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

2010 Student Practice in JINR Field of Research 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 Packing Parameter P= V/aL a – Head group cross-sectional area l – Length of tail V – Volume of tail P<1/3 P<1/2 P ≈ 1 6 October 20155

2010 Student Practice in JINR Field of Research 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 C 16 TABr – cetyltrimethylammonium bromide C 16 H 33 N(CH 3 ) 3 Br cationic Triton X-100 – C 14 H 22 O(C 2 H 4 O) n nonionic n=10 p-(1,1,3,3-tetramethyl )poly(oxyethylene) 6 October 20158

2010 Student Practice in JINR Field of Research 9 Information from SANS Size Shape Molecular weight Interaction distance Self-Assembly 0.008˚ - 8˚ polymers biomolecules nanomaterialssurfactants Magnetic liquids

2010 Student Practice in JINR Field of Research 10 SANS fundamentals Neutron source Θ/2 sample detector Q 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 6 October Atomic nucleus b [fm] Molar weight [g/mol] 1H1H H2H C N O Br – heavy water density [g/ml] 20 – molecular weight of D 2 O N A – Avogadro`s number 6.02·10 23 mol , – scattering length of oxygen and deuterium

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

2010 Student Practice in JINR Field of Research 12 The scattering vector The modulus of the resultant between the incident, k i, and scattered, k s, wavevectors, given by: Neutron source sample detector kiki ksks 6 October

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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. N p – number concentration of scattering bodies V p 2 – square of the volume of scattering body ∆σ 2 – square of the difference in neutron scattering length densities Q – the modulus of the scattering vector B inc – the isotropic incoherent background signal 6 October

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2010 Student Practice in JINR Field of Research 16 IBR – 2 Fast Pulsed Reactor Main movable reflector Additional movable reflector Core, PuO 2 Reactor vessel Stationary reflector moderator 6 October

2010 Student Practice in JINR Field of Research 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 12- ring-wire detector 13 – position-sensitive detector “Volga” 14 – direct beam detector 6 October

2010 Student Practice in JINR Field of Research 18 Main parameters of YuMO instrument Parameters Value Flux on the sample (thermal neutrons) 10 7 – 4x10 7 n/(s cm 2 ) [1] Used wavelength 0.5 Å to 8 Å # Q-range 7x10 -3 – 0.5 Å -1 Dynamic Q-range q max /q min 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 mm Collimation system Axial Detectors He 3 -fulfiled, home made preparation, 8 independent wires [5] Detector (direct beam) 6 Li-convertor (home made preparation) Condition of sample In special box in air Q-resolution low, 5-20% Temperature range -50 o C o C ^ (Lauda) Temperature range 700 o C ** (Evrotherm) Number of computer controlled samples 14 *** Background level 0.03 – 0.2 cm -1 Mean time of measurements for one sample 1 h + Frequency of pulse repetition 5 Hz Electronic system VME The instrument control software complex SONIX [6]SONIX 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] # - without cold -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

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 program Author: Prof. Glatter Otto University 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: 30 0, 50 0, 70 0, 90 0 C for each set 6 October

2010 Student Practice in JINR Field of Research 22 Results for TX-100/C16TABr mixtures + D2O 6 October p(r) vs r for ratio 1:1 at temp 30 0 C – 90 0 C Experimental data for ratio 1:1 at temp C – 90 0 C

2010 Student Practice in JINR Field of Research 23 Results for TX-100/C16TABr mixtures + D2O Experimental data for ratio 2:1 at 30 0 C – 90 0 C 6 October p(r) vs r for ratio 2:1 at temp 30 0 C – 90 0 C

2010 Student Practice in JINR Field of Research 24 Results for TX-100/C16TABr mixtures + D2O p(r) vs r for ratio 3:1 at temp 30 0 C – 90 0 C 6 October Experimental data for ratio 3:1 at 30 0 C – 90 0 C

2010 Student Practice in JINR Field of Research 25 Mixture systems TX-100/C16TABr + D2O for different ratio at temp C … 6 October

2010 Student Practice in JINR Field of Research 26 and 70 0 C 6 October

2010 Student Practice in JINR Field of Research 27 Nonionic surfactant heptaethylene glycol monotetradecyl ether (C 14 E 7 ) in dilute heavy water solutions. Influence of concentration and temperature on aggregation in solutions Nonionic classic surfactant C 14 E 7 ( heptaethylene glycol monotetradecyl ether ) in water solution was investigated for temperatures below the cloud point for seven temperatures 6 o, 10 o, 15 o, 20 o, 25 o, 30 o and 35 o C in dilute solutions for concentrations: c 1 = 0.17%, c 2 = 0.5% with small-angle neutron scattering (SANS) method. hydrophobic tail hydrophilic head

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.

2010 Student Practice in JINR Field of Research 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 + D2O Concentration 0.17 %

2010 Student Practice in JINR Field of Research 31 Results for C14E7 + D2O Concentration 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 C 16 TABr 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 ) 6 October

2010 Student Practice in JINR Field of Research 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% r [nm]L [nm]T [˚C] r [nm]L [nm]T [˚C]

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, 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, October

2010 Student Practice in JINR Field of Research 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.