Transcript Slajd 1

The investigation of surfactant
aggregation in micellar water
solutions by SANS method
Kamila Mikołajczuk
Magdalena Mieścicka
University of Natural Sciences and Humanities in Siedlce
Direction of Chemistry
Frank Laboratory of Neutron Physics
Supervisor of the project:
Aldona Rajewska, PhD
Frank Laboratory of Neutron Physics
FLNP is the place where:
• ultracold neutrons were discovered;
• enhancement of the space parity violation effect in neutron
resonances was found
• use the neutron as an instrument to investigate the structure
and dynamics of condensed matter, including crystals and
nanosystems, functional materials, complex liquids and
polymers, rocks
What about surfactants?
Surfactants are compounds that lower the
surface tension of a liquid, the interfacial
tension between two liquids, or that
between a liquid and a solid.
A micelle - the lipophilic tails of the surfactant molecules remain on
the inside of the micelle due to unfavourable interactions. The polar
"heads" of the micelle, due to favourable interactions with water,
form a hydrophilic outer layer that in effect protects the hydrophobic
core of the micelle. The compounds that make up a micelle are
typically amphiphilic in nature, meaning that not only are micelles
soluble in protic solvents such as water but also in aprotic solvents
as a reverse micelle.
Classification of surfactants for the
sake of functional group
Classical/Gemini
Surfactants
ionic
cationic
Non-ionic
anionic
zwitterionic
Micellization, CMC point and Krafft point
Surfactants molecules occur as monomers in very diluted solution. However
after exceed permissible concentration participles are spontaneous
associated. They form aggregations called micelles.
Determined surfactant concentration cause micellization after exceed CMC
point (critical micelle concentration).
Krafft point
The temperature (more precisely, narrow temperature range) above
which the solubility of a surfactant rises sharply. At this temperature it
becomes equal to the critical micelle concentration. It is best
determined by locating the abrupt change in slope of a graph of the
logarithm of the solubility against t or 1/T.
Small-Angle Neutron Scattering
(SANS)
In this technique radiation is elasically scattered by
a sample and the resulting scattering pattern is
analysed to provide information about the size,
shape and orientation of some component of the
sample.
SANS are used in situations where the important
physical aspects ( size, range of interaction etc.)
occur at distances extanding typically from 10 to
1000 Å.
IBR-2 Pulsed Reactor
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;
9 – goniometer;
10-11 – Vn-standard;
12 – ring-wire detector;
13 – position-sensitve detector "Volga";
14 – direct beam detector.
What should we know about the experiment?
• Firstly the sample is prepared by chemists, who are responsible to
determine a CMC and Krafft point, then physicists realized
researchs in reactor
• The source of neutrons beam is plutionium (IV) oxide PuO2 which is
located in reactor
• Collimated neutron beam fall on a sample
• One part of radiation is scattered, second one is transmitted and
third is absorbed
• Scattering beam is recorded by the detector
• On the basis of obtain results by the detector, we can determine ex.
scattering angle, neutron intensity
• We obtain experimental plots then analyse their by GIFT programme
(Generalized Indirect Fourier Transformation)
• This analysis provide information about the shapes, aggregation
number, size of micelles for the sample
EXPERIMENTAL SECTION
Nonionic surfactant hepta (ethylene glycol)
monodecyl ether (C10E7)* in dilute heavy water
solutions.
• Surfactant hepta (ethylene glycol) monodecyl ether (C10E7) was
study with SANS method.
• Solutions for concentrations: 0.17%, 0.5%, 1% was investigated at
temperatures: 10oC, 15oC, 20oC, 25oC and 35oC for each sample
(the temperature was kept constant with accuracy of ±0.5oC).
• The measurements were made for the momentum transfer Q range
0.02 -0.43 Å-1.
• The CMC value for surfactant C10E7 is equal 0.96 mmol/dm3,
*C10E7=>heptaethylene glycol monodecyl ether(C24H50O8)
Surfactant type CiEj CH3(CH2)9O(CH2CH2O)7H
0.5
0.4
C10E7+D2O
c=0.17%
o
10 C
o
15 C
o
20 C
o
25 C
o
35 C
d(Q)/d, cm
-1
0.3
0.2
0.1
0.1
1
-1
Q [A ]
Fig.1. Intensity of neutron scattering vs scattering vector for concentration
c1=0.17% at temperatures: 10o, 15o, 20o, 25o, 30o and 35oC.
1
C10E7+D2O
d(Q)/d, cm
-1
c=0.5%
o
10 C
o
15 C
o
20 C
o
25 C
o
30 C
o
35 C
0.1
0.1
-1
Q [A ]
Fig.2. Intensity of neutron scattering vs scattering vector for concentration
c2=0.5% at temperatures: 10o, 15o, 20o, 25o, 30o and 35oC.
C10E7+D2O
c=1%
o
10 C
o
15 C
o
20 C
o
25 C
o
30 C
o
35 C
d(Q)/d, cm
-1
1
0.1
0.1
-1
Q [A ]
Fig.3. Intensity of neutron scattering vs scattering vector for concentration
c3=1% at temperatures: 10o, 15o, 20o, 25o, 30o and 35oC.
0.008
10 deg
15 deg
20 deg
35 deg
25 deg
0.006
p (r)
0.004
0.002
0.000
0
2
4
6
8
r [nm]
• Fig. 4. Pair distance distributon function (PDDF) for the C10E7
(c=0,17%) system from SANS measurements for temperatures 10,
15, 20, 25 and 35 Celsius degree
Conclusions
• If intensity of neurons scattering increases the number of
micelles grow up in micellar solution
• For the bigger concentrations and temperatures the
maximum have a higher value
• If the curve p(r) is symmethric – micelle have spherical
shape
• Moreover, distance between zero point and point where
curve p(r) cross axis r is equal to diameter of micelle
• When the curve is not symmetric it is example of micelle
with ellipsoidal shape
• Received diagram is characteristc for ellipsoid micelles
References
• „Structure Analysis by Small-Angle X-Ray and Neutron
Scattering” L.A. Feigin and D.I. Svergun, Plenum Press,
New York and London
• Otto Glater and others Langmuire, 2000, 16, 8692-8701
„Nonionic Micelles near the Critical Point; Micellas
Growth and Attractive Interaction”
• A.Guiner, G. Fournet „Small- Angle Scattering of X-rays”,
John Wiley, 1955
• O.Glatter, O.Kratky „Small- Angle X-ray Scattering”
Academic Press, 1982
• „Small Angle Neutron Scattering” Stephen M.King ISIS
Facility, Rutheford Appleton Laboratory, December 1995
THANK YOU FOR
ATTENTION