SWITCHABLE SOLVENTS ANDSURFACTANTS

Philip G. JessopQueen’s UniversityKingston, Ontario

Charles A. Eckert and Charles L. LiottaGeorgia Institute of Technology

Atlanta, Georgia

SWITCHABLE SOLVENTS

"Switchable" = able to switch on and off, or switch between one property and another,when a trigger is applied.

A solvent could switch between:

• high polarity / low polarity• volatile / nonvolatile• protic / aprotic• fluorophobic / fluorophilic

OUTLINE

POLARITY SWITCHABLE SOLVENTS

• elevated pressure• atmospheric pressure

OTHER KINDS OF SWITCHABLE SOLVENTS

SWITCHABLE SURFACTANTS

nonpolarsolvent highpolaritysolvent

lowpolaritysolvent

Makita et al., Refrigeration Tokyo Nippon Reito Kyokui (1976) 52, 543.Rhodes et al., J. Phys. Chem. (1995) 99, 9903.

Pressure, bar

10°C

100°C

7

9

4

0 40 120

8

6

2

80 160

5

3

1

50°C

Diel

ectri

c Co

nsta

nt

POLARITY SWITCHING OF A SUPERCRITICAL FLUID (CHF3)

POLARITY SWITCHING OF A SUPERCRITICAL FLUID

Works for the following SCFs:

• low Tc, high price: CHF3, CH2F2

• high Tc, low price: MeOH, NH3, H2O

Advantages Disadvantages

Continuous variability Limited polarity range

Non-reactive solvents High pressure

Stability High price for some,high T for others

addCO2

Green Chem. (2003), 5, 123-128

1 barCO2

high PCO2

POLARITY SWITCHING BY SOLVENT EXPANSION

releaseCO2

EXPANSION OF LIQUIDS BY CO2

CO2-expanded NEt3 (Jessop, 1996)

vo

lum

etr

ic e

xp

an

sio

n,

%

1000

800

600

400

200

0

P, bar

0 20 40 8060

dioxaneethyl acetate

acetonitrile

Volumetric expansion of aprotic solvents by CO2 at 40˚C (Kordikowski, 1995)

EFFECT OF EXPANSION ON π∗

EtOC4F9

[bmim]BF4

MeOHacetone

[bmim]PF6

Wyatt, J. Supercrit. Fluids 2005, 36, 16. Fredlake, PhysChemChemPhys. 2004, 6, 3280. Kho, Fluid Phase Eq. 2003, 206, 179.

incr

easin

g po

larit

y

POLARITY SWITCHING BY EXPANSION

Advantages Disadvantages

Continuous variability Pressure

Non-reactive solvents Acidity

Stability

A ROOM PRESSURE SWITCHABLE SOLVENT

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

• Immediate heat release and viscosity rise upon bubbling CO2

• Ions confirmed by MS, NMR, IR• Reversible at room temperature but faster at 70 ˚C• This reaction first observed by Linehan.

Jessop, patent application Jessop, Nature (2005) 436, 1102

DBU

CO2

N2 or Ar

DOES THE POLARITY CHANGE?

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

535.2CH2Cl2

538DBU + hexanol

538CHCl3

541DMF

542Propanoic acid

545DBU + hexanol

548[bmim]PF6

550Methanol

504.4Ether

λmax (Nile Red)nm

Solvent

Refs for other solvents:

Muldoon, JCS Perkin 2 (2001) 433Deye, Anal Chem (1990) 615Carmichael, J Phys Org Chem (2000) 591

incr

easin

g po

larit

y

POLARITIES

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

λmaxnm

ionic form

non-ionic form

incr

easin

g po

larit

y

MELTING POINTS

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

OTHER BASES AND ALCOHOLS

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

Base ROH Result

DBU 2˚ ROH Low conversion

DBU 3˚ ROH No conversion

DBU H2O Solid

N

N

PhN H2O

N

NPh

N+

H

-OC(O)OH

CH3CH2CH2OH No conversion

NEt3 CH3CH2CH2OH No conversion

N

DOES THE POLARITY CHANGE AFFECT SOLUBILITY?

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

DecaneROHDBU

N2

Decane

CO2

ionic liquid

CO2

N2 or Ar

R = Hexyl

DOES THE POLARITY CHANGE AFFECT SOLUBILITY?

N

N CO2

N2 N

N+

H

-OC(O)OR+ ROH

InsolInsolGlucose

SolSolToluene

InsolSolPolystyrene

SolInsol[PhCH2NMe3]Cl

InsolInsol[NMe4][O3SC6H4Me]

InsolSolIbuprofen

InsolSolDecane

Ionic formNon-ionic formSolute

For solids: 50 mg of solute in 2.22 mL of solventFor liquids: 0.5 mL of liquid in 2.22 mL of solvent

R = Propyl

APPLICATION OF POLARITY SWITCHING

CO2

1.0 mL styrene4.5 mL DBU/PrOH45 mg initiator

75 ˚C

6 h

filter or centrifuge

+

Mn = 412,000PDI = 1.57

No pressure required

CO2-TRIGGERED SWITCHABLE SOLVENTS

Advantages Disadvantages

Switches polarity Reactivity

Price

Benign triggers Polarity difference could be wider

nonpolarsolvent

Polarnonvolatilesolvent

volatilesolvent

RETRO-CHELOTROPIC REACTIONS

S

O

O

+ SO2

S + SO

+ COO

C

O

O

+ CO2

O

Melting Point of Sulfolene

CHOICE OF SULFOLENE

+ SO2 S

O

O

+ SO2 S

O

O

+ SO2 S

O

O

+ SO2 S

O

O

64-65 ˚C

63-64 ˚C

134-136 ˚C

~ -12 ˚C

(Pvap = 7 mmHg @ 85°C)

42.646.7ε189.0189.0ET(30) (kJ/mol)0.871π*0.460.76β0.00.0α

Piperylene SulfoleneDMSOProperty

S

O

OS

O

SOLVENT PROPERTIES

2.3 x 10-41.0 x 10-4KSCN

> 1.8 x 10-1> 1.8 x 10-1KTA

> 1.8 x 10-1> 1.8 x 10-1NaPDTC

1.5 x 10-55.5 x 10-4KCN

1.9 x 10-53.4 x 10-4KOAc

3.5 x 10-52.2 x 10-3CsOAc

5.8 x 10-46.8 x 10-3CsN3

2nd Order RateConstant in moist PS(L/mol sec)

2nd Order Rate Constantin DMSO (L/mol sec)

Nucleophile

KTA

NaPDTC

Cl

M+Nu-

Nu

+ + M+Cl-

40 °C

REACTIONS IN SWITCHABLE SULFOLENE

N

S S Na

O

CH3SK

m.p. = –12 °C b.p. = 42 °C -10 °C

+ SO2S

O

O

10

100

1000

10000

75 100 125 150

T (0C)

t 1/2

(m

in)

Butadiene sulfone

Piperylene sulfone

Isoprene sulfone

Drake et al. JACS, 1946, 68, 2521.

SWITCHING THE SULFOLENE SOLVENT

!

Cl

KTA+

PS

S

O

Cl S

40 °C

KTA

O

+ SO2

SWITCHING THE SULFOLENE SOLVENT

SO2-TRIGGERED SWITCHABLE SOLVENTS

Advantages Disadvantages

Switches volatility Some loss of diene

No pressure required Irritating odor

Less reactive than DBU

water

A SWITCHABLE SURFACTANT

oil

A SWITCHABLE SURFACTANT

oil/wateremulsion

oil

oil

oil

water

A SWITCHABLE SURFACTANT

oil/wateremulsion

oil

oil

water

A SWITCHABLE SURFACTANT?

patent application (2005)Science (2006)

hydrophobichydrophilic

hydrophobic hydrophobic

A SWITCHABLE SURFACTANT?

patent application (2005)Science (2006)

hydrophobichydrophilic

hydrophobic hydrophobicLiterature examples:

ferrocene head-group Sakai et al, 1990’s

Azobenzene head-group Sakai et al. 1999Viologen head-group Anton et al. 1992

A SWITCHABLE SURFACTANT?

C16H33

N NMe2

Me

CO2, H2OC16H33

NH

NMe2

Me

+

-O2COH

C16H33NH2 +

-2MeOH60 ˚C10-20 minno solvent

Me C NMe2

OMe

OMe

N2

patent application (2005)Science (2006)

hydrophobichydrophilic

MICELLE FORMATION

C12H25

NH

NMe2+

-O2COH

C12H25

NH

NMe2+

-Cl

C16H33

NH

NMe2+

-Cl

CMC

2.2 mM

0.5 mM

0.5 mM

[C14H29Pyr]Br 2.7 mM

THE SURFACTANTS SWITCH ON AND OFF

C16 amidine (20 mM) in DMSO at room temperature

Under CO2 Under Ar

EMULSION TEST WITH HEXADECANE

Hexadecane (4 ml), H2O (2 ml),C16 amidine 90 mg,shaken 10 min After 5 min

After 30 min

After 24 h

After Ar & ∆

Under CO2 Under Ar

EMULSION TEST WITH CRUDE OIL

After 5 min

After 30 min

After 60 min

After 15.5 h

No amidineCrude oil (4 ml),H2O (2 ml), C16amidine 90 mg,shaken 10 min

MICROSUSPENSION POLYMERIZATION

Ph

Ph

1. initiator

H2O/styrene emulsion

4 % [C12H+][HCO3]

65-70 ˚C under CO2

2. hydroquinone quench

Latex

Ar, !

Ph

ppt

n n

Mn = 276,000 g/mol PDI = 2.14 number-weighted mean diameter = 2.79 µm

CONCLUSIONS

Switchable solvent Advantages

Supercritical fluid Inert

Expanded liquids Inert

Atmospheric pressure systems No pressure

Disadvantages

Pressure, price

Pressure, acidity

Reactivity

Solvents don’t have to be unchangeable.

We can demand more flexibility from them.

Funding

Queen’s UniversityCFI/OIT (Canada)NSERC (Canada)DOE (USA)Canada Research Chairs Program

Collaborators

Dr. M. Cunningham (Queen’s)Dr. D. Darensbourg (Texas A&M)Dr. A. Daugulis (Queen’s) Dr. B. Davis (Queen’s)Dr. C. A. Eckert (Georgia Tech)Dr. C. L. Liotta (Georgia Tech)Dr. A. Rheingold (Delaware)

ACKNOWLEDGEMENTS

Grads/PDFs Contributing to This Work

Ms. Sindy Liu (Queen’s)Mr. Li Xiaowang (Queen’s)Mr. Lam Phan (Queen’s)Ms. Dolores Wynne (UCDavis)

Mr. C. Thomas (Georgia Tech)Mr. J. Hallett (Georgia Tech)Ms. E. John (Georgia Tech)Dr. Daniele Vinci (Georgia Tech)

Liotta Eckert