In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was cause...In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.展开更多
A novel experimental route to fabricate porous polyimide membranes （PPMs） with ideal air permeability was reported. The polymer solution layer consisting of the corresponding polyamic acid （PAA）, solvent, and dibu...A novel experimental route to fabricate porous polyimide membranes （PPMs） with ideal air permeability was reported. The polymer solution layer consisting of the corresponding polyamic acid （PAA）, solvent, and dibutyl phthalate （DBP） with a boiling temperature of 340℃ was treated by a simple process. The polymer solution layer was first treated at a lower temperature （about 150℃）, then the received solid membrane was further imidized at a higher temperature （about 270℃）, and finally, DBP was removed from the membrane at a temperature above its boiling temperature. The final asymmetric polyimide membrane with a dense skin layer was obtained. To improve the air permeability of the polyimide membranes, the polymer solution layer was treated between two substrates. And the PPMs with open pores on both sides are fabricated and the air permeability of the films is improved greatly.展开更多
A 4,4＇-（ hexafluoroisopropylidene ） diphthalic anhydride- bis [ 4-（ 4-aminophenoxy ） phenyl J sulfone （ 6FDA-BAPS） polyamic acid （PAA） was synthesized by using 6FDA and BAPS as reactive monomers and N-methyl-...A 4,4＇-（ hexafluoroisopropylidene ） diphthalic anhydride- bis [ 4-（ 4-aminophenoxy ） phenyl J sulfone （ 6FDA-BAPS） polyamic acid （PAA） was synthesized by using 6FDA and BAPS as reactive monomers and N-methyl-2-pyrrolidone（NMP） as a solvent. The PAA solution was prepared into membranes by casting technology and was also prepared into PAAhollow fiber membranes by dry wet spinning process. The PAA membranes and PAA hollow fiber membranes were exposed tothe high-temperature thermal cyclization at about 300 ℃ to produce a 6FDA-BAPS polyimide （PI） membranes and hollow fibermembranes. The structure and properties of 6FDA-BAPS PI products were studied. The results showed that the obtained 6FDA-BAPS PI was the target product which was of fairly good solubility in NMP, dimethylaeetamide and tetrahydrofuran ;the 6FDA-BAPS PI possessed the dense outer layer and the loose and porous support layer;the hollow fiber membranes had the 5 % weightloss temperature of 511 ℃ and breaking strength 26.5 MPa, indicating relatively high thermal and mechanical properties.展开更多
Flexible UV-sensitive photodetectors and optoelectronic synapses are highly desired in numerous sensing areas and neuromorphic computations.Herein,the large-size,flat,and continuous sheet of polyamic acid(PAA),a two-d...Flexible UV-sensitive photodetectors and optoelectronic synapses are highly desired in numerous sensing areas and neuromorphic computations.Herein,the large-size,flat,and continuous sheet of polyamic acid(PAA),a two-dimensional(2D)porous organic polymer(POP),was synthesized at the liquid/liquid interface.Combining with graphene(G),the hybrids demonstrate efficient UV-selective photodetection.On the soft substrate of polyethylene glycol terephthalate(PET),the UV-selective detecting ability is retained even under 90◦bending and after 20,000 bending cycles,indicating the remarkable flexibilities.And our PAA/G/PET devices exhibit self-healing capability via a simple thermal annealing at 45℃.The remarkable flexibilities can be attributed to the high mechanical strength of 2D covalent-bonded backbones of PAA and G,the adaptive porous connections,and reversible broken/reformation of the large number of hydrogen bonds in PAA.Furthermore,the PAA/G/PET devices can mimic the functions of biosynapse very well,including paired-pulse facilitation,short-term plasticity(STP)and long-term plasticity(LTP),transition of STP to LTP,spike time,number,and intensity-dependent plasticity.With this optoelectronic synapse,the human brain-like process and wireless communications are realized.The memory time can achieve 10,000 s after 45 s learning.And the synaptic functions persist at the bending angle of 90◦.The results in this work provide valuable support for developing flexible wavelength-selective photodetectors and artificial synapses with 2D POPs and their hybrid films.展开更多
基金financially supported by the National Basic Research Program of China(No.2014CB643603)the National Natural Science Foundation of China(No.51173178)
文摘In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.
基金supported by the National Natural Science foundation of China (No.10772024)
文摘A novel experimental route to fabricate porous polyimide membranes （PPMs） with ideal air permeability was reported. The polymer solution layer consisting of the corresponding polyamic acid （PAA）, solvent, and dibutyl phthalate （DBP） with a boiling temperature of 340℃ was treated by a simple process. The polymer solution layer was first treated at a lower temperature （about 150℃）, then the received solid membrane was further imidized at a higher temperature （about 270℃）, and finally, DBP was removed from the membrane at a temperature above its boiling temperature. The final asymmetric polyimide membrane with a dense skin layer was obtained. To improve the air permeability of the polyimide membranes, the polymer solution layer was treated between two substrates. And the PPMs with open pores on both sides are fabricated and the air permeability of the films is improved greatly.
文摘A 4,4＇-（ hexafluoroisopropylidene ） diphthalic anhydride- bis [ 4-（ 4-aminophenoxy ） phenyl J sulfone （ 6FDA-BAPS） polyamic acid （PAA） was synthesized by using 6FDA and BAPS as reactive monomers and N-methyl-2-pyrrolidone（NMP） as a solvent. The PAA solution was prepared into membranes by casting technology and was also prepared into PAAhollow fiber membranes by dry wet spinning process. The PAA membranes and PAA hollow fiber membranes were exposed tothe high-temperature thermal cyclization at about 300 ℃ to produce a 6FDA-BAPS polyimide （PI） membranes and hollow fibermembranes. The structure and properties of 6FDA-BAPS PI products were studied. The results showed that the obtained 6FDA-BAPS PI was the target product which was of fairly good solubility in NMP, dimethylaeetamide and tetrahydrofuran ;the 6FDA-BAPS PI possessed the dense outer layer and the loose and porous support layer;the hollow fiber membranes had the 5 % weightloss temperature of 511 ℃ and breaking strength 26.5 MPa, indicating relatively high thermal and mechanical properties.
基金supported in part by the National Natural Science Foundation of China(grant numbers 22272177 and 21872146)the Weiqiao-UCAS Joint Research Project(grant number GYY-GDHY-2023-WT-013)the Fundamental Research Funds for the Central Universities.
文摘Flexible UV-sensitive photodetectors and optoelectronic synapses are highly desired in numerous sensing areas and neuromorphic computations.Herein,the large-size,flat,and continuous sheet of polyamic acid(PAA),a two-dimensional(2D)porous organic polymer(POP),was synthesized at the liquid/liquid interface.Combining with graphene(G),the hybrids demonstrate efficient UV-selective photodetection.On the soft substrate of polyethylene glycol terephthalate(PET),the UV-selective detecting ability is retained even under 90◦bending and after 20,000 bending cycles,indicating the remarkable flexibilities.And our PAA/G/PET devices exhibit self-healing capability via a simple thermal annealing at 45℃.The remarkable flexibilities can be attributed to the high mechanical strength of 2D covalent-bonded backbones of PAA and G,the adaptive porous connections,and reversible broken/reformation of the large number of hydrogen bonds in PAA.Furthermore,the PAA/G/PET devices can mimic the functions of biosynapse very well,including paired-pulse facilitation,short-term plasticity(STP)and long-term plasticity(LTP),transition of STP to LTP,spike time,number,and intensity-dependent plasticity.With this optoelectronic synapse,the human brain-like process and wireless communications are realized.The memory time can achieve 10,000 s after 45 s learning.And the synaptic functions persist at the bending angle of 90◦.The results in this work provide valuable support for developing flexible wavelength-selective photodetectors and artificial synapses with 2D POPs and their hybrid films.
