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The NMR of solid polymer: an overview

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Part 1

NMR from liquid to solid

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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

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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

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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

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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

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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

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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

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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.

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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

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The Hamiltonian and the nature

of spin interaction

H=Hext+Hint

Hext: interaction with external field

Hint: interaction with internal field

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Hext=Hz+Hrf

Hz: Zeeman interaction with

external static magnetic field B0

Hrf: Zeeman interaction with radio

frequency field B1

Zeeman

interaction

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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.

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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).

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Quadrupole interaction

)(5

2 22 abZQ eN

1H 13C 2H 14N 33S 35Cl

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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.

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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.

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Chemical shift anisotropy

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MSA

(magic spin angle)

)"2"")(cos31(6

1

)"""(3

1'

332211

2

33221133

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MAS with different spin speed

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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

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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

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Combination of DD, CP and MAS

PMMA a、stationary b、DD/CP c、MAS/DD d、MAS/DD/CP

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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