The development of high-performance transparent substrates is critical for next-generation flexible electronic devices.Herein,we designed two novel meta-substituted diamines incorporating trifluoromethyl(―CF_(3))and ...The development of high-performance transparent substrates is critical for next-generation flexible electronic devices.Herein,we designed two novel meta-substituted diamines incorporating trifluoromethyl(―CF_(3))and methyl(―CH_(3))groups to synthesize colorless copolyimide(CPI)films via copolymerization with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)/3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA).The combination of meta-substituted architecture and substituents enables the simultaneous attainment of an ultralow dielectric constant(D_k)and high transparency.The meta-substitution geometry and electronic effects of―CF_(3)/―CH_(3) effectively suppressed charge-transfer complex(CTC)formation,expanded fractional free volume(FFV),and restricted π-electron conjugation,as validated by DFT calculations and wide-angle X-ray diffraction(WAXD)analysis.The optimized CPI film(PIA_(1)-6FDA/BPDA(10/0))achieved outstanding transmittance(T_(450)=88.15%),ultralow dielectric constant(D_(k)=2.08 at 1 k Hz),and minimal dielectric loss(D_(f)=0.0012),while maintaining robust thermal stability(T_(d5%)>523℃)and mechanical strength(σ=87.5 MPa).This work establishes a molecular engineering strategy to concurrently enhance the optical and dielectric properties,positioning meta-substituted CPIs as promising candidates for transparent flexible devices.展开更多
Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enh...Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enhancement via traditional trial-and-error methods.In this work,we proposed a materials genome approach to design and screen phenylethynyl-terminated polyimides for films with enhanced mechani-cal properties.We first established machine learning models to predict Young's modulus,tensile strength,and elongation at break to explore the chemical space containing thousands of candidate structures.The accuracies of the machine learning models were verified by molecular dynamics simulations on screened polyimides and experimental testing on three representative polyimide films.The performance advantages of the best-selected polyimides were analyzed by comparing well-known polyimides based on molecular dynamics simulations,and the structural rationale was revealed by"gene"analysis and feature importance evaluation.This work provides a cost-effective strategy for designing polyimide films withenhancedmechanical properties.展开更多
Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To...Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.展开更多
Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity ...Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity of the polymer chains and intermolecular interactions can ensure low D_(k)/D_(f)at high frequency,which is attributed to the effective restriction of dipole orientations.However,it is difficult to achieve tight chain packing in an overly rigid polymer chain,whereas an overly flexible polymer chain might be insufficient to restrain small-scale molecular motions below T_(g).To balance the trade-off between the rigidity of the polymer chains and tight chain packing,MPI was developed with a rigidsoft structure based on a naphthalene-alkyl-based diamine.On the one hand,incorporating the soft unit can enhance the movability of polymer chains to achieve dense chain packing for polyimides(PIs).On the other hand,the presence of rigid aromatic units can enhance intermolecular interactions and further restrict the motion of polar imide groups below T_(g).As a result,the resultant MPI can prevent small-scale molecular motion below T_(g).In contrast to the reference PI-TFMB-6FDA,D_(k)/D_(f)is significantly reduced from 2.72/0.0075 to 2.73/0.005 at a high frequency of 10 GHz Furthermore,the rigid-soft structure endows PIs with good thermoplasticity owing to the good chain flexibility above T_(g).In addition,PIs based on rigid-soft structures can preserve favorable thermal stability.展开更多
Based on monomer 2,6,12-triaminotriptycene, hyperbranched polyimides with high molecular weight modified with different terminal functional groups were obtained by polymerization of A2 ＋ B3 system. The prepared hyper...Based on monomer 2,6,12-triaminotriptycene, hyperbranched polyimides with high molecular weight modified with different terminal functional groups were obtained by polymerization of A2 ＋ B3 system. The prepared hyperbranched polyimides had good solubility in CHCl3, DMF and THF, and performed no detective Tgs in the range of 50-330℃ and high TdS （5%） above 455℃.展开更多
Designing and preparing a compatible electromagnetic interference(EMI)shielding,radar and infrared stealth material exhibits significant prospect in the military field.Hence,a novel conductive/magnetic polyimide-based...Designing and preparing a compatible electromagnetic interference(EMI)shielding,radar and infrared stealth material exhibits significant prospect in the military field.Hence,a novel conductive/magnetic polyimide-based nonwoven fabric(PFN_y)is prepared by alkali treatment,Fe~(3+)ion exchange,thermal reduction,and electroless nickel(Ni)plating process.Its impedance/insulation characteristics can be easily adjusted by controlling the in situ growth of Fe_(3)O_(4) and electroless nickel plating.Subsequently,a new strategy of constructing hierarchical dual-gradient impedance/insulation structure is implemented to achieve EMI shielding,radar and infrared stealth via stacking PFN_y with gradually decreased impedance/insulation characteristics from top to bottom.The formation of impedance matching gradient structure promotes effective introduction and dissipation of electromagnetic waves,endowing the composite with outstanding EMI shielding and radar stealth performance.Meanwhile,the construction of thermal insulation gradient structure can effectively inhibit thermal radiation from target,bringing an excellent infrared stealth performance.Importantly,the strong interfacial interactions between Fe_(3)O_(4),Ni and polyimide fiber accelerate PFNy to resist the stresses originated from high-temperature heat source,achieving a compatible high-temperature resistant radar/infrared stealth performance.Such excellent comprehensive properties endow it with a great potential in high-temperature military camouflage applications against enemy radar and infrared detection.展开更多
基金financially supported by the National Key R&D Program of China(No.2023YFB3812400)the National Natural Science Foundation of China(No.51890871)the GJYC Program of Guangzhou(No.2024D02J0004)。
文摘The development of high-performance transparent substrates is critical for next-generation flexible electronic devices.Herein,we designed two novel meta-substituted diamines incorporating trifluoromethyl(―CF_(3))and methyl(―CH_(3))groups to synthesize colorless copolyimide(CPI)films via copolymerization with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)/3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA).The combination of meta-substituted architecture and substituents enables the simultaneous attainment of an ultralow dielectric constant(D_k)and high transparency.The meta-substitution geometry and electronic effects of―CF_(3)/―CH_(3) effectively suppressed charge-transfer complex(CTC)formation,expanded fractional free volume(FFV),and restricted π-electron conjugation,as validated by DFT calculations and wide-angle X-ray diffraction(WAXD)analysis.The optimized CPI film(PIA_(1)-6FDA/BPDA(10/0))achieved outstanding transmittance(T_(450)=88.15%),ultralow dielectric constant(D_(k)=2.08 at 1 k Hz),and minimal dielectric loss(D_(f)=0.0012),while maintaining robust thermal stability(T_(d5%)>523℃)and mechanical strength(σ=87.5 MPa).This work establishes a molecular engineering strategy to concurrently enhance the optical and dielectric properties,positioning meta-substituted CPIs as promising candidates for transparent flexible devices.
基金supported by the National Key R&D Program of China(No.2022YFB3707302)the National Natural Science Foundation of China(Nos.52394271 , 52394270).
文摘Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enhancement via traditional trial-and-error methods.In this work,we proposed a materials genome approach to design and screen phenylethynyl-terminated polyimides for films with enhanced mechani-cal properties.We first established machine learning models to predict Young's modulus,tensile strength,and elongation at break to explore the chemical space containing thousands of candidate structures.The accuracies of the machine learning models were verified by molecular dynamics simulations on screened polyimides and experimental testing on three representative polyimide films.The performance advantages of the best-selected polyimides were analyzed by comparing well-known polyimides based on molecular dynamics simulations,and the structural rationale was revealed by"gene"analysis and feature importance evaluation.This work provides a cost-effective strategy for designing polyimide films withenhancedmechanical properties.
基金supported by the National Key Research and Development Program of China(No.2022YFB3603101)。
文摘Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.
基金supported by the National Natural Science Foundation of China(Nos.U20A20340 and 52001068)Key-Area Research and Development Program of Guangdong Province(No.2020B010182001)+3 种基金Dongguan Key Research&Development Program(No.20231200300192)Science and Technology Projects in Guangzhou(No.2025A04J3832)Foshan Introducing Innovative and Entrepreneurial Teams(No.1920001000108)Guangzhou Hongmian Project(No.HMJH-2020-0012)。
文摘Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity of the polymer chains and intermolecular interactions can ensure low D_(k)/D_(f)at high frequency,which is attributed to the effective restriction of dipole orientations.However,it is difficult to achieve tight chain packing in an overly rigid polymer chain,whereas an overly flexible polymer chain might be insufficient to restrain small-scale molecular motions below T_(g).To balance the trade-off between the rigidity of the polymer chains and tight chain packing,MPI was developed with a rigidsoft structure based on a naphthalene-alkyl-based diamine.On the one hand,incorporating the soft unit can enhance the movability of polymer chains to achieve dense chain packing for polyimides(PIs).On the other hand,the presence of rigid aromatic units can enhance intermolecular interactions and further restrict the motion of polar imide groups below T_(g).As a result,the resultant MPI can prevent small-scale molecular motion below T_(g).In contrast to the reference PI-TFMB-6FDA,D_(k)/D_(f)is significantly reduced from 2.72/0.0075 to 2.73/0.005 at a high frequency of 10 GHz Furthermore,the rigid-soft structure endows PIs with good thermoplasticity owing to the good chain flexibility above T_(g).In addition,PIs based on rigid-soft structures can preserve favorable thermal stability.
基金supported by the National Natural Science Foundation of China(Nos.50673031 and 50973036)the Natural Science Foundation of Fujian Province(No.2008F3067)
文摘Based on monomer 2,6,12-triaminotriptycene, hyperbranched polyimides with high molecular weight modified with different terminal functional groups were obtained by polymerization of A2 ＋ B3 system. The prepared hyperbranched polyimides had good solubility in CHCl3, DMF and THF, and performed no detective Tgs in the range of 50-330℃ and high TdS （5%） above 455℃.
基金the financial support from China Postdoctoral Science Foundation(2024M760348)National Natural Science Foundation of China(52373077)。
文摘Designing and preparing a compatible electromagnetic interference(EMI)shielding,radar and infrared stealth material exhibits significant prospect in the military field.Hence,a novel conductive/magnetic polyimide-based nonwoven fabric(PFN_y)is prepared by alkali treatment,Fe~(3+)ion exchange,thermal reduction,and electroless nickel(Ni)plating process.Its impedance/insulation characteristics can be easily adjusted by controlling the in situ growth of Fe_(3)O_(4) and electroless nickel plating.Subsequently,a new strategy of constructing hierarchical dual-gradient impedance/insulation structure is implemented to achieve EMI shielding,radar and infrared stealth via stacking PFN_y with gradually decreased impedance/insulation characteristics from top to bottom.The formation of impedance matching gradient structure promotes effective introduction and dissipation of electromagnetic waves,endowing the composite with outstanding EMI shielding and radar stealth performance.Meanwhile,the construction of thermal insulation gradient structure can effectively inhibit thermal radiation from target,bringing an excellent infrared stealth performance.Importantly,the strong interfacial interactions between Fe_(3)O_(4),Ni and polyimide fiber accelerate PFNy to resist the stresses originated from high-temperature heat source,achieving a compatible high-temperature resistant radar/infrared stealth performance.Such excellent comprehensive properties endow it with a great potential in high-temperature military camouflage applications against enemy radar and infrared detection.
