Applications of SANS II

THE NIST SANS USER RESEARCH Use of the NG3 SANS Instrument at NIST Condensed Matter Other Materials Science Biology Polymers Complex Fluids Polymers 50% Complex Fluids 26% Biology 11% Other Material Science 9% Condensed Matter 4% SANS RESEARCH TOPICS Boualem Hammouda National Institute of Standards and Technology Center for Neutron Research 1. SANS from Pluronics 2. Polymer Blend Thermodynamics 3. Helix-to-Coil Transition in DNA 1. SANS FROM PLURONICS Pluronics are triblock copolymers: PEO-PPO-PEO PEO: -CH2CH2O- is hydrophillic PPO: -CH2CH2(CH3)O- is hydrophobic 10% P85 pluronic in d-water at 60 o C 100 SANS data 10 coherent cross section 1 0.1 incoherent cross section 0.01 0.001 0.01 0.1 -1 1 Scattering Vector (Å ) P85 Pluronic forms micelles at high temperatures 10% P85 Pluronic in d-water 100 60 C 50 C 40 C 10 30 C 20 C o o o o o Porod region 1 Guinier region 0.1 0.001 0.01 0.1 -1 1 Scattering Vector (Å ) GUINIER PLOT I(Q) = I(0) exp(-Q2Rg2/3) 1 Pluronics/d-water, 10 %, 20 o C Guinier Plot Guinier region 0.8 0.6 R = 34 Å g 0.4 Guinier region 0.2 0 0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 Q (A ) 2 -2 SANS from Pluronics Micelles PPO PEO PEO PPO PEO PEO PPO low temperature 100 high temperature 100 100 polymer 10 sphere 10 sphere and polymer 10 1 1 1 0.1 0.1 0.1 0.01 0.001 0.01 0.1 1 0.01 0.001 0.01 0.1 1 Scattering Wavenumber Q (Å-1) 0.01 0.001 0.01 0.1 1 Scattering Wavenumber Q (Å-1) Scattering Wavenumber Q (Å-1) Polymer Sphere Sphere and polymer 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+Q2Rg2]/(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 Percus Yevick Model 100 100 sphere 10 10 Solution of Spheres 1 1 0.1 0.1 0.01 0.001 0.01 0.1 1 0.01 0.001 0.01 0.1 1 Scattering Wavenumber Q (Å-1) Scattering Wavenumber Q (Å-1) Single sphere Solution of spheres Solution of Spheres with Polymers PEO PPO PEO PEO PPO PEO 100 solution of spheres with polymers 10 PEO PPO PEO 1 0.1 PEO PPO PEO PEO PPO PEO 0.01 0.001 0.01 0.1 1 Scattering Wavenumber Q (Å-1) Fit SANS Data to a Model of Concentrated Core-Shell Particles  d  N   b A I(Q)  (Q)     dΩ  V   v A  b b   C  V F(QR )  B  A v v  A  B C  b  C  V F(QR ) V F(QR )    B A A v  B   C   2 S( Q ) 10% P85 Pluronic/D2O, 40 oC solvent region C shell region B In the core: 2,795 PPO monomers 690 PEO monomers 490 D2O molecules core region A In the shell: 2,943 PEO monomers 34,167 D2O molecules (b/v)C = 6.4*10-6 Å-2 (b/v)B = 5.9*10-6 Å-2 (b/v)A = 1*10-6 Å-2 RA=42.6 Å RB=71.4 Å 2. POLYMER BLENDS THERMODYNAMICS SANS Intensity: I(Q) = d(Q)/dW = (b1/v1-b2/v2)2 ST(Q) Thermodynamics: ST-1(Q=0) = (1/kBT)(d2G/df12); G: Gibbs Free Energy. The Random Phase Approximation: ST-1(Q) = 1/(n1f1v1P(QRg1) + 1/(n2f2v2P(QRg2) -2 c12(T)/v0 Mixed polymer blend Phase separated blend 1 nm 0.1 mm Gibbs Free Energy hPEB/dPMB, M =40,100 g/mole/88,400 g/mole 2 10 1 10 -6 w -6 270 K 220 K 200 K 0 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -6 binodal points spinodal points critical point -6 -6 -6 -6 -6 0 0.2 0.4 0.6 1 0.8 1 Volume Fraction f hPEB/dPMB, M =40,100 g/mole/88,400 g/mole w 300 one-phase spinodal region 250 200 150 spinodal line 100 two-phase spinodal region 50 0 0 0.2 0.4 0.6 1 0.8 1 Volume Fraction f SANS FROM POLYMER BLEND MIXTURES Polymers: Polyethylbutylene / Polymethylbutylene hPEB -(C6H12)Molecular Weights: Volume Fractions: Mw=44,100 g/mole fhPEB=0.57 / dPMB -(C5H5D5)Mw=88,400 g/mole fdPMB=0.43 hPEB/dPMB, M =40,100 g/mole/88,400 g/mole w 120 100 10 C 80 20 C 30 C 60 40 C 50 C o o o o o 40 20 0 0 0.01 0.02 0.03 0.04 0.05 -1 0.06 0.07 Scattering Vector Q (Å ) ZIMM PLOT hPEB/dPMB, M =40,100 g/mole/88,400 g/mole w 0.2 0.15 Data at 10 C o 0.1 slope gives radius of gyration 0.05 0 0 intercept gives 1/I(Q=0) 0.0005 0.001 2 0.0015 -2 0.002 0.0025 Q (Å ) hPEB/dPMB, M =40,100 g/mole/88,400 g/mole w 0.01 0.009 0.008 0.007 0.006 T = 220 K s 0.005 0.003 0.0031 0.0032 0.0033 0.0034 -1 0.0035 0.0036 Inverse Temperature (K ) hPEB/dPMB, M =40,100 g/mole/88,400 g/mole w 300 250 one-phase mixed region critical point 200 1 nm 150 spinodal line two-phase spinodal region 100 50 0.1 mm 0 0 0.2 0.4 0.6 1 0.8 1 Volume Fraction f 3. HELIX-TO-COIL TRANSITION IN DNA DNA is the basic building block for life. It encodes for the synthesis of proteins. THE DNA MOLECULE Phosphate group Amine bases Purines H N N H HOCH2 O O O Sugar Pyrimidines O N H H3C H N H N O H N N OH H H H H O H HO H Adenine (A) H Thymine (T) H H N N P O D-desoxyribose H N H N H O N H N N H Guanine (G) H N O H Cytosine (C) Nucleotide H N H O Phosphate groupO P O N Base N C H O H O CH2 C H H O Sugar H H C C H HO THE DNA HELIX A G T Major groove A T A G A Minor groove C T A T C Pitch 30-40 Å A G A C Repeat distance per base pair=3.4 Å HELIX-TO-COIL TRANSITION IN DNA 4 % DNA in d-ethylene glycol and in d-water, 0.1 M NaCl Second Temperature 2.6 4% DNA/d-ethylene glycol 4% DNA/d-water 2.4 UV 2.8 Transition Temperatures 2.2 2 First Temperature 1.8 20 30 40 50 60 70 o 80 90 100 Temperature ( C) 4% DNA in d-ethylene glycol, 0.1M NaCl SANS 10 25 C 50 C o o 1 0.1 0.01 0.1 -1 Scattering Wavenumber (Å ) POROD PLOT I(Q) ~ C/Qm 4% DNA in d-ethylene glycol, 0.1 M NaCl, T=50 C -1.6 o -1.7 -1.8 slope = -1.76 -1.9 -2 -2.1 Porod Plot -2.2 -2.3 -0.75 -0.7 -0.65 -0.6 -0.55 -0.5 -0.45 -0.4 -0.35 Log(Q) NONLINEAR LEAST-SQUARES FIT Functional form: I(Q) = C/[1+(QL)m] + Background C: solvation intensity L: correlation length m: Porod exponent 4 % DNA in d-ethylene glycol, 0.1 M NaCl, 25 C o SANS Data 0.2 solvation intensity C 0.1 0.09 0.08 0.04 0.06 0.08 0.1 0.3 -1 background Scattering Wavenumber ( Å ) Solvation Intensity 4 % DNA in d-ethylene glycol, 0.1 M NaCl 0.17 0.165 0.16 helix transition 0.155 0.15 0.145 coil 0.14 0.135 0 20 40 o 60 80 Temperature ( C) Correlation Length 4% DNA in d-ethylene glycol, 0.1 M NaCl 15 14 13 coil 12 12.3 Å transition 11 12.3 Å 10 helix 9 8.5 Å 8 0 20 40 60 o 80 100 8.5 Å Temperature ( C) Porod Exponent 4 % DNA in d-ethylene glycol, 0.1 M NaCl 4 3.5 helix 3 transition 2.5 coil 2 1.5 0 20 40 60 o 80 100 Temperature ( C) Reference: B. Hammouda and D. Worcester, “The DNA Denaturation Transition of DNA in Mixed Solvents”, Biophysical Journal (accepted 2006). POROD EXPONENTS Porod region 1D object 1/Q1 2D object 1/Q2 3D object 1/Q4 1/Q1.67 1/Q2 MASS FRACTALS 1/Q3 1/Q3 1/Q4 SURFACE FRACTALS 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/ hammouda@nist.gov