relaxation in polymers with conformational memory
TRANSCRIPT
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
Relaxation in Polymers with Conformational Memory
Introduction •
Isotropization in PEMA •
Acylates vs Methacrylates •
Conclusions •
interactions in solid state NMR
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
Slow processes in amorphous polymers
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
mechanicsdielectrics
BeinerFiorettoFitzgeraldGomez RibellesHayakawaJourdanReissig
Beiner
NOE same sample
mechanicsdielectrics
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
Relaxation in Polymers with Conformational Memory
Introduction •
Isotropization in PEMA •
Acylates vs Methacrylates •
Conclusions •
interactions in solid state NMR
line narrowing, length scale, sidechain length
Dipolar filter, NOE, sidechain dynamics
Slow processes in amorphous polymers
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