The NMR of solid polymer: an overview
2
Part 1
NMR from liquid to solid
3
Liquid NMR
High solution NMR refer to liquid NMR whose
line width are less than 1 Hz.
This spectrum affords considerable information
concerning structure, composition,
microstructure, conformation, defects, branching,
and in some cases, number-average molecular
weights of synthetic polymer
4
A nuclear magnetic moment μ in H0
a)relationship between two frames b)movement of μ in rotating frame
5
Magnetization
0H
ptH1
N
i
iM
Larmor frequence
Pulse angle
6
Relaxation
Bloch equation
"
1
'
11
)1(
222
max
0
2
1
0
2
1
TTT
eMM
eMM
T
M
dt
dM
T
MM
dt
dM
T
t
T
t
Z
ZZ
7
刚性固体
液体 半刚性
凝胶
弛豫时间与分子运动 相关时间的关系
弛豫与分子运动
9
Determination of T1
Inversion recovery:(180o,τ,90o,acq)
10
11
Calculation of T1
)21( 1
0
1
0
T
t
Z
ZZ
eMM
T
MM
dt
dM
12 12
Determination of T2
Spin echo(90o,τ,180o, τ
,acq)
'
2
0'
]"2
)2([
'
0'
2
2
2
2
)(
2
)(
T
y
T
t
T
t
y
eMtM
twhen
eeMtM
13
CPMG
Sequence:(90ox’, ,180o
y’, 2 , 180oy’ ……)
Merit: eliminate the errors of dephasing and inexact
pulse length
自旋回波测量T2弛豫时间
14
It is one of the key goals of material science to establish
structure-property relationships in order to improve known and
design new materials. This holds in particular for synthetic
polymers, whose materials properties depend on both the molecular
structure and the organization of the macromolecules in the solid
state: their phase structure, morphology, molecular order and
molecular dynamics.
Flory, 1953; Kroschwitz, 1990
15
Therefore, experimental techniques like solid state NMR
are needed that can characterize the behavior of polymers
on a molecular level and on mesoscopic scales in order to
relate it to the macroscopic properties.
16
Solid State NMR
Suitable for the study of:
1. structure of unsolvable polymer
2. conformation、crystallization and morphology of solid state polymers
3. miscibility
4. domain size
17
The Hamiltonian and the nature
of spin interaction
H=Hext+Hint
Hext: interaction with external field
Hint: interaction with internal field
18
Hext=Hz+Hrf
Hz: Zeeman interaction with
external static magnetic field B0
Hrf: Zeeman interaction with radio
frequency field B1
Zeeman
interaction
19
Hint=HD+Hcs+HJ+HQ+HSR+Hen
HD: dipolar interaction
HCS:chemical shift interaction
HJ: indirect dipolar interaction
HQ: quadrupole interaction for nuclei with I>1/2
HSR: spin-rotation interaction
Hen: spin interaction of nuclei and electrons which creates
the Knight shift in magnetic or conducting materials.
20 20
Dipolar interaction
In liquid,fast relative movement between nuclei makes the dipole-dipole
interaction reduced dramatically(line width less than10-4 gauss). In the solid, the
relative movement is slow because nuclei are close to each other. So the dipole-
dipole interaction broaden the line width greatly(line width:10~20gauss).
21
Quadrupole interaction
)(5
2 22 abZQ eN
1H 13C 2H 14N 33S 35Cl
22
Pulse sequence design
Pulse sequence is the combination of pulses and delay
time between them. To identify different magnetic
circumstance, different pulse sequence, which enhance
some interaction and eliminate others, is used to get
wanted signal. The mutual point of special pulse
sequence is the adding of evolution time (e), which
permits selective interaction between spins.
23
DD(dipole decoupling)
Continuous high power irradiation on one spin species
eliminates the heteronuclear couplings to the other spin
species, regardless of the states of the magnetizations.
It should be noted that, because of the natural dilution
of the 13C atoms, homonuclear dipolar coupling
between two 13C nuclei can be neglected.
24
Chemical shift anisotropy
25
MSA
(magic spin angle)
)"2"")(cos31(6
1
)"""(3
1'
332211
2
33221133
26
MAS with different spin speed
27
CP(cross polarization)
HH condition (Hartmann-Hahn)
Enhancement factor: γ1H/γ13C≈4
Merit: the recycle delays, and thus the
measuring times are reduced due to the shorter
T11H, rather than T1
13C.
CHH CHH 131311
28
29
Efficiency of dipole-dipole relaxation
γ:gyromagnetic ratio
r: internuclear distance
τ:molecular correlation time
2 2 6
1
1H C H CH CDD
N rT
30
Combination of DD, CP and MAS
PMMA a、stationary b、DD/CP c、MAS/DD d、MAS/DD/CP
31
Reference:
1、薛奇 高分子结构研究中的光谱方法 高等教育出版社 1995第一版
2、王金山 核磁共振波谱仪与实验技术 机械工业出版社 1982第一版
3、Tongyin Yu and Mingming Guo Recent developments in 13C solid state high-resolution NMR of polymers Prog.Polym.Sci. Vol.15 pp:825-908 1990
4、K. Schmidt-Rohr and H.W.Spiess Multidimensional solid-state NMR and polymers academic press 1994
5、Alan E. Tonelli NMR Spectroscopy and Polymer Microstructure: The Conformational Connection AT&T Bell Laboratories 1989