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Goal: Understand Principles of Rheology:
stress = f (deformation, time) NeoHookean: Newtonian:
• shear thinning (thickening) • time dependent modulus G(t)
• normal stresses in shear N1
• extensional > shear stress u>
Key Rheological Phenomena
Gτ B - I = 2D
Outline
1. Definitions
2. Stress relaxation
3. Maxwell element
4. Dynamic moduli
5. Compliance
6. Polymer solutions, gels, and melts
Definitions
t log t
log G
Stress: Strain: Strain rate:
(shear) modulus: G = / viscosity: = /
stress relaxation modulus: G(t,) = (t,) /
linear response: small enough so that G is independent of
Limiting cases
time
time
Hookean
time
Newtonian
time
viscoelastic solid
viscoelastic liquid
Maxwell Element
o el vis
Ý o 0 Ý el Ý vis
0 1
GoÝ
1
o
(t) (0) exp( t /)
(0) Go o
o / Go
Go o
G(t)
t
Dynamic shear modulus
o sint Ý o cost
o sin(t )
o ' sint o"cost
G' o '
o, G"
o"
o, tan
G"
G'
Elastic “storage” modulus, viscous “loss” modulus, loss tangent
'
"
time
.
Maxwell element
G' Go22
122 ; G" Go
122
Limiting slopes:
low , G’ ~ 2 , G” ~
high , G’ ~ 0 , G” ~
10-4
10-3
10-2
10-1
100
101
10-3 10-2 10-1 100 101 102
G'/Go
G"/Go
Complex notation
G*() *
* G' i G"
*() *
Ý * ' i "
G* i*; G' "; G" '
Dynamic viscosity:
* 2 2 1/2( ' " ) /G G
Maxwell element
10-4
10-3
10-2
10-1
100
101
10-3 10-2 10-1 100 101 102
G'/Go
G"/Go
10-4
10-3
10-2
10-1
100
101
10-3 10-2 10-1 100 101 102
'/ Go
''/ Go
Creep compliance
J(t) (t)
o
(t) el vis o
Go
1
odt
J(t) 1
Go1 t
Maxwell element:
J(t) J eo
t
General LVE:
time
o
time
J
1/
Jeo
Jeo
Outline
1. Definitions
2. Stress relaxation
3. Maxwell element
4. Dynamic moduli
5. Compliance
6. Polymer solutions, gels, and melts
Meet the suspects6 typical materials
Surfactant Solution
Dilute Polymer Solution
Entangled Polymer (M/S)
EmulsionSuspension
Gel
G’, G” for a single flexible chain in a solvent
P. E. Rouse, Jr. J. Chem. Phys. 21, 1872 (1953)
B. H. Zimm, J. Chem. Phys. 24, 269 (1956)
www.joogroup.com/graphics/single_poly_cg.jpg
Random coil Bead-spring model
G’, G” for a high M chain in an oligomer
10-1100101102103104105106100101102103104105106G', G" (Pa) aTPS-650,0003.1% in PS-3,000Tref = 180 ºC
10-1
100
101
102
103
104
105
106
100 101 102 103 104 105 106
G',
G"
(Pa
)
aT
PS-650,000
3.1% in PS-3,000
Tref
= 180 ºC
= G”/
“Internal modes”
Longest relaxation time“Terminal” regime
G” always > G’
D. Tan, unpublished results
G’, G” for a single chain in a theta solvent
Sahouani and Lodge, Macromolecules, 25, 5632 (1992)
10-9
10-8
10-7
10-6
10-5
10-4
10-2 10-1 100 101 102 103
[G'] R
, [G
"]R
1
Polybutadiene in DOP
T = 18.0 oC ()
Zimm theory(Dynamic scaling, = 0.50
Polyisoprene: an entangled melt
101
102
103
104
105
106
107
10-2 100 102 104 106
G' a
nd G
" ,
Pa
aT
Polyisoprene
Mw
= 80,000
Tr = 20
oC
G'
G"
J. C. Haley, Ph. D. Thesis, Univ. Minn., (2005)
New solid-like regime
QuickTime™ and a decompressor
are needed to see this picture.
The “Gel” Samples Can be Interpreted Simply
Worm-like micelles
Bernheim-Groswasser, A., Zana, R., and Talmon, Y., J. Phys. Chem. B 104, 4005 (2000).
4 nm
The “Gel” Samples Can be Interpreted Simply
Maxwellian response
100 mmol cetyl pyridinium chloride60 mmol sodium salicylate 100 mmol sodium chloride
QuickTime™ and a decompressor
are needed to see this picture.
Candau et al., J. Phys. IV, 3, 197 (1993).
Gelation of ABA triblock copolymers
G’, G”
Liquid
Physical gel
Gel point
C > C*
Triblock copolymers
C << C*
SOS gel point in an ionic liquid
0.001
0.01
0.1
1
10
100
1000
G',
G"
(Pa
)
0.01 0.1 1 10 100
(rad/s)
G' G''10 wt% 4 wt% 1 wt%
G' ~ 2
G'' ~
G'=G'' ~
G' ~
A
O
Y. He, P. G. Boswell, P. Bühlmann, T. P. Lodge, J. Phys. Chem. B, 111, 4645, (2007)
The “Gel” Samples Can be Interpreted Simply
Newtonian droplets in a Newtonian fluid
I. Vinckier et al., J. Rheol. 40, 613 (1996)
10% low molar mass PIB in low molar mass PDMS
Polyisoprene: an entangled melt
101
102
103
104
105
106
107
10-2 100 102 104 106
G' a
nd G
" ,
Pa
aT
Polyisoprene
Mw
= 80,000
Tr = 20
oC
G'
G"
J. C. Haley, Ph. D. Thesis, Univ. Minn., (2005)
Meet the suspects6 typical materials
Surfactant Solution
Dilute Polymer Solution
Entangled Polymer (M/S)
EmulsionSuspension
Gel
NIST standard
11 wt% high MW PIB (MW~106, Aldrich) in Pristane
LVE properties
Entangled polymers
Data from Snijkers et al, J. Rheology, 53, pp. 459-480 (2009)
L. Raynaud et al, J. Coll. Int. Sci, 81, 11 (1996))
Colloidal Suspension
(rad/s)
10-2 10-1 100 101 102
G' (P
a)
10-2
10-1
100
101
102
103
104
0.4210.4260.4370.4520.4550.4710.4820.5020.5150.534
φc
Polystyrene-butylacrylate latices