《 Modern Research Methods in Polymer
Science》Drs. Wei Tian & Yanhui Chen
Sep-Dec. 2014
X-ray diffraction analysis
Fundamental for X-ray diffraction
Wide Angle X-ray Diffraction (WAXD)
Small Angle X-ray Scattering (SAXS)
Modern Research Methods in Polymer Science
Fundamental for X-ray diffraction
Production of X-rays
λ = 0.5 ~ 2.5Å
Cross section of sealed-off filament X-ray tube
Fundamental for X-ray diffraction
Production of in situ Synchrotron X-rays
0.1nm 100nmConfiguration order Crystallization Phase separation Nano self-assembly
BNL NSLSI
Fundamental for X-ray diffraction
Advantages of in situ Synchrotron X-rays• High Flux: high intensity photon beam allows rapid
experiments or use of weakly scattering crystals.
• High Brilliance: highly collimated photon beam generated by a small divergence and small size source (spatial coherence)
• Small Beam Footprint: 2D or 3D studies to sub-mm/micron length scale
• Wavelength Tunability: Choice of energy region (from IR to Hard X-Ray) to suit the problem
Fundamental for X-ray diffraction
Bragg’s Law and DiffractionConstructive interference
Destructive interference
n λ =2dsinθ
Fundamental for X-ray diffraction
Diffraction methods
multicrystal
monocrystal
Photographic method
Diffractometer method
Debye Scherrer method
Focusing method
Pinhole method
Lauemethod
Rotation method
入射X射线
Fundamental for X-ray diffraction
General Application
• Measure the average spacings between layers or rows of atoms
• Determine the orientation of a single crystal or grain
• Find the crystal structure of an unknown material
• Measure the size, shape and internal stress of small crystalline regions
Fundamental for X-ray diffraction
Description
Tiwari, V. K.; Macromolecules 2013, 46 (14), 5595-5603.
Wide Angle X-ray Diffraction (WAXD)
Basic conceptWAXD is an X-ray-diffraction technique that is often used to determine the crystalline structure of polymers. This technique specifically refers to the analysis of Bragg peaks scattered to wide angles (2θ ≥ 6º), which (by Bragg's law) implies that they are caused by sub-nanometer-sized structures.
(a) Random crystals
(b) Partial oriented crystals
(c) Completely oriented crystals
(d) Amorphous phase
Wide Angle X-ray Diffraction (WAXD)
Application
Crystal determination
Crystal parameters: grain size, crystallinity, orientation
Crystal lattice distortion
β-crystals
Wide Angle X-ray Diffraction (WAXD)
Extended Application--in situ detection
Description
Wide Angle X-ray Diffraction (WAXD)
Che, J.; et al. Macromolecules 2013, 46, 5279-5289.
Small Angle X-ray Scattering (SAXS)
Basic conceptSmall-angle X-ray scattering (SAXS) is a small-angle scattering technique where the elastic scattering of X-rays (wavelength 0.1 ~ 0.2 nm) by a sample, which has inhomogeneities in the nm-range, is recorded at very low angles (typically 2 6º) 。
Small Angle X-ray Scattering (SAXS)
Application
Qualitative analysis:(1) Homogeneity or homogeneity of
system electronic density
(2) Dispersibility of scatters
(3) Significance of interphase
(4) Self-similarity of scatters
Systems : colloids of all types, metals, cement, oil, polymers, plastics, proteins, foods and pharmaceuticals and can be found in research as well as in quality control.
0 % 5.8 % 17.6 % 40 % 50 %
Small Angle X-ray Scattering (SAXS)
Quantitative analysis : Averaged particle sizes
Shapes, distribution
Surface-to-volume ratio
Long period in crystalline system
Application
References
1. 田 威,孔 杰,胡思海 . 高聚物的现代研究方法 [M] ,西北工业大学出版社, 2014.
2. http://en.wikipedia.org/wiki/X-ray_crystallography#Synchrotron_Radiation
3. http://en.wikipedia.org/wiki/Wide-angle_X-ray_scattering
4. http://en.wikipedia.org/wiki/Small-angle_X-ray_scattering