Download Dynamic Light Scattering and Rheological Studies of some Micellar Copolymer Solutions PDF

TitleDynamic Light Scattering and Rheological Studies of some Micellar Copolymer Solutions
LanguageEnglish
File Size9.8 MB
Total Pages177
Table of Contents
                            Acknowledgements
Synopsis
Publication List
Introduction
	Soft matter
	Examples of soft matter systems
		Amphiphilic molecules
		Colloidal suspensions
		Hydrogels
	Intermolecular interactions in soft matter
		van der Waals interaction
		Electric double layer interaction
		Hydrophobic interaction
	Some examples of phase transitions in soft matter
		Self assembly of amphiphilic molecules:
		Jamming transition
	Materials studied
		Pluronic F127
		Pectin gels
		Cornstarch suspensions
	Experimental studies
		Rheology
		Dynamic Light Scattering
	Chaotic dynamics in dissipative systems:
	Thesis Organization
References
Experimental Techniques and Data Analysis
	Introduction:
	Experimental techniques:
		Rheological measurements:
		Dynamic light scattering:
		Cryo-SEM (scanning electron microscopy) measurements:
		Fluorescence measurements.
		Small angle X-ray scattering (SAXS).
	Data Analysis:
		Analysis of observed chaotic data:
References
Jamming Behavior of Triblock Copolymer Solutions and Triblock Copolymer-Anionic Surfactant Mixtures
	Introduction
	Sample preparation
	Results
	Conclusions
References
Encapsulation of drugs in Pluronic F127 Micelles: The Effects of Drug Hydrophobicity, Solution Temperature and pH
	Introduction
	Sample preparation
	Results and Discussion
	Conclusion
References
Formation and Rupture of Ca2+ Induced Pectin Biopolymer Gels
	Introduction
	Sample preparation
	Results and Discussions
		Gel Formation:
		Gel Rupture:
	Conclusions
References
Chaotic Rheological Response in the Shear Banding Region of Cornstarch Suspensions
	Introduction
	Sample Preparation
	Results and Discussions
	Conclusion
References
Summary and Future Directions
                        
Document Text Contents
Page 1

Dynamic Light Scattering and Rheological

Studies of some Micellar Copolymer Solutions,

Biopolymer Gels and Concentrated Colloidal

Suspensions


BY


RAJIB BASAK





A THESIS SUBMITTED TO THE JAWAHARLAL NEHRU UNIVERSITY

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY




DEPARTMENT OF SOFT CONDENSED MATTER

RAMAN RESEARCH INSTITUTE

BANGALORE 560 080

JUNE 2014

Page 2

© Rajib Basak, 2014.

Typeset in LATEX 2" .

ii

Page 89

3.3 RESULTS

0 2 4 6 8 10 12

-2

0

2

3.0x10
-4

6.0x10
-4

9.0x10
-4

0.08

0.16

0.24



q2[nm-2]

1/
t R

[
m
s-

1 ]





ln [t ]

ln
(-

ln
(C

[t
])

)





1

0.05

0.12

1 10 100 1000 10000 100000

10
-3

10
-2

10
-1

10
0

1 10 100 1000 10000

0.2

0.4

0.6

0.8

1.0





C
[t

]

Delay time [ms]





C
[

t]

t [ms]

(a) (b)

FIGURE 3.6: In (a), the normalized intensity autocorrelation functions C[τ] are plot-
ted on a logarithmic-logarithmic scale for a pure F127 sample (�), for F127-SDS mix-
tures containing 10 mM (◦), 300 mM (4), 500 mM (∇) SDS and a dilute aqueous
solution of 95 nm polystyrene spheres (shown by dashed line) at T = 40◦C and θ =
90◦. The concentration of the F127 solution is fixed at 0.25 g/cc. The inset shows the
linear-logarithmic plots of C[τ] vs. τ for the same data sets, with the corresponding
exponential fits to the faster relaxation processes shown by solid lines (data sets are
shifted vertically for better visibility). The data of 3.6(a) is replotted as ln(-ln(C[τ])) vs.
ln[τ] in 3.6(b). The inset of 3.6(b) shows the linear fits to 1/τR (extracted from the
exponential fits) vs. q2 for all the samples.

samples (the F127 solution and the F127-SDS mixture with 10 mM SDS, de-

noted by red squares and blue circles respectively) do not show complete de-

cays to the noise level within the experimental time window. This confirms the

slowing down of the slow relaxation times of these samples due to the kinetic

constraints experienced by the close-packed micelles. For F127-SDS mixtures

with higher SDS content (300 mM and 500 mM, denoted by magenta up trian-

gles and green down triangles respectively), C[τ] shows a comparatively faster

decay within the experimental time window, indicating that the relaxation times

of mixtures with higher SDS content are much faster than those with lower SDS

content. The data of Fig. 3.6(a) is recast in Fig. 3.6(b) where ln(-ln(C[τ])) is

plotted vs. ln[τ]. For all the samples, the initial part of the plot comprises a

straight line of slope 1, indicating a fast monoexponential component in the

sample dynamics. For the pure F127 solution and the F127-SDS mixtures,

77

Page 176

7. SUMMARY AND FUTURE DIRECTIONS

network at CaCl2 concentrations greater than Ccr. Rheological studies of gel

breakage show that the critical stress required to break the gel network de-

creases with increase in CaCl2 concentration. Further rheological experiments

reveal that increasing CaCl2 concentration increases the elasticity of the gel,

but decreases the limit of linearity of the strain response of the samples. Using

a scaling analysis, it is shown that ion-mediated pectin gels can be categorized

to lie in the ‘strong link’ regime, where interfloc links are stronger than intrafloc

links. To complement this work, the study of the dynamics of pectin gels after

gelation need to be performed. For this investigation, DLS experiments per-

formed over much longer delay times, along with diffusive wave spectroscopy

(DWS) measurements, may be employed. Such DLS and DWS experiments

on pectin gels may also be performed while simultaneously shearing the pectin

gel in a shear cell. Such studies will help to address the issue of the correla-

tion between the mechanical properties and microscopic dynamics of bipoly-

mer pectin gel solutions.

Cornstarch suspensions are known for their complex mechanical response.

Chapter 6 presents rheological measurements on concentrated cornstarch

suspensions. The flow curve measurements on cornstarch suspensions show

a shear thinning region, followed by a shear thickening and a shear banding

region with increasing shear rate. The extents of the different regions of corn-

starch suspensions depend upon the concentration and sample volume. Small

angle light scattering experiments, which are simultaneously performed with

rheology, show huge intensity fluctuations in the shear banding region. Non

linear time series analysis of the stress fluctuation data acquired from sheared

cornstarch samples lying in the shear banding region indicates the presence

of rheological chaos. The route to rheochaos in the shear banding region of

cornstarch suspensions remains to be explored. For this investigation, SALS

and stress fluctuation data have to be acquired and analyzed. The power spec-

tra of fluctuations near the critical shear rate where the thickening to banding

164

Page 177

transition occurs have to be investigated.

165

Similer Documents