Chasing Extreme Morphologies with Ed

R. Mezzenga, J. Ruokolainen,

N. Lynd, F. Oyerokun, W. Shi, K. Delaney, Q. Demassieux

C. Creton, A. Avgeropoulos, C. Ntaras, A. Hamilton, Y-X. Liu

Glenn H. Fredrickson, Edward J. Kramer

Departments of Chemical Engineering and Materials

Materials Research Laboratory

University of California, Santa Barbara

17 years together at UCSB, 55+ papers, countless co-

advised students and postdocs

Outline

High internal phase polymeric emulsions (2002-2004)

Micron scales, non-equilibrium structures

Miktoarm copolymer alloys (2007-present)

Nanometer scales, equilibrium structures

In both cases, we were focused on achieving unusual

cellular morphologies with a discrete phase present up to

very high volume fractions

High Internal Phase Polymeric Emulsions

Raffaele Mezzenga, Janne Ruokolainen Glenn H. Fredrickson

Edward J. Kramer

Departments of Chemical Engineering and Materials

Materials Research Laboratory

University of California, Santa Barbara

Research supported by PolyE Inc.

Time period: 2002 - 2003

4

High Internal Phase Emulsions

(HIPE)

• An oil, water, and surfactant mixture having: – One continuous phase

and one discrete phase

– The discrete phase is present at a volume fraction beyond close packing, > 75%

• HIPEs are widely used in the food and personal care industry

1-100 μm

5

High Internal Phase Polymeric

Emulsion: HIPPE

• The HIPE concept can be extended to the situation of an

all-polymer composition:

– Oil Polymer A

– Water Polymer B

– Surfactant A’-B’ copolymer

• The HIPPE concept has been partially realized in

commercial porous products, e.g. synthetic (PVOH)

chamois cloths

• Other novel all-polymer emulsion morphologies have been

realized, but the HIPPE concept has not been well

exploited

HIPPE

6

Potential Applications of HIPPE

Structures

• Continuous minor phase creates opportunities for exceptional and controlled transport properties at low cost: – Ion or electron-conducting films or membranes

– Films with barrier properties or chemical resistance

– Membranes with unusual dielectric properties, e.g. polymer electrets

– Controlled release materials and structures: medical and agricultural applications

7

Strategies for Producing HIPPE

Compositions

• Selective solvent casting of A + B + A’B’

• Selective solvent casting of particle-A + A’B’ + B

• Selective solvent casting of particle-A + A’B’

• Melt processing of A + B + A’B’ (Never realized)

8

Material Selection

Non-polar polymer:

Polystyrene (PS)

N

Polar polymer:

Poly-2-vinylpyridine (PVP)

One of Ed’s favorite

systems!

9

Non-equilibrium solvent preparation:

-PolyHIPE via emulsification-

Materials Procedures

(A continuous/B discrete)

Polymers

Solvents

• Polystyrene (PS) • Poly2vinylpyridine (PVP)

PS-PVP block copolymers

• PS-PVP1, fPVP=0.84

• PS-PVP2, fPVP=0.13

Common solvent for PS and PVP: Chloroform

Good solvents for PS: Toluene, Cyclohexane

Good solvent for PVP: Ethanol

+ + solvent A A 1)

+ solvent B B 2)

A

3)

10

PVP/PS/PS-PVP1 blend morphology

from common solvent casting

+

+ Chloroform + 1:5 1:1 Chloroform

PS-PVP1

MW = 70000

PVPMW=8000

PSMW=35000

PVP: wet brush, low volume fraction

PS: dry brush, high volume fraction ( )

Mix

2 μm

PVP phase (dark) is maintained dispersed

within a continuous PS phase (clear)

(1)

11

+

+ Ethanol + 1:5 1:1 Toluene

PS-PVP1

PVPMW=8000

PSMW=35000 Mix

Emulsification process

20 μm

Liquid emulsion Emulsion after solvent removal

1 μm

PVP/PS/PS-PVP1 blend morphology

from selective solvent casting

(2)

12

+

+ Toluene + 1:5 1:1 Ethanol

PS-PVP2

MW=114000

PSMW=9000

PVPMW=42000 Mix

NO EMULSIFICATION !

20 μm

Still liquid…. …after solvent removal

2 μm

PVP/PS/PS-PVP2 blends from

selective solvent casting

13

PVP/PS/PS-PVP2 Poly(HIPE):

emulsion from cyclohexane

+

+ Cyclohexane + 1:5 1:1 Ethanol

PS-PVP2

PSMW=9000

PVPMW=42000 Mix

EMULSIFICATION OCCURS !

Correlation function EmulsionCorrelation function

1 10 100 1000 104

105

6.5 105

7 105

7.5 105

8 105

8.5 105

9 105

9.5 105

1 106

0.2 % PS-PVP

in Cyclohexane at 50 C

(s)

c()

2º

EMULSIFICATION OCCURS !

Correlation function EmulsionCorrelation function

1 10 100 1000 104

105

6.5 105

7 105

7.5 105

8 105

8.5 105

9 105

9.5 105

1 106

0.2 % PS-PVP

in Cyclohexane at 50 C

(s)

c()

2º

1 10 100 1000 104

105

6.5 105

7 105

7.5 105

8 105

8.5 105

9 105

9.5 105

1 106

0.2 % PS-PVP

in Cyclohexane at 50 C

(s)

c()

2º

Must be above CMC in

copolymer-rich solution!

14

+

+

PS beads (x-linked) and PS-PVP1

are mixed in Ethanol

Precipitation

15% PS-PVP

85% PS

0.8 μm

After solvent evaporation

PS colloid-block copolymer dispersions

15

Annealing and morphology evolution

Cohesive forces and copolymer packing frustration drive particle

deformation

250 nm

Samples were annealed under vacuum for 10 h at 140 °C

(Tg of PS-PVP = 100 °C, Tg of PS colloid = 108 °C )

100 nm

16

Continuous phase: percolation threshold for

proton transport

400 nm

500 nm

N

0

1 10-7

2 10-7

3 10-7

4 10-7

5 10-7

6 10-7

0 0.05 0.1 0.15 0.2

Conduct

ivit

y (

S/c

m)

PVP volume fraction

17

Double percolation: doped PANI electron

conductive blends

The percolation threshold fp for PANI in a blend with PVP should be reduced by the continuous phase fraction φ when confined to the continuous scaffold

PANI

18

Double percolation in PANI-PSA + PS

colloids + PS-PVP (cast from formic acid)

PANI-PSA

+ PVP

fPANI = 0.01, 0.05, 0.20

fp = 0.12

PANI-PSA

+ PS-PVP

+ PS

particle

1% PANI 3% PANI

fp = 0.01

PSA: phenol

sulfonic acid

19

Barrier coatings (never realized!)

Exploit the barrier or chemical resistance properties of a high performance polymer in the continuous phase, while diluting it by a cheaper or more robust polymer

PS PVDF

Example: PS-PVDF barriers

PS latex PS-PMMA

+ +

PVDF

(PMMA-PVDF ) < 0

20

Remaining Opportunities

Demonstrate barrier coatings in a solvent base

Find a solvent-less, melt processing route to Poly-HIPEs would enable

bulk material applications!

21

Papers and Patents • R. Mezzenga, J. Ruokolainen, G. H. Fredrickson, E. J. Kramer, D. Moses, A. J.

Heeger, O. Ikkala, “Templating Organic Semiconductors via Self-Assembly of

Polymer Colloids,” Science 299, 1872 (2003).

• R. Mezzenga, G. H. Fredrickson, E. J. Kramer, “Tailoring Morphologies in Polymeric

High Internal Phase Emulsions by Selective Solvent Casting,” Macromolecules 36,

4457 (2003).

• R. Mezzenga, G. H. Fredrickson, and E. J. Kramer, “High Internal Phase Polymeric

Emulsions by Self-Assembly of Colloidal Systems,” Macromolecules 36, 4466 (2003). • “High Internal Phase Polymeric Emulsion Composition,” G. H. Fredrickson, US

6,897,247, Issued May 24, 2005

• “Process for Creating High Internal Phase Polymeric Emulsion Compositions,” R.

Mezzenga, G. H. Fredrickson, and E. J. Kramer, US 7,432,311, Issued October 7,

2008

Miktoarm Copolymer Alloys

E. J. Kramer, F. Oyerokun, Nate Lynd, Weichao Shi,

K. Delaney, A. Hamilton, Q. Demassieux, C. Creton,

A. Avgeropoulos, C. Ntaras, Y-X. Liu, G. H. Fredrickson,

Departments of Chemical Engineering and Materials

Materials Research Laboratory

University of California, Santa Barbara

Time period: 2007 - 2016

“bricks-and-mortar” phase

Background: Styrenic Copolymer Thermoplastic Elastomers

•SBS, SIS, SEBS, … are triblock elastomers commercialized in the 1970s by

Shell Chemical, now Kraton Polymers, which sells > $1B/yr

B

S

S S

In conventional SBS triblock

copolymers, the PS domains are only

discrete for fS < 0.3

elastic plastic

Kraton’s question (~2007): Is it possible to design block copolymers that maintain the

hard phase (PS) discrete at volume fractions greatly exceeding 30%, and in combination

with high toughness and recoverable elasticity?

--Motivation (high price of B and I; thermal stability of S)

The “Mikto-arm” Design

Our design is based on using two polymer physics principles in concert for driving interfacial

curvature towards PS: - Mikto-polymer frustration (Milner, Gido, Pochan)

- PS block polydispersity (Milner-Witten-Cates, Matsen)

•Commercially viable synthesis by

coupling living PS with living PS-PB

PS

PB

AB2 mikto-polymer Asymmetric ABA

Poor mechanical strength! Should be strong, but what are morphologies

and properties?

A concept patent and theoretical

study – properties unexplored!

D. Handlin, P. Pasman, G. H. Fredrickson,

U.S. 20,090,234,059 (2009)

N. A. Lynd et. al., Macromolecules 43, 3479 (2010)

SCFT Phase Diagram (n=3 arms)

N =40

Block length asymmetry:

Optimal design:

¼ 0.9, PS phase discrete at fS > 0.6!!

We conducted a theoretical study using unit cell self-consistent field theory

(SCFT) to assess the equilibrium morphology of pure A(BA)3 mikto-polymers

N. A. Lynd et. al., Macromolecules 43, 3479 (2010)

Experimental Effort ~2011-2015

We collaborated Prof. Apostolos Averopoulos and student Cristos Nataras of the

University of Ioannina in Greece, who supplied ~100 g samples of carefully

prepared miktopolymers.

Ed Kramer joined the team and postdoc Weichao Shi led the characterization and

mechanical analysis at UCSB. Costantino Creton and student Q. Demassieux

joined subsequent to Ed’s passing.

Samples from Greece have ¿ =

0.89, n =1, 2 and 3, and PS

fractions varying from 20% to

80% in 10% increments.

All were carefully

fractionated/purified

80K PS

10K PS

PS-PI-PS Triblock:

PS-(PI-PS)3 Mikto-

polymer:

Characterization: TEM

Claude Denier (MS), Dr. Weichao Shi

ÁS = 0:5

LAM

CYL TEM and SAXS consistent with SCFT

prediction of a cylindrical morphology! Macromolecules 2014, 47, 2037−2043

Characterization: Cyclic Tensile Tests

Necking at small strain

PS-PI-PS Linear triblock (50% PS)

Macromolecules 2014, 47, 2037−2043

Characterization: Cyclic Tensile Tests

No necking at small strain

PS-(PI-PS)3 Mikto-polymer (50% PS)

450% strain!

Macromolecules 2014, 47, 2037−2043

Higher Hard Phase Volume via Blends

Even more extreme compositions with a discrete PS phase – a nanoscale analog

to a polymeric “High Internal Phase Emulsion” – might be achievable by blending

in PS homopolymer!

Mikto-blend: • 10 nm scale • Equilibrium • Tough, elastic?

HIPPE: • 1 μm scale • Non-equilibrium • Brittle

??

Facets are with precedent in ABCs, but in AB systems?

n=3 Miktoarm (40%PS) + hPS (10.5K)

0% hPS 10% 20% 30% 40%

50% 60% 70% 80%

n=3 Miktoarm (40%PS) + hPS (21K)

0% hPS 10% 20% 30% 40%

50% 60% 70% 80% 90%

“Bricks and Mortar” phase

Weichao Shi

Miktoarm (40%PS) + hPS (44K)

0% hPS 10% 20% 30% * 40%

50% * 60% 70% 80% 90%

Weichao Shi

Morphology Diagram

cylinder lamella

bricks-mortar

micelle

macro

Fluctuation-stabilized??

Weichao Shi

Weichao Shi

Bricks-and-Mortar Phase has continuous or near-continuous elastomeric (PI) domains

Weichao Shi

SCFT Phase Diagrams

Andrew Hamilton

As expected, SCFT simulations reveal asymmetric phase diagrams with a

smooth order-disorder boundary. No indication of a disordered B&M phase is

present.

The B&M phase must thus arise from thermal fluctuations destroying (at least)

long-range positional order from a reference LAM or HEX phase.

fA = 0.40, 21K

χN

B&M

Fluctuation Scenarios: B&M Phase Emergence

Scenario 1: B&M isotropic and a

continuous extension of DIS

ODT boundary creased

(similar to bicontinuous

microemulsion)

B&M

Scenario 2: B&M nematic and a

separate phase from DIS

ODT boundary not creased

B&M or

Macro

or

Macro

Beyond SCFT—CL-FTS Simulations

C = 7, f = 0.4, ϕh = 0.5 χN = 30

χN = 28

χN = 26

χN = 25

χN = 24

LAM

B&M?

DIS

No evidence for deflected ODT Scenario 2 likely

Yi-Xin Liu, K. Delaney

Ed’s Legacy at UCSB

Michael Chabinyc

Rachel Segalman

E. N. Kramer Chair Many thanks to Rachel and Sara for their

outstanding coordination of this event!