Electronic Supplementary Material
Spontaneous Evolution of Self-assembled Phases from Anisotropic Colloidal Dispersions
Ravi Kumar Pujala1,2, Nidhi Joshi2 and H. B. Bohidar*2,3
1
FORTH, Institute of Electronic Structure & Laser, Heraklion,
Crete, Greece
2
School of Physical Sciences, Jawaharlal Nehru University
3
Special Center for Nanosciences, Jawaharlal Nehru University
*
Corresponding author email: bohi0700@mail.jnu.ac.in
Tel: +91 11 2670 4637, Fax: + 91 11 2674 1837
(i) MMT Sample Preparation
Na MMT (Na Cloisite), a hydrated aluminium silicate, was purchased from Southern Clay
Products, U.S. and used as received. Chemically it is hydrated sodium calcium aluminium
magnesium silicate hydroxide (Na, Ca)0.33(Al, Mg)2(Si4O10)(OH)2·nH2O. The powder was first
dried in an oven at 3000C to remove the moisture content. An aqueous dispersion of MMT was
prepared by dispersing the fractionated MMT in deionized water at pH 8.5. Since the native clay
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contains large fractions of particles ranging from 10nm to 2μm, fractionation of the particles was
done to obtain the desired size of the clay particles (~ 250 nm). The sample was stirred
vigorously using magnetic stirrer for 48 hours to ensure complete dissolution of the clay particles
and the fractionation was done as described in ref. [1]. The samples were prepared in a clean
environment and exposure to air was avoided by sealing them in tight vials. We have carried out
experiments in the broad concentration range 0.1 - 6 % (w/v). All the experiments were
performed under room temperature conditions, temperature 250 C and relative humidity < 40%.
For reproducibility of the results we have prepared three sets of samples with a gap of one month
for each set and performed the measurements.
1.0
g1(t)
0.8
0.6
0.4
0.2
0.0
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
t (s)
Figure S1 Correlation function of 0.1 % (v/w) MMT from which the hydrodynamic size is
deduced.
Polydispersity of the clay dispersions was obtained from TEM micrographs. The polydispersity
is defined as  D 
D2  D
2
D with D the dimension considered i.e either width or
2
length. This parameter is deduced from the average over ten TEM micrographs. Even after the
systematic fractionation some amount of polydispersity presented in the dispersions in length and
width, but the method we adopted for fractionation is more improved one. Polydispersity of
MMT particles was found to be 21% in length and 14% in width.
(ii) Methods
(a) Rheology
Rheology experiments were performed using an AR-500 model stress controlled rheometer (T.A.
Instruments, UK). Frequency sweep experiments were performed using cone-plate geometry (4
cm diameter, 20 cone angle and 50 mm truncation gap) with the oscillatory stress value set at 0.1
Pa specially to observe low frequency behavior of storage and loss modulii.
The clay dispersions exhibit aging and hence we performed the time sweep to assess the
thixotropic effect before the experiment and amplitude tests to determine the viscoelastic
domain. The dispersion showed the thixotropic loop and hence time dependent.Since the material
is thixotropic, the viscosity is time dependent leading to a hysteresis effect: the increasing and
decreasing curves do not overlap. Solvent traps are used to ensure no evaporation or drying takes
place during each procedure.
(b) Dynamic light scattering
Dynamic light scattering (DLS) experiments were performed on a 256 channel digital correlator,
(PhotoCor Instruments, USA)
that was operated in the multi-tau mode (logarithmically
spaced channels). The time scale spanned 8-decades, i.e. from 0.5s to 10s. This instrument used
a 35mW linearly polarized He:Ne laser. The probe length scale is defined by the inverse of the
modulus of the scattering wave vector q where the wave vector q=(4πn/)sin(/2), the medium
refractive index is n, excitation wavelength is  (632.8nm) and  is scattering angle. The
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scattered intensity values were measured at the scattering angle 900. Further details on dynamic
light scattering can be obtained from ref. [2]. The instrument was used in the polarized mode to
determine the particle size of clay particles. In all the experiments, the difference between the
measured and calculated base line was not allowed to go beyond ±0.1% and the signal
modulation was maintained above 85%. The data that showed excessive baseline difference were
rejected. This ensured smooth correlation curves with well defined baseline. The measured
intensity auto-correlation functions were analyzed by the CONTIN regression software to check
the relaxation time distribution function. Robustness of the fitting results was decided based on
two criteria: sample to sample accuracy, and data reproducibility within the same sample.
(c) Transmission Electron Microscopy
Particle morphology was examined by JOEL 2100F transmission electron microscope (Digital
TEM with image analysis system and maximum magnification = × 15,000,000) operating at a
voltage of 200 KV. The aqueous dispersions were drop-cast onto a carbon coated copper grid
which was air dried at room temperature (20 oC) before loading onto the microscope.
(d) Scanning Electron Microscope:SEM images were captured using Zeiss EVO40. The
morphology of the sample were studied from the SEM micrographs.
The Individual particles without aggregates were seen in the TEM picture. Which may indicate
that the particles are homogeneously dispersed in the medium in the initial aging period. The
percolating net work have been observed in the SEM images.
(e) Viscosity: Measurement of viscosity was done using a Sine-wave Vibro Viscometer (model –
SV10, A and D company, Japan). The instrument uses a matched pair of gold plated flat
electrodes which are driven with electromagnetic force at the same frequency by vibrating at
4
constant sine-wave vibration in reverse phase. When the spring plates are vibrated with a
uniform frequency of 30Hz, the amplitude of less than 1 mm varies in response to the amount of
frictional force produced by the viscidity between the sensor plates and the sample. In order to
control the electrical current that drives the vibration of the spring plates has to be controlled.
The driving electric current which is the origin of exciting force, will be detected as the
magnitude of the viscidity between the sensors plates and the sample fluids. The Vibro
Viscometer measures electric current, and then viscosity is given by the positive correlation
between driving electric current and the viscosity.
1.1
103
-1
102
(Pa.s)
m
1.0
0.9
0.8
0.7
10
3
1
4
5
c % (w/v)
6
100
10-1
10-1
100
101
102
103
shear rate (s-1)
Figure S2Steady-state viscosity of the system plotted as a function of the shear rate for different
clay concentrations (○) 3.0%; (□) 3.5%; () 4.0%; (◊) 4.5.0%; ( ) 5.0%; ( ) 5.5%. The data is
least- squares fitting to the equation. Inset shows the variation of exponent m with clay
concentration.
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(b)Viscoelastic studies:
2.0 %
1.5 %
G'' (Pa)
0.1
slope = 1
slope = 1
0.01
2.5 %
3%
1st day
2nd day
3rd day
4th day
5th day
G" (Pa)
0.1
slope = 1
slope = 1
0.01
1
10
rad/s
rad/s
1
10
1
G'' (Pa)
1 DAY
2 DAY
3 DAY
4 DAY
5 DAY
0.7
0.7
0.1
0.85
slope = 1
1
3.5%
1
4%
4.5 %
0.01
10
0.3
G'' (Pa)
0.35
1
0.2
0.5
0.4
0.5
0.7
0.8
slope = 1
slope = 1
slope = 1
rad/s
6%
5.5 %
5%
0.1
1
0
rad/s
1
0
rad/s
1
Figure S3 Loss modulii data of MMT suspensions shown for different concentrations and at
various aging times as indicated. Note that the deviation from the Maxwellian behavior starts
when c > cg (= 3.0 % w/v).
6
3
2%
2
2.5%
G' (Pa)
1
0
slope = 2
-1
1 DAY
2 DAY
3 DAY
4 DAY
5 DAY
-2
-3
slope = 2
-4
1
3.5%
3%
G' (Pa)
0
slope = 2
-1
slope = 2
-2
0
20
1
1
(rad/s)
2
(rad/s)
2
4.5%
4%
1
5%
1.1
G' (Pa)
0
1.6
-1
1.6
1.5
slope = 2
-2
slope = 2
slope = 2
-3
-4
2
G' (Pa)
1
(rad/s)
0.3
0.4
0
1
6%
5.5%
0.7
1.1
1.4
-1
slope = 2
slope = 2
Day 1
Day 2
Day 3
Day 4
Day 5
-2
-3
0
1
(rad/s)
2 0
1
(rad/s)
Figure S4 Storage modulii data of MMT suspensions is shown different for concentration and at
various aging times as indicated. Note that the deviation from the Maxwellian behavior starts
when c > cg (3.0 % (w/v)) as the exponent started decreasing with aging which is indicated
against each curve.
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References
1.CiprianoBH, KashiwagiT, ZhangX, RaghavanSR (2009)A simple method to improve the
clarity and rheological properties of polymer/clay nanocomposites by using fractionated clay
particles. ACS Appl. Mater. Interfaces. 1:130-135.
2.BerneBJ,PecoraR (1976) Dynamic Light Scattering with Applications to Chemistry,
Biology
and Physics: Wiley-Interscience, New York, USA.
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