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
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
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
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
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
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
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.
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
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)
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)
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
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
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
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
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
)
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
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
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
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
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
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
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
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
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
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
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
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).
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
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/