Shear-induced onion formationof complex bilayer lamellar phase

Nagaoka University of Technology
S. Fujii

Shear induced onion phase
LαCylinder
Buckled LαOnion

SDS / Dodecane / Pentanol / Water System
O. Diat, D. Roux, F. Nallet, (1993)
Mesoscopic structure
C10E3/H2O system
Rheology of Lα phase

Rheometry + SANS
W. Richtering, et al., (2003)

Onion is defects ?
Focal Conic Domain

FCD I

FCD II

Oily streak defectOnion

What is difference between defect and onion ?

Rheology of lamellar phase modified by polymer
H. E. Warriner, et al., (1997)

Lα gelLα
Segregation of polymer chains

Defect-induced gelation

Complex bilayer lamellar phase＋CiEj nonionic surfactant

PEO
PPO

Guest component

PEO
C12E5/Pluronic/H2O

Repulsive force due to the exclusive volume effect
Increase of the effective bilayer thickness

Increase of the bending rigidity(in microscopic scale)

T. Taniguchi

M. Imai, et al., JCP (2006)

Dislocations in Smectic LC
Edge dislocation

Screw dislocation

Edge and Screw dislocations form loops.

Defect-mediated rheology of SmA•

Shear-thinning behavior

Surfactant lyotropic lamellar phase
C12E5 (35wt%)

C.-Y. D. Lu, et al., EPJE (2008)

m=1.45m=1.5Sample
Nonionic surfactant : C10E3
Tri-ethyleneglycol mono-n-decyl ether

Concentration 40wt%
d〜3.3nmdW〜3.5nm

Polymer mole fraction(= 6.87 x 10-3 mol)Pluronic （triblock copolymer）
Degree of polymerization
PEO
PPO
PEO

B. Cabanne, et al., (1993)

Different confinement regime of polymer in the water layer
C. Ligoure, et al., (1997)

dW = 3.5nm

Shear rate dependence of viscosity (C10E3/H2O)
3s-1

5s-1

10s-1

20s-1

Shear-thickening is a sign of the onion formation.

C10E3 / Pluronic (XP=1mol%) / H2O system
NEO = 17, 27, 37
NPO ~ 60
NEO = 17

1/3

NEO = 27
1/3

NEO = 37
1/3

Increasing NEO hinders shear induced onion formation.
Shear thinning behavior at low shear rates,

Shear thinning behavior … dislocation loop motion

Polymer concentration dependence of Lα/Onion transition
NEO = 37, Rg = 1.2 nm
NPO = 60, Rg = 1.8 nm

η /PasPluronic P105 (c*=1.1mol%)

1/3
1/3

Induction of the onion formation
Inhibition of the onion formation
No Onion formation

At low polymer concentration,
the onion phase is easily induced by shear.

Viscoelasticity of polymer-doped lamellar phase
G’ and G’’ measurements after pre-shear at 1s-1 (in the lamellar phase)

Polymer segregation (inhomogeneous distribution) on the membrane causes
the increase in the defects density.
High viscoelasity gives the Onion formation.

Development of modulus with pre-shear

0.2%

0.4%

1.0%

Shear modulus develops with pre-shear rate.
C10E3/H2O
Conc.=40wt%

Defect density increases with shear.

Viscolasticity of lamellae/onion transformation process

Onion formation is controlled by defect density ?
G’ starts to increase at the tenth of the critical shear rate.

Bending modulus and Critical shear stress

At XP=1mol%,

Critical shear stress can be scaled by the increment of the bending modulus.

Summary
Shear induced onion formation can be controlled by polymer.
Defect formation triggers the onion formation.
Defect density depends on the polymer concentration.
Defect density increases with pre-shear.

Shear stress controls the shear induced onion formation behavior.