Branching Analysis of Star Polymers by SEC

Artjom Döring Martin Schneider Agnes Wycisk Dirk Kuckling

International Symposium on GPC/SEC and Related Techniques Frankfurt, 2014

log

(intri

nsic

vis

cosi

ty)

log (molar mass)

hard sphere (α = 0)

linear coil ( 0.6 < α < 1.0)

star polymer ( 0.1 < α < 0.6)

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Paderborn

• founded in 1972 • currently more than 20.000 students • material science profile in chemistry, physics and

mechanical engineering

University of Paderborn:

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Research Interests of Prof. Kucklings Working Group:

Smart Polymers

Controlled Radical Polymerization

(NMRP, ATRP, RAFT)

Smart block copolymers for micro heterogeneous organocatalysis

or pigment stabilization

X Y + Z

Smart nanohydrogels for targeted transport and

controlled release systems

Smart and biodegradable block copolymers for

triggered release systems

enzyme

Free Radical Polymerization and photo cross-linking /

photo patterning

Hydrogels for applications in biomedicine and as actuators and sensors in micro-system

technology

Receptor/Ligand modified (hydro)gels for sensor

applications

Multisensitive phase separated hydrogel layers

- NMR - IR &

UV/VIS - SEC

- MS (MALDI, ESI-IMS) - SPR

Analytics

4

core-shell type nanoparticle

hydrophilic shell hydrophobic core

Induced Morphology Change in Star-Shaped Temperature-Responsive Block Copolymers:

unimolecular colloidal nanoparticles: - small dimension (< 20 nm) - spherical morphology

hydrophilic block

temperature-responsive block (LCST) T > Tc

T < Tc

Characterization of the obtained star (co)polymers:

- mean copolymer composition: 1H-NMR

- molecular weight: 1H-NMR, ESI-IMS-MS

SEC (THF, CHCl3, DMAc, HFIP)

- number of arms: viscosity (Kuhn-Mark-Houwink Plot)

5

SEC Setup for Branching Analysis

eluent: N,N-dimethylacetamide (DMAc)

flow: 1 ml/min

injector: manuel injection valve (100 µl, Knauer)

columns: PSS-GRAM (104 Å, 103 Å, 102 Å)

column temp.: 50 ºC (Shimadzu CTO 6A)

detectors: Merck-Hitachi L3000 PDA

Waters RI 2410

PSS ETA 2010 viscosity detector

PSS SLD 7000 MALLS detector

6

Synthesis of Star Polymers

Cl

O NH n

O

Om

multifunctional initiator

O

OO O

OR

OR

OR

OR

Penta-Cl4: R =

H, X =

ClPenta-Br

4: R

= CH3

, X = Br

X

X

X

X

OO

Cl

O

O O

O7

OCl

O

Cl

21-Cl-β-CD

ATRP

Br

n

O

Om

Sample

Initiator

ATRP catalyst

Mn,GPC

[g/mol] D

PS 4-arm Penta-Br4 Cu(I)Br / Me6Tren 40.300 1.26

PNIPAAm 4-arm Penta-Cl4 Cu(I)Cl / Me6Tren 70.000 1.13

PNIPAAm 7-arm 7-Cl-β-CD Cu(I)Cl / Me6Tren 149.800 1.11

PNIPAAm 14-arm 14-Cl-β-CD Cu(I)Cl / Me6Tren 155.000 1.17

PNIPAAm 21-arm 21-Cl-β-CD Cu(I)Cl / Me6Tren

250.000 1.25

7

log

(intri

nsic

visco

sity)

log (molar mass)

hard sphere (α = 0)

linear coil ( 0.6 < α < 1.0)

star polymer ( 0.1 < α < 0.6)

Branching Analysis of Star Polymers

2

2*3ffg −

=

[ ][ ]linear

branchedgη

η='

5.0with)'( /1 == εεgg

[ ]

=

→→ c

spez

Gc

ηη lim

00

B. H. Zimm, W. H. Stockmayer, Journal of Chemical Physics 1949, 17, 1301-1314 B. H. Zimm, R. W. Kilb, Journal of Polymer Science 1959, 37, 19-42

- standard calibration - viscosity detector (universal calibration) - MALLS detector (absolute method) refractive index increment dn/dc is

required

Kuhn-Mark-Houwink Plot

8

Refractive Index Increments in N,N-Dimethylacetamide

Sample Origin dn/dc Poly(styrene) PSS Standard 0.15430±0.0022 Poly(styrene) Synthesized by FRP 0.15520±0.0024 Poly(methylmethacrylat) PSS Standard 0.05829±0.0021 Poly(methylmethacrylat) Synthesized by FRP 0.05737±0.0006 Poly(N-isopropylacrylamide) Synthesized by ATRP 0.06497±0.0013 Poly(N-isopropylacrylamide) 14-arm star polymer Synthesized by ATRP 0.06330±0.0041

dn/dc-measurements of linear and star polymers in DMAc were performed with a refractometer Model 2010/540 (PSS, Mainz)

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Branching Analysis of Poly(styrene) Star Polymers

Sample Origin Mn [g/mol] PD Poly(styrene) broad, linear PSS 144.000 2.03 Poly(styrene) 3-arm star polymer PSS 265.000 1.14 Poly(styrene) 4-arm star polymer Synthesized by ATRP 40.300 1.26 Poly(styrene) 8-arm star polymer PSS 216.000 1.07

Sample Origin Mn [g/mol] PD Poly(styrene) broad, linear PSS 140.000 2.23 Poly(styrene) 3-arm star polymer PSS 288.000 1.06 Poly(styrene) 8-arm star polymer PSS 220.000 1.06

Sample data provided by PSS

SEC results (universal calibration)

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24 26 28 300,000

0,002

0,004

0,006

0,008

[η] sp

ez

Elution volume

1,2

1,4

1,6

1,8

log

[η] in

tr(fitt

ed)

Branching Analysis of Poly(styrene) Star Polymers 4-Arm PS star polymer (Aw 152)

20 21 22 23 24 250,000

0,002

0,004

0,006

0,008

0,010

0,012

0,014

Elution volume

[η] sp

ez

0,6

0,9

1,2

1,5

1,8

2,1

2,4

2,7

log

[η] in

tr(fitt

ed)

21 22 23 24 25 260,000

0,002

0,004

0,006

Elution volume

[η] sp

ez

0,6

0,9

1,2

1,5

1,8

2,1

2,4

log

[η] in

tr(fitt

ed)

3-Arm PS star polymer (PSS)

8-Arm PS star polymer (PSS) Results: - ηspez (elution volume) - [η] (elution volume); not always linear - Molar mass (elution volumen) from universal calibration

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Sample Average number of

arms f Poly(styrene) 3-arm star polymer 2.8 Poly(styrene) 4-arm star polymer 4.0 Poly(styrene) 8-arm star polymer 8.0

Branching Analysis of Poly(styrene) Star Polymers [η] (elution volume) Molar mass (elution volume)

4,4 4,6 4,8 5,0 5,2 5,4 5,6 5,8

1,4

1,6

1,8

2,0

2,2

2,4 Linear Poly(styrene) I (PSS) Linear Poly(styrene) II 3-Arm star PS star polymer (PSS) 4-Arm star PS star polymer 8-Arm star PS star polymer (PSS)

log

[η]

log M

Kuhn-Mark-Houwink Plot [η] (molar mass)

Ve = const

5,2 5,4 5,6

2,0

2,2

2,4

2,6 Broad linear Poly(styrene) y = - 2,48639 + 0,85068 x3-Arm Poly(styrene) star polymer(PSS Mainz)y = - 0,26797 + 0,44200 xCalculated number of armsf = 2,88-Arm Poly(styrene) star polymer(PSS Mainz)y = - 1,02749 + 0,15266 xCalculated number of armsf = 8,0

log

[η]

log M

[ ][ ]linear

branchedgη

η=' ε/1)'(gg = 2

2*3ffg −

=

12

4,4 4,6 4,8 5,0 5,2 5,4 5,6 5,8

1,4

1,6

1,8

2,0

2,2

2,4 PS I PS II 3-arm exp 3-arm theo 4-arm exp 4-arm theo 8-arm exp 8-arm theolo

g [η

]

log M

Branching Analysis of Poly(styrene) Star Polymers

4,5 5,0 5,52

4

6

8

10 3-Arm Poly(styrene) star polymer 4-Arm Poly(styrene) star polymer 8-Arm Poly(styrene) star polymer

f 1

log M

number of arms f increases together with molar mass Synthesis mechanism offers no convienient explanation

slope of the KMH plot lines is too small to provide a constant ratio for g‘:

[ ][ ]linear

branchedgη

η='

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Branching Analysis of Poly(N-isopropylacrylamide) Star Polymers 4-Arm Poly(NIPAAm) star polymer (MS 344-4) 7-Arm Poly(NIPAAm) star polymer (Aw 312)

14-Arm Poly(NIPAAm) star polymer (Aw 234)

22 23 24 25 26 27 280,000

0,002

0,004

0,006

0,008

0,010

[η] sp

ez

Elution volume

1,4

1,6

1,8

log

[η] in

tr(fitt

ed)

21 22 23 24 250,000

0,002

0,004

0,006

0,008

0,010

0,012

0,8

1,0

1,2

1,4

1,6

1,8

2,0

log

[η] in

tr(fitt

ed)

20 22 24 26

0,000

0,002

0,004

0,006

0,008

0,3

0,6

0,9

1,2

1,5

1,8

2,1

log

[η] in

tr(fitt

ed)

[η] sp

ez

Elution volume19 20 21 22 23 24 25

0.000

0.002

0.004

0.006

0.008

0.010

0.012

log

[η] in

tr(fitt

ed)

[η] sp

ez

Elution volume

1.0

1.2

1.4

1.6

1.8

21-Arm Poly(NIPAAm) star polymer (Aw 221)

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5,2 5,3 5,4 5,5 5,6 5,7 5,8 5,9

1,7

1,8

1,9

2,0

2,1

2,2

2,3

2,4Linear Poly(NIPAAm): α = 0.53 7-Arm Poly(NIPAAm) star polymer: α = 0.42 14-Arm Poly(NIPAAm) star polymer: α = 0.27 21-Arm Poly(NIPAAm) star polymer: α = 0.18

log

[η]

log M4,7 4,8 4,9 5,0 5,1 5,2 5,3

1,6

1,7

1,8

1,9 Broad linear Poly(NIPAAm)y = - 1.65638 + 0.68093 x4-Arm Poly(NIPAAm) star polymer(MS 344-4)y = - 0.47662 + 0.42752 xCalculated number of arms f = 3.9

log

[η]

log M

Branching Analysis of Poly(N-isopropylacrylamide) Star Polymers

Sample Average number of arms f α-value PNIPAAm 4-arm star polymer 3.8 0.43 PNIPAAm 7-arm star polymer 6.0 0.42

PNIPAAm 14-arm star polymer 14.5 0.27 PNIPAAm 21-arm star polymer 22.3 0.18

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Branching Analysis of Poly(N-isopropylacrylamide) Star Polymers

4,8 5,0 5,2 5,4 5,63

6

9

12

15

18

21

24 4-Arm Poly(NIPAAm) star polymer 7-Arm Poly(NIPAAm) star polymer14-Arm Poly(NIPAAm) star polymer21-Arm Poly(NIPAAm) star polymer

f 1

log M

100000 10000000,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5 7-arm star polymer 14-arm star polymer 21-arm star polymer

W (l

og M

)

M / g/mol

number of arms f increases together with molar mass Synthesis mechanism offers no convenient explanation

Molecular weight distributions are monomodal and show no signs of star cross-coupling.

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Summary - branching analysis could be applied to synthesized star polymers based on poly(sytrene) or poly(N-isopropylacrylamide) - average number of arms is consistent to the functionality of the ATRP initiator - number of arms is not constant over the molecular weight range

Outlook - optimization of the SEC system (especially with respect to the MALLS detector) - analysis of star polymer samples with unknown number of arms

multifunctional initiator

click reaction or core cross-linking

arm-first method (grafting onto)

core-first method (grafting from)

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• 3- and 8-Arm Poly(styrene) star polymers (PSS)

20 21 22 23 24 25

4,8

5,1

5,4

5,7

6,03-Arm Poly(styrene) star polymer (PSS)

Data of the viscosity dector Data of the multi-angle lightscattering

device

log

M [g

/mol

]

Elution volume [ml]20 21 22 23 24

4,4

4,8

5,2

5,6

6,0

8-Arm Poly(styrene) star polymer (PSS) Data of the viscosity dector Data of the multi-angle lightscattering

device

log

M [g

/mol

]

Elution volume [ml]

• Linear Poly(styrene) (PSS)

18 20 22 24 26 28 304,4

4,8

5,2

5,6

6,0

6,4

6,8 Linear Poly(styrene) (PSS) Data of the viscosity dector Data of the multi-angle lightscattering

device

log

M [g

/mol

]

Elution volume [ml]

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o

24 26 28 30

4,0

4,5

5,0

5,5

4-Arm Poly(styrene) star polymer Data of the viscosity dector Data of the multi-angle lightscattering

device

log

M [g

/mol

]

Elution volume [ml]

• 4-Arm Poly(styrene) star polymer (Aw 152)