The refining process of fluorene by melt crystallization was experimentally studied.The effects of the cooling rate,final temperature in the crystallization process,heating rate and final temperature in the sweating p...The refining process of fluorene by melt crystallization was experimentally studied.The effects of the cooling rate,final temperature in the crystallization process,heating rate and final temperature in the sweating process on the purity and yield of the product were investigated.The optimum conditions of the refining process of fluorene by melt crystallization were determined and a product with purity of 97.4% was obtained.The binary solid-liquid equilibrium phase diagram for fluorene and 2-methyl-diphenylene oxide is analyzed according to the experimental results.展开更多
A diamine(WuFDA) containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C―F)was designed and synthesized through three steps of reactions(halogenated reaction, Suzuki coupling re...A diamine(WuFDA) containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C―F)was designed and synthesized through three steps of reactions(halogenated reaction, Suzuki coupling reaction, and reduction reaction).Four kinds of high performance functional polyimides(WuFPI-6 F, WuFPI-BP, WuFPI-BT, and WuFPI-PM) were thus prepared by the condensation polymerization of WuFDA with four commercial dianhydride 6 FDA, BPDA, BTDA, and PMDA, respectively. The polyimides exhibited low dielectric constant, excellent thermal stability, outstanding solubility, good film-forming property, and mechanical properties. The dielectric constants of the polyimides were in the range of 2.28-2.88(f = 10~4 Hz). The 5% weight-loss temperatures(Td 5%)in nitrogen were in the range of 555-584 °C, and the glass transition temperatures(T_g) were in the range of 408-448 °C. The weight loss of WuFPI-BP maintaining at 450 and 500 °C for half an hour was only 0.33% and 1.26%, respectively. All the WuFPIs could be dissolved in almost all organic solvents, even chloroform. The tensile strength and tensile modulus of these films were in the ranges of 78.6-85.7 MPa and 3.1-3.2 GPa, respectively. In addition, the polyimides displayed light color with special fluorescent and resistive switching(ON-OFF) characteristics; the maximum fluorescence emission was observed at 422-424 nm in NMP solution and at 470-548 nm in film state. The memory devices with the configuration of indium tin oxide/WuFPIs/aluminum(ITO/WuFPIs/Al) exhibited distinct volatile memory characteristics of static random access memory(SRAM), with an ON/OFF current ratio of 10~5-10~6. These functional polyimides showed attractive potential applications in the field of high performance flexible polymer photoelectronic devices or polymer memory devices.展开更多
To improve the processability and thermal stability of polyimide, a series of novel phenylethynyl-endcapped oligoimides （PEPA-oligoimides） with calculated molecular weights （M_nC） were successfully prepared from t...To improve the processability and thermal stability of polyimide, a series of novel phenylethynyl-endcapped oligoimides （PEPA-oligoimides） with calculated molecular weights （M_nC） were successfully prepared from thermal imidization of 4,4＇-（9-fluorenylidene） dianiline （BAFL） as fluorenyl diamine, 4,4＇-oxy-diphthalic anhydride （ODPA） as aromatic dianhydride and 4-phenylethynylphthalic anhydride （4-PEPA） acted as reactive end-capping reagent at elevated temperatures. Experiment results indicated that the oligoimides were the mixtures of PEPA-endcapped oligomers with different degrees of polymerization characterized by MALDI-TOF mass spectra. The influence of chemical structures on the melt processabilities of the oligoimides, the thermal, dielectric and mechanical properties of the thermoset resins was studied. The typical oligoimide resin owned minimum melt viscosity of 0.2 Pa＇s at around 310 ℃and wide melting processing window, suitable for resin transfer molding （RTM）. Besides, its corresponding thermal-cured polyimide resin possessed glass transition temperature （T_g） as high as 514 ℃. The dielectric constants of polyimide resins decreased from 3.15 to 2.80 by reducing the M_nC. The mechanical properties of the polyimide neat resins were improved gradually with increasing M_nC. Finally, the carbon fiber/polyimide （C_f/PI） composite laminates showed excellent mechanical strength retention rate at 350 ℃, might be long-term served at extremely high temperature in aerospace and aviation field.展开更多
文摘The refining process of fluorene by melt crystallization was experimentally studied.The effects of the cooling rate,final temperature in the crystallization process,heating rate and final temperature in the sweating process on the purity and yield of the product were investigated.The optimum conditions of the refining process of fluorene by melt crystallization were determined and a product with purity of 97.4% was obtained.The binary solid-liquid equilibrium phase diagram for fluorene and 2-methyl-diphenylene oxide is analyzed according to the experimental results.
基金financial support by the National 973 Program of China (No. 2014CB643605)the National Natural Science Foundation of China (Nos. 51373204 and 51873239)+3 种基金the Science and Technology Project of Guangdong Province (Nos. 2015B090915003 and 2015B090913003)the China Postdoctoral Science Foundation (No. 2017M612801)the Leading Scientific, Technical and Innovation Talents of Guangdong Special Support Program (No. 2016TX03C295)the Fundamental Research Funds for the Central Universities (No. 161gzd08)
文摘A diamine(WuFDA) containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C―F)was designed and synthesized through three steps of reactions(halogenated reaction, Suzuki coupling reaction, and reduction reaction).Four kinds of high performance functional polyimides(WuFPI-6 F, WuFPI-BP, WuFPI-BT, and WuFPI-PM) were thus prepared by the condensation polymerization of WuFDA with four commercial dianhydride 6 FDA, BPDA, BTDA, and PMDA, respectively. The polyimides exhibited low dielectric constant, excellent thermal stability, outstanding solubility, good film-forming property, and mechanical properties. The dielectric constants of the polyimides were in the range of 2.28-2.88(f = 10~4 Hz). The 5% weight-loss temperatures(Td 5%)in nitrogen were in the range of 555-584 °C, and the glass transition temperatures(T_g) were in the range of 408-448 °C. The weight loss of WuFPI-BP maintaining at 450 and 500 °C for half an hour was only 0.33% and 1.26%, respectively. All the WuFPIs could be dissolved in almost all organic solvents, even chloroform. The tensile strength and tensile modulus of these films were in the ranges of 78.6-85.7 MPa and 3.1-3.2 GPa, respectively. In addition, the polyimides displayed light color with special fluorescent and resistive switching(ON-OFF) characteristics; the maximum fluorescence emission was observed at 422-424 nm in NMP solution and at 470-548 nm in film state. The memory devices with the configuration of indium tin oxide/WuFPIs/aluminum(ITO/WuFPIs/Al) exhibited distinct volatile memory characteristics of static random access memory(SRAM), with an ON/OFF current ratio of 10~5-10~6. These functional polyimides showed attractive potential applications in the field of high performance flexible polymer photoelectronic devices or polymer memory devices.
基金financially supported by the National Basic Research Program of China(No.2014CB643604)
文摘To improve the processability and thermal stability of polyimide, a series of novel phenylethynyl-endcapped oligoimides （PEPA-oligoimides） with calculated molecular weights （M_nC） were successfully prepared from thermal imidization of 4,4＇-（9-fluorenylidene） dianiline （BAFL） as fluorenyl diamine, 4,4＇-oxy-diphthalic anhydride （ODPA） as aromatic dianhydride and 4-phenylethynylphthalic anhydride （4-PEPA） acted as reactive end-capping reagent at elevated temperatures. Experiment results indicated that the oligoimides were the mixtures of PEPA-endcapped oligomers with different degrees of polymerization characterized by MALDI-TOF mass spectra. The influence of chemical structures on the melt processabilities of the oligoimides, the thermal, dielectric and mechanical properties of the thermoset resins was studied. The typical oligoimide resin owned minimum melt viscosity of 0.2 Pa＇s at around 310 ℃and wide melting processing window, suitable for resin transfer molding （RTM）. Besides, its corresponding thermal-cured polyimide resin possessed glass transition temperature （T_g） as high as 514 ℃. The dielectric constants of polyimide resins decreased from 3.15 to 2.80 by reducing the M_nC. The mechanical properties of the polyimide neat resins were improved gradually with increasing M_nC. Finally, the carbon fiber/polyimide （C_f/PI） composite laminates showed excellent mechanical strength retention rate at 350 ℃, might be long-term served at extremely high temperature in aerospace and aviation field.
