step-growth polymers as macro chain transfer agents – an ... · 7 13th april 2017 unesco iupac...

CRICOS No. 00213J

a university for the world®real

T. Gegenhuber, L. De Keer, A. S. Goldmann, P.H.M. Van Steenberge,

M.F. Reyniers, D. R. D´hooge, C. Barner-Kowollik

STEP-GROWTH POLYMERS AS MACRO CHAIN TRANSFER

AGENTS – AN EXPERIMENTAL AND THEORETICAL STUDY

2 13th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

The Road into the Light?

And if You feel that You can´t go on,

in the Light You will find the Road. (“In the Light“, Physical Graffiti, Led Zeppelin © 1975)

Tetrazole to

Nitrile-imine

Methyl-

Benzaldehyde

to ”Photoenol“

Phenacylsulfide to

Thioaldehyde

Azirine to

Nitrile-ylide


Reaction Pathway and Motivation

• Incorporation of RAFT group within the backbone of a step-

growth polymer


General Polymerization Concept

• Step-growth polymerization using a bifunctional ortho-methyl

benzaldehyde and a bisfumarate with a trithiocarbonate group

• Chain extension by conventional RAFT polymerization

M1 M2 P1

P2


2.5 3.0 3.5 4.0 4.5

Inte

nsi

ty/ a.u

.

log(M)

Simulation

Monomer Stability and Homopolymerization

• Irradiation with conditions for step-growth polymerization of M1

and M2

• Determination of kside

RAFT-fumarate M1 stable, benzaldehyde M2 reacts with itself

2.5 3.0 3.5 4.0 4.5 5.0 5.5

M1

M2

M1 after irradiation

M2 after irradiation

No

rma

lize

d R

I R

esp

on

selog(M)

M1

M2

PS calibration


Side Reactions and kside Determination

• Possible side reactions of activated M2 ortho-quinodimethane

and the carbonyl species of the benzaldehyde

• Determination of kmain in relation to kside via small molecules

M2 FF-M2-F

M2 M2


kmain vs. kside and Off-Stoichiometry in Simulations

• Side reaction, imbalance and k values

• If kside = kmain, still strong

suppression of side

reaction

• With excess A more side

reaction occuring

0 2 4 6 8 100.0

0.2

0.4

0.6

0.8

1.0

f AB

kside

/ kmain

r = 1

1.0 1.2 1.4 1.6 1.8 2.0

0.2

0.4

0.6

0.8

1.0 k

side < k

main

kside

= kmain

kside

> kmain

f AB

r

𝑟 =𝑁𝐴,0𝑁𝐹,0

0 800 1600 2400 32000.000

0.005

0.010

0.015

0.020

cX / m

olL

-1

Time / min

AA

AF

r = 1

kside

= kmain


Small Molecule Reaction: kmain Determination

Conversion (NMR): 93 %

Conversion (NMR): 87 %

M2 F

2.0 2.5 3.0 3.5 4.0

r = 1

r = 1.43

Norm

aliz

ed R

I R

esp

onse

log(M)

2.4 2.8 3.2 3.6

0.0

0.2

0.4

0.6

0.8

1.0

F-M2

log(M)

r = 1

r = 1.43

norm

aliz

ed f

m

F-M2-F

r = 1 with kside = 0.2 kmain


Step-Growth Polymerization Kinetics with Equimolarity

28 30 32 34 36 38

45 min

1 h

4 h

8 h

t0

10 min

20 min

30 min

Retention time / min

No

rmaliz

ed

RI R

esp

on

se

r = 1 and kside = 0.2 kmain

0 20 40 60 80 1000

10

20

30

40 Experimental

Simulation

Xw

Conversion / %


10 15 20 25 30

r = 0.99

r = 1.05

r = 1.20

r = 1.30

r = 1.50

r = 1.75

r = 2.00

Norm

aliz

ed

RI

Resp

on

se


Step-Growth with Imbalance using the Side Reaction

• Increasing the amount of M2 (photoenol)

• Highest Mw for the 1/1.75 ratio of M1/M2 (excess photoenol)

• At ½ ratio decrease of the Mw

1.00 1.25 1.50 1.75 2.00

10

20

30

40

50

60

70

80 Mw (exp.)

trendline

Mw / k

gm

ol-1

r

𝑟 =𝑁𝑀2𝑁𝑀1

M1 M2


Step-Growth Polymerization with Off-Stoichiometry

• Excess of M2 (also increased concentration, c(M1) = const.)

• High molecular weight species formed due to coupling of

further M2-M2

12 16 20 24 28 32

M1

M2

t0

10 min

20 min

30 min

45 min

60 min

90 min

2 h

4 h

6 h

No

rma

lize

d R

I R

esp

on

se


20 40 60 80 1000

75

150

225

300

375 Experimental

Simulation

Xw

Conversion / %

0 20 40 60 80 1000.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08 r = 1

r = 1.75

ma

ss f

ractio

n M

2 h

om

opo

lym

er

Conversion / %

M1 M2


Mechanistic Considerations

• Insertion of M2M2 homopolymer in M2M1M2M1 (M2+M1)

copolymer after exhaustion of M2

• Formation of high molecular species according to Carother

CopolymerHomopolymer

M2 M1


Chain Extension by RAFT Polymerization

• Conventional RAFT polymerization using step-growth polymer

with ratio of 1/1.5 M1/M2 (1/1.75 polymer with solubility issues)

2 3 4 5 6

Step-growth

0.25 h

0.5 h

1 h

1.5 h

2 h

3 h

4 h

Norm

aliz

ed Inte

nsi

ty

log(M)

1.0 1.5 2.0 2.5 3.0 3.5 4.0

10

20

30

40

50

60

Mn / k

gm

ol-1

Conversion / %


Mechanistic Considerations

• Symmetric trithiocarbonate fragmentation in a random fashion

– Up to 200 different reactions theoretical taken in account

– Statistical balancing of chain length by mixing long and short chains

during the addition and fragmentation

-


Summary

• Step-growth polymerization by light-induced reactions

Use of ortho-quinodimethanes and fumarates

Side reaction and theoretical description of kside/kmain

Off-stoichiometry to obtain high molecular species

• Chain extension by RAFT polymerization

Controlled reactio

Calculations and simulations currently under investigation

High molecular species obtained


Acknowledgements – Barner-Kowollik Team

Follow Macroarc @BarnerKowollik

Prof. Dagmar

D´hooge and

colleagues

step-growth polymers as macro chain transfer agents – an ... · 7 13th april 2017 unesco iupac...

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