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Analysis of spatial orientation distribution of highly oriented polyimide film using micro ATR-FTIR spectroscopic imaging method
- Source :
- Polymer. 221
- Publication Year :
- 2021
-
Abstract
- Molecular orientation of aromatic polyimides (PIs) and their precursor of poly(amic ester)s (PAE) in the biaxially oriented films were analyzed by polarized microscopic attenuated-total-reflection Fourier-transform infrared absorption spectroscopy (micro pATR-FTIR) imaging. The films were prepared by shearing a lyotropic liquid crystal (LC) solution of the PAE on a glass substrate and subsequent drying under a N2 flow, and the long axis of polymer chains were distributed around the shear direction. In the film, streak-shaped defects were observed along the shear direction with optical microscopy. Such structural heterogeneities on the micrometer (μm) scale are expected to be visualized in spatial distribution map of molecular orientation order acquired with micro pATR-FTIR imaging. In this study, uniaxial orientation order parameter, S, and a mean square cosine value, ⟨cos2ψ⟩, were used to quantify the degree of orientation of the PI main chain and that of aromatic imide plane, respectively. It was revealed that the films are apparently homogeneous in the spatial distribution map of the S, while the films exhibited obvious heterogeneity in that of ⟨cos2ψ⟩, in which “face-on” and “edge-on” orientation domains coexist. The results indicate that orientation direction of the rigid PI chains is fixed in the averaged orientation direction of the oriented PAE matrix during thermal imidization, while the aromatic imide ring can be rotated around the main chain. Furthermore, cracks in the PI film were successfully visualized by ATR-FTIR imaging, and the orientation distribution inside the cracks was investigated. Through this structural study, we validated the quantitative capability of the micro pATR-FTIR imaging method thorough the analyses of highly oriented PI films and demonstrated its ability to investigate μm-scale heterogeneity on the basis of molecular orientation analyses.
- Subjects :
- Shearing (physics)
Materials science
Polymers and Plastics
Organic Chemistry
Infrared spectroscopy
02 engineering and technology
Substrate (electronics)
010402 general chemistry
021001 nanoscience & nanotechnology
01 natural sciences
0104 chemical sciences
law.invention
Micrometre
Optical microscope
Lyotropic liquid crystal
law
Materials Chemistry
Composite material
Fourier transform infrared spectroscopy
0210 nano-technology
Polyimide
Subjects
Details
- Language :
- English
- ISSN :
- 00323861
- Volume :
- 221
- Database :
- OpenAIRE
- Journal :
- Polymer
- Accession number :
- edsair.doi.dedup.....e578359984299dbdddf00da9bf2575c8