J . Phys. Chem. 1989, 93, 4825-4829
4825
Fluorescence Polarlzation Study of Aerosol-OT Reversed Micelles at High Pressures Katsuhiro Tamura* and Nobumasa Nii Department of Chemical Engineering, Faculty of Engineering, The University of Tokushima. Tokushima 770, Japan (Received: April 22, 1988; In Final Form: January 12, 1989)
The properties of Aerosol-OT (AOT) reversed micelles in n-alkanes were studied by spectrophotometrictechniques, including fluorescence polarization of probe molecules under high pressures up to 98.1 MPa. The degree of fluorescence polarization was determined with 8-anilinonaphthalene-1-sulfonate(ANS) and rhodamine B. At water content R([H,O]/ [AOT]) = 30, the degree of fluorescence polarization significantly increased with pressure. The results suggest that pressure promotes the fusion of reversed micelles in this water concentration range. Phenol betaine (ETreagent), an internal probe of solvent polarity, was used to monitor the size changes of the micelles with water content. Fading rates of crystal violet in AOT/H20/heptane solutions were also measured at high pressure to examine the properties of interior water phases of AOT.
Introduction Bis(2-ethylhexy1)sodium sulfosuccinate (Aerosol-OT, AOT) has the ability to solubilize relatively large amounts of water in various hydrophobic organic liquids and forms reversed micelles. The polar head groups of AOT surround water molecules and make water pool,' while the hydrocarbon chains are in contact with nonpolar organic solvents. These systems are often used as models of water pockets in bioaggregates because they are well-defined in size, shape, and aggregation number. The transparent emulsions of these micelles that scatter only a little light are called microemulsions,2 swollen micelles, solubilizing micelles, and micellar solution^.^-^ Fluorescence techniques have been used by various workers to investigate the properties of the aqueous core (microviscosity,6-8 effective polarity: biphasic effectsI0) of the reversed micelles of AOT at atmospheric pressure. In the present study, high pressure was applied to obtain further insight into the structure of AOT reversed micelles and fluorescence polarization was determined with use of 8-anilinonaphthalene-1-sulfonate(ANS) and rhodamine B as fluorescent probes at high pressures. Fhorescence polarization data of rhodamine B provide the information on the microviscosity around the probe (mobility of the probe). Furthermore, a solvent polarity parameter, ET value,I1 was also used. Zachariasse et al.', employed ET reagent [2,6-diphenyl-4(2,4,6-triphenyl-1-pyridinio)phenoxide] as a polarity probe to study the polarity of its microenvironment in micelles, microemulsions, and phospholipid bilayers. Since this reagent is only slightly soluble in water and n-alkanes, it is expected to be located at the polar zone of the surfactants. It is therefore ideally suited to examine directly the polarity of the interface between water and surfactants. The properties of micelles greatly affect rates of chemical rea~ti0ns.I~Fading rates of crystal violet in AOT reversed micelles ( I ) Menger, F. M.; Saito, G.; Sanzero, G. V.; Dcdd, J. R. J . Am. Chem. SOC.1975, 97, 909. (2) (a) Schulman, J. H.; Stoeckenius, W.; Price, L. M. J . Phys. Chem. 1959, 63, 167. (b) Prince, L. M. J . Colloid Interface Sci. 1975, 52, 182. (3) (a) Eicke, H. F.; Arnold, V. J . Colloid Interface Sci. 1974, 46, 101. (b) Eicke, H. F.; Shepherd, J. C. W. Helu. Chim. Acta 1974, 57, 1951. (4) Eicke, H. F.; Rehak, J. Helu. Chim. Acra 1976, 59, 2883. (5) Ekwall, P.; Mandell, L.; Fontell, K. J . Colloid Interface Sci. 1970, 33, 215. (6) Bridge, N. J.; Fletcher, P. D. I. J . Chem. SOC.,Faraday Trans. 1 1983, 79, 2161. (7) Zinsli, P. E. J . Phys. Chem. 1979, 83, 3223. (8) Eicke, H. F.; Zinsli, P. E. J . Colloid Interface Sci. 1978, 65, 131. (9) Wong, M.; Thomas, J. K.; Gratzel, M. J . Am. Chem. SOC.1976, 98, 2391. (10) Kondo, H.; Miwa, I.; Sunamoto, J. J . Phys. Chem. 1982,86, 4826. (1 1) Dimroth, K.; Reichard, C.; Siepmann, T.; Bohlmann, F. Jusrus Liebigs Ann. Chem. 1963, 661, 1. (12) Zachriasse, K. A.; Phuc, N. V.; Kozankiewicz, B. J . Phys. Chem. 1981, 85,2676. (13) (a) Fendler, J. H.; Fendler, E. J. Catalysis in Micellar and Macromolecular Systems; Academic Press: New York, 1975. (b) Fendler, J. H. Membrane Mimetic Chemistry; Wiley: New York, 1982.
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were measured at high pressures to elucidate the structure of the AOT reversed micelles and to discuss the properties of the interior water phase of AOT reversed micelles.
Experimental Section Bis(2-ethylhexy1)sodium sulfosuccinate was obtained from Tokyo Kasei. The material was dissolved in methanol and filtered, and the solvent was removed under vacuum. 8-Anilinonaphthalene- 1-sulfonate (Tokyo Kasei), rhodamine B (Nakarai), and crystal violet (Ishizu) were used without further purification. 2,6-Diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenoxide, ET reagent (see Figure 6b), was synthesized by the method of Dimroth et al."3I4 n-Alkanes (heptane, octane, and dodecane) were purified by dj~ti1lation.l~Water was distilled twice, once from potassium permanganate solution. A high-pressure vessel with three optical windows to measure fluorescence has been reported elsewhere.I6 To measure fading rates of crystal violet at high pressures, a high-pressure vessel with two optical windows was designed. This vessel has a sliding inner cell for the sample solution; one side is directly glued on a quartz window with epoxy resin. This vessel was placed in the cell compartment of a Hitachi 100-60 UV-vis spectrophotometer. Pressure was generated by a hand-operated hydraulic pump and measured by a Heise Bourdon gauge. Temperature was kept constant by circulation of water from a water bath through the jacket and measured by a digital thermometer with 0.01 K resolution and by a filament thermistor probe inserted into the body of the high-pressure vessel block. Degree of Fluorescence Polarization. After AOT was dried for 1 h under vacuum, 3 wt % AOT/alkane solutions were prepared and mixed with proper amounts of probe aqueous solutions of rhodamine B (4 X M solution) and A N S (4 X M solution plus desired amounts of water). The concentrations of the probe in the water pool of reversed micelles are constant for rhodamine B but different based on the size of the pool for ANS. The concentration of water was expressed by the molar ratio of water and AOT, R = [H,O] / [AOT]. These solutions were deoxygenated by bubbling nitrogen gas and stirred for 30 min. The wavelength of maximal excitation and emission and fluorescence intensities were determined by a Hitachi 650-40 fluorescence spectrophotometer at atmospheric pressure. The intensities and the degree of fluorescence polarization were determined at high pressures from the data on the wavelength of maximal excitation at atmospheric pressure. The degree of fluorescence polarization was defined by the equation p = (11,- I d / ( I l , + 11) (1) Determination of ET Values. Sample solutions with various water content were prepared by mixing 3 wt % AOT/heptane (14) Tamura, K.; Ogo, Y.; Imoto, T. Bull. Chem. Soc. Jpn. 1973.46, 2988.
(IS) Riddick, J. A.; Bunger, W. B. Organic Soluenr; Wiley: New York, 1970. (16) Tamura, K.; Nii, N.; Suzuki, A. Biophys. Chem. 1986, 25, 169.
0 1989 American Chemical Society
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The Journal of Physical Chemistry, Vol. 93, No. 12, 1989
Tamura and Nii
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L
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Figure 1. Maximum wavelengths, intensity, and the degree of polarization of A N S fluorescence in AOT/HzO/heptane solutions as a function of water content (R = [HzO/[AOT]): excitation, 360 nm;temperature, 298.15 K; pressure, 0.1 MPa.
solution and water. The absorbance and the wavelengths of in nm) were determined for these somaximal absorption (A,, lutions saturated with ET reagent.
ET = 2.859
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104/A,,,
(kcal/mol)
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The absorption spectra were run on a Hitachi 100-60 UV-vis spectrophotometer. Fading Rate of Crystal Violet. The fading rates were determined by following the absorbance of crystal violet at 598 nm. The reaction solution was prepared by mixing 3 wt % AOT/ heptane solution, Na2C03/NaHC03buffer (pH 10.5), and crystal violet aqueous solution.
Results and Discussion Fluorescence. Fluorescence was not observed in n-alkanes over the ANS concentration range of this study, while the fluorescence intensity of ANS in pure water was about l/loothof that in AOT reversed micelle solution at R 0 (without added water). The presence of AOT was necessary to produce the intense fluorescence emission; hence, ANS should be located at the interface of the polar heads of AOT. Figure 1 shows the maximum wavelengths (A,,), the intensity, and the degree of polarization (P) for ANS fluorescence as a function of water/AOT molar ratio ( R = [H,O]/[AOT]) in AOT/H20/heptane solutions at atmospheric pressure. Similar results at atmospheric pressure have been reported by Wong et aL9 These results show that all parameters greatly change at lower concentrations of water, especially the intensity, which drastically decreases. This is because water sharply enhances the decay rate of the A N S excited state. The maximum wavelength was 457 nm in AOT reversed micelle so-
0’ 0
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1
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Pressure/MPa Figure 3. Pressure dependence of fluorescence intensities of A N S in AOT/H,O/heptane at 298.15 K: excitation, 360 nm; R = [HzO]/ [AOT].
lution at R = 0 and shifted to longer wavelengths with the addition of water and approached a plateau at water content around R = 10 (Figure la). The degree of fluorescence polarization ( P ) also showed a similar pattern to A,, with the addition of water. In contrast to ANS, the degree of the polarization of rhodamine B decreased with the increase in water content at atmospheric pressure (Figure 2). These different behaviors of the P values are mainly caused by the differences in the effects of water on the fluorescence lifetime for the two probes. From Perrin’s equation, the degree of fluorescence polarization ( P ) is related to the microviscosity in the vicinity of the probes and fluorescence lifetime l / P - 1 / 3 = ( I / P o - 1/3)(1
+ ~TT/?VO)
(3)
where Po is the degree of polarization measured in an extremely
The Journal of Physical Chemistry, Vol. 93, No. 12, 1989 4827
Aerosol-OT Reversed Micelles at High Pressures
0.3 E
.-c0 Q
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0.1
0
0
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Pressure/MPa Figure 4. Pressure and temperature dependence of the degree of fluorescence polarization of ANS in AOT/H20/heptane: R = [H20]/[AOT].
viscous solvent, T is the average lifetime of the molecule in the excited state, V, is its effective volume, 9 is the viscosity, T i s the absolute temperature, and k is Boltzmann's constant. In this equation, 7 of A N S is strongly influenced by the properties of the microenvironment that surrounds the probes. For instance, its T has values from 10 to 2.5 ns when R increases from 0 to 4.1.9 In contrast to ANS, the T of rhodamine B does not change with the polarity of the system. Therefore, the reduction of the P values (proportional to the ratio V/T) for rhodamine B with water content indicates that the microviscosity around the probe decreases. Meanwhile, the rapid increase of the P value for A N S at lower water concentration (Figure IC) is attributable to a faster decrease of T than of 7. Depolarization of light, emitted from probes that are associated with micelles, can originate from two different rotational processes: (1) movement of the probe in the micelle core and (2) rotation of the micelle itself. The decrease of P value of AOT reversed micelle caused by the second process is estimated to be 0.1 3 at R = 0.9 This value, however, reduces as water content increases, because the size of the micelles becomes continuously larger and the rotation of micelle per se is depressed. Consequently, the contribution of the first process becomes more important a t higher water concentrations. Nevertheless, there is a case where the second process greatly contributes to the overall P values, e.g., sudden increase in micellar sizes by the fusion of micelles. Figure 2 shows that pressure increases the P values of rhodamine B, and its effects are significant at R = 1.16. At higher water content, the pressure effects became smaller, and the P values at pressures higher than 29.41 MPa are almost the same a t R = 35. Rhodamine B molecules are located in the polar zone of AOT molecules at R = 0 and gradually shift to the water phase when the water content is increased. Therefore, the mobilities of the probes are lower at lower water content because they cannot freely move in these phases compared to in water phase. However, the micelles have compressible structures with gaps, and they are more compressible than the water core and the movement of the probe molecules is more restricted with pressure. At R > 35 the pressure effects become markedly large again. Such a steep increase in the P values with pressure cannot be explained in terms of the mobilities of probes in micelles; these results suggest sudden changes of micellar structures. This led to phase separation, which became visible with the naked eye at R = 52 and 98.1 MPa. Figure 3 indicates the pressure dependence of the fluorescence intensities of ANS in AOT/H20/heptane solutions. The intensity at the lowest water content ( R = 1.16) increases with increasing pressure. When the water content is over the R range from 10 to 30, however, the intensity is hardly influenced by pressure. When R > 30, the pressure effect appears again. The effect
appears at lower pressure the higher the value of R > 30. These results mean that AOT reversed micelles transfer ANS molecules from the polar aqueous core to a less polar environment with increasing pressure at R = 1.16 and R > 30, because the intensity decreases with increasing polarity of the environment. As described later, the distance among the polar heads of AOT molecules increases at R > 30 by pressure compared to the lower water content. This promotes the transfer of the probe with pressure to the less polar zone of reversed micelles. Figure 4 shows pressure and temperature dependence of the P values of ANS in AOT/H20/heptane solutions at various water contents. At 298.15 K, the pressure effects were hardly observed up to R = 24.3. The P values, however started to increase gradually with pressure at R = 37.5 and then sharply increased when water content exceeded 49.4. At 313.15 K,the pressure effects were more evident at water contents above 36.9. At 283.15 K,the P values were hardly affected by pressure at least up to R = 36.8. At atmospheric pressure, the P values at higher water content were almost constant (Figure 1). This is attributable to a balance of decrease of 7 and 7 despite their small changes. Therefore, the strong dependence of the P values on pressure at higher water concentration can be related to the large changes in micellar structures: an increase in the size. These results suggest the increase of aggregation number of AOT reversed micelles with pressure. On the contrary, the aggregation number of sodium dodecyl sulfate micelles in aqueous solutions is known to decrease with pressure up to about 100 MPa.I7 The critical micelle concentrations (cmc) of micelles and reversed micelles also show different behaviors under high pressure. For example, the cmc of sodium dodecyl sulfate in aqueous solution increases up to 100 MPa with pressure,17while that of dodecylammonium propionate reversed micelle in carbon tetrachloride decreases with pressure.'* Figure 5 shows plots of P values against pressure for AOT/ H20/octane and AOT/H20/dodecane solutions at various water contents and 298.15 K. From comparison of these results with the data for heptane solution at 298.15 K (Figure 4), the carbon numbers of alkanes apparently affect the mobilities of micelles. The alkane solutions with longer hydrocarbon chains tend to depress more the mobilities. These may be partly due to the higher viscosities of the alkanes with longer hydrocarbon chains. ET Values. Zachariasse et al." found that a plot of ET values vs the aggregation number of sodium dodecyl sulfate micelles showed a discontinuity due to the changes in the shape of the (17) Nishikido, N.; Shinozaki, M.;Sugihara, G.; Tanaka, M.;Kaneshina, S . J . Colloid Interface Sci. 1980, 74, 414. (18) Tamura, K.; Suminaka, M. J . Chem. SOC.,Faraday Trans. 1 1985, 81, 2287.
The Journal of Physical Chemistry, Vol. 93, No. 12, 1989
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0
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[H2 01 / CAOTl Figure 7. Effects of water content and pressure on the pseudo-first-order rate constants of alkaline fading of crystal violet in AOT/H20/heptane solutions at 3 13.15 K: [CV]= 7 X lod M;water phase, Na,C03-NaHCO, buffer (pH i0.5).
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micelles. This result was applied to analyze the changes of the structure of AOT reversed micelles with the increase in water content. Figure 6 shows ET values and the absorbance of ET reagent as a function of the water content (R). ET values increase with increasing R over 55-57 kcal/mol; these values approximately correspond to the polarities between methanol (55.5) and formic acid (56.6).19 As the ET reagent is sparingly soluble in n-alkanes and water, it should be a localized interface between polar heads and water or in the polar zone of AOT molecules. Consequently, the high polarities corresponding to these organic solvents reflect these environments. The absorbance of ET reagent is proportional to its solubility in AOT/H20/heptane solution. In Figure 6, the lines of both ET values and the absorbance have points of inflection at R = 30, but not at R = 10. These results also suggest that the micellar structures change at water content around R = 30, but the appearance of bulk water does not affect interface polarity. (19) Reichardt, C.Angew. Chem., Int. Ed. Engl. 1965, 4 , 29.
Quite recently, D’Aprano et al. obtained similar conclusions with Raman spectrophotometry.20 Fading Rates of Crystal Violet. Chemical reactions in micellar phases are influenced by the properties of the micelles. We previously reported that a photoreaction in aqueous micelle solutions at high pressures was greatly affected by the shapes of the micelle.21 In the present study, alkaline fading of crystal violet in AOT/H20/heptane solution was used to examine the changes in the reversed micelles structures by the water content at high pressures. Figure 7 shows the relations between its pseudofirst-order rate constants and water content at atmospheric and high pressures. At atmospheric pressure, the reaction did not occur at R < 2; however, the reaction suddenly took place at alkaline aqueous solutions (pH 10.5) of R = 5 . The rates gradually decreased with increasing water content at R > 10. Crystal violet does not dissolve in water phases of micelles containing OH- ions at R < 2 and therefore hardly contacts the OH- ions. However, at R = 5, crystal violet starts to appear in aqueous solutions of OH- ions that are concentrated by the electrical repulsion against the polar heads of AOT with negative charges and the reaction is markedly accelerated. At water content larger than 10, the water pool grows large enough to have the properties of bulk water. Consequently, two water phases appear. One is strongly solvated and structured water, the other is bulklike water. The appearance of bulklike water leads to the reduction of micellar effects on the reaction. The patterns of changes in the rate constants with water content are very similar to those of the fluorescence properties of A N S shown in Figure 1 except in the very low water content range. Pressure retarded the reaction because the reaction is accompanied by the reduction of the electric charges, resulting in release of electrostriction. At (20) D’Aprano, A.; Lizzio, A.; Liveri, V. T.; Aliotta, F.;Vasi, C.; Migliardo, P.J . Phys. Chem. 1988, 92, 4436. (21) Tamura, K.;Aida, M.J . Chem. SOC.,Faraday Trans. I 1986, 82,
1619.
J . Phys. Chem. 1989,93,4829-4833 lower water content than R = 10, the micelles are very rigid;22 however, the pressure effects on this reaction are the largest in this water content range. Furthermore, special behaviors for the fading rates were not observed at R = 30. These results indicate that the alkaline fading of crystal violet in AOT reversed micelles is strongly influenced not by the properties of the micelles (size, shape, or rigidity) but by the properties of interior water phases. Zulauf and Eicke studied the temperature effects on the structures of AOT reversed micelles in isooctane by photoncorrelation spectroscopy.u They found that Stokes radii of micelles increased rapidly and the scatter intensities of the solution had minimum values at R i= 30 and concluded that the microemulsions were polydisperse in this water concentration range. Our experimental results for the degree of fluorescence polarization and ET values support their conclusions. From the microscopic view point, the points of inflection of E T values and the absorbance at R = 30 indicate the changes of the interactions between AOT (22)
Zulauf, M.; Eicke, H. F. J . Phys. Chem. 1979, 83, 480.
4829
molecules. This is attributable to the changes of the curvature of the micelle surface by the formation of larger micelles. The great increase in the degree of fluorescence polarization with pressure a t high water content (Figure 4b,c) also suggests the decrease of the mobilities of micelles themselves and the promotion of the formation of polydisperse phases. The polydispersity of these systems was recently reported by North et al.23 and Kotlarchyk et al.24 from small-angle scattering techniques. Acknowledgment. We express our appreciation to Professor I. Ueda of University of Utah and Professors A. Suzuki, S. Kaneshina, and T. Moriyoshi of The University of Tokushima for their valuable comments. Registry No. AOT, 577-1 1-7; ANS, 82-76-8; rhodamine B, 81-88-9; ET reagent, 1008 1-39-7; crystal violet, 548-62-9; heptane, 142-82-5. ~
~~~~
(23) North, A. N.; Dore, J. C.; Macdonald, J. A.; Robinson, B. H.; Heenan, R. K.; Howe, A. M. Colloids Surf. 1986, 19, 21. (24) Kotlarchyk, M.; Stephens, R. B.; Huang, J. S. J . Phys. Chem. 1988, 92, 1533.
Micellar Behavior of a Nonionic Surfactant, Surfynol 465, from 13C NMR Resonance Frequencies in D,O Shizuko Sat0 Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori 3-1, Mizuho- ku, Nagoya 467, Japan (Received: April 27, 1988; In Final Form: November 23, 1988)
13CNMR spectra of a nonionic surfactant, Surfynol 465, in D 2 0 were measured and assigned at various concentrations from 0.01 to 2.8 mol kg-'. When the molality of surfactant, m2,was increased, the resonance frequencies, u2, of all carbons varied either upfield or downfield with a different magnitude for each carbon from others, depending on its position, but kept the similar profile of v2 vs m2relation to others. Each of the profiles had two characteristic bends, which corresponded to the micellization of surfactant at ca. 12 mmol kg-' and the interaction among micelles nearly at 1 mol kg-', respectively. We analyzed the v2 vs m2 plot for each carbon on the basis of an association equilibrium model for the micellization and an overlapping model for the micellar interaction. The specific values of v2 allocated to monomer and micelle were evaluated to be discussed for each carbon. Also, the effective radius of the micelle, R , was evaluated from the analysis of data for each carbon. The variation of R among carbons is discussed with respect to their positions in the Surfynol 465 molecule.
Introduction N M R spectroscopy provides a powerful technique to elucidate the molecular structure of surfactant and also serves to examine its solution behavior, such as micellization.'-' The information from N M R has often reinforced other physicochemical knowledge on the nature of micellization, which might otherwise be ambigu~us.*-'~Previously, we found on the relation of thermodynamic properties of a nonionic surfactant, Surfynol465, in water vs concentration that, at first, the surfactant sharply changes its (1) Nakagawa, T.; Tokiwa, F. In Surface and Colloid Science; Matijevic, E., Ed.; Wiley: New York, 1976; Vol. 9, p 69. (2) Ribeiro, A. A,; Dennis, E. A. J . Phys. Chem. 1976, 80, 1746. (3) Persson, B. 0.;Drakenberg, T.; Lindman, B. J . Phys. Chem. 1976,80, 2124. (4) (5)
Ribeiro, A. A.; Dennis, E. A. J . Phys. Chem. 1977,81, 957. Maeda, H.; Ozeki, S.; Ikeda, S.;Okabayashi, H.; Matsushita, K. J.
Colloid Interface Sci. 1980, 76, 532. (6) Corno, C.; Platone, E.; Ghelli, S. Polym. Bull. (Berlin) 1984, 1 I , 69. (7) Montana, A. J. In Nonionic SurJactants: Chemical Analysis; Cross, J., Ed.; Marcel Dekker: New York, 1987; p 295. (8) Corkill, J. M.; Goodman, J. F.; Wyer, J. Trans. Faraday SOC.1969, 65, 9. (9) Christenson, H.; Friberg, S.E.; Larsen, D. W. J . Phys. Chem. 1980, 84, 3633. (10) Ueno, M.; Kishimoto, H. Nippon Kagaku Kaishi 1980, 375. (11) Ueno, M.; Kishimoto, H. J . Phys. Chem. 1983, 87, 850. (12) Lindman, B.;SGderman, 0.;WennerstrBm, H. In Surfactant Solu-
tions: New Methods of Investigation; Zana, R., Ed.;Marcel Dekker: New York, 1987; p 295. (13) Sato, S.;Kishimoto, H. J . Surf. Sci. Tech. 1988, 4, 43.
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behavior due to micellization and after some interval, it shows a gradual change of behavior, probably reflecting a sort of micellar intera~tion.'~*'~ A similar behavior was found from the 'H N M R chemical shifts of the surfactant in D20.13 However, since their changes at the higher concentrations were scarcely distinguished among different protons, no significant transformation of the chemical structure of the surfactant molecule could be confirmed about the micellar interaction in spite of our expectation. In order to verify the effect of the supposed micellar interaction on the chemical structure as well as strengthen the previously obtained results, we studied the 13CN M R chemical shifts of Surfynol465 in D20, taking into consideration that "C N M R has many distinctive features that are more than complemental to 'H NMR.16.17
Experimental Section Materials. Surfynol 104 (Figure l a ) is 2,4,7,9-tetramethyl5-decyne-4,7-diol; Surfynol 465 (Figure 1b) is a,a'-[2,4,7,9tetramethyl-5-decyne-4,7-diyl] bis [w-hydroxylpoly(oxyethylene)] with ca. 8.5 oxyethylene segments in total and the number-average molar mass, M2, at ca. 600 g m0l-'.'~9'* They were gifts from (14) Sato, S.; Kishimoto, H. J . Colloid Interface Sci. 1988, 123, 216. (15) Sato, S.; Kishimoto, H. J . Colloid Interface Sci. 1988, 126, 108. (16) Breitmair, E.; Voelttr, W. I3C-NMR Spectroscopy. Methods and
Applications in Organic Chemistry, 2nd ed.; Verlag Chemic: New York, 1978; Chapters 2-5. (17) Stothers, J. B. Carbon-13NMR Spectroscopy; Academic Press: New York, 1972; Chapter 3.
0 1989 American Chemical Society
