Characteristic  sizes of sodium octanoate micelles have been determined (by nucleus radius) with the 
use of small angle X-ray scattering technique at various molar concentrations, which are for a spherical 
shape 1 and nonspherical 1.2 nm, respectively. The value of the critical concentration for micelle formation
(CMC2) has been also found equal to 0.7 M.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3628

Burikov, S.A.

Chekadanov, A.S.

Dobromyslov, M.B.

Dolenko, T.A.

Kuzmenko, A.P.

Mirgorod, U.A.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 6 No 3, 03036(3pp) (2014) Том 6 № 3, 03036(3cc) (2014)   The article was reported at the International Conference «The Advanced Technology, Equipment and Analytical Systems for Materials», Kursk, 13-14 May, 2014 2077-6772/2014/6(3)03036(3) 03036-1  2014 Sumy State University Temperature and Concentration Effects of Aqueous Solution of Sodium Octanoate on  Micelle Formation Measured by Small angle X-ray Scattering  A.P. Kuzmenko1, A.S. Chekadanov1, U.A. Mirgorod1, T.A. Dolenko2, S.A. Burikov2, M.B. Dobromyslov2  1 South-West State University, 94, 50 let Oktyabrya Str., 305040 Kursk, Russia 2 Pacific National University, 136, Tihookeanskaya Str., 680035 Khabarovsk, Russia  (Received 19 May 2014; revised manuscript received 09 July 2014; published online 15 July 2014)  Characteristic sizes of sodium octanoate micelles have been determined (by nucleus radius) with the use of small angle X-ray scattering technique at various molar concentrations, which are for a spherical shape 1 and nonspherical 1.2 nm, respectively. The value of the critical concentration for micelle formation (CMC2) has been also found equal to 0.7 M.  Keywords: Small-angle X-ray scattering, Sodium octanoate, Micelles, Spherical and nonspherical structures.   PACS number: 61.05.cf   1. INTRODUCTION  Among some special features of “soft” nanostruc-tures such as micelles in contrast to solid structures is exchange of monomeric molecules between micelles and water, two relaxation times, absence of supersatura-tion, hysteresis of properties, which dictates their wide practical application. Capability of micelles to include metals, including rear-earth metals, is applied for iso-lation and purification of metals, and which is critically important, for deposition of thin metal and oxide coat-ings by using gas-phase thermolysis and layered sedi-mentation [1]. Despite the fact that these structures are intensively studied by scientists of various fields, there is no, unfortunately, complete understanding of interrelation between form and electronic structures of these formations, also for the reason of limitations of hardware possibilities [2].  2. EXPERIMENTAL SECTION  This work studies micelle solutions of sodium oc-tanoate by small angle X-ray scattering (SAXS) tech-nique in characteristic ranges of critical micelle for-mation concentration (CMC): CMC1 – the formation stage, CMC2 – crossover of spherical micelles to non-spherical. Solutions of sodium octanoate (Fluka) with concentration of 0.4-1.00 mol/l between CMC1 and CMC2 were studied. SAXS was studied with small angle X-ray diffrac-tometerSAXSess mc2 (Anton Paar, Austria) in a linear collimation mode (Cu Kα with a wavelength of 0.154 nm). Resolution of the system was 0.03 nm – 1. Measurements were conducted in the range from 0.03 to 28 nm – 1, which corresponds to the objects with sizes from 0.12 to 100 nm. Thermocell (with range of – 30 to 120 С) made it possible to conduct temperature meas-urements at 10, 25 and 40 С.  3. RESULTS AND DISCUSSION  With small angle X-ray scatterings spectra pair-distance distribution functions (1) were constructed  both in treating with indirect Fourier transformation (IFT) and also with the help of its expansion, namely, generalized indirect Fourier transformation (GIFT) [3, 4].  2 01( ) ( )( )sin( )2p r I q qr qr dq   (1)  These functions are Fourier-transformation of scatter-ing function   0sin( )( ) 4 ( )qrI q p r drqr   (2)  where q – scattering vector determined as q  (4 / )sin(θ / 2),  – wavelength of X-ray beam,  θ – scattering angle between incident and scattered radiation, r – distance between two scattering centers inside a particle. For diluted disperse systems the IFT method is ap-plied, in which the particle interaction is ignored. For high concentrations the particle interaction influences heavily on the scattering intensity I(q), which is consid-ered in the GIFT method. The method is predicated onthe assumption that the scattering intensity is de-termined by the production of contributions P(q) – form-factor and S(q) – structural factor, where the latter in-cludes interparticle interaction [3, 4]:   I(q)  n P(q) S(q), (3)   20sin( )( ) 1 4 ( )qrS q n h r r drqr    (4)  where n – the particle density, h(r)  g(r) – 1–  common correlation function, g(r) – radial distribution function. For spherical monodisperse isotropic systems equa-tion (3) gives the exact solution. Nevertheless, as was shown with many examples [3], introduction of “aver-aged structural factor” Save or more exact “effective structural factor” Seff (q) provides good results for poly-disperse spheres and  inhomogeneous particles. In this work polydisperse system of solid spheres was chosen for model computations.Typical curves of SAXS obtained for micelle structures of NaC8 with vari-ous concentrations: 0.4, 0.5, 0.7 and 1 M are given in Fig.1. Noticeable ordering is observed which is due to the increase of molar concentration of NaC8 solution, which is illustrated by the approximating curve ob-tained according to calculation with IFT and GIFT and superimposed on the spectral distribution. However,  A.P. KUZMENKO, A.S. CHEKADANOV, ET AL. J. NANO- ELECTRON. PHYS. 6, 03036 (2014)   03036-2 more detailed conclusions about possible structural formations of micelles of NaC8 may be derived from analysis ofpair-distance distribution functions and elec-tron density distributions.    Fig. 1 – Spectra of small angle X-ray scattering on micelle structure of sodium octanoate at concentrations of 0.4, 0.5, 0.7, and 1 M (from bottom to top, respectively)  It should be noted that as physical object micelle structures are highly sensitive to form-factor and in-terparticle interactions, which must be considered in the structural factor of their interactions [3, 4]. In real-world conditions, by the SAXS spectra pair-distance distribu-tion functions – p(r) can be constructed for all changing parameters – temperature and concentration. Charac-teristic view of p(r) for the object studied with a concen-tration of 1 M at a temperature of 25 С is shown in Fig. 2, which is in accord with conclusions in [2, 5]. Such kind of distribution does not allow one to establish un-ambiguously enough of which form the structure of NaC8 micelle is – spherical or not. This is indicated by the change, with respect to zero, of a relationship between two first peaks of dependence p(r), and also by its sign variability at great values of the wave vector.    Fig. 2 – Pair-distance distribution functions of micelle struc-ture of sodium octanoate with a concentration of 1 M at a temperature of 25 С  At the same time, the electron density profiles (r) con-structed with p(r) for concentrations of micelle solutions equal to 0.5 and 1 M (Fig. 3a, b) make it possible to estab-lish the micelles form unambiguously enough. Pattern of dependence of (r) for the concentration of 0.5 M is typical for micelles of spherical shape (Fig. 3a), whereas for the concentration of 1 M (Fig. 3b) – for nonspherical shape with a nucleus radius of  1.1 and  1.2 nm respectively.    Fig. 3 – Electron density profiles of micelle structure of sodi-um octanoate at a temperature of 25 Сwith a concentration of: a – 0.5 M, b – 1 M  SAXS on micelles in quartz capillary at temperature variations from10 to 40 C with the use of pair-distance distribution function p(r) made it possible to find concentra-tion and temperature distinction (Fig. 4). For example, p(r) for solution of NaC8 with a concentration of 0.7 M at tem-peratures of 10, 25, and 40 C distribution is observed close to lamellar structure with a size of around 5 nm, which is indicative of the transition from spherical micelles to non-spherical ones, i.e. corresponds to CMC2.    Fig. 4 – Temperature effect on micelle structure of sodium octanoate determined by pair-distance distribution function:  --- –  at 10 C, ––– – at 25 C, ···· – at 40 C   I(q) p(r)  TEMPERATURE AND CONCENTRATION EFFECTS OF AQUEOUS SOLUTION… J. NANO- ELECTRON. PHYS. 6, 03036 (2014)   03036-3 4. CONCLUSIONS  Thus, the investigation results of SAXS on micelle so-lutions of sodium octanoate at various molar concentra-tions and temperatures make it possible to characterize both possible shapes of the micelles with variations from spherical to nonspherical, by analogy with [6], and their sizes and also CMC2   REFERENCES1. K. Holmberg, B. Jonsson, B. Kronberg, B. Lindman, Sur-factants and Polymers in Aqueous Solution. 2nd Ed. (Chinchester: 2003). 2. T. Zemb, P. Charpin, J. Phys. France 46, 249 (1985). 3. Marija Bešter-Rogač, Acta Chim. Slov. 54, 452 (2007). 4. A.P. Kuzmenko, A.N. Chaplygin, A.S. Chekadanov, Proc. SWSU, Series Physics and Chemistry 1, 34 (2012). 5. N. Hassan, L.R.S. Barbosa, R. Itri, J.M. Ruso, J. Colloid Interface Sci. 362, 118 (2011). 6. J. Merta, M. Torkkeli, T. Ikonen, R. Serimaa, P. Stenius, Macromolecules 34, 2937 (2001).  

Temperature and Concentration Effects of Aqueous Solution of Sodium Octanoate on  Micelle Formation Measured by Small angle X-ray Scattering

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Temperature and Concentration Effects of Aqueous Solution of Sodium Octanoate on Micelle Formation Measured by Small angle X-ray Scattering

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