Contains reports on two research projects.National Science Foundation (Grant DMR-84- 18718)Wan-Yuan Company, Beijing, Peoples Republic of China Contrac

Carvalho, Bruce L.

Chen, Sow-Hsin

Ricci, M. A.

Sheu, E. Y.

Wang, Xue-Yuan

Wei, Xui-Bin

Wu, Chuan-Fu

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Photon Correlation Spectroscopy and Applications14.0 Photon Correlation Spectroscopy andApplicationsAcademic and Research StaffProf. S.-H. Chen, Dr. M.A. Ricci'Graduate StudentsT.L. Lin, E.Y. Sheu, C.F. Wu, B. Carvahlo, X.B. Wei, K.Y. Wang14.1 Structure and Dynamics of Colloidal SolutionsStudied by Small Angle Neutron Scattering andPhoton Correlation SpectroscopyNational Science Foundation (Grant DMR-84- 18718)Sow-Hsin Chen, M.A. Ricci, E.Y. Sheu, C.F. Wu, B. CarvahloSmall angle neutron scattering technique has been used to study systematically thestructure and interaction of ionic and zwiterionic micelles formed from ionic and polarsurfactants in aqueous solutions. A recently developed theory of highly asymmetic ionicliquids has been shown to apply to dense micellar solutions where the charge densityon the micellar surface is very high. Combination of the structural studies and the the-oretical evaluation of the inter-micellar correlations allow an unambiguous analysis ofneutron scattering data to obtain: 1) micellar aggregation number; 2) renormalizedmicellar charge; and 3) micellar shape, size and hydration as functions of the surfactantand salt concentrations. Thus, the micellar growth and polydisperity can be simul-taneously studied.A series of zweiterionic micelles formed from short chain lecithins(dihexanoylphosphatidylcholine, diheptanoylphophatidylcholine, etc.) have beenstudied. In contrast to the long-chain lecithins (C14 and longer) which form bilayers andtherefore are important for studies of artificial membranes, the short-chain lecithins formglobular micelles. However, the conformational features of the head groups are ex-pected to be the same in the two cases. We have analyzed the SANS data using athermodynamic model, called ladder model, which is expected to be valid for cylindricalmicelles. This model contains three parameters, namely, the minimum size micelle No,the free energy advantage of inserting No monomers in the straight section of the cyl-inder as compared to that in the end caps, (A - No) /KBT, and the free energy of insertinga monomer, 6/KT, once the minimum micelle is formed. This model is capable of ex-plaining the phenomenon of critical micelle concentration and the growth andpolydispersity of the micellar system as functions of concentration and temperature.SANS data was shown to yield all three basic parameters of the theory and to providethe size and size distribution of the cylinders.1 Visiting ScientistPhoton Correlation Spectroscopy and ApplicationsA high resolution spectroscopic technique based on analyses of scattered light in-tensity fluctuations has been in use for some time. Our method is based on the digitaltime-domain pulse correlation technique using a 256-channel clipped correlator devel-oped in the laboratory. The correlator-multichannel memory system is controlled by aPDP 11/MINC computer system which is capable of high-speed data acquisition andanalysis necessary for the study of time-varying phenomena.We have applied this photon correlation technique to study the Brownian dynamicsof strongly interacting colloidal systems. Interesting results on the variation of mutualdiffusion coefficient of the micellar solutions with addition of salts and alcohol havebeen observed.PublicationsBratko, D., H.L. Friedman, S.-H. Chen, and L. Blum, "Intrepretation of the IntermicellarStructure Factors in the Hypernetted-chain Percus-Yevick Approximation," Phys.Rev. A 34, 2215 (1986).Chao, Y.S., E.Y. Sheu, and S.-H. Chen, "Experimental Test of a Theory DressedMicelles," J. Phys. Chem. 89, 4862 (1985).Chao, Y.S., E.Y. Sheu, and S.-H. Chen, "Intermicellar Interactions in Lithium DodecylSulfate Solutions, Effects of Divalent Ions," J. Phys. Chem. 89, 4395 (1985).Chen, S.-H., "Interactions and Phase Transitions in Micellar and Microemulsion Sys-tems Studied by SANS," Physica 137B, 183 (1986).Chen, S.-H., "Small Angle Neutron Scattery Studies of the Structure and Interaction inMicellar and Microemulsion Systems," Ann. Rev. Phys. Chem. 37, 351 (1986).Chen, S.-H. and J.S. Huang, "Dynamic Slowing-down and Nonexponential Decay ofDensity Correlation Functions in Dense Microemulsions, " Phys. Rev. Lett. 55,1888 (1985).Sheu, E.Y., C.F. Wu, S.-H. Chen, and L. Blum, "Application of a Rescaled MeanApherical Approximation to Strongly Interacting Ionic Micellar Solutions," Phys.Rev. A 32, 3807 (1985).Sheu, E.Y., C.F. Wu, and S.-H. Chen, "Effects of Ion Sizes on the Aggregation andSurface Change of Ionic Micelles in 1:1 Electrolytes," J. Phys. Chem. 90, 4179(1986).14.2 Basic Studies of Laser-Cell InteractionsWan-Yuan Company, Beijing, Peoples Republic of China ContractSow-Hsin Chen, X.B. Wei, X.Y. WangAn instrument consisting of a copper vapor laser coupled to an optical fiber/chemicalinjector catheter for the treatment of occluded arteries has been constructed and tested.74 R.L.E. P.R. No. 129Photon Correlation Spectroscopy and ApplicationsThe combined application of three steps: the pre-irradiation injection of a light ab-sorbing dye, HPD, brief copper laser irradiation (at 578 nm), and a urokinase infusionafter the irradiation, produced the striking effect of liquification and resolution ofthrombus. The histological examination of the arteries after the treatment showed noapparent damage of the arterial wall.PublicationWei, X.B., X.Y. Wang, and S.-H. Chen, "A Copper Vapor Laser and Optical FiberCatheter System for Liquification and Removal of Thrombus in OccludedArteries." Sent to Lasers in Surgery and Medicine. "Method and Apparatus forLaser Angiosurgery," to be published in 1987.76 R.L.E. P.R. No. 129~,,~~,CT'" ia:.,;i

Photon Correlation Spectroscopy and Applications

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Photon Correlation Spectroscopy and Applications

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