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Investigation of the Assembly of Surfactants at the Solid-Liqid Interface for Adsorption and Materials Applications

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Investigation of the Assembly of Surfactants at the Solid-Liqid Interface for Adsorption and Materials Applications University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2007 INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS APPLICATIONS Rong Xing University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Xing, Rong, "INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS APPLICATIONS" (2007). University of Kentucky Doctoral Dissertations. 510. https://uknowledge.uky.edu/gradschool_diss/510 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Rong Xing The Graduate School University of Kentucky 2007 INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS APPLICATIONS ABSTRACT OF DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Engineering at the University of Kentucky By Rong Xing Lexington, Kentucky Director: Dr. Stephen E. Rankin, Professor of Lexington, Kentucky 2007 Copyright © Rong Xing 2007 ABSTRACT OF DISSERTATION INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS TEMPLATING APPLICATIONS This dissertation addresses two topics associated with the assembly of surfactants at the solid-liquid interface for adsorption and materials synthesis. The first is the adsorption of an anionic fluorinated surfactant, tetraethylammonium perfluorooctylsulfonate (TEA-FOS), at the solid/liquid interface. Attenuated total reflection Fourier transform infrared spectroscopy is used to study the adsorption kinetics and average orientation of surfactants at the hydroxylated germanium surface. Atomic force microscopy provides complementary images of the adsorbed layer structure on mica. The adsorption follows unusual three-stage kinetics in which the rate of adsorption starts fast, slows as the surface becomes crowded, and then (surprisingly) accelerates due to nucleation of a heterogeneous multilayer structure. These fast-slow-fast three stage adsorption kinetics are observed for a wide range of concentrations at pH 6, and the rates of the three stages are modulated by pH and salt by tuning electrostatic interactions among surfactants, counterions, and the surface. The results suggest that tetraethylammonium mediates interactions between surfactants and with negatively charged surfaces. The dichroism measurements and AFM are consistent with a mechanism in which TEA-FOS first forms an incomplete layer with chains oriented randomly or somewhat parallel to the surface, followed by formation of flattened multilayer clusters with the chains oriented somewhat normal to the substrate. The second topic is the sol-gel synthesis of mesoporous silica materials using dual surfactant templates. Studies of templating with mixed cetyltrimethylammonium bromide and octyl- beta-D-glucopyranoside surfactants shows that the ternary phase diagram of surfactants in water can be used to predict mesoporous materials structure, and that vapor-phase ammonia treatments can either stabilize the structure or induce swelling by the Maillard reaction. Studies of sol-gel reaction-induced precipitation with demixed hydrocarbon and fluorocarbon cationic surfactant micelles show a wide variety of pore structures. A number of synthesis parameters are adjusted to tune the pore structure, for instance to adjust the size and populations of bimodal mesopores. Selective swelling of the two surfactants by liphophilic and fluorophilic solvents is observed. Finally, protein- accessible hollow spherical silica particles with mesoporous shells are reported. The methods for engineering mesoporous materials reported here have potential applications in adsorption, controlled drug delivery and for catalysis. KEYWORDS: Surfactant Assembly, Adsorption, Sol-Gel Reaction, Solid-Liquid Interface, Bimodal Mesopores, Organic/Inorganic Hybrid Materials Rong Xing 06/08/2007 INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS TEMPLATING APPLICATIONS By Rong Xing Stephen E. Rankin Director of Dissertation Dr. Barbara L. Knutson Director of Graduate Studies 06/08/2007 RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor's degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date DISSERTATION Rong Xing The Graduate School University of Kentucky 2007 INVESTIGATION OF THE ASSEMBLY OF SURFACTANTS AT THE SOLID-LIQID INTERFACE FOR ADSORPTION AND MATERIALS TEMPLATING APPLICATIONS DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Engineering at the University of Kentucky By Rong Xing Lexington, Kentucky Director: Dr. Stephen E. Rankin, Professor of Lexington, Kentucky 2007 Copyright © Rong Xing 2007 ACKNOWLEDGMENTS First and foremost I would like to thank my research supervisor and committee chairman, Professor Stephen E. Rankin, for letting me join his research group and for providing the opportunity to work on the interesting projects, and his patient guidance, encouragement and support that he gave me throughout my research studies. I greatly acknowledge his help and suggestions not only in my research, but also outside the academy. Without his continuous support, I could not complete my research work, and the following dissertation would not exist. I would like to thank my committee members, Professor B. Knutson, Professor P. M. Bummer, Professor J. Z. Hilt and Professor F. Ladipo for the useful discussions and spending time reading my dissertation. Professor B. Knutson and her group members gave me help for access to some facilities in their lab. Professor P. M. Bummer was always helpful whenever needed. My appreciation is also expressed to an earlier committee member Prof. L. S. Penn. I would like to thank Professor H. J. Lehmler for providing the cationic pyridinium- based fluorinated surfactants used for materials synthesis in chapters 7 and 8. I thank Professor K. Anderson for allowing access to polarized optical microscope for the phase studies in chapter 6. I thank Professor B. Hinds for allowing access to plasma instruments. I thank Mrs. M. G. Engle for assisting me in using scanning confocal fluorescence microscope. I thank Dr. A. Dozier and Mr. L. A. Rice for assisting me and sharing their invaluable experience in using electron microscopy (SEM and TEM). I thank Mr. H. Francis for training and access to the XRD instruments in the Kentucky Geological Survey. I want to thank Mr. G. Spiggle for training and assistance with AFM and sputtering instruments in the Center for Nanoscale Science and Technology. I acknowledge financial support for the work completed as part of this dissertation from the National Science Foundation (NSF) (Grant Nos. DMR-0210517 and EAR- 0521405) and from the Kentucky Science and Engineering Foundation (Grant No. KSEF- 159-RDE-101). iii I would like to thank all members in my research group for being good friends that I could count on them in every way. In particular, I want to thank Dr. B. Tan for his help when I first joined the group. Finally, I am deeply grateful to my wife Wenqin Shen for her love and support. I want to thank my mom and dad for their continuous support and sacrifice. I hope that the choices I have made and the things I have accomplished would have made my dead mother proud. This dissertation is devoted to all people who care about me. iv TABLE OF CONTENTS Acknowledgements…………………………………………………………………...iii List of Tables………………………………………………………………………….ix List of Figures………………………………………………………………………....x List of Schemes…………………………………………………………………….xviii Chapter 1: An Overview of Surfactant Adsorption Kinetics and Molecular Orientation at the Solid/Liquid Interface…………………………………………………………...1 1.1. Introduction…………………………………………………………………...1 1.2. Literature review…………………………………………………………...…2 1.2.1. Generalities about surfactant…………..………………………………2 1.2.2. Surfactants at the solid/liquid interface………………………………..3 1.2.2.1.Critical Surface Aggregation Concentration……………………....3 1.2.2.2.Surface Aggregation Characterization………………………….…4 1.2.3. Role of ATR-FTIR in surface analysis………………………………...5 1.2.4. Adsorption and molecular orientation of surfactant at the solid/liquid interface………………………………………………………………..5 1.3. Theory of ATR-FTIR……..…………………………………………………..6 1.3.1 Principles of total attenuated reflection spectroscopy…………………6 1.3.2 IRE materials…………………………………………………………..7 1.3.3 Quantitative determination of surface excess from unpolarized ATR spectra………………………………………………………………….7 1.3.4
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