研究目的
To develop polyimide films with high Tg and optical transmittance in visible range as the flexible substrate for optoelectric applications, as well as high gas permeability for small molecular gas as the gas separation membranes.
研究成果
The acetate-containing copoly(ether-imide)s exhibited excellent optical transparency (over 80% at 450 nm), high thermal stability (Tg > 333°C), and improved mechanical properties. Gas separation performance showed high permeabilities and selectivities, particularly for CO2/CH4, surpassing Robeson's 1991 upper bound and approaching the 2008 bound. The introduction of acetate groups and flexible ether linkages effectively enhanced properties, making these materials promising for optoelectronic and gas separation applications. Future work could focus on optimizing compositions for specific uses and exploring thermal rearrangement for further improvements.
研究不足
The study is limited to specific copolymer compositions and may not generalize to other polyimides. Gas permeability tests were conducted only for single gases at low pressure (0.05 MPa) and room temperature, which might not represent real-world conditions. The synthesis yield for BAHPPF was moderate (53.9%), and thermal stability decreased with higher BAHPPF content. Optimization of molar ratios and scaling up for industrial applications were not addressed.
1：Experimental Design and Method Selection:
The study involved synthesizing a diamine monomer (BAHPPF) using a modified two-step method, followed by copolymerization with BAF and 6FDA to prepare acetate-containing copoly(ether-imide)s via chemical imidization. The rationale was to incorporate bulky fluorene, flexible ether linkages, and acetate groups to reduce charge transfer complex effects and improve properties.
2：Sample Selection and Data Sources:
Samples were prepared with varying molar ratios of BAHPPF to BAF (e.g., PI-a to PI-g as listed in Table 1), using commercially available chemicals. Data were sourced from synthesized polymers and films.
3：List of Experimental Equipment and Materials:
Equipment included NMR spectrometer (Agilent-500), FTIR spectrometer (Nicolet IS 10), XRD (X'Pert powder), DSC (DSC 4000), TGA (Diamond TG-DTA 6300), UV-VIS spectrophotometer (Lambda 900), tensile tester (HY-0580), and gas permeability test setup with GC
4：Materials included BHF, 5-fluorine-2-nitrophenol, BAF, 6FDA, Pd/C, hydrazine hydrate, K2CO3, ethanol, acetic anhydride, pyridine, DMF, DMAc, and high-purity gases. Experimental Procedures and Operational Workflow:
78 Synthesis of BAHPPF involved nucleophilic substitution and reduction reactions. Copolymerization was done in DMAc with mechanical stirring, followed by chemical imidization using acetic anhydride and pyridine. Films were cast and thermally treated. Characterization involved FTIR, NMR, XRD, DSC, TGA, UV-VIS, tensile testing, and gas permeability measurements at 30°C and
5：05 MPa. Data Analysis Methods:
Data were analyzed using standard techniques: FTIR and NMR for structural confirmation, XRD for d-spacing calculation via Bragg's law, DSC for Tg determination, TGA for thermal stability, UV-VIS for transmittance, tensile tests for mechanical properties, and gas permeability calculated using equations for permeability and selectivity, with statistical averaging and comparison to Robeson's bounds.
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