relaxation in polymers with conformational memory

Relaxation in Polymers with

Conformational Memory

Robert Graf

Max-Planck-Institut für PolymerforschungMainz

5th IDMRCS, Lille (France)July 8th, 2005

Relaxation in Polymers with Conformational Memory

Introduction •

Isotropization in PEMA •

Acylates vs Methacrylates •

Conclusions •

interactions in solid state NMR

1D and 2D 13C NMR lineshapes, dynamicmodel for line narrowing, conformationalexchange, length scale of isotropizationprocess, sidechain dependence.

M. Wind, R. Graf, L. Brombacher, H.W. Spiess

Dipolar filter, NOE, sidechain dynamics

Slow processes in amorphous polymers

Molecular Structures and Dynamics via NMR

i

i0iZ BH I∑γ−=

Important NMR interactions in the solid state:

Zeemann Interaction :

i

i0iCS BH Iσ∑γ−=Electronic Shielding :

i

i

i)1I2(I2

eQQH IVI∑ −−= hQuadrupol Interaction :

[ ]∑≠

γγπ

μ ⋅−⋅⋅−=ji

jijir3

r4D )r)(r(H 23ji0 IIIIh

Dipol-Dipol Interaction :

H = HZ + HQ + HCS + HD

180°C

O13

0° - 180°

a-PEMA: Isotropisation of Chain Dynamics

180°

CO

13

ω33<10°

ω22

ω11

180°

CO

13 ω

50°ω

400 K

405 K

411 K

433 K

472 K

394 K

250 200 150 100

298 K

ω

ω

ω22

ω33

ω11

1D 13C NMR: experimentsimulation

Melt

Gla

ss

Tg

Melt

a-PEMA: Isotropisation of Chain Dynamics

200

150

100200 150 100250

250

[ppm

]ω

2

[ppm]ω1

T = 300 K

ω11

ω22 ω33

180°

CO

13

ω33<10°

ω22

ω11

200

150

100

200 150 100

T = 416 K

tc = 2,1.10-5 s

[ppm

]ω

2

[ppm]ω1

180°C

O13

0° - 180°

T = 394 K

tc = 3,3.10-4 s

200

150

100

200 150 100

[ppm

]ω

2

[ppm]ω1

ωω

180°

CO

13 ω

50°ω

Dynamic Models: Random Jump vs. Rotational Diffusion

rotational diffusion experimental results random jump

200

150

200 150 [ppm]

[ppm]

200

150

200 150 [ppm]

[ppm]

200

150

200 150

tc=3,3 .10-4s

[ppm]

[ppm]tc =3,3.10-4s T = 394 K

200

150

200 150

tc =8,3.10-5s

[ppm]

[ppm]

200

150

200 150 [ppm]

[ppm]

200

150

200 150

tc=8,3.10-5s

[ppm]

[ppm]T = 405 K

Time Sclaes of Molecular Dynamics PEMA Melts

Arrhenius-diagram of dynamic processes in PEMA

corr

elat

ion

time

[s]

10-8

10-6

10-4

10-2

100

102

2.2 2.4 2.6 2.8 3.0 3.2 3.4

1000 / T [K-1]2.0

Tg = 338K

α-relaxation( tα)

β-relaxation( tβ)

αβ-relaxation( tαβ)

NMR

DielectricsPCS

conformationalisotropisation (tR/I)

tem

pera

ture

a-PEMA: Conformation and Conformational Dynamics

(mr)

(rr)

CH3 (main chain)

CD3(side chain)

(mm)

T = 303 K

t.tt.g / g.t

g.g

t.g / g.tg.g / g.g

g.g

35 30 25 20 15 10 ppm

[ [

Tg - 50 K

s-PEMA

T = 353 K

Tg + 65 K

Tg

T = 418 K

35 30 25 20 15 10 ppm

(mm)(mr)

(rr)

13C MAS NMR

Separation of Dynamic Timescales in PEMA-Melts

Correlation Times from NMR, PCS, Dielectrics

Tg = 338K

α-Relaxation(WLF)

β-relaxation(Arrhenius)

NMR: spatial randomisation

(tI, WLF)

NMRPCSDielectric

2.2 2.4 2.6 2.8 3.0 3.2 3.410-8

10-6

10-4

10-2

100

102

2.0

1000 / T [K-1]

time

[s]

NMR: confromationalrelaxation

Mw Dependence of the Isotropization Process

corre

latio

n tim

e [s

]

T - Tg [K]

10 -8

10 -6

10 -4

10 -2

0

isotropization

(β)

20 40 60 80 100 120 140 160

(α)

(αβ)

669 kg mol-1120 kg mol-1

15.9 kg mol-1

a-PEMA (radical)

7.6 kg mol-1

6.7 kg mol-1

1.25 kg mol-1

0.46 kg mol-1

a-PEMA (anionic)

The break down of the isotropization process is determinedby the polydispersity of the polymers.

Polydispersity of Low Molecular Weight PEMAs

0

20

40

60

80

100

120

0 2 4 6 8 10

Mw= 0.46 kg mol-1(anion.; MALDI TOF)

Mw = 1.37 kg mol-1(anion.; MALDI TOF)

Mw= 7.6 kg mol-1(radic.; GPC)

Mw= 6.4 kg mol-1(anion.; GPC)

inte

nsity

[a. u

.]

molecular weight [kg mol-1]

Length Scale of Isotropisation Process

**

*

*

**

*

*

T - Tg

95 K

55 K

410 K

449 K

395 K

434 K

387 K

426 K

322 K

346 K

379 K

403 K

Mw = 600 kg mol -1 Mw = 15,9 kg mol -1 Mw = 7,6 kg mol -1 Mw = 1,4 kg mol -1 Mw = 0,46 kg mol -1

Mw/Mn = 1,53 Mw/Mn = 1,07 Mw/Mn = 1,14

300 K 300 K 300 K 221 K278 K

δ [ppm]100150200250

δ [ppm]100150200250

δ [ppm]100150200250

δ [ppm]100150200250

δ [ppm]100150200250

from radicalic polymerisation from anionic polymerisation

Mw/Mn = 1,61 Mw/Mn = 1,48

Influence of Tacticity on the Insotropization of PEMA

corre

latio

n tim

e [s

]

1000 / T [K-1]

10-8

10-6

10-4

10-2

100

102

2.2 2.6 3.0 3.83.4

isotropization (WLF)

α-relaxation (WLF)

Tg = 291K

dielectric relaxationmechanical relaxation1D 13C NMR2D 13C NMR

i-PEMA

isotactic PEMA(mm = 0.92)

Poly(Methacrylates): Separation of Time Scales of

Chain Randomization and α/β-Prozess

2.2 2.6 3.0 2.2 3.0

t c[s

]

10-8

10-6

10-4

10-2

100

102

1000 / T [K-1]

PEMA PBMA PHMA

3.0 3.83.42.63.42.6

Tg = 338 K Tg = 307 K Tg = 277 K

Tc

Tc

Tc

3.4

tI

tαβ

tαβ

tαβ

tI tI

increasing separation of tI and tαβ

decreasing Tg (internal plastification)

β-relaxation with constant activation

Tc at lower temperature T

and longer tc


Introduction •



Conclusions •


line narrowing, length scale, sidechain length

Dipolar filter NMR experiments, NOE polarization transfer, poly(n-alkylmethacrylates), poly(n-alkyl acrylates).

M. Gaborieau, R. Graf, H.W. Spiess


Correlation Times from Dipolar Filter Experiments

70 60 50 40 30 20 10 ppm

70 60 50 40 30 20 10 ppm

70 60 50 40 30 20 10 ppm

CH2CH2 Cq CH3

CH3

DD1 H13 C

90°

1 H13 C

DDLG-CP90°

DF

1 H13 C

DD90°DF τm

LG-CP

LG-CP

LG-CP

LG-CP

LG-CP

1 H90°

DF τmPEMA

(monomeric unit)

Scheme of dipolar filter experiment

Probing the selection of the dipolar filter:

Correlation Times from Dipolar Filter Experiments

2.0 2.5 3.0 3.5 4.0

10-6

10-4

10-2

100

102

PEMA

τ [s]

1000 / T [1/K]

( )mABCABm qIII τττ ⋅⋅⋅−⋅+= 5exp)( 05

205

3

NOE magnetization decayin a CH2-CH3 moiety:

qAB : static dipolar couplingparameter,determinedvia M2measurements .

Experimental results in PEMAT>Tg: pure exponential decayT~Tg: biexponential decay

Correlation times fromdipolar filter experiments

NOE Relaxation Times in PnAMA samples

2.0 2.5 3.0 3.5

PEMA

corr

elat

ion

time

[s]

1000 / T [K-1]2.5 3.0 3.5

PBMA

2.5 3.0 3.5 4.0

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

PHMA

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

1000 / T [K-1] 1000 / T [K-1]

Relaxation Times of Poly(n-alkyl acrylates)

Literature data (dielectrics):

McCrumGomez,RibellesReissig et al.

10-10

10-8

10-6

10-4

10-2

100

102

3 4 5 6

NOE same sample

mechanicsdielectrics

local

1000/T [1/K]3 4 5 6

1000/T [1/K]3 4 5 6

1000/T [1/K]

10-10

10-8

10-6

10-4

10-2

100

102

PEA

corr

elat

ion

time

[s]

local

β

αPBA

NOE same sample


BeinerFiorettoFitzgeraldGomez RibellesHayakawaJourdanReissig

Beiner

NOE same sample


β

local

αPHA

Local Dynamics in PnAA from NOE Analysis

PEA PBA

- 18

10

13

8-14

18

PHA

β relaxation ca 15-25

local relaxation 10

slow process (NOE) 12

apparent activation energies Ea [kJ·mol-1] :

Quantified processes in PnAA samples, correspond to asuperposition of β- and local processes in the side chain.

Non-isotropic side chain modes indicate organizationon time scales significantly longer than the α-process


Introduction •



Conclusions •


line narrowing, length scale, sidechain length

Dipolar filter, NOE, sidechain dynamics


Organisation in Poly(Methacrylats): WAXS(LVDW)

PMMA

PEMA

PBMA

PHMA

Inte

nsity

[a.u

.]

q [nm-1]0 10 20

II/I

WAXS-DataIII

(VDW)

III

?

0

0.4

0.8

1.2

1.6

0 2 4 6 8 10 12number of side chain C atoms

Bra

ggdi

stan

ce d

[nm

]

I

II

III

(VDW)

(LVDW)

Bragg distances

syndiotacticpoly(methacrylate)

main chain

side chains

dI

dIII

d0

dIII

dII

"Nano Layers"

isotacticPEMA

main chains

side chains

extrapolatedlokal structur:

Introduction •

Solid State NMR •

Polymer Dynamics •

Conclusions •

Interaction in solid state NMR

MAS, recoupling, double-quantum NMR

Reptation-model, polybutadiene, PEMA

How unstructured are amorphous polymers ?

How Unstructured are Amorphous Polymer Melts? Solid-State NMR Studies of Local Dynamic Order in

Amorphous Polymer Melts

Acknowledgements

Prof. Dr. Hans Wolfgang Spiess ($, €, …)

Dr. Michael Wind

Dr. Marianne Gaborieau

Dr. Werner Steffen

Prof. Dr. Do Y. Yoon

relaxation in polymers with conformational memory

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