Imaging of Two-Dimensional Distribution of Molecular Orientation in Poly(ethylene oxide) Spherulite Using IR Spectrum and Birefringence

Abstract

The two-dimensional quantitative imaging of molecular chain orientation is presented together with a chemical FT-IR imaging, in comparison with the optical birefringence imaging. The molecular chain orientation of the spherulite of poly(ethylene oxide) (PEO) is visualized using the four polarizations method of FT-IR imaging. The magnitude of orientation function and the azimuth angle of orientation axis are calculated with the FT-IR absorbance measured with a linear polarizer settled at four different angles. Retardation and the slow axis in a refractive index ellipsoid are calculated using transmission intensity measured with an electrical-controlled variable elliptical analyzer and a circular polarizer. In spite of the 6 times difference of the spatial resolution, the azimuth angle image determined from FT-IR imaging detects the change of molecular chain orientation, giving the similar line profiles of azimuth angle to that of slow axis determined from birefringence on the spherulite interface. A good correspondence in the direction of orientation axis of the molecular chain with the slow axis of a refractive index ellipsoid at each point is confirmed visually from the comparison of vector representation. The FT-IR imaging with four polarizations method enables to visualize the difference of molecular chain orientation of each component of the polymer blend spherulite.

Orientational Mapping Augmented Sub-Wavelength Hyper-Spectral Imaging of Silk

“…To quantify the order the standard second momentum P 2 (θ) of the orientation function also known as the Herman’s function can be expressed via the absorbance ratio at two perpendicular linear polarisations, the dichroic ratio, (see Supplement for details) as 32 , 37 : where θ is the angle between the transition dipole moment and the selected orientation (along silk fiber). The second momentum of the C=O (Amide I) band was found P 2 ( θ ) = −0.36 from the Raman measurements 36 (−0.5 corresponds to a pure perpendicular orientation to the fiber axis).…”

Macromolecular Orientation in Biological Tissues Using a Four-Polarization Method in FT-IR Imaging

“… 5 , 6 , 9 , 10 Later, a four-polarization method was proposed, 11 − 13 which gave a great tool for further polymer analysis, 14 , 15 especially when combined with imaging modalities. 12 , 13 , 16 A variety of other techniques may be used to determine molecular orientation: nuclear magnetic resonance, X-ray diffraction, polarized visible microscopy, fluorescence microscopy, second-harmonic generation (SHG), or Raman spectroscopy (RS). 17 However, each has specific requirements or drawbacks, such as a specific sample form (liquid or crystallized), lack of biochemical information, a complex instrumentation setup, or the need for labeling.…”

Super-resolved 3D mapping of molecular orientation with vibrational techniques

“…The disadvantages of the two-polarization method have been aided by the development of the fourpolarization approach which allows molecular bond orientation determination, independently from the choice of incident light polarization. Absorbance dependence from linear polarization may be described by a simple formula, as follows 12,13,30 :…”

“…Next, the fourpolarization method (4P) has been proposed, which enabled the study of the in-plane organization of molecules in complex systems. The first applications of IR imaging with 4P on polymeric systems [11][12][13][14] were followed by active compound visualization 15 and recently by human tissue microarrays analysis by Koziol et al in 2020 16,17 .…”