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Presentation Spring 2015
1. Rheology of Hard Sphere/Soft
Sphere Mixtures
Emily Jeng
5/6/15 Presentation
2. Rheology resultsMixture of Hard and Soft Spheres
2
Polybutadiene star polymers,
with MW~67000g/mol(soft)
and 1270g/mol(Hard)
dissolved in Squalene.
Addition of Hard spheres leads
to a transition from glassy to
liquid to glassy state.
Truzolillo, PRL (2013).
3. Rheology resultsMixture of Hard and Soft Spheres
3
Core: Silica ~10nm
Corona: PEG,
MW~550 g/mol
Corona: PEG,
MW~2k,5k and 10k g/mol
Systems with different xHS=(φHS/(φHS +φsoft))
Where, HS≡ Silica with PEG 550 corona
5. 0
2
4
6
8
10
12
14
16
1.00E-02 1.00E-01 1.00E+001.00E+011.00E+021.00E+03
G''/G''[slope=0]
Strain %
Relative Heights of the Loss Modulus:
550-2k
20-80
40-60
50-50
60-40
80-20
0.00E+00
5.00E+05
1.00E+06
1.50E+06
2.00E+06
2.50E+06
0 0.2 0.4 0.6 0.8 1
G'
Xhs
Storage Modulus vs Concentration of
Hard Spheres, 2k systems
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 0.2 0.4 0.6 0.8 1
tanδ
Xhs
Tanδ vs Concentration of Hard
Spheres, 2k systems
6. 0
2
4
6
8
10
12
0.01 0.1 1 10 100 1000
G''/G''(slope=0)
Strain %
Relative Heights of the Loss
Modulus: 550-5k
(10-90)
20-80
50-50
60-40
80-20 0.00E+00
1.00E+05
2.00E+05
3.00E+05
4.00E+05
5.00E+05
6.00E+05
7.00E+05
0 0.2 0.4 0.6 0.8 1
G'
Xhs
Storage Modulus vs Concentration of
Hard Spheres, 5k systems
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 0.2 0.4 0.6 0.8 1
tanδ
Xhs
Tanδ vs Concentration of Hard
Spheres, 5k systems
7. 0
1
2
3
4
5
6
0.01 0.1 1 10 100 1000
G''/G''(slope=0)
Strain %
Relative Height of Loss Modulus: 550-
10k
20-80
40-60
60-40
70-30
80-20
0.00E+00
2.00E+05
4.00E+05
6.00E+05
8.00E+05
1.00E+06
1.20E+06
1.40E+06
0 0.2 0.4 0.6 0.8 1
G'
Xhs
Storage Modulus vs Concentration of
Hard Spheres, 10K systems
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0 0.2 0.4 0.6 0.8 1
tanδ
Xhs
Tanδ vs Concentration of Hard
Spheres, 10k systems
Series1
8. Conclusion
• Two-step yielding in 10k systems
– Variation in length scales of PEG 550 and PEG 10K is
very high and distinguishable
• Effect of increase in concentration of hard
spheres
– Relative heights of loss modulus increase and then
decrease
– Similar trend in storage modulus
– Tan delta decreases and then increases
– Addition of hard spheres leads to jamming of system
and then unjamming
Editor's Notes
Lower molecular weight PEG with high molecular weight PEG in NOHMs
Studies show interesting transitions on mixture of hard spheres and soft spheres
(high MW Star polymers with low MW star polymers (acts as the hard spheres))
Varied concentration of hard spheres
Measure modulus of system
As they go on adding hard spheres system transitions from repulsive glass to a liquid and back to a glassy state
State diagram of how they transition
Small amount of hard spheres, system is still in glassy state
Adding more, hard spheres pushing soft spheres together, more space (free volume), hard spheres can move around, transition to a liquid state
Add more hard spheres, a lot of compactness, neither soft nor hard spheres can move around- arrested state
Gp storage modulus
T relaxation time
Experimental phase diagram constructed of different concentrations of hard spheres with soft spheres
Motivation with NOHMs
Size of the silica is the same
Varying realitive fraction of hard spheres (core volume fraction of hard spheres divided by core volume fraction of all the spheres)
Size of the silica is the same
Varying realitive fraction of hard spheres (core volume fraction of hard spheres divided by core volume fraction of all the spheres)
Xhs increases, relative height of loss modulus goes up then down
Tan delta and storage modulus follow the same trend
Showing signature shear measurements, as has been seen before in NOHMs, the increase in strain shows a maxima in G’’ and then a crossover where G’’>G’
(not showing all the graphs)
Bigger change in storage modulus for 5k compared to 2k
Very flat at first, then peaks increase a lot more
2 step yielding, similar trends in loss modulus and storage modulus and tan delta
Increases when adding hard spheres, then decreases
Effects are more pronounced
