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
Microporous polyimides(PIM-PIs)have emerged as promising high-performance membranes for gas separation.However,achieving an optimal balance between permeability and selectivity remains a major challenge.In this study,...Microporous polyimides(PIM-PIs)have emerged as promising high-performance membranes for gas separation.However,achieving an optimal balance between permeability and selectivity remains a major challenge.In this study,we designed and synthesized a series of PIM-PIs by combining rigid dianhydrides 9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride(6FCDA)and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)with contorted diamines,including 9,9-bis(4-aminophenyl)fluorene(FDA),9,9′-spirobifluorene-2,2′-diamine(SBFDA),and 3,3,3′,3′-tetramethyl-1,1′-spirobiindane-5,5′-diamine-6,6′-diol(TSDA),to systematically elucidate the relationship between hierarchical microstructure and gas transport behavior.Comprehensive characterization revealed that the 6FCDA-based polymers exhibited a higher microporosity(V_(micro)/V_(total)up to 54.7%)and fractional free volume compared to their 6FDA counterparts.Gas permeation measurements showed that the 6FCDA/SBFDA membrane delivered a CO_(2)permeability of 386 Barrer and CO_(2)/CH_(4)selectivity of 30.2,exceeding the 2008 Robeson upper bound.Structure-property correlation analyses indicated that diffusion selectivity predominantly governed gas separation performance,with rigid,spirocyclic architectures suppressing chain packing to generate sub-5Åmicropores,as further validated by molecular simulations.The optimized 6FCDA/FDA membrane achieved a BET surface area of 423 m^(2)·g^(−1),while maintaining excellent mechanical strength and high thermal stability.This work establishes an effective monomer design strategy to overcome the permeability-selectivity trade-off through backbone rigidification,thereby advancing PIM-PIs for practical applications in natural gas purification and carbon capture.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
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financially supported by the Sinopec Seed Program Project(No.223281)State Key Laboratory of Advanced Papermaking and Paper-based Materials(No.2024ZD06)+3 种基金Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515110543 and 2023A1515110170)the Natural Science Foundation of Guangdong Province(No.2024B1515040023)Guangjuyingcai program of Guangzhou(No.2024D03J0002)111 Project(No.B18023).
文摘Microporous polyimides(PIM-PIs)have emerged as promising high-performance membranes for gas separation.However,achieving an optimal balance between permeability and selectivity remains a major challenge.In this study,we designed and synthesized a series of PIM-PIs by combining rigid dianhydrides 9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride(6FCDA)and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)with contorted diamines,including 9,9-bis(4-aminophenyl)fluorene(FDA),9,9′-spirobifluorene-2,2′-diamine(SBFDA),and 3,3,3′,3′-tetramethyl-1,1′-spirobiindane-5,5′-diamine-6,6′-diol(TSDA),to systematically elucidate the relationship between hierarchical microstructure and gas transport behavior.Comprehensive characterization revealed that the 6FCDA-based polymers exhibited a higher microporosity(V_(micro)/V_(total)up to 54.7%)and fractional free volume compared to their 6FDA counterparts.Gas permeation measurements showed that the 6FCDA/SBFDA membrane delivered a CO_(2)permeability of 386 Barrer and CO_(2)/CH_(4)selectivity of 30.2,exceeding the 2008 Robeson upper bound.Structure-property correlation analyses indicated that diffusion selectivity predominantly governed gas separation performance,with rigid,spirocyclic architectures suppressing chain packing to generate sub-5Åmicropores,as further validated by molecular simulations.The optimized 6FCDA/FDA membrane achieved a BET surface area of 423 m^(2)·g^(−1),while maintaining excellent mechanical strength and high thermal stability.This work establishes an effective monomer design strategy to overcome the permeability-selectivity trade-off through backbone rigidification,thereby advancing PIM-PIs for practical applications in natural gas purification and carbon capture.
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.
