid-air interface. The mechanical manipulation of the nano-systems, i.e. optically driven nano-rotors and the trapping, as well as transportation of palladium decorated single wall carbon nanotubes using optical tweezers have been discussed in the next two chapters. In the next chapter, the study of physical property of a bio-inspired system -the cell membrane deformability of human erythrocytes with increasing calcium ion concentration has been described. This Thesis is an endeavor to understand different mesoscopic systems using optical trapping and manipulation. Chapter 1 gives an introduction on optical tweezers. The working principle of optical trapping and manipulation are discussed along with their applicability in different fields of physics. Chapter 2 discusses the experimental setup in detail. The setup used for the experiments is a dual optical trap around an inverted microscope. The formation of the traps, the technique to steer the trapping beams and to place the traps at the desired positions in 3D without affecting the symmetry or stiffness are described. Instantaneous position tracking of the trapped particle is a very crucial part of optical trapping experiments. A tracking beam is used for this purpose and the trapped bead is imaged on a quadrant photo diode which provides the current signals that corresponds to the particle’s position in the focal plane. Then the calibration of the setup using various calibration methods are explained. Calibration of the setup includes the calibration of the position sensing devices, e.g. the quadrant photo diode and the CCD camera attached to the microscope, calibration of the electronic devices, e.g. the stage nano-positioner, nano-tilt mirror mount etc., and finally calibration of the trap stiffnesses (in both X and Y ) at varying laser powers. Precautions taken during the experiments to minimize the artifacts are also mentioned. In Chapter 3, a nonlinear microrheology experiment to probe directional viscoelasticity of a sheared worm-like micellar system has been described. Many wormlike micellar systems exhibit appreciable shear thinning due to shear induced alignment. As the micelles get aligned, introducing directionality in the system, the viscoelastic properties no longer remain isotropic. An optical tweezers based technique enables us to probe the out-of-equilibrium rheological properties of CTAT (cetyltrimethylammonium tosylate, cationic surfactant) system simultaneously along two orthogonal directions -parallel to the applied shear, as well as perpendicular to it. A trapped bead is dragged through the medium (1 wt% CTAT) and the position fluctuations of the bead, along the direction of motion (X) and perpendicular to it (Y ), are recorded in both ‘drive on’ and ‘drive off’ states. While the displacement of the bead along X -in response to the active drag force -carry signature of conventional shear thinning, its spontaneous position fluctuations along Y , following the fluctuation dissipation theorem, provide the loss modulus (G∗∗ along Y ) which manifests a dramatic orthogonal shear thickening, an effect hitherto unobserved. Chapter 4 describes an irreversibility to reversibility crossover in the transient response of a particle in optical trap; and the verification of the fluctuation theorem for a non-ergodic description of this system. The transient position fluctuations of a colloidal bead is studied as it approaches equilibrium after being released from varying heights (by using an additional very strong optical trap) in the potential energy landscape created by a weak optical trap. The time evolution of the system shows dramatic changes as the release point energy is decreased. Starting from a small-time-reversible to long-time-irreversible transition for a higher energy release, a time independent completely reversible state could be reached just by lowering the initial potential energy a bit. For an even lower energy release, the system shows an anomalous irreversibility. In this state, it progressively extracts useful work from the thermal fluctuations and surprisingly goes to a higher energy phase point. Highlighting the competition between the micro-reversibility and the irreversible dissipative loss in determining the long-time system behavior, this study exhibits the prominent emergence of a completely reversible state even at long time, in between the two irreversible states of opposite kind. The Transient Fluctuation Theorem (TFT) and the Integrated Transient Fluctuation Theorem (ITFT) which are defined to be valid only for ergodic systems, have been verified even for non-ergodic descriptions (separately for different release points) of this system. Chapter 5 illustrates the study of high velocity Brownian vortex at the liquid-air interface. A general kind of Brownian vortexes are constituted by applying an external non-conservative force field to a colloidal particle bound by a conservative optical trapping force at a liquid-air interface. As the liquid medium is translated at a constant velocity with the bead trapped at the interface, the drag force near the surface provide enough rotational component to bias the particle’s thermal fluctuations in a circulatory motion. The frequency of that circular motion increases linearly with the stage velocity, while an increment in the trapping laser power shows the opposite effect. The properties of these Brownian vortexes have been studied extensively to demonstrate how the thermal fluctuations and the advection of the bead play their role in the vortex motions, with an inference that the angular velocity of the circulatory motions offer a comparative measure of the interface fluctuations. In Chapter 6 the optical manipulation of asymmetric nanorods that constitutes optically driven nanorotors are described. The light force, irrespective of its polarization, is used to run a simple nanorotor. While the gradient force of a single beam optical trap holds an asymmetric nanorod, the scattering force is utilized to generate a non-zero torque on the nanorod making it rotate about the optic axis. The inherent textural irregularities or morphological asymmetries of the nanorods give birth to chirality which is responsible for generation of the torque under the radiation pressure. A farther study on nanorotors that are more transparent to infra-red (trapping beam) confirms that the scattering force is indeed the origin of the torque. A model is proposed to explain the rotational motion of the nanorods and estimate the speed of rotation. If the nanorods are not fairly transparent to the laser beam, even a small surface irregularity with non-zero chirality is sufficient to produce enough torque for moderate rotational speed. Different sized rotors can be used to set the speed of rotation over a wide range, with fine tuning possible through the variation of the laser power. Chapter 7 discuses optical trapping and transportation of palladium decorated single wall carbon nanotubes (Pd-SWNT). Individual carbon nanotubes being substantially smaller than the wavelength of light are not much responsive to optical manipulation. Decorating those single-walled carbon nanotubes with palladium particles changes that scenario dramatically, making the optical trapping and manipulation much easier. Palladium decorated nanotubes (Pd/SWNTs) have higher effective dielectric constant and are trapped at much lower laser power level with greater ease. In addition to that, an asymmetric line trap makes it possible to transport the Pd decorated SWNTs to a desired distant location in the sample cell. In the asymmetric line trap the Pd/SWNTs are first get attracted by the gradient force and then the scattering force push them away towards the other end of the line trap. In Chapter 8, how the rotational motion of crenated erythrocytes in an optical trap can be used to probe their membrane deformability is explained. When placed in a hypertonic buffer medium, discocytic human erythrocytes are subjected to crenation and take deformed shapes. The deformation of the cells brings in chirality and asymmetries in shape that make them rotate under the scattering force of a linearly polarized optical trap. A change in the deformability of the erythrocytes, due to any internal or environmental factor, is reflected in the rotational speed of the trapped crenated cells. Therefore the average rotational speed and the probability of rotation of the crenated erythrocytes in an optical trap can be considered as a direct signature of their membrane deformability. As an example, the relative increment in erythrocyte membrane rigidity with adsorption of Ca++ ions is examined quantitatively through this approach. The Thesis concludes with a summary of the main results and a brief discussion of the scope of future work in Chapter 9.

L'objectif de la thèse a été d'élucider le processus de réhydratation des caséines micellaires et des protéines solubles dans un milieu complexe et opaque : le lait. L'influence de l'état d'hydratation de ces ingrédients laitiers en fonction du temps (5, 120, 180, 240, 300, 480, 900 et 1440 min de réhydratation) sur les propriétés rhéologiques, texturales, physiques ainsi que la microstructure des gels laitiers acides a également été étudiée. Il en résulte que le processus de réhydratation des caséines micellaires diffère de celui des protéines solubles, et est extrêmement long avec trois étapes : une étape de mouillage des particules, suivie d'une étape de gonflement caractérisée par une augmentation de la taille des particules et enfin une étape de dispersion marquée par la diminution de la taille des particules. La réhydratation des protéines solubles est caractérisée par une grande rapidité, avec deux phases : le mouillage et la phase de dispersion (superposée). D'autre part, l'allongement de la durée de réhydratation des caséines micellaires est associé à une augmentation du point de gélification ainsi qu'à une nette amélioration des propriétés physiques, texturales et rhéologiques des gels : augmentation de leur fermeté et de leur force, diminution de la synérèse et de la formation de grumeaux. La durée de réhydratation des protéines solubles n'a pas d'influence sur ces paramètres. En revanche, leur dénaturation (par chauffage à sec) est associée à une dégradation des propriétés texturales des gels acides. Finalement, il s'avère que les gels acides formulés à partir des protéines solubles sont de meilleure qualité texturale (à l'exception de la formation de grumeaux) que ceux préparés à partir des caséines micellaires / The main objectives of this work were to elucidate the rehydration mechanism of the two major milk proteins (micellar casein and whey protein) into a complex and opaque medium such as milk and to assess the influence of hydration state (defined as a function of rehydration length after 5,120,180,240,300, 480, 900 and 1440 minutes of rehydration) on the rheological, textural, physical properties and microstructure of the obtained acid milk gels. Whereas, micellar casein presented a long rehydration process into milk characterized by three stages: a wetting, swelling and dispersion phase, whey protein displayed a quick rehydration process characterized by an overlapping of wetting and dispersion phase. Furthermore, an extended rehydration time of micellar casein powder into the milk base was associated with a postponed onset of gelation and enhanced physical, textural as well as rheological properties of the obtained acid milk gels characterized by increases in gel firmness, strength, and decreases in syneresis susceptibility and grains formation. In contrast, acid milk gels prepared with whey protein powder exhibited comparable overall textural properties regardless the different rehydration times. Nevertheless, denaturation of whey protein powder (by dry heating) was associated with a deterioration of the textural properties of the acid milk gels. Finally, acid gels prepared with whey proteins displayed better overall textural quality than those prepared with micellar casein (except for grains formation)

The study of protein and surfactant interactions is of great significance in a number of applications, such as the cosmetic, food or pharmaceutical industries and many others. However, they require further study due to their compositional complexity and the limitations of current analytical approaches. In this thesis, the cationic surfactant septonex in combination with two differently charged proteins lysozyme and bovine serum albumin under different physiological conditions (temperature, surfactant concentration, environment and others) was selected to study the interactions. Characterization of protein-surfactant interactions is a very important but challenging task, therefore it is essential to use appropriate approaches to explore the nature of these interactions. In order to unify the information to provide rational models, calorimetric methods (DSC, ITC) and dynamic light scattering were used. Isothermal titration calorimetry monitors the evidence for the formation of the system of the mentioned substances and information on aggregation behavior, differential scanning calorimetry characterizes the thermal stability of proteins and dynamic light scattering made it possible to monitor changes in particle size. Both proteins have been proven to interact with positive septonex, even if the lysozyme molecule is also positively charged. However, significant differences were found between the two proteins. From the obtained results it is evident that the identical charge of the protein with the surfactant has an effect on the intensity of the measurement, although all measured interactions showed an endothermic character.

The thesis deals with the study of the influence of concentration and different types of surfactants (Igepal CO-520, Arkopal N110, Igepal CO-890, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium bromide and Dehyton PL) on the environmental stress cracking resistance of high-density polyethylene by means of Full Notch Creep Test. Furthermore, the influence of ligamental stress (3,5; 4,0 a 4,5 MPa), pH of the prepared active environment and type of the water used as a solvent for the surfactants on the time to failure was monitored. An accelerating effect was observed at increased concentration, stress and molecular weight. Faster failure was achieved after exposure to ionic types compared to nonionic. The rate of the notch opening was determined. The brittle and ductile behavior during the process of failure was evaluated by microscopic analysis of the morphology of the fracture surfaces. Based on the pH change after the test, the stability of the active environment was evaluated. Deteriorating quality of surfactant solutions was observed. Raman spectroscopy and Fourier transform infrared spectroscopy were used to detect the surfactant on the surface of the test specimen after the test.

No description available.

Nach den Ergebnissen der zweiten Nationalen Verzehrsstudie sind in Deutschland bereits 66 % der Männer und 51 % der Frauen übergewichtig (BMI > 25) oder adipös (BMI > 30) [BMELV, 2008]. Bisher auf dem Markt befindliche „Light-Lebensmittel“ mit Fettaustausch- bzw. Fettersatzstoffen weisen jedoch häufig sensorische Mängel auf. Im Kooperationsprojekt „Pflanzliche Fettaustauschstoffe aus sphärischen Proteinmizellen“ (Universität Leipzig: Institut für Lebensmittelhygiene; Freising: Fraunhofer IVV) wurde ein Lupinenproteinisolat entwickelt, welches micellare Strukturen mit hydrophober Oberfläche ausbilden kann und sich aufgrund seiner fettähnlichen Eigenschaften als neuer proteinbasierter Fettaustauschstoff in Lebensmitteln eignet. Aufgrund der geringen mikrobiologischen Stabilität und einer hohen Belastung mit sporenbildenden Bakterien, z. T. Bacillus cereus, waren jedoch Maßnahmen zur Entkeimung der Rohstoffe sowie des Proteinisolats notwendig. Die Arbeit stellt diese Maßnahmen und deren Einfluss auf die mikrobiologische Beschaffenheit sowie sensorische, technofunktionelle und ausgewählte ernährungsphysiologische Eigenschaften dar. In der vorliegenden Arbeit wurde eine physikalische Methode der Saatgutentkeimung etabliert (130 °C/60 min), welche die mikrobielle Stabilisierung des lupinenproteinbasierten Fettaustauschstoffes sicherstellte, wobei die sensorische Qualität (Geschmack, Cremigkeit, Farbe) nur minimal, die ernährungsphysiologische (in-vitro-Verdaubarkeit, Maillard-Produkte, Polyphenolgehalt) jedoch nicht beeinflusst wurde. Starke Veränderungen der technofunktionellen Eigenschaften (z. B. Gelbildung, Wasserbindung, Emulgierbarkeit, Schaumbildung etc.) konnten sowohl im positiven als auch im negativen Sinne nicht beschrieben werden. Lichtmikroskopische Aufnahmen und Untersuchungen der Proteine mittels SDS-PAGE und DSC bestätigten eine nur geringfügige Beeinflussung der micellaren Struktur und Proteinzusammensetzung. Die Anwendung als Fettaustauschstoff in Lebensmitteln würde somit nicht beeinträchtigt. Der Einfluss der Saatgutbehandlung auf das Protein war wesentlich geringer als eine direkte thermische Behandlung des Proteinisolats. Im Hinblick auf den Gesamtprozess sollte eine Pasteurisierung der feuchten Proteinisolate im nichtproteinschädigenden Temperaturbereich (75 °C/5 min) dennoch durchgeführt werden, um während des Prozesses eingetragene Mikroorganismen zu inaktivieren.:1 Einleitung und Zielstellung 1 2 Stand des Wissens 4 2.1 Die Lupine 4 2.1.1 Anbau und Verbreitung 4 2.1.2 Einsatz von Lupinenprodukten und -proteinen in der Humanernährung 5 2.1.3 Inhaltsstoffe und deren Verteilung 5 2.1.4 Lupinenproteine 10 2.1.4.1 Einteilung und Struktur der Lupinenproteine 10 2.1.4.2 Lupinenproteine und Allergenität 12 2.1.5 Eigenschaften der verschiedenen Lupinenproteinfraktionen 13 2.1.5.1 Ernährungsphysiologische Eigenschaften 13 2.1.5.2 Funktionelle Eigenschaften 15 2.1.5.3 Modifikation der Proteinstruktur 15 2.1.5.4 Herstellung verschiedener Lupinenproteinpräparate 16 2.1.5.5 Micellare Proteine 17 2.2 Möglichkeiten der Fettreduktion in Lebensmitteln 18 2.2.1 Fettaustauschstoffe 18 2.2.1.1 Fettaustauschstoffe auf Proteinbasis (Mikropartikulierte Proteine) 18 2.2.1.2 Fettaustauschstoffe auf Kohlenhydratbasis 19 2.2.1.3 Quellstoffe 19 2.2.2 Fettersatzstoffe 19 2.2.2.1 Spezielle Triglyceride 20 2.2.2.2 Kohlenhydratpolyester 20 2.2.2.3 Retrofette 20 2.3 Herstellung des lupinenproteinbasierten Fettaustauschstoffes 20 2.4 Saatgutbehandlung 21 2.4.1 Methoden der Lebensmittelkonservierung 22 2.5 Proteinfunktionalität 25 2.5.1 Definition und Zusammenhang zu Proteinen 25 2.5.2 Ausgewählte funktionelle Eigenschaften 26 2.5.2.1 Wasserbindevermögen 26 2.5.2.2 Ölbindevermögen 26 2.5.2.3 Löslichkeit 27 2.5.2.4 Emulgiervermögen 27 2.5.2.5 Schaumbildungsvermögen 28 2.5.2.6 Gelbildungsvermögen 29 2.5.2.7 Oberflächenhydrophobität 30 2.5.2.8 Bedeutung für die Lebensmittelentwicklung 30 3 Material und Methoden 32 3.1 Material 32 3.1.1 Saatgut 32 3.1.2 Geräte, Chemikalien, Verbrauchsmaterial, Software 32 3.1.3 Pufferlösungen 39 3.1.4 Herstellung Bradford-Reagenz, 5-fach 39 3.1.5 Auswahl der Vergleichssubstanzen 39 3.2 Methoden 40 3.2.1 Herstellung der Proteinisolate 40 3.2.2 Mikrobiologische Analysen 41 3.2.3 Bestimmung der Trockenmasse 41 3.2.4 Bestimmung des Proteingehalts 42 3.2.5 Thermische Behandlungsmethoden im Prozess 42 3.2.5.1 UHT-Erhitzung des Extraktes 42 3.2.5.2 Pasteurisierung des Isolats 44 3.2.6 Saatgutentkeimung 44 3.2.6.1 UVC-Bestrahlung 44 3.2.6.2 Trockene Erhitzung 45 3.2.6.3 Autoklavieren 46 3.2.7 Sensorische Untersuchungen 46 3.2.8 Proteinfunktionalität 47 3.2.8.1 Ölbindevermögen 47 3.2.8.2 Wasserbindevermögen 47 3.2.8.3 Gelbildungsvermögen 47 3.2.8.4 Emulgiereigenschaften 47 3.2.8.5 Schaumbildungsvermögen 48 3.2.8.6 Proteinlöslichkeit 48 3.2.8.7 Oberflächenhydrophobität 49 3.2.9 Ernährungsphysiologische Eigenschaften 50 3.2.9.1 in-vitro-Verdaubarkeit 50 3.2.9.2 Maillard-Produkte 50 3.2.9.3 Nachweis reduzierender Zucker .50 3.2.9.4 Nachweis von Glykoproteinen 50 3.2.9.5 Polyphenolgehalt der Lupinenflocken und Proteinisolate 51 3.2.10 Proteincharakterisierung 51 3.2.10.1 Lichtmikroskopie 51 3.2.10.2 Dynamische Differenzkalorimetrie 51 3.2.10.3 Natriumdodecylsulfat-Polyacrylamidgelelektrophorese 52 4 Ergebnisse und Diskussion 54 4.1 Thermische Behandlungsmethoden im Prozess 54 4.1.1 UHT-Erhitzung des Extraktes: Einfluss auf Mikrobiologie und Proteinausbeute 54 4.1.2 Pasteurisierungsversuche: Einfluss auf Mikrobiologie und Proteinqualität 55 4.2 Saatgutentkeimung - Mikrobiologie und Proteinausbeute 56 4.2.1 Versuchsreihe I 56 4.2.2 Versuchsreihe II 61 4.3 Sensorische Untersuchungen 63 4.3.1 Verkostungen 64 4.3.2 Farbmessung der Proteinisolate und Flocken 65 4.4 Proteinfunktionalität 69 4.4.1 Wasser- und Ölbindevermögen 69 4.4.2 Gelbildungsvermögen 72 4.4.3 Emulgiereigenschaften 74 4.4.4 Schaumbildungsvermögen 78 4.4.5 Proteinlöslichkeit 81 4.4.6 Oberflächenhydrophobität 83 4.5 Ernährungsphysiologische Eigenschaften 86 4.5.1 Maillard-Produkte 86 4.5.2 Nachweis reduzierender Zucker 87 4.5.3 Nachweis von Glykoproteinen 87 4.5.4 Verdaubarkeit 88 4.5.5 Polyphenolgehalte 89 4.6 Proteincharakterisierung 91 4.6.1 Lichtmikroskopie 91 4.6.2 Dynamische Differenzkalorimetrie 95 4.6.3 Natriumdodecylsulfat-Polyacrylamidgelelektrophorese 98 5 Zusammenfassung 105 Anhang 109

In day to day life we encounter many different materials which are intermediate between crystalline solids and simple liquids that include paints , glues , suspensions, polymers, surfactants, food and cosmetic products and so on. ‘Soft condensed matter’ is an emerging field of science that aims to generalize the flow and various deformation mechanisms in this apparent diverse class of materials from a ‘mesoscopic’ point of view (important length scales for these systems is usually 10nm-1μm) where the actual atomic and molecular details governed by various quantum mechanical laws are not very important. These soft systems are held together by weaken tropic forces and therefore can be perturbed easily (the typical elastic modulus of these materials is many orders of magnitude lower compared to metallic solids). Moreover, very long relaxation times in these systems(∼10−3 to 1 s) have made them ideal candidates to study non-equilibrium physics. The present Thesis is an endeavor to understand linear and non-linear flow behavior and low Reynolds number instabilities in various soft matter systems like suspensions of flocculated carbon nanotubes and carbon black, surfactant gels, colloidal glasses, Langmuir monolayers etc probed mainly by bulk and interfacial rheology, in-situ light scattering, particle image velocimetry(PIV) techniques and Fourier transform rheology. We also use dynamic light scattering techniques for particle sizing and characterization of Brownian systems. Chapter 1 gives a general introduction to soft condensed matter, particularly, the important length and time scales, various interactions and the rich phase behavior emerged from the delicate balance between energy and entropy in these systems. In this context, We describe the detailed phase behavior of two such systems studied in this thesis. We next describe briefly a few important concepts which motivate the main problems studied in the present thesis like the shear-thickening in suspensions of Brownian and non-Brownian particles, non-equilibrium steady state fluctuation relations in driven systems, elasticity driven instabilities in complex fluids, jamming transitions and aging behavior. This is followed by a discussion of the experimental techniques like linear and nonlinear rheology, including the Fourier transform rheology. Chapter 2 discusses the experimental techniques used by us in detail. We first describe the different components and mode of operations of the MCR-300 stress-controlled rheometer (Paar Physica, Germany) and various experimental geometries. Next we discuss the set up for two dimensional rheological measurements. The homebuilt imaging set up for in-situ polarized light scattering and direct imaging studies is described along with the in-situ particle image velocimetry (PIV) to map out the exact spatially resolved velocity profiles in 2D systems. We give a brief account of the techniques of Fourier transform rheology. At the end of this chapter, we briefly describe the angle resolved dynamic light scattering (DLS) set up (Brookhaven Instruments, USA). In Chapter 3, we study colossal discontinuous shear-thickening transition in confined suspensions of fractal clusters formed by multi-wall carbon nanotubes (MWNT) by rheology and in-situ imaging experiments. Monotonic decrease in viscosity with increasing shear stress, known as shear thinning, is a known rheological response to shear flow in complex fluids in general and for flocculated suspensions in particular. In the present experiments we demonstrate a discontinuous shear thickening transition where the viscosity jumps sharply above a critical shear stress by four to six orders of magnitude in flocculated suspensions of MWNT even at very low weight fractions(∼0.5%). Rheo-optical observations reveal the shear-thickened state as a percolated structure of MWNT flocs spanning the system size. We present a dynamic phase diagram of the non-Brownian MWNT dispersions revealing a starting jammed state followed by shear-thinning and shear-thickened states. The present study further suggests that the shear-thickened state obtained as a function of shear stress is likely to be a generic feature of fractal clusters under flow, albeit under confinement. An understanding of the shear thickening phenomena in confined geometries is pertinent for flow controlled fabrication techniques in enhancing the mechanical strength and transport properties of thin films and wires of nanostructured composites as well as in lubrication issues. We try to understand the flow of jammed and shear-thickened states under constant applied strain rate by studying the building up and relaxation of individual stress fluctuation events similar to the flow in dense granular materials. We also characterize the metastable shear thickened states by superposing a small sinusoidal stress component on a steady applied stress as well as by studying the a thermal entropy consuming fluctuations which are also observed for other jammed systems under an applied steady shear stress as described in the next chapter. Chapter 4 reports the study of non-equilibrium fluctuations in concentrated gels and glassy systems(in jammed state), the nature of fluctuations and their systemsize dependence in the framework of fluctuation relation and Generalized Gumbel distribution. In the first part, we show that the shear rate at a fixed shear stress in a micellar gel in a jammed state exhibits large fluctuations, showing positive and negative values, with the mean shear rate being positive. The resulting probability distribution functions (PDFs) of the global power flux to the system vary from Gaussian to non-Gaussian, depending on the driving stress and in all cases show similar symmetry properties as predicted by Gallavotti-Cohen steady state fluctuation relation. The fluctuation relation allows us to determine an effective temperature related to the structural constraints of the jammed state. We have measured the stress dependence of the effective temperature. Further, experiments reveal that the effective temperature and the standard deviation of the shear rate fluctuations increase with the decrease of the systemsize. In the second part of this chapter, we report a universal large deviation behavior of spatially averaged global injected power just before the rejuvenation of the jammed state formed by an aging suspension of laponite clay under an applied stress. The probability distribution function (PDF) of these entropy consuming strongly non-Gaussian fluctuations follow an universal large deviation functional form described by the Generalized Gumbel (GG) distribution like many other equilibrium and non-equilibrium systems with high degree of correlations but do not obey Gallavotti-Cohen Steady State Fluctuation Relation (SSFR). However, far from the unjamming transition (for smaller applied stresses) SSFR is satisfied for both Gaussian as well as non-Gaussian PDF. The observed slow variation of the mean shear rate with system size supports a recent theoretical prediction for observing GG distribution. We also establish the universality of the observations reported in this chapter in the light of other jammed systems under shear. We examine in the first part of Chapter 5, the shear-thinning behavior of a two dimensional yield stress bearing monolayer of sorbitan tristearate at air/water interface. The flow curve (stress vs shear rate) consists of a linear region at low shear stresses/shear rates, followed by a stress plateau at higher values. The velocity profile obtained from particle imaging velocimetry indicates that shear banding occurs showing coexistence of fluidized region near the rotor and solid region with vanishing shear-rate away from the rotor. In the fluidized region, the velocity profile which is linear at low shear rates becomes exponential at the onset of shear-thinning, followed by a time varying velocity profile in the plateau region. At low values of constant applied shear rates, the viscosity of the film increases with time, thus showing aging behavior like in soft glassy three-dimensional (3D) systems. Further, at the low values of the applied stress in the yield stress regime, the shear-rate fluctuations in time show both positive and negative values, similar to that observed in sheared 3D jammed systems. By carrying out a statistical analysis of these shear-rate fluctuations, we estimate the effective temperature of the soft glassy monolayer using the Galavatti-Cohen steady state fluctuation relation. In the second part of this chapter, we study in detail the non-linear viscoelastic behavior of Langmuir monolayers. Under oscillatory shear usually observed in many 3D metastable complex fluids with large structural relaxation times. At large strain amplitudes(γ), the storage modulus (G”) decreases monotonically whereas the loss modulus (G”) exhibits a peak above a critical strain amplitude before it decreases at higher strain amplitudes. The power law decay exponents of G” and G” are in the ratio 2:1. The peak in G” is absent at high temperatures and low concentration of sorbitan tristearate. Strain-rate frequency sweep measurements on the monolayers do indicate a strain-rate dependence of the structural relaxation time. The present study on sorbitan tristearate monolayers clearly indicates that the nonlinear viscoelastic behavior in 2D Langmuir monolayers is very general and exhibits many of the features observed in 3D complex fluids. We report in the first part of Chapter 6 scattering dichroism experiments to quantify the spatio-temporal nematodynamics of shear-thinning worm like micellar gels of surfactant Cetyltrimethylammonium Tosylate (CTAT) in the presence of salt sodium chloride (NaCl) enroute to rheochaos. For shear rates past the plateau onset, we observe a presence of alternating bright and dark‘ intertwined’ birefringent structures along the vorticity direction. The orientational order corresponding to these structures are predominantly oriented at +45deg and−45deg to the flow (v) in the (v,∇v) plane. The orientational dynamics of the nematics especially at the interface between the structures, has a one-to-one correspondence with the temporal behavior of the stress. Experiments show that the spatial motion of the vorticity structures depend on the gap thickness of the Couette cell. We next discuss the random temporal flow behavior of this system at high values of applied shear rate/stress in the framework of elastic turbulence in the second part of this chapter. Here, we study the statistical properties of spatially averaged global injected power fluctuations for the worm-like micellar system described above. At sufficiently high Weissenberg numbers (Wi) the shear rate and hence the injected power p(t) at a constant applied stress shows large irregular fluctuations in time. The nature of the probability distribution function (PDF) of p(t) and the power-law decay of its power spectrum are very similar to that observed in recent studies of elastic turbulence for polymer solutions. Remarkably, these non-Gaussian pdf scan be well described by an universal large deviation functional form given by the Generalized Gumbel (GG) distribution observed in the context of spatially averaged global measures in diverse classes of highly correlated systems. We show by in-situ rheology and polarized light scattering experiments that in the elastic turbulent regime the flow is spatially smooth but random in time, in agreement with a recent hypothesis for elastic turbulence. In Chapter 7, we study the vorticity banding under large amplitude oscillatory shear (LAOS) in a dilute worm-like micellar gel formed by surfactant CTAT by Fourier transform rheology and in-situ polarized light scattering. Under LAOS we found the signature of a non-trivial order-disorder transition of Taylor vortices. In the non-linear regime, higher harmonicde composition of the resulting stress signal reveals that the third harmonic I3 shows a very prominent maximum at the strain value where the number density (nv) of the Taylor vortices is maximum for a wide range of angular frequencies both above and below the linear crossover point. Subsequent increase in applied strain results in distortions of the vortices and a concomitant decrease in nv when I3 also drops very sharply and acts like an order parameter for this order-disorder transition. We further quantify the transition by defining an independent order parameter like quantity from the spatial correlation function of the scattered intensity and equivalently its Fourier transform which essentially captures the non monotonous third harmonic behavior. Lissajous plots indicate an intra-cycle strain hardening for the values of γ corresponding to the peak of I3 similar to that observed for hard-sphere glasses. Our study is an important step forward to correlating the structures developed in the system under LAOS to the appearances of the higher harmonics in the non-linear regime. The Thesis concludes with a summary of the main results and a brief account on the scope of future work as described in Chapter 8.

Álcoois primários sulfatados de cadeia longa, usualmente na forma de sais de sódio, são tensoativos de grande interesse comercial utilizados em diversas formulações de higiene pessoal e limpeza doméstica. Eles são produzidos comercialmente através da reação de álcoois etoxilados com trióxido de enxofre seguida de imediata neutralização com hidróxido de sódio. O produto formado é uma solução neutra de álcool primário etoxilado sulfatado em água. Sabe-se que a armazenagem desse produto por longos períodos de tempo em temperaturas elevadas pode levar à hidrólise completa, mas, em condições normais de uso e temperatura ambiente é esperado que o produto seja resistente à hidrólise. No entanto observou-se que algumas amostras comerciais de lauril éter sulfato de sódio que foram estocadas por diferentes períodos de tempo em frascos fechados à temperatura ambiente sofreram hidrólise em intervalos de tempo relativamente curtos. Isso leva à hipótese de que o comportamento de hidrólise seria influenciado por outras variáveis além da temperatura e do tempo de estocagem. O presente trabalho consistiu em identificar as variáveis de maior impacto na reação de hidrólise por meio de experimentos planejados. O teor de ativos foi acompanhado ao longo da reação para avaliar o efeito da presença de eletrólitos, de material insulfatado, em diferentes temperaturas, variando-se o pH inicial por meio da adição de ácido clorídrico. O comportamento da reação de hidrólise observado foi compatível com aquele descrito na literatura para o dodecil sulfato de sódio. A hidrólise apresentou-se como sendo autocatalítica, com a aceleração da taxa de reação provavelmente causada pela presença de íons hidrogênio liberados na reação. Foi possível identificar que as variáveis de maior efeito na reação foram: pH inicial, o teor de cloreto de sódio e a temperatura. O modelo de troca iônica em pseudo-fase foi utilizado para o tratamento dos resultados experimentais e mostrou-se adequado tendo sido, portanto, utilizado para prever o comportamento de estabilidade do produto à temperatura ambiente e nas condições em que o produto é normalmente comercializado. Um modelo empírico de redes neurais foi desenvolvido com sucesso para prever o comportamento do pH ao longo do tempo para as condições estudadas. / Long-chain primary alkyl sulfuric acids, usually as their sodium salts, are important commercial surfactants used in a large number of household and personal care formulations. They are commercially produced by treatment of mixtures of ethoxylated fatty alcohols with sulfur trioxide followed by immediate neutralization with sodium hydroxide, a neutral aqueous mixture of sodium primary alkyl ether sulfate is obtained. It is known that prolonged storage of the material at elevated temperature can lead to complete hydrolysis but under normal use and typical environmental conditions the product is expected to be resistant to hydrolysis. In spite of that it has been observed that some commercial samples of sodium lauryl ether sulfate stored for different periods of time in sealed containers at room temperature have undergone hydrolysis in a relatively short period of time which leads to the hypothesis that the hydrolysis behavior would be strongly influenced by variables other than temperature and storage time. The present work consisted of identifying the process variables with the most significant effect on the acid hydrolysis by using experimental design. The rate of hydrolysis has been followed acidimetrically to evaluate the effect of electrolytes as well as the concentration of unsulfated matter at different temperatures, over a wide initial pH range, under the presence of added hydrochloric acid. The pattern of kinetic behaviour observed was broadly the same as previously described for the sodium dodecyl sulfate. The hydrolysis presented the characteristic autocatalytic form, the catalysis presumably arising from the production of hydrogen sulfate ions. It was possible to observe that the most significant effects on the rate of hydrolysis were the initial pH, the total amount of sodium chloride and the temperature. The results were also discussed in terms of the ion-exchange pseudophase model of the micelle reaction. Accordingly to the fitting of parameters that was carried out it is possible to conclude that the pseudo-phase ion-exchange theory is found to account satisfactorily for the results reported and it was used to predict the stability behavior of the product at room temperature and under normal commercial conditions. A neural network based model was also successfully developed in order to predict the pH behavior in the conditions studied.

Álcoois primários sulfatados de cadeia longa, usualmente na forma de sais de sódio, são tensoativos de grande interesse comercial utilizados em diversas formulações de higiene pessoal e limpeza doméstica. Eles são produzidos comercialmente através da reação de álcoois etoxilados com trióxido de enxofre seguida de imediata neutralização com hidróxido de sódio. O produto formado é uma solução neutra de álcool primário etoxilado sulfatado em água. Sabe-se que a armazenagem desse produto por longos períodos de tempo em temperaturas elevadas pode levar à hidrólise completa, mas, em condições normais de uso e temperatura ambiente é esperado que o produto seja resistente à hidrólise. No entanto observou-se que algumas amostras comerciais de lauril éter sulfato de sódio que foram estocadas por diferentes períodos de tempo em frascos fechados à temperatura ambiente sofreram hidrólise em intervalos de tempo relativamente curtos. Isso leva à hipótese de que o comportamento de hidrólise seria influenciado por outras variáveis além da temperatura e do tempo de estocagem. O presente trabalho consistiu em identificar as variáveis de maior impacto na reação de hidrólise por meio de experimentos planejados. O teor de ativos foi acompanhado ao longo da reação para avaliar o efeito da presença de eletrólitos, de material insulfatado, em diferentes temperaturas, variando-se o pH inicial por meio da adição de ácido clorídrico. O comportamento da reação de hidrólise observado foi compatível com aquele descrito na literatura para o dodecil sulfato de sódio. A hidrólise apresentou-se como sendo autocatalítica, com a aceleração da taxa de reação provavelmente causada pela presença de íons hidrogênio liberados na reação. Foi possível identificar que as variáveis de maior efeito na reação foram: pH inicial, o teor de cloreto de sódio e a temperatura. O modelo de troca iônica em pseudo-fase foi utilizado para o tratamento dos resultados experimentais e mostrou-se adequado tendo sido, portanto, utilizado para prever o comportamento de estabilidade do produto à temperatura ambiente e nas condições em que o produto é normalmente comercializado. Um modelo empírico de redes neurais foi desenvolvido com sucesso para prever o comportamento do pH ao longo do tempo para as condições estudadas. / Long-chain primary alkyl sulfuric acids, usually as their sodium salts, are important commercial surfactants used in a large number of household and personal care formulations. They are commercially produced by treatment of mixtures of ethoxylated fatty alcohols with sulfur trioxide followed by immediate neutralization with sodium hydroxide, a neutral aqueous mixture of sodium primary alkyl ether sulfate is obtained. It is known that prolonged storage of the material at elevated temperature can lead to complete hydrolysis but under normal use and typical environmental conditions the product is expected to be resistant to hydrolysis. In spite of that it has been observed that some commercial samples of sodium lauryl ether sulfate stored for different periods of time in sealed containers at room temperature have undergone hydrolysis in a relatively short period of time which leads to the hypothesis that the hydrolysis behavior would be strongly influenced by variables other than temperature and storage time. The present work consisted of identifying the process variables with the most significant effect on the acid hydrolysis by using experimental design. The rate of hydrolysis has been followed acidimetrically to evaluate the effect of electrolytes as well as the concentration of unsulfated matter at different temperatures, over a wide initial pH range, under the presence of added hydrochloric acid. The pattern of kinetic behaviour observed was broadly the same as previously described for the sodium dodecyl sulfate. The hydrolysis presented the characteristic autocatalytic form, the catalysis presumably arising from the production of hydrogen sulfate ions. It was possible to observe that the most significant effects on the rate of hydrolysis were the initial pH, the total amount of sodium chloride and the temperature. The results were also discussed in terms of the ion-exchange pseudophase model of the micelle reaction. Accordingly to the fitting of parameters that was carried out it is possible to conclude that the pseudo-phase ion-exchange theory is found to account satisfactorily for the results reported and it was used to predict the stability behavior of the product at room temperature and under normal commercial conditions. A neural network based model was also successfully developed in order to predict the pH behavior in the conditions studied.