PHASE BEHAVIOR AND 

MORPHOLOGY OF 

MICROEMULSIONS IN A POLYMERSURFACTANT SYSTEM

Alexa B Cano

NIST Center for Neutron Research, 

Neutron Condensed Matter Science Group

2018 SURF Colloquium
OVERVIEW

• Microemulsions and phase morphologies

• The Pluronic system

• Using SANS to determine structural phases

• Rheological properties related to structural 

phases
MICROEMULSIONS

• Ternary system of oil, water, and surfactant

• Self assembly

• Size domain: ~1-100 nm

• Prominent roles in pharmaceutical and industrial applications

• Understanding nanostructures is critical for understanding bulk material 

properties

https://sites.ualberta.ca/~csps/JPPS8(2)/C.Rangel-Yagui/solubilization.htm https://www.semanticscholar.org/paper/Lyotropic-liquid-crystal-systems-in-drug-delivery%3A

-Kim-Jahn/020c104ac5d99038e0493d684489fa737ad2bede
LYOTROPIC LIQUID 

CRYSTALLINE MESOPHASES

• Oil-in-water or water-in-oil (reverse microemulsion)

• Intermediate phases depending on surface curvature

• Preferred surface curvature is given by volume ratio between 

hydrophobic and hydrophilic domains

https://www.semanticscholar.org/paper/Lyotropic-liquid-crystal-systems-in-drug-delivery%3A-Kim-Jahn/020c104ac5d99038e0493d684489fa737ad2bede
PLURONICS AS POLYMERIC 

SURFACTANTS

• System of interest: Pluronic P84 – p-xylene – water

• 60 wt% and 70 wt% pluronic microemulsions

• Exhibits many phases

• Phase boundaries may be identified by turbidity 

in response to temperature

https://www.acsu.buffalo.edu/~m27/projects.html

http://iopscience.iop.org/article/10.1088/0957-

4484/17/13/007

p-xylene
DETERMINATION OF PHASE 

BOUNDARIES

Increasing oil to water ratio

60-40-0

60 wt% P84 at 35°C

60-23-17 60-27-13 60-29-11 60-31-9 60-33-7

surfactant-oil-water

Increasing oil to water ratio

60-0-40 60-2-38 60-5-35 60-14-26 60-19-21
PHASE BOUNDARY 

TEMPERATURE DEPENDENCE
SMALL ANGLE NEUTRON 

SCATTERING (SANS)

https://www.ncnr.nist.gov/programs/sans/pdf/part_ii_sans_nuts_and_bolts.pdf

For elastic scattering,

https://www.ncnr.nist.gov/summerschool/ss10/pdf/SANS_NR_Intro.pdf

• Beam of neutrons scatters off sample at an angle and onto detector

• Scattered distance (Q) is measured in reciprocal space

• Q reveals structures and dimensions within sample
CRYSTALLOGRAPHY

• Mesophases can be liquid 

crystalline in structure 

• Periodicity of liquid crystal 

results in Bragg reflections from 

different sets of crystallographic 

planes

• Reflections probed by SANS 

serve as structure IDs for 

mesophases

https://www.researchgate.net/profile/David_Mannock/publication/6309243/figure/fig2/AS:28124453855641

9@1444065331801/A-schematic-drawing-of-various-lipid-water-mesophases-and-states-of-aggregationadopted.png

V1

H1 La
REVERSE BICONTINUOUS 

CUBIC MESOPHASE

0.00 0.05 0.10 0.15 0.20 0.25 0.30

1

10

I(Q) (1/cm)

Q (1/A)

0 1 2 3 4

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

211 1.1

420

422

332

321

P84: 70%

p-xylene: 16%

water: 14%

T=25°C

hkkkk → qq =

2ππ h2 + kk2 + 2

aa

• The relative peak positions identify 

the phase

• The q values of peaks are a function 

of the plane indices (hkl) and the unit 

cell dimension (a)
IDENTIFYING PHASE 

TRANSITIONS USING SANS

7

8

9

1

2

3

4

5

6

7

8

I(q)

0.00 0.05 0.10 0.15 0.20 0.25

q (ᅤ-1

)

 T=25C

 T=65C

 T=75C

P84: 60%

p-xylene: 33%

water: 7%

• Reverse micellar cubic at 

25°C

• Phase transition around 

65°C

• Reverse micellar solution 

at 75°C

Gel at 25°C Fluid at 75°C
PHASE BOUNDARY 

TEMPERATURE DEPENDENCE
RHEOLOGY

• Small-Amplitude Oscillatory Shear

• Elastic modulus G’

• Viscous modulus G’’

• Moduli expected to change upon phase transition

http://plate.goodwheel.site/parallel-plate-geometry-rheometer/
PHASE BOUNDARY 

TEMPERATURE DEPENDENCE
RHEOLOGY RESULTS

• Example of transition: 70 % P84, 10 % oil, 20 % water

• Transition at ca. 50 °C

• From lamellar gel to bicontinuous gel

• Bicontinuous gel has higher connectivity and is therefore stronger

20 30 40 50 60 70

-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

G',G'' (Pa)

Temperature (°C)

G'

G''

1 10 100

1000

10000

 G',25C

 G'',25C

 G',35C

 G'',35C

 G',65C

 G'',65C

G',G'' (Pa)

Angular Frequency (rad/s)

P84: 70%

p-xylene: 10%

water: 20%

P84: 70%

p-xylene: 10%

water: 20%

ω = 150 rad/s
RHEOLOGY RESULTS

• The storage modulus generally increases with connectivity:

0D 1D 2D 3D 3D

Liquid Gel Gel Gel Gel

• Bulk rheological properties can be explained by mesophase nanostructures

< < < < 
CONCLUSION

• Temperature dependent phase behavior determined from 

SANS

• Connectivity of mesophase directly relates to rheological 

properties

• Future study: Relate connectivity and rheology to electrical 

conductivity
ACKNOWLEDGEMENTS

• Mentors: Grethe Jensen and John Riley

• Joe Dura, Julie Borchers and the staff at the NIST Center 

for Neutron Research

• National Science Foundation

• Center for High Resolution Neutron Scattering