研究目的
To characterize the phase transition of amorphous poly(9,9-di-n-octyl-2,7-fluorene) thin film during thermal annealing and investigate the underlying mechanism.
研究成果
The amorphous PFO thin film undergoes phase transitions to κ-phase above 80 °C and nematic phase at 160 °C during heating, with reverse transitions during cooling. The κ-phase exhibits ordered main chains and less ordered side chains, while the α-phase has increased side-chain order below 80 °C. The rearrangement of side chains dominates below 80 °C, and main chains dominate above 80 °C.
研究不足
The study used thick films for FTIR measurements which may not fully represent thin film behavior; the critical temperature of 80 °C and mechanisms are specific to PFO and may not generalize to other polymers; in situ techniques may have limitations in resolution or sensitivity for detecting subtle phase changes.
1：Experimental Design and Method Selection:
In situ characterization using grazing incidence X-ray diffraction (GIXRD), UV-visible absorption spectroscopy, and Fourier transform infrared spectroscopy (FTIR) to study phase transitions during thermal annealing.
2：Sample Selection and Data Sources:
PFO thin films spin-coated from 10 mg/mL PFO/toluene solution onto silicon wafers for GIXRD, ITO glass for UV-visible absorption, and thick films on KBr for FTIR.
3：List of Experimental Equipment and Materials:
Rigaku Smart Lab X-ray diffractometer with copper target, Anton Parr DHS900 thin-film hot stage, scintillation counter; Beijing Synchrotron Facility beam line 1W1A with Huber diffractometer and Mar345 imaging plate for 2D GIXRD; Persee TU-1901 UV-visible spectrophotometer with hot stage; Nicolet 6700 spectrometer with MCT detector and Linkam FTIR-600 hot stage.
4：Experimental Procedures and Operational Workflow:
Samples were annealed at various temperatures (20 °C to 160 °C), held for 30 min at each temperature before measurements. GIXRD scans from 3° to 30° at
5：05° steps, UV-visible scans from 300 to 500 nm at 1 nm steps, FTIR scans averaged 16 times at 4 cm?1 resolution. Data Analysis Methods:
Bragg equation for d-spacing calculation, analysis of diffraction peak intensities and shifts, spectral changes in absorption and IR peaks to infer structural changes.
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X-ray diffractometer
Smart Lab
Rigaku
Conducting grazing incidence X-ray diffraction (GIXRD) measurements to analyze crystal structure and phase transitions.
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Thin-film hot stage
DHS900
Anton Parr
Controlling temperature during in situ measurements for thermal annealing experiments.
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Scintillation counter
Detecting X-ray diffraction signals in the GIXRD setup.
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Imaging plate
Mar345
Recording two-dimensional GIXRD patterns at the synchrotron facility.
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UV-visible spectrophotometer
TU-1901
Persee
Measuring in situ UV-visible absorption spectra to study electronic transitions and conjugation length changes.
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FTIR spectrometer
Nicolet 6700
Conducting Fourier transform infrared spectroscopy to analyze molecular vibrations and side chain packing.
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Hot stage
FTIR-600
Linkam
Controlling temperature for in situ FTIR measurements.
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PFO
Sigma-Aldrich Inc.
The polymer material used for thin film preparation in the study.
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