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Investigation of aggregation in surfactants solutions by the SANS method

Investigation of aggregation in surfactants solutions by the SANS method. Dominika Pawcenis Faculty of Chemistry, University of Wroclaw, Poland Frank Laboratory of Neutron Physics Small – Angle Neutron Scattering Team Supervisor: A. Rajewska. Purpose of the project.

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Investigation of aggregation in surfactants solutions by the SANS method

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  1. Investigation of aggregation in surfactants solutions by the SANS method Dominika Pawcenis Faculty of Chemistry, University of Wroclaw, Poland Frank Laboratory of Neutron Physics Small – Angle Neutron Scattering Team Supervisor: A. Rajewska

  2. Purpose of the project • Investigation of shape and size of micelles in mixture systems of surfactants solutions (nonionic + ionic) at different temperatures. • Investigation of shape and size of micelles in nonionic surfactant solutions only. 2010 Student Practice in JINR Field of Research

  3. Surfactants • SURFace ACTive AgeNT • Soap • Detergents (anionic, cationic, zwitterionic, nonionic) Hydrophobic “tail” and hydrophilic “head” 2010 Student Practice in JINR Field of Research

  4. Micelles – structure of aggregations 2010 Student Practice in JINR Field of Research

  5. Self – assembly P<1/3 P ≈ 1 P<1/2 Packing Parameter P= V/aL • a – Head group cross-sectional area • l – Length of tail • V – Volume of tail 2010 Student Practice in JINR Field of Research 5

  6. Synergistic effect in mixtures of nonionic and ionic surfactants • It was observed that for mixtures of nonionic and ionic surfactant solutions (in water or in heavy water) CMC of mixture system is smaller than each of these two surfactants (in water or heavy water). 2010 Student Practice in JINR Field of Research

  7. Thermodynamics of micellization CMC – Critical Micelle Concentration 2010 Student Practice in JINR Field of Research

  8. Chemicals used in mixed system C16TABr – cetyltrimethylammonium bromide C16H33N(CH3)3Br cationic Triton X-100 – C14H22O(C2H4O)n nonionic n=10 p-(1,1,3,3-tetramethyl )poly(oxyethylene) 2010 Student Practice in JINR Field of Research 8

  9. Information from SANS • Size • Shape • Molecular weight • Interaction distance • Self-Assembly 0.008˚ - 8˚ 2010 Student Practice in JINR Field of Research

  10. SANS fundamentals Neutron source Q Θ/2 sample detector I(Q) – intensity A – const. P(Q) – normalized form factor S(Q) – structure factor (for dilute solutions S=1) n – number of density ν – volume of particle ∆ρ – difference of length density scattering Q – scattering vector 1.1 – heavy water density [g/ml] 20 – molecular weight of D2O NA – Avogadro`s number 6.02·1023 mol-1 0.5805, 0.6674 – scattering length of oxygen and deuterium 2010 Student Practice in JINR Field of Research 10

  11. Scattering length density 2010 Student Practice in JINR Field of Research

  12. The scattering vector The modulus of the resultant between the incident, ki, and scattered, ks, wavevectors, given by: Neutron source ks ki sample detector 2010 Student Practice in JINR Field of Research 12

  13. 2010 Student Practice in JINR Field of Research

  14. Differential cross – section • Contains all the information on the shape, size and interactions of the scattering bodies in the sample. Np – number concentration of scattering bodies Vp2 – square of the volume of scattering body ∆σ2 – square of the difference in neutron scattering length densities Q – the modulus of the scattering vector Binc – the isotropic incoherent background signal 2010 Student Practice in JINR Field of Research 14

  15. 2010 Student Practice in JINR Field of Research

  16. IBR – 2Fast Pulsed Reactor Core, PuO2 Reactor vessel Main movable reflector Stationary reflector Additional movable reflector moderator 2010 Student Practice in JINR Field of Research 16

  17. Spectrometer YuMO 1 – two reflectors 2 – zone of reactor with moderator 3 – chopper 4 – first collimator 5 – vacuum tube 6 – second collimator 7 – thermostate 8 – samples table and holder for samples 9 – goniometr 10 – V-standard 11 – V-standard • - ring-wire detector 13 – position-sensitive detector “Volga” 14 – direct beam detector 2010 Student Practice in JINR Field of Research 17

  18. #   - without cold moderator @    -could be easy changed to decreasing *    - only for estimation (Radii of giration from 200 Å - to 10 Å  -  Angstroem) ^    - in basic configuration of instrument **   - in special box, using nonstandard devices +    - for estimation only *** - simultaneosly in standard cassete with Hellma Main parameters of YuMO instrument Parameters Value Flux on the sample (thermal neutrons) 107 – 4x107 n/(s cm2) [1] Used wavelength  0.5 Å to 8 Å   # Q-range 7x10-3 – 0.5 Å-1 Dynamic Q-range qmax/qmin up to 100 Specific features Two detectors system [2,3], central hole detectors Size range of object      500 – 10 Å Intensity (absolute units -minimal levels) 0.01 cm-1 Calibration standard Vanadium during the experiment [4] Size of beam on the sample 8 – 22 mm2  @ Collimation system Axial  Detectors He3 -fulfiled, home made preparation, 8 independent wires [5] Detector (direct beam) 6Li-convertor (home made preparation)  Condition of sample In special box in air Q-resolution low, 5-20% Temperature range -50oC -+130oC      ^      (Lauda) Temperature range 700 oC      **      (Evrotherm) Number of computer controlled samples  14            *** Background level 0.03 – 0.2 cm-1 Meantime of measurements for one sample 1 h          +  Frequency of pulse repetition 5 Hz Electronic system VME The instrument control software complexSONIX [6] Controlling parameters  Starts (time of experiments), power, vandium standard position , samples position, samples box temperature, vacuum in detectors tube. Data treatment SAS, Fitter [7-9] 2010 Student Practice in JINR Field of Research

  19. Holder for samples 2010 Student Practice in JINR Field of Research

  20. PCG v. 2.0 programAuthor: Prof. Glatter OttoUniversity of Graz, Austria • PCG v. 2.0 consists of 6 pieces (GIFT, Length Profile, Mini Viewer, Multibody, PDH, Rasmol PCG) • element of this program is GIFT. GIFT`s element is IFT. • With IFT program p(r) vs r was computed • With GIFT program S(Q) can be computed 2010 Student Practice in JINR Field of Research

  21. Experiment for mixture system conditions • Investigation of influence of composition of micelle solution on the aggregation; • Mixtures of dilute solutions of Triton X -100 and C16TABr in ratio: at temperatures: 300, 500, 700, 900 C for each set 2010 Student Practice in JINR Field of Research 21

  22. Results for TX-100/C16TABr mixtures + D2O p(r) vs r for ratio 1:1 at temp 300 C – 900 C Experimental data for ratio 1:1 at temp. 300 C – 900 C 2010 Student Practice in JINR Field of Research 22

  23. Results for TX-100/C16TABr mixtures + D2O Experimental data for ratio 2:1 at 300 C – 900 C p(r) vs r for ratio 2:1 at temp 300 C – 900 C 2010 Student Practice in JINR Field of Research 23

  24. Results for TX-100/C16TABr mixtures+ D2O p(r) vs r for ratio 3:1 at temp 300 C – 900 C Experimental data for ratio 3:1 at 300 C – 900 C 2010 Student Practice in JINR Field of Research 24

  25. Mixture systems TX-100/C16TABr + D2O for different ratio at temp. 300 C … 2010 Student Practice in JINR Field of Research 25

  26. and 700 C 2010 Student Practice in JINR Field of Research 26

  27. Nonionic surfactant heptaethylene glycol monotetradecyl ether (C14E7) in dilute heavy water solutions. Influence of concentration and temperature on aggregation in solutions • Nonionic classic surfactant C14E7 ( heptaethylene glycol monotetradecyl ether ) in water solution was investigated for temperatures below the cloud point for seven temperatures 6o, 10o, 15o, 20o, 25o, 30o and 35o C in dilute solutions for concentrations: c1= 0.17%, c2 = 0.5% with small-angle neutron scattering (SANS) method. hydrophobic tail hydrophilic head 2010 Student Practice in JINR Field of Research

  28. CiEj The surfactant studies have included C14E7 where “C” and “E” refer to alkyl(CH)x and ethoxylate(CH2CH2O) units in the conventional shorthand notation.

  29. NONIONIC SURFACTANTS Nonionic surfactants such as oligo( oxyyethylene)-n-alkyl ether ( abbreviated as CiEj ) show a rich phase behaviour in aqueous mixtures. At very low surfactant concentrations the surfactant dissolves in the form of unimers. With an increase in the surfactant concentration the temperature dependent critical micelle concentration ( cmc ) is passed and the surfactant molecules form mostly globular micelles at least at low temperatures. A common feature of these surfactants in mixtures with water is an upper miscibility gap with a lower critical point in the temperature – composition diagram. Above the so-called cloud curve the solutions first become very turbid and then phase separate into two micellar solutions of extremely different surfactant contents. The position of the critical point depends on the overall chain length of the amphiphile and hydrophilic-lipophilic balance. The understanding of the binary phase behaviour and structural properties is central for understanding of ternary mixtures with oil ( microemulsions ). 2010 Student Practice in JINR Field of Research

  30. Results for C14E7 + D2OConcentration 0.17 % 2010 Student Practice in JINR Field of Research

  31. Results for C14E7 + D2OConcentration 0.5 % 2010 Student Practice in JINR Field of Research

  32. Shape of micelles 2010 Student Practice in JINR Field of Research

  33. Shape of micelles 2010 Student Practice in JINR Field of Research

  34. Conclusions • Synergistic effect in mixed systems TX-100/C16TABr we observed. At the same temperature but for different compositions of solutions the shift of maximum of intensity of scattering neutrons to bigger values of q wavescattering vector –show us that the size of micelles is smallest for ratio 3:1 according relation below - q ~ 1/D where q – wavescattering vector D – size of object ( for us micelle ) • With increasing ratio of Triton X-100 to C16TABr and temperature mixture system changes properties from nonionic to ionic – like. • Shape of micelles – for lowest temperature and ratio 1:1 near spherical (with r = 3 nm) than biaxial ellipsoids ( with short axis a = 6.5 nm and long axis b = 3 nm ) 2010 Student Practice in JINR Field of Research 34

  35. Conclusions • For nonionic surfactants with growing temperature size of micelles increases; • Shape of micelles of nonionic surfactant C14E7 for concentration 0.17% and 0.5% for temperature range 6˚ - 35˚C is cylindrical; • Table for concentration 0.17% 0.5% 2010 Student Practice in JINR Field of Research

  36. Special thanks: Aldona Rajewska Ewa Chmielowska Roman Zawodny Władysław Chmielowski 2010 Student Practice in JINR Field of Research

  37. Literature • Structure Analysis by Small-Angle X-Ray and Neutron Scattering, L. A. Fegin, D. I. Svergun, New York: Plenum Press, pp 33, 1988 • Small Angle X – ray Scattering, O. Glatter, O. Kratky, Academic Press, 1982 • Structure and interaction in dense colloidal systems: evaluation of scattering data by the generalized indirect Fourier transformation metohod, G. Fritz, O. Glatter, J. Phys.: Condens. Matter 2006, 18, 2403 - 2419 • Study of Mixed Micelles with Varying Temperature by Small-Angle Neutron Scattering, V. M. Garamus, Langmuir 1997, 13, 6388 – 6392 • Micelle Formation and the Hydrophobic Effect, L. Maibaum, A. R. Dinner, D. Chandler, J. Phys. Chem. B 2004, 108, 6778 – 6781 • Dubna Pulsed Neutron Resources, A. V. Belushkin, Neutron News, Vol. 16, Number 3, 2005 • Small-Angle Scattering of X-rays, A. Guinier, G. Fournet, John Wiley & Sons Inc.,New York 1955 • Two-Detector System for Small- Angle Neutron Scattering Instrument, A. I. Kuklin, A. Kh. Islamov, V. I. Gordeliy, Scientific Reviews, 2005, 16, 16-18 2010 Student Practice in JINR Field of Research 37

  38. Indirect Fourier Transformation 2010 Student Practice in JINR Field of Research

  39. From scattering amplitudes to scattering intensities 2010 Student Practice in JINR Field of Research

  40. Spatially Averaged Intensity 2010 Student Practice in JINR Field of Research

  41. The q–dependent scattering intensity is the complex square of the scattering amplitude , which is the Fourier transform of the scattering length density difference describing the scattering particle in real space. In solution scattering one measures the spatial average of these functions, and we finally have: Where p(r) is the pair distance distribution function (PDDF) of the particle: 2010 Student Practice in JINR Field of Research

  42. is the convolution square (spatial correlation function) of ∆ρ(r) averaged over all orientations in space. The functional form of I(q) or p(r) can be used to determine the shape and the internal structure of the scattering object . 2010 Student Practice in JINR Field of Research

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