by D Zimin · 2004 · Cited by 4 — interfaces and their interaction. The first two sections deal with surfactants and polymers, respectively. A summary of classification,

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i Synergetic Effects of Polymer-Surfactant Mixtures on Solid-Liquid Interfaces DISSERTATION Zur Erlangung des Doktorgrades Der Naturwissenschaften Der Naturwissenschaftlichen Fakultät IV Chemie und Pharmazie Der Universität Regensburg vorgelegt von Diplom-Biophysiker Denys Zimin aus Kiev im Dezember 2003 Gutachter: Prof Dr. Werner Kunz; Prof. Dr. Georg Schmeer

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ii Die Arbeit wurde angeleitet von: Prof. Dr. W. Kunz Promotionsgesuch eingereicht am: 07.01.2004 Prüfungsausschuss: Vorsitzender Prof. Dr. A. Pfitzner 1. Prüfer Prof. Dr. W. Kunz 2. Prüfer Prof. Dr. G. Schmeer 3. Prüfer Prof. Dr. M. Liefländer Das Kolloquium fand statt am: 30.01.2004

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iii ACKNOWLEDGMENTS DANKSAGUNGEN . Meinen ersten und größten Dank möchte ich an meinen Doktorvater, Herrn Prof. Dr. Werner Kunz aussprechen. Ohne seine Hilfe wäre diese Dissertation überhaupt nicht entstanden. Ich möchte mich auch bei meinem Gutachter Herrn Prof. D. Georg Schmeer für wertvolle Hinweise und die Idee von —Übergang vom Chaos zur Ordnungfi bedanken. Weiterhin bedanke ich mich bei allen Kollegen und Mitarbeitern des Instituts für Physikalische und Theoretische Chemie, besonders bei Dr. Edith Schnell für die Einführung und Begleitung in der wunderschönen Welt der Rastersondenmikroskopie sowie für ihre stetige Hilfsbereitschaft, bei Dr. Didier Touraud für wertvolle und sachliche Diskussionen, bei Dr. Josef Duschl, Dr. Michael Eberwein, Diplom-Chemikerin %arka Fernandes, Diplom-Chemikern Christian Blattner und John DeRoche sowie bei Frau Barbara Widera für ihre Hilfe, stete Ermunterungen und Diskussionen. &$’$($), ‘, 2$*’ /.,*’$: Œ .˝34+,*, 0 *,>˘?@0. My last, but in no case least, acknowledgments go to the colleagues from the Department of Applied Mathematics of the Research School of Physical Sciences and Engineering in the Australian National University in Canberra, especially to Foundation Professor Barry Ninham and Professor Stephen Hyde, Head of the Department who invited me to Canberra, to Dr. Vincent Craig and Dr. Tim Senden for their constant help, brilliant ideas and valuable discussions, to Anthony Hyde for wonderful devices, without which no work was possible. Danke! ! Thanks!

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iv TABLE OF CONTENTS ACKNOWLEDGMENTS..III TABLE OF CONTENTSIV ABSTRACT..VI PUBLICATIONS.VII LIST OF USED ABBREVIATIONS AND SYMBOLSVIII 1 CHAPTER 1. INTRODUCTION..1 1.1 Aim of this thesis2 1.2 Outline of this thesis.2 2 CHAPTER 2. THEORY AND BACKGROUND..4 2.1 Surfactants..4 2.1.1 General structure and properties..4 2.1.2 Surfactant behaviour at liquid-air interfaces and in bulk solution..6 2.1.3 Surfactant adsorption at solid/liquid interfaces, dependence on mutual charge relations and hydrophobicity.13 General considerations..13 Measurements of surfactant adsorption15 Substrate17 Influence of solution conditions19 2.1.4 Sodium dodecyl sulphate Πan anionic surfactant.20 2.2 Polymers..22 2.2.1 Polymer solubility, polyelectrolytes22 Polymer conformations in solution.24 Various classes of water-soluble polymers.25 2.2.2 Adsorption of polymers at solid-liquid interfaces26 2.2.3 JR 400 Polymer..31 2.3 Polymer-Surfactant Interactions..32 2.3.1 General aspects of polymer-surfactant interactions in solution.33 How do surfactants and polymers interact?34 Characteristic points34 Degree of binding ().37 Interaction models38 2.3.2 Interactions between ionic polymers and surfactants bearing opposite charges 40 2.3.3 Adsorption of polymer-surfactant mixtures of opposite charge at solid-liquid interfaces Πcooperative adsorption..43 2.3.4 Use of scanning probe microscopy for the study of adsorption at solid-liquid interfaces 45 2.4 Solid/liquid Interfaces and their influence on colloid solutions..46 2.4.1 Interfaces, general aspects47 Surface charge and hydrophobicity, theories of interactions at solid-liquid interfaces 47 2.4.2 Types of surfaces (used in this work).48 Mica49 Silica..50 3 CHAPTER 3. EXPERIMENTAL METHODS AND MATERIALS..52 3.1 Materials and preparative procedures52

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v 3.1.1 Water, Chemicals and Solutions52 Samples preparation54 3.1.2 Surfaces and their preparation55 Mica (Muscovite).55 Silica..55 Plasma treating Πcleaning and hydrophobizing..55 Plasma reactor55 Hydrophobizing of surfaces58 3.2 Investigations in the bulk solution..58 3.2.1 Phase diagram establishment..58 3.2.2 Dynamic light scattering measurements59 Method basics59 Instrumentation principles..61 Data acquisition and processing62 3.3 Atomic Force Microscopy..62 3.3.1 Basics of Scanning Probe Microscopy..63 Probe Techniques.65 3.3.2 How does an atomic force microscope work..65 Method Variations..67 Force-distance curves and the soft-contact mode68 AFM Limitations.70 3.3.3 Instrumentation and Operation..72 Software74 Imaging.74 fiScratchingfl74 Acquirement and evaluation of force-distance curves..75 4 CHAPTER 4. RESULTS AND DISCUSSION76 4.1 SDS / JR 400 Mixture in solution76 4.1.1 The ternary phase diagram76 General Description76 Important samples78 4.1.2 Results of particle size measurements with DLS..79 Region 1 Πpolymer rich mixtures before precipitation79 Region 4 Πhighly diluted mixtures.83 Region 3 Πsurfactant rich mixtures in the resolubilisation area..84 4.1.3 Summary and discussion of investigations in the bulk solution86 4.2 Adsorption of the SDS / JR 400 Mixtures on Surfaces88 4.2.1 General adsorption picture88 Comparison of different mixtures adsorbed on mica.88 Comparison of the same mixture adsorbed at different surfaces.93 4.2.2 Comparison of structures in the adsorbed layer and in the bulk97 Processing of results of DLS measurements..98 AFM Investigations99 Comparison of sample sizes on different surfaces..99 Volume analysis.105 4.2.3 Changes of the adsorbed mixture as a result of changes in the solution composition.107 First series.110 Second series120 5 CHAPTER 5. SUMMARY AND CONCLUSIONS.125 6 LITERATURE128

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vi ABSTRACT Despite the existing scientific and commercial interest in surfactant-polymer systems, there is still not enough connection between the understanding of the polymer-surfactant interactions in solution and at solid-liquid interfaces. In this work, the surfactant-polymer system SDS-JR400 with different component ratios was studied in the bulk solution using DLS and during adsorption at solid-liquid interfaces using AFM. DLS measurements delivered data concerning the size and uniformity of micelle-like clusters formed in the bulk solution. Soft-contact AFM imaging was used to visualize the structure of the adsorbed layer, the acquirement of the force-distance curves together with the special fiscratchingfl treatment brought information about the mechanical properties of the layer. The adsorption from the mixed solutions in the concentration range from below CAC to above PSP was cooperative at native mica, hydrophobized mica and hydrophobized silica surface. The surfactant-rich mixtures showed the less and the polymer-rich mixtures Πthe most pronounced adsorption at all surfaces. In all cases of adsorption from mixtures the adsorbed layer was structured showing a presence of polymer-surfactant aggregates. A correlation between light scattering data concerning sturcturizing and particle size, on the one hand, and AFM images, on the other hand, was observed. A resemblance between images of mixture samples of the same or similar composition, but acquired on different surfaces, was found. It turned out that the influence of surface properties is of less importance for adsorption, compared to the influence of the mixture composition in bulk. It should be remarked that this conclusion can only be drawn, when surfactant and polymer are mixed prior to adsorption. A dependence between the surface charge and hydrophobicity, on the one hand, and the strength of adsorption, on the other hand, was visualized: SDS-JR400 mixtures of the same composition demonstrated different properties of the adsorbed layer after adsorption at native mica, hydrophobized mica and hydrophobized silica. The data obtained during fiwashing-offfl experiments including a subsequent substitution of mixtures in the bulk phase with increasing surfactant/polymer ratio demonstrated that the composition and structure of the adsorbed layer follow the same changes that occur in the bulk phase: SDS penetrates the adsorbed layer and causes changes in its properties.

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viiiLIST OF USED ABBREVIATIONS AND SYMBOLS Substances C14TAB tetradecyltrimethylammonium bromide C16TAB hexadecyltrimethylammonium bromide DDAPS dodecyldimethylammoniopropanesulfonate EHEC ethyl hydroxyethylcellulose HEC hydroxyethylcellulose HM-EHEC hydrophobically modified ethyl hydroxyethylcellulose HOPG highly oriented pyrrolithic graphite JR400 Cellulose, 2-hydroxyethyl 2-[2-hydroxy-3- (trimethylammonio)propoxy]ethyl 2-hydroxy-3- (trimethylammonio)propyl ether, chloride LM200 hydrophobically modified JR400 polymer PAA polyacrilic acid PAAm polyacrylamide PCMA poly{(propionyloxy)ethyl}trimethylammonium chloride PEI polyethyleneimine PMA polymetacrylic acid POE polyoxyethylene PP polypropylene PVAl polyvinyl alcohol PVC polyvinyl chloride PVP polyvinylpyrrolidone RNA ribonucleic acid SDS sodium dodecyl sulphate TMCS trimethylchlorosilane Triton X-400 alkyaryl polyether alcohol Descriptions CAC critical aggregation (or association) concentration CMC critical micellar concentration CPP critical packing parameter

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ixDLVO Derjaguin, Landau, Verwey and Overbeek DS degree of substitution MW molecular weight PSP polymer saturation point PSPD position-sensitive photodiode SFA surface forces apparatus SG substitution grade Methods AFM atomic force microscopy and atomic force microscope CFM chemical force microscopy DLS dynamic light scattering FFM frictional force microscopy FT-IR/ATR Fourier transform infrared spectroscopy/ attenuated total internal reflection spectroscopy LFM lateral force microscopy MFM magnetic force microscopy NFTM near-field thermal microscopy NMR nuclear magnetic resonance NSOM near-field scanning optical microscopy PCS photon correlation spectroscopy SEM scanning electron microscopy SPM scanning probe microscopy SPR surface plasmon resonance STM scanning tunnelling microscopy TAM tunnelling acoustic microscopy TEM transmission electron microscopy Symbols N surfactant aggregation number a0 the effective surfactant headgroup area v the volume of the surfactant hydrocarbon chain

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xlc the critical surfactant chain length polymer solubility parameter Hvap enthalpy of vapourization Vm molar volume Rg radius of gyration degree of binding K binding constant kB Boltzmann constant D diffusion coefficient shear viscosity of solvent

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1 1CHAPTER 1. INTRODUCTION Surfactants and polymers find application in nearly every field of human activity, their interactions are of importance for many industrial processes, and investigations in the mechanisms of these interactions may be useful in fundamental sciences as well as in many industrial applications. The application of surfactants is essential in detergency and emulsion technology in the chemical industry, medicine and personal care, in oil recovery and mineral separation in the oil and mining industries [68]. The behaviour of surfactants at solid-liquid interfaces attracts attention due to their role in colloid stabilization and wetting processes that are important in most of the applications mentioned above. There exists still a considerable need in better understanding of the mechanisms of this behaviour. Polymers consist of numerous molecular units or monomers. Both natural (polysaccharides, polynucleotides or other biopolymers, such as natural caoutchouc) and synthetic (polyvinyl acetate, nylon) polymers are used in nearly any technical or industrial application. For their use, especially for the use of soluble polymers, the understanding of the interfacial behaviour (adsorption and desorption, interaction with other components) is of critical importance. The branches where polymers and surfactants find their application intersect frequently with one another (personal care, cosmetics and pharmaceuticals, paints and inks, detergents, flotation). On the one hand, in practical applications, the addition of every component has its own purpose. However, interactions between polymers and surfactants occur and have influence on the effectiveness of both components. On the other hand, a fundamental interest in the mechanisms of these intermolecular interactions and hydrophobic aggregation phenomena is a reason of the great research activity in this field. Many applications of surfactant-polymer systems are connected with their interaction with liquid-air and solid-liquid interfaces. This has been described in several reviews in this area. The special attention of the reviewers was attracted by applied systems, like mineral processing and solid suspensions, detergency, and personal care and cosmetics [17, 44, 136]. For the latter application field, the system comprising sodium dodecyl sulphate (SDS) and the cationic polymer JR400 (cationically modified hydroxyethyl cellulose ether) is of special importance due to the broad use of the both components.

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