retical descriptions of the nonlinear optics can be read in ref. 8.Interfacial tension and SHG measurements at an Aqueous solutions of nonionic amphiphiles play an important role in various chemical, physical and biological processes. Because of their specific surface activity, they are often a subject of many investigations. Of particular interest is the behavior of amphiphile molecules at an oil/water interface. The characterization of the molecular and structural properties between two immiscible liquids is of important scientific interest. 1Experiments on the adsorption behavior of a nonionic amphiphile at an air/water interface has been studied by surface second-harmonic generation (SHG).2 The surface-sensitive technique of optical SHG has been sucessfully employed in various studies of liquid/liquid and liquid/gas interfaces. [3][4][5][6][7] Under the electric dipole approximation SHG is not allowed in the bulk of centrosymmetric media such as liquids. However, between two adjoined centrosymmetrical phases such as at a water/air interface, the symmetry is apriori broken and the nonlinear polarization can be induced.The polarization can be written as:( 1) whereis the incident electric field and χ ↔ (n) is the dielectric susceptibility of the n-th order. The dielectric susceptibility is described by a (n+1)-th level tensor. In Eq.(1) the dielectric polarization is split into a linear and a nonlinear part corresponding to the properties of the medium. Further theo-31 ANALYTICAL SCIENCES FEBRUARY 1998, VOL. 14 1998 © The Japan Society for Analytical Chemistry Fig. 2 Interfacial tension, σ, dependence on the bulk surfactant concentration, c. Orientation Analysis of a Nonionic Amphiphile at the WaterSurface by Second-Harmonic GenerationUta ELSTNER*, Gerd MAROWSKY*, Gerhard BUSSE** and Manfred KAHLWEIT** *Laser-Laboratorium Göttingen e.V., 37077 Göttingen, Germany **Max-Planck-Institut für biophysikalische Chemie, Abt. Kinetik der Phasenbildung, 37077 Göttingen, GermanySecond-harmonic generation and interfacial tension measurements have been used to study the adsorption behavior of a nonionic amphiphile, 1-(3', 5'-di-t-butyl)phenyl-3-glycero-rac-glycerin at an air/water interface. The tensor components of the nonlinear surface susceptibility of the amphiphile have been determined by polarization rotation of the incident fundamental radiation. The comparison of the values of the several tensor components allows the description of the adsorption and orientation behavior of the molecules at an air/water interface.Keywords Second-harmonic generation, nonionic amphiphile, second-order susceptibility, air/water interface Fig. 1 Structure of 1-(3', 5'-di-t-butyl)phenyl-3-glycero-racglycerin.
Modification reactions are reported for fully-hydrogenated butadiene-acrylonitle (35.8 mol-% AN) copolymer, ethylene(E)-butyl acrylate (4.7 mol-% BA) copolymer, and ethylene(E)-methyl acrylate (45 mol-% MA) copolymer in dense, near-critical water at 250 "C and 300 "C and at 300 bar and 1 500 bar. Nitrile, amide, and ester moieties can be converted into COOH groups. Kinetic analysis of the ester to acid transformations suggests autocatalytic activity of the acid groups.
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