THE NIST SANS USER RESEARCH. SANS RESEARCH TOPICS Boualem Hammouda National Institute of Standards...
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![Page 1: THE NIST SANS USER RESEARCH. SANS RESEARCH TOPICS Boualem Hammouda National Institute of Standards and Technology Center for Neutron Research 1. SANS.](https://reader036.fdocuments.in/reader036/viewer/2022062321/56649e585503460f94b517da/html5/thumbnails/1.jpg)
Use of the NG3 SANS Instrument at NIST
Polymers 50%Complex Fluids 26%Biology 11%Other Material Science 9%Condensed Matter 4%
Polymers
Complex Fluids
Biology
Other Materials Science
Condensed Matter
THE NIST SANS USER RESEARCH
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SANS RESEARCH TOPICS
Boualem Hammouda
National Institute of Standards and TechnologyCenter for Neutron Research
1. SANS from Pluronics
2. Polymer Blend Thermodynamics
3. Helix-to-Coil Transition in DNA
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Pluronics are triblock copolymers: PEO-PPO-PEO
PEO: -CH2CH2O- is hydrophillicPPO: -CH2CH2(CH3)O- is hydrophobic
0.01
0.1
1
10
100
0.001 0.01 0.1 1
10% P85 pluronic in d-water at 60 oC
SANS data
Scattering Vector (Å -1)
incoherent cross section
coherent cross section
1. SANS FROM PLURONICS
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0.1
1
10
100
0.001 0.01 0.1 1
10% P85 Pluronic in d-water
60 oC
50 oC
40 oC
30 oC
20 oC
Scattering Vector (Å -1)
Guinier region
Porod region
P85 Pluronic forms micelles at high temperatures
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GUINIER PLOT
I(Q) = I(0) exp(-Q2Rg2/3)
Guinier region
Guinier region
0
0.2
0.4
0.6
0.8
1
0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016
Pluronics/d-water, 10 %, 20 oC
Guinier Plot
Q2 (A-2)
Rg = 34 Å
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SANS from Pluronics Micelles
PEO
PEO
PPO
PEO
0.01
0.1
1
10
100
0.001 0.01 0.1 1
sphere
Scattering Wavenumber Q (Å-1)
0.01
0.1
1
10
100
0.001 0.01 0.1 1
polymer
Scattering Wavenumber Q (Å-1)
0.01
0.1
1
10
100
0.001 0.01 0.1 1
sphere and polymer
Scattering Wavenumber Q (Å-1)
Polymer Sphere Sphere and polymer
PPO
PEO
PPO
low temperature high temperature
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SINGLE PARTICLE AND INTER-PARTICLE STRUCTURE FACTORS
I(Q) = (NA/V)VA2 (bA/vA-bB/vB)2 P(Q) S(Q)
NA: number of particles, VA: particle volume, V: sample volume
(bA/vA-bB/vB)2 = contrast factor
P(Q): single-particle structure factor
S(Q): inter-particle structure factor
P(Q) = [F(QR)]2 = 3[sin(QR)/(QR)3-cos(QR)/(QR)2]2 for sphere of radius R.
P(Q) = 2[exp(-Q2Rg2)-1+Q2Rg
2]/(Q2Rg2)2 for polymer of radius of gyration Rg.
S(Q) given by Percus Yevick model for solution of hard spheres.
S(Q) given by the Random Phase Approximation model for polymer mixtures.
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Solution of Spheres
0.01
0.1
1
10
100
0.001 0.01 0.1 1
sphere
Scattering Wavenumber Q (Å-1)
Single sphere Solution of spheres
0.01
0.1
1
10
100
0.001 0.01 0.1 1
Solution of Spheres
Scattering Wavenumber Q (Å-1)
Percus Yevick Model
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Solution of Spheres with Polymers
PPOPEOPEO
PPOPEOPEO
PPOPEOPEO
PPOPEOPEO
PPOPEOPEO
0.01
0.1
1
10
100
0.001 0.01 0.1 1
solution of spheres with polymers
Scattering Wavenumber Q (Å-1)
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Fit SANS Data to a Model of Concentrated Core-Shell Particles
RA=42.6 Å
RB=71.4 Å
(b/v)A = 1*10-6 Å-2
(b/v)B = 5.9*10-6 Å-2
(b/v)C = 6.4*10-6 Å-2
core region A
shell region B
solvent region C
In the core:2,795 PPO monomers690 PEO monomers490 D2O molecules
In the shell:2,943 PEO monomers34,167 D2O molecules
10% P85 Pluronic/D2O, 40 oC
)Q(S)Q(
2
)A
F(QRAV)
BF(QR
BV
Cv
Cb
Bv
Bb
)A
F(QRAV
Cv
Cb
Av
Ab
V
N
dΩ
dI(Q)
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SANS Intensity: I(Q) = d(Q)/d = (b1/v1-b2/v2)2 ST(Q)
Thermodynamics: ST-1(Q=0) = (1/kBT)(2G/1
2); G: Gibbs Free Energy.
The Random Phase Approximation:
ST-1(Q) = 1/(n11v1P(QRg1) + 1/(n22v2P(QRg2) -2 12(T)/v0
2. POLYMER BLENDS THERMODYNAMICS
0.1 m1 nm
Mixed polymer blend Phase separated blend
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Gibbs Free Energy
-6 10-6
-5 10-6
-4 10-6
-3 10-6
-2 10-6
-1 10-6
0
1 10-6
2 10-6
0 0.2 0.4 0.6 0.8 1
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
270 K220 K200 K
Volume Fraction 1
spinodal points
binodal points
critical point
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0
50
100
150
200
250
300
0 0.2 0.4 0.6 0.8 1
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
Volume Fraction 1
two-phase spinodal region
spinodal line
one-phase spinodal region
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SANS FROM POLYMER BLEND MIXTURES
Polymers: Polyethylbutylene / Polymethylbutylene
hPEB -(C6H12)- / dPMB -(C5H5D5)-
Molecular Weights: Mw=44,100 g/mole Mw=88,400 g/mole
Volume Fractions: hPEB=0.57 dPMB=0.43
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0
20
40
60
80
100
120
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
10 oC
20 oC
30 oC
40 oC
50 oC
Scattering Vector Q (Å-1
)
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0
0.05
0.1
0.15
0.2
0 0.0005 0.001 0.0015 0.002 0.0025
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
Data at 10 oC
Q2 (Å-2)
intercept gives 1/I(Q=0)
slope gives radius of gyration
ZIMM PLOT
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0.005
0.006
0.007
0.008
0.009
0.01
0.003 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
Inverse Temperature (K -1)
Ts = 220 K
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0
50
100
150
200
250
300
0 0.2 0.4 0.6 0.8 1
hPEB/dPMB, Mw=40,100 g/mole/88,400 g/mole
Volume Fraction 1
two-phase spinodal region
one-phase mixed region
spinodal line
critical point
0.1 m
1 nm
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3. HELIX-TO-COIL TRANSITION IN DNA
DNA is the basic building block for life. It encodes for the synthesis of proteins.
H
H
H
H
H
H
P
O
C
C C
O
C
N
N
NH OO
HO
CH2
O
O
Nucleotide
H H
Phosphate group
Sugar
Base
P O
O
O
O
Phosphate group
SugarAmine bases
O
H
HHO
OHHOCH2
HH
D-desoxyribose
Purines Pyrimidines
HAdenine (A)
Guanine (G) Cytosine (C)
Thymine (T)
H HN
N
NN
NH
H
H
H
H
H H
HN
N
N
NN
OH
H
H
H
N
N
N O
H
H
H
O
ON
NH3C
THE DNA MOLECULE
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THE DNA HELIX
A
A
A
A
A
A
A
T
T
T
T
G
G
G C
C
C
Pitch30-40 Å
Repeat distanceper base pair=3.4 Å
Major groove
Minor groove
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HELIX-TO-COIL TRANSITION IN DNA
1.8
2
2.2
2.4
2.6
2.8
20 30 40 50 60 70 80 90 100
4 % DNA in d-ethylene glycol and in d-water, 0.1 M NaCl
4% DNA/d-ethylene glycol4% DNA/d-water
Temperature ( oC)
Transition Temperatures
First Temperature
Second Temperature
UV
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0.1
1
10
0.01 0.1
4% DNA in d-ethylene glycol, 0.1M NaCl
25 oC
50 oC
Scattering Wavenumber (Å -1)
SANS
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POROD PLOT I(Q) ~ C/Qm
-2.3
-2.2
-2.1
-2
-1.9
-1.8
-1.7
-1.6
-0.75 -0.7 -0.65 -0.6 -0.55 -0.5 -0.45 -0.4 -0.35
4% DNA in d-ethylene glycol,
0.1 M NaCl, T=50 oC
Porod Plot
Log(Q)
slope = -1.76
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NONLINEAR LEAST-SQUARES FIT
0.08
0.09
0.1
0.2
0.04 0.06 0.08 0.1 0.3
4 % DNA in d-ethylene glycol,
0.1 M NaCl, 25 oC
SANS Data
Scattering Wavenumber ( Å -1)
background
solvation intensity C
Functional form: I(Q) = C/[1+(QL)m] + Background
C: solvation intensityL: correlation lengthm: Porod exponent
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0.135
0.14
0.145
0.15
0.155
0.16
0.165
0.17
0 20 40 60 80
4 % DNA in d-ethylene glycol, 0.1 M NaCl
Temperature ( oC)
helix
coil
transition
Solvation Intensity
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8
9
10
11
12
13
14
15
0 20 40 60 80 100
4% DNA in d-ethylene glycol, 0.1 M NaCl
Temperature ( oC)
helix
coil
transition
Correlation Length
12.3 Å
12.3 Å
8.5 Å
8.5 Å
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1.5
2
2.5
3
3.5
4
0 20 40 60 80 100
4 % DNA in d-ethylene glycol, 0.1 M NaCl
Temperature ( oC)
helix
coil
transition
Porod Exponent
Reference: B. Hammouda and D. Worcester, “The DNA Denaturation Transition of DNA in Mixed Solvents”, Biophysical Journal (accepted 2006).
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1D object 2D object 3D object
1/Q1.67 1/Q2 1/Q3
MASS FRACTALS SURFACE FRACTALS
1/Q1 1/Q2 1/Q4
1/Q3 1/Q4
Porod region
POROD EXPONENTS
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CONCLUSIONS
-- The SANS technique is a valuable characterization method.
-- SANS has been effective in complex fluids, polymers, biology, etc.
-- SANS can determine structures, phase transitions, and morphology.
-- The NG3 SANS instrument at NIST gets over 150 users per year, resulting in over 40 publications per year.
ACKNOWLEDGMENTS
NSF-DMR, Steve Kline, Nitash Balsara, David Worcester.
CHECK IT OUT: http://www.ncnr.nist.gov/programs/sans/
http://www.ncnr.nist.gov/staff/hammouda/