Diffraction Study of a Three - Component Lamellar Phase

Three-component lamellar phase has been investigated which consists of C12E5 , octane and water . This is a layered phase, the lyotropic equivalent of a thermotropic smectic-A phase. X-ray scattering techniques were used on powder and aligned samples, as well as the optical microscopy investigations to understand the structure and the interactions that govern this lyotropic system, and also the temperature dependence of such important parameters as layer-periodicity, the layer thickness and the exponent 77 which characterizes quasi-long range order. Experiments were done with various surfactant concentrations and oil/water volume ratios. The system was chosen for two reasons. First of all, a lamellar phase continuously exists from an oil-rich through an equal oil-water to a water rich region in the accessible temperature range (33oc). Also the lamellar phase continue to exist with the wide range of the surfactant concentrations, which allowed us to study the dilution of the lamellar phases. Secondly. since it is a nonionic surfactant. there are no electrostatic interactions present in this system, i.e. it is a purely sterically stabilized lamellar phase. Our investigations pointed out the following: (1) The structure factor that describes the broad lamellar peaks that we found from the powder scattering should not be confined in the vicinity of peak-position (qo), also the contributions from higher harmonic terms has to be taken into considerations. (2) The form factor had to be incorporated because of the finite size of the lamellar layers. A model has been proposed to describe the electronic density distribution within the layer and in the direction perpendicular to the layers. The form factor based on this model has successfully described the scattering intensity profiles with the variation of laver thickness. (3) Excess scattering was measured as q --+ 0. This has been theoretically predicted to be due to concentration fluctuations (4) The x-ray scattering from aligned samples provided information on the temperature dependence of the layer periodicity within the lamellar phase with the constant surfactant concentration. This dependence can be described by the fluctuations of membranes. Thesis Supervisor: J. David Litster Title: Professor of Physics Acknowledgement It is with the help of so many people that I could finish this thesis. First of all, I would like to thank Prof. J. D. Litster for having given me the oppotunity to work in his laboratory. and having supported me for all the years. I would also like to thank Prof. S.J.G. Mochrie for having introduced me to the x-ray scattering technique, as well as having allowed me to use Rigaku Ru2000 in his laboratory. George Nounesis gave me a tremendous amount of help and support until the end. What I have learned from him are invaluable, starting from the way to plot figures correctly, to where to look and find the essential points in data, more importantly, how to be a serious researcher without losing the integrity of a humanbeing. I would like to thank him for everything, and his patience for having dealt with me. The MRS meeting on 1991 brought Pascale Fabre to Boston, since then she has been an incredible support for me. As she is an expert of the lamellar phases, she always gave me the light for the interpretations of my observations. The numerous e-mails, faxes and telephone calls between here and Paris are the precious records. Also I would like to thank her for her friendship as being one of my best friends. Most of the analysis benefitted from the discussions with Frederic Nallet, not only from my several visits to Bordeaux. but the flood of my e-mails and faxes filled with questions, he always patiently passed me on his adequate ideas and analysis. Without his help, these analysis could not have been possible. I would like to thank Raymond Ober at College de France for his generousity to let me use his x-ray source. Although I was an outsider, during my 6 weeks stay, he not only tried his best to accomodate the busy schedule of the usage of the machine he also helped me for the experiments and the data analysis, because of my poor French. our discussions always took more than it should. but he always was very patient. I benefitted a lot from the several short but intense discussions with Prof. Didier Roux. With his acute sense of experiment, he gave me many eye-opening insights and directions. Also the discussions with Prof. R.Strey were extremely useful, who pointed out some of the big mistakes I have been making for a long time. In Building 13, I would like to thank almost everybody on the floor for their help as I was always running around, asking for helps. In my group. I specially benefitted from the interaction with Brian McClain who passed on his experimental knowledge based on the numerous experiences. Gerry Swislow, with his red bicycle, arrived always when I was lost. I would also like to thank Michael Yoo, especially with programming, when I get into the complete mess which was quite often, he somehow always managed to find the problems and straighten them out. I also enjoyed our long discussions about various subjects during the late night experiments. Claudio Cesar has been one of the most important friends all the time . I would like to thank him and his wife Raquel for their friendship as well as their help in the numerous occasions. George and Charlotte Clark, I would never be able to thank them enough for their kindness as my second parents, without their warmness and love, my life in Boston would have been much more difficult. I would like to thank Ivan Huc for his encouragement across the sea during the last few months which were specially difficult. His support gave me the strength and determination to go through the end. And finally. my parents, Minoru and Tomoe Oda. It was with their support. love. and trust. that it was possible for me to continue. And I thank them as well as my brother and his wife. Katsuro and Naoko Oda, for their encouragement through all those years.