Synthesis and extensive study of end-to-end cyclization of monodisperse pyrene-labeled

poly(ethylene oxide) (PEO)

Shaohua ChenSupervisor: Dr Jean Duhamel

IPR SeminarMay 1st, 2009

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IntroductionPyrene and pyrene-labelled PEOSynthesisResultsConclusions and future workAcknowledgements

Outline

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INTRODUCTION

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Associative Polymers

In water

Hydrophobe Water-soluble polymer

• In water, hydrophobes cluster to form aggregates

• Water-soluble polymers with a small amount (<5 mol%) of hydrophobic pendants

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Associative Polymers

Above C*

• Above C* (semi-dilute concentration), a polymeric network created by intermolecular bridging, the solution viscosity increases

• Applications – paints, coatings, dispersants, drug delivery, etc.

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HEUR Polymers

• Hydrophobically modified PEO belongs to the HEUR family

• Hydrophobically modified Ethoxylated URethane (HEUR) polymer

Wetzel, W. H.; Chen, M.; Glass, J. E. Hydrophilic Polymers, Performance with Environmental Acceptability, Ed. Glass, J. E. Advances in Chemistry Series 248, American Chemical Society, Washington, DC, 1996, 163.

CH2CH2O x Ethylene Oxide Repeating Unit

NH C NHO

Urea Interconnecting Unit

Terminal Hydrophobe

NH C OO

Urethane Interconnecting Unit

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CMC

C*

Yekta, A.; Xu, B.; Duhamel, J.; Adiwidjaja, H.; Winnik, M. A. Macromolecules 1995, 28, 956.

Network and Viscoelastic Behaviors of HEUR Polymer in Water

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Advantages of using hydrophobically end-capped PEO to

study the long-range polymer chain dynamics (LRPCD)

• A well-defined architecture The position of the hydrophobic groups is known – at chain ends

• A fixed distance between end hydrophobesUsing a monodisperse PEO (PDI=Mw/Mn≤1.1) as the polymer backbone

Hydrophobically end-capped PEO is an ideal model system to investigate the chain dynamics

LRPCD are best studied in organic solvents where no aggregation takes place between hydrophobic pendants.

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PYRENE AND PYRENE-LABELLED PEO

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Pyrene and Pyrene-labelled PEO

Pyrene – an ideal chromophore

• Highly hydrophobic (0.3-0.7μM in water)

• Large extinction coefficient

• Good quantum yield

• Long lifetime

• Isolated excited monomer fluoresces around 375nm and shifts to 480nm when associates with ground-state pyrene to form an excimer

Pyrene (the hydrophobe) end-labelled PEO

OOn

h ν

*+

*k1

k-1

Pyrene

Why Use Pyrene?

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0

4

8

12

350 400 450 500 550 600

Wavelength (nm)

Inte

nsity

(a.u

.)

Pyrene Fluorescence

Monomer ExcimerIM IE

hν + Py + Py Py* + Py (PyPy)*τM τE

kdiff

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Birks’ Scheme

kcy

k-cy

Py Py*

(PyPy)*

Py Py

hν

kM=1/τM kE=1/τE

Py-PEO-Py

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Birks’ Scheme

Winnik M. A. Acc. Chem. Res. 1985, 18, 73-79.

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1

10

100

1000

10000

100000

0 100 200 300 400 500

Time (ns)

Cou

nts

(Py Py)*Py Py hν

Py *→ ← Py1/τ E

1

10

100

1000

10000

100000

0 100 200 300 400 500

Time (nm)

Cou

nts

( ) ( ) ( )2211 expexp ττ tatatI MMM −+−=

( ) ( ) ( )4231 expexp ττ tatatI EEE −+−=

31 ττ = 42 ττ = 21 EE aa −=

Birks’ Scheme

IE

IM

Py-PEO(5K)-Pyin DMF

Py-PEO(2K)in waterIE

Rise time No rise time

PyPy

hν

1/τ E

(PyPy)*

( )MM ta τ−+ expPy

in

Py

PyIP

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SYNTHESIS

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Overall SchemeOH CH2 CH2 O CH2 CH2 O CH2 CH2 OH

n

TsClCH2Cl2Triethylamine

SO

O

CH3OSO

O

CH3 O CH2 CH2 O CH2 CH2 O CH2 CH2n

1-Pyrenemethanol

NaHDMF

OO CH2 CH2 O CH2 CH2 O CH2 CH2CH2CH2n

60oC

RT

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1H NMR Characterization – PEO

OH CH2 CH2 O CH3n

H2O

DMSO-d6

a

ac

c

b b

b

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SO

O

CH3 O CH2 CH2 O CH2 CH2 O CH3n

H2O DMSO-d6

a

a

b b b

b

c

c

d

d

d

e

e

e f

f

1H NMR Characterization – Tos-PEO

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CH2 CH2 O CH3n

OCH2

H2O DMSO-d6a

a

b b

b

cc

c

c

cc

c

c

c

c

d

d

1H NMR Characterization – Py-PEO

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-5

5

15

25

35

45

55

65

5 10 15 20 25 30 35 40

Elution Time (min)

Inte

nsity

(a.u

.)GPC Characterization

Py-PEO

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0

0.2

0.4

0.6

0.8

1

1.2

250 300 350 400 450 500 550 600

Wavelength (nm)

Abso

rban

ce

UV-Vis Characterization0.059g/L Py-PEO in DMF

Absorbance = 0.98 at 344 nm

1190038 −= cm M, -ε (Py-CH2-OH in DMF)

)/(109.5)/(1900,38/98.0

)/]([)/]([

2 LgLmol

LgPolyLmolPy

Py −××

==λ

polymer /1028.4 4 gmol−×=

PEOpyPy M −

≈1λFor fully labeled chains:

2

2

PyPEOPy M −

≈λ for end-labeled samplesIP

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Sample Mn (PEO) (g/mol) PDI

PEO(2K)-Py 2,000 1.05

PEO(2K)-Py2 2,000 1.10

PEO(5K)-Py2 5,000 1.08

PEO(10k)-Py2 10,000 1.05

PEO(16.5k)-Py2 16,500 1.05

Samples

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RESULTS

PART 1 – Birks’ Scheme

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Pyrene end-labeled and mono-labeled PEOs in acetone at 0.1OD

0

20

40

60

80

100

120

140

160

350 400 450 500 550 600

Wavelength (nm)

Flu

ores

cenc

e In

tens

ity (

a.u.

)

PEO(2K)-Py2

PEO(5K)-Py2

PEO(10K)-Py2

PEO(16.5K)-Py2

PEO(2K)-Py

y = -1.69 x + 13.07

-4.0

-3.0

-2.0

-1.0

0.0

1.0

7.0 7.5 8.0 8.5 9.0 9.5 10.0

Ln(M n )

Ln(I

E/I

M)

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PEO(5K)-Py2 in various organic solvents at 0.1OD

0

20

40

60

80

100

120

350 400 450 500 550 600

Wavelength (nm)

Flu

ores

cenc

e In

tens

ity (

a.u.

)

acetoneacetonitrileTHFtolueneDMFdioxaneDMAbenzyl alcohol IP

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0.0

0.2

0.4

0.6

0.8

1.0

0 1 2 3 4 5 6

η (mPa.s)

a M

1

10

100

1000

10000

100000

0 100 200 300 400 500 600 700 800 900 1000

Time (ns)C

ount

s

PEO(2K)-Py in dioxane

PEO(10K)-Py2 in dioxane

PEO(2K)-Py2

PEO(5K)-Py2

PEO(10K)-Py2

PEO(16.5K)-Py2

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0

50

100

150

200

250

0 1 2 3 4 5 6

η (mPa.s)

τ E (

ns)

τE=48ns

nsE 214=τ

PEO(2K)-Py2

PEO(5K)-Py2

PEO(10K)-Py2

PEO(16.5K)-Py2

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0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30

(0.34×10-4)×(η/τM )0.5×M n (Pa0.5g/mol)

a M

PEO(2K)-Py2PEO(5K)-Py2PEO(10K)-Py2PEO(16.5K)-Py2

0

50

100

150

200

250

0.00 0.05 0.10 0.15 0.20 0.25 0.30

(3.4×10-4)×(η/τM )0.5×M n (Pa0.5g/mol)

τ E (n

s)

PEO(2k)-Py2PEO(5k)-Py2PEO(10k)-Py2PEO(16.5k)-Py2

τE=48nsIP

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0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

1/η (mPa.s)-1

k cy (n

s-1)

PEO(2K)-Py2PEO(5K)-Py2PEO(10K)-Py2PEO(16.5K)-Py2

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.00 0.05 0.10 0.15 0.20 0.25 0.30

(3.4×10-4)×(η/τM )0.5×M n (Pa0.5g/mol)

k cy (n

s-1)

PEO(2K)-Py2PEO(5K)-Py2PEO(10K)-Py2PEO(16.5K)-Py2IPR 20

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Revisions of Birks’ Scheme

Ground-state dimer (GSD)1

A short lifetime,1

Biexponential decay for mono-labeled PEO

nsS 5.3=τ

nsE 48=τ

1

10

100

1000

10000

100000

0 100 200 300 400

Time (ns)C

ount

s

Excimer decay for PEO(10K)-Py2in ACN

A spike

+− = EE aa

1 Costa, T.; Seixas de Melo, J.; Burrows H. D. J. Phys. Chem. B 2009, 113, 618-626.

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Program Fits (Res. vs t, ns; chisq) Resultsno GSD;mexp. m-labeled decay;

is not fixed; no 1.03

Good fits but can not startanalysis from max. lamp and , aM increase with

no GSD;mexp. m-labeled decay;

is not fixed; 1.04

Good fits but and aMincrease with

no GSD;mexp. m-labeled decay;

; 1.13

Monomer residuals are not randomly distributed.

GSD;mexp. m-labeled decay;

; 1.21

Monomer residuals are not randomly distributed.

no GSD;mexp. m-labeled decay;

;4.37

Bad fits!

GSD;bexp. m-labeled decay;

;1.14

Good fits but aM increases with and the excimerresiduals are not perfect.

=2χ+− ≠ EE aa

Eτ Sτ

+− ≠ EE aa

Eτ nsS 5.3=τ

+− ≠ EE aa

nsE 48=τ nsS 5.3=τ

+− = EE aa

nsS 5.3=τnsE 48=τ

+− = EE aa

nsE 48=τ nsS 5.3=τ

+− = EE aa

nsE 48=τ nsS 5.3=τ

=2χ

Eτ

Eτ

=2χ

=2χ

=2χ

=2χ

PEO(10K)-Py2 in DMF, the decays were fitted by various revisions of Birks’ Scheme

η

η

η

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RESULTS

PART 2 – A Blob Model

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Py* Py

Py Py

kblob

kex[M1] kex[M0]

blob

P0%

P1%

aM IP

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PEO(10K)-Py2 in DMF:

08.12 =χMonomer Excimer

Assumptions: ; ; GSD presents; bexp. decay for mono-labeled PEO; the fraction of is not fixed but no more than 5% for all samples; all PEO chains end-labeled.

nsS 5.3=τ nsE 48=τ1Mτ

Assumptions and fits of Blob Model

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6

η (mPa.s)

P1%

PEO(2K)-Py2

PEO(5K)-Py2

PEO(10K)-Py2

PEO(16.5K)-Py2

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0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

h (nm)

W(h

)

PEO(2K)-Py2PEO(5K)-Py2PEO(10K)-Py2PEO(16.5K)-Py2

Py*

Py

x

y

z

h

Kuhn length of PEO lK = 0.707nm,the number of segments NK = 0.0141MP

1

( ) 23

422

hehW h ππβ β−

⎟⎟⎠

⎞⎜⎜⎝

⎛=

where 22

23

KK lN=β

End-to-end distance distribution

1 Pattanayek, S. K.; Juvekar, V. A. Macromolecules 2002, 35, 9574-9585.

P1%

Rblob

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Blob radii (Rblob) in organic solvents

y = 0.18 x + 2.20

0

1

2

3

4

5

6

7

8

9

0 5 10 15 20 25 30 35

(τM /η )0.5

Rbl

ob (n

m)

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Conclusions

• The blob model is more comprehensive than Birks’scheme to study this pyrene end-labeled PEO system in organic solvents; Birks’ scheme is limited to the excimer formation within one blob

• The radii of blob in various organic solvents were determined and are proportional to

ητ M

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Future Work

• Characterize the micelle formation of this system in water

• Study the chain kinetics by blob model

• Quantitatively investigate how a quencher reduce the size of blob

• Study the effect of backbone stiffness on the size of blob IPR 20

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Acknowledgements

• Dr. Jean Duhamel

• Dr. Mario Gauthier

• Duhamel and Gauthier Lab Groups

• Petroleum Research Fund (ACS)IPR 20

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Questions/Comments?IPR 20

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