investigation of aggregation in surfactants solutions by the sans method dominika pawcenis faculty...

2010 Student Practice in JINR Field of Research

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Investigation of aggregation in surfactants solutions by the SANS

method

Dominika PawcenisFaculty of Chemistry,

University of Wroclaw, Poland

Frank Laboratory of Neutron PhysicsSmall – 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.


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Surfactants

• SURFace ACTive AgeNT• Soap• Detergents (anionic, cationic, zwitterionic,

nonionic)

Hydrophobic “tail” and hydrophilic “head”


4

Micelles – structure of aggregations


5

Self – assembly

Packing ParameterP= V/aL• a – Head group cross-sectionalarea• l – Length of tail• V – Volume of tail

P<1/3

P<1/2

P ≈ 1

April 19, 2023 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).


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Thermodynamics of micellization

CMCRTG

CMCS

SRTG

SRTMn

RT

n

GG

SnMRTG

KRTG

SnKSC

S

MK

MnS

n

n

nt

nn

n

ln

][

]ln[

]ln[]ln[

])ln[](ln[

ln

][][

][

][

0

0

CMC – Critical Micelle Concentration


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Chemicals used in mixed system

C16TABr – cetyltrimethylammonium bromide C16H33N(CH3)3Br cationic

Triton X-100 – C14H22O(C2H4O)n nonionicn=10p-(1,1,3,3-tetramethyl )poly(oxyethylene)

April 19, 2023 8

http://upload.wikimedia.org/wikipedia/commons/3/36/Cetrimonium_bromide.png

http://upload.wikimedia.org/wikipedia/commons/8/89/Triton_X-100.png


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Information from SANS

• Size• Shape• Molecular weight• Interaction distance• Self-Assembly

0.008˚ - 8˚


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SANS fundamentals

Neutron source Θ/2

sample

detector

Q

2122

22

23

23

10)6674.025805.0()20/1.1(

:

)()()(

)()()(

cmN

example

nA

drrdrerQP

QSQPAQI

AOD

iQr

I(Q) – intensityA – const.P(Q) – normalized form factorS(Q) – structure factor (for dilute solutions S=1)n – number of densityν – volume of particle∆ρ – difference of length density scatteringQ – scattering vector

April 19, 2023 10

Atomic nucleus b [fm] Molar weight

[g/mol]

1H - 3.741 12H + 6.674 2

C + 6.646 12

N + 9.362 14

O + 5.805 16

Br + 6.795 173

1.1 – heavy water density [g/ml]20 – molecular weight of D2ONA – Avogadro`s number 6.02·1023 mol-1

0.5805, 0.6674 – scattering length of oxygen and deuterium


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Scattering length density


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The scattering vectorThe modulus of the resultant between the incident, ki, and scattered, ks, wavevectors, given by:

)2/sin(4

n

kkQQ is

Neutron source

sample

detector

kiks

April 19, 2023 12


13


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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 densitiesQ – the modulus of the scattering vectorBinc – the isotropic incoherent background signal

incpp BQSQPVNQ

)()()()( 22

April 19, 2023 14


15


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IBR – 2Fast Pulsed Reactor

Main movable reflector

Additional movable reflector

Core, PuO2

Reactor vessel

Stationary reflector

moderator

April 19, 2023 16


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Spectrometer YuMO1 – two reflectors2 – zone of reactor with moderator3 – chopper4 – first collimator5 – vacuum tube6 – second collimator7 – thermostate8 – samples table and holder

for samples9 – goniometr10 – V-standard11 – V-standard12 - ring-wire detector13 – position-sensitive detector “Volga”14 – direct beam detector

April 19, 202317


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Main parameters of YuMO instrument ParametersValueFlux 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 detectorsSize range of object 500 – 10 ÅIntensity (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 airQ-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

Mean time of measurements for one sample 1 h + Frequency of pulse repetition 5 HzElectronic system VMEThe instrument control software complex SONIX [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]

# - 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

http://flnp.jinr.ru/477/~kirilov/Sonix/sonix_index.htm


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Holder for samples


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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


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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

April 19, 2023 21


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Results for TX-100/C16TABr mixtures + D2O

0.00 0.05 0.10 0.15 0.20 0.25 0.300.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

d(q

)/d

, cm

-1

q[A-1]

n1_30 n1_t50 n1_t70 n1_t90

0 2 4 6 8 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

p(r

)

r[nm]

n1_30 n1_t50 n1_t70 n1_t90

April 19, 2023 22

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


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Results for TX-100/C16TABr mixtures + D2O

Experimental data for ratio 2:1 at 300 C – 900 C

0.00 0.05 0.10 0.15 0.20 0.25 0.300

1

2

3

4

5

d(q

)/d

, cm

-1

q [A-1]

n2_30 n2_t50 n2_t70 n2_t90

0 2 4 6 8 100.00

0.05

0.10

0.15

0.20

p(r

)

r[nm]

n2_30 n2_t50 n2_t70 n2_t90

April 19, 2023 23



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Results for TX-100/C16TABr mixtures+ D2O


0 2 4 6 8 100.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

p(r

)

r[nm]

n3_30 n3_t50 n3_t70 n3_t90

0.00 0.05 0.10 0.15 0.20 0.25 0.300

1

2

3

4

5

6

7

8

d(q

)/d

,cm

-1

q[A-1]

n3_30 n3_t50 n3_t70 n3_t90

April 19, 2023 24

Experimental data for ratio 3:1 at 300 C – 900 C


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Mixture systems TX-100/C16TABr + D2O for different ratio at temp. 300 C …

0.00 0.05 0.10 0.15 0.20 0.25 0.300.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

d(q

)/d

,cm

-1

q[A-1]

n1_30 n2_30 n3_30

0 2 4 6 8 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

p(r

)

r[nm]

n1_30 n2_30 n3_30

April 19, 2023 25


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and 700 C

0.00 0.05 0.10 0.15 0.20 0.25 0.300.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

d(q

)/d

, cm

-1

q[A-1]

n1_t70 n2_t70 n3_t70

0 2 4 6 8 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

p(r

)

r[nm]

n1_t70 n2_t70 n3_t70

April 19, 2023 26


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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


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CiEj

The surfactant studies have includedC14E7 where “C” and “E” refer to alkyl(CH)x and ethoxylate(CH2CH2O) units in the conventional shorthand notation.


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NONIONIC SURFACTANTS

Nonionic surfactants such as oligo( oxyyethylene)-n-alkylether ( abbreviated as CiEj ) show a rich phase behaviour inaqueous mixtures. At very low surfactant concentrations thesurfactant dissolves in the form of unimers. With an increasein the surfactant concentration the temperature dependent critical micelle concentration ( cmc ) is passed and the surfactantmolecules 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 andhydrophilic-lipophilic balance. The understanding of the binary phase behaviour and structural properties is central for understanding of ternary mixtures with oil ( microemulsions ).


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Results for C14E7 + D2OConcentration 0.17 %

0.01 0.1

1E-3

0.01

0.1

1

10

d(

Q)/

d,

cm

-1

Q [A-1]

C14

E7+D

2O

c=0.17%

6oC

10oC

15oC

20oC

25oC

30oC

35oC

0 2 4 6 8 10 12 14 16 18 20

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

p (r

)

r [nm]

C14

E7+D

2O

c=0.17%

6oC

10oC

15oC

20oC

25oC


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Results for C14E7 + D2OConcentration 0.5 %

0.01 0.11E-3

0.01

0.1

1

10

d(Q

)/d,

cm

-1

Q [A-1]

C14

E7+D

2O

c=0.5%

6 oC

10 oC

15 oC

20 oC

25 oC

30 oC

35 oC

0 2 4 6 8 10 12 14 16 18 20 22

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

p (

r)

r [nm]

C14

E7+D

2O

c=0.5%

6oC

10oC

15oC

20oC

25oC


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Shape of micelles


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Shape of micelles


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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 )

April 19, 2023 34


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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]

3 3 6

4 8 10

4.2 9.8 15

5 12 20

5 16 25

r [nm] L [nm] T [˚C]

3 3.5 6

3 8 10

3.5 9.5 15

3.5 12.5 20

4 114 25


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Special thanks:

Aldona Rajewska

Ewa Chmielowska

Roman Zawodny

Władysław Chmielowski


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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

April 19, 2023 37


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Indirect Fourier Transformation

min)(

)(

)(

)()((1

)()(~

)(

)(

)()(

sin)(

4)(

1

1

21

12

1

2exp

1exp

1

1

0

c

N

vvvc

M

i i

N

v ivvi

N

vvv

N

vvv

N

vvv

vv

NL

ccN

q

qcqI

ML

qcqIqI

cqI

rcrp

drqr

qrr

q


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From scattering amplitudes to scattering intensities


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Spatially Averaged Intensity


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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:

)(qI

)(qF

)(r

0

sin)(4)( dr

qr

qrrpqI

)(~)( 22 rrrp


42

)(~ 2 r 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 .

investigation of aggregation in surfactants solutions by the sans method dominika pawcenis faculty...

Documents

scattering vectorbinc

scattering length of

scattering length densitythe

nonionic surfactant

length densitiesq

mixtures of nonionic

size of micelles

size of beam