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
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
Lithium-ion batteries(LIBs)have helped revolutionize the modern world and are now advancing the alternative energy field.Several technical challenges are associated with LIBs,such as increasing their energy density,im...Lithium-ion batteries(LIBs)have helped revolutionize the modern world and are now advancing the alternative energy field.Several technical challenges are associated with LIBs,such as increasing their energy density,improving their safety,and prolonging their lifespan.Pressed by these issues,researchers are striving to find effective solutions and new materials for next-generation LIBs.Polymers play a more and more important role in satisfying the ever-increasing requirements for LIBs.Polyimides(PIs),a special functional polymer,possess unparalleled advantages,such as excellent mechanical strength,extremely high thermal stability,and excellent chemical inertness;they are a promising material for LIBs.Herein,we discuss the current applications of PIs in LIBs,including coatings,separators,binders,solid-state polymer electrolytes,and active storage materials,to improve high-voltage performance,safety,cyclability,flexibility,and sustainability.Existing technical challenges are described,and strategies for solving current issues are proposed.Finally,potential directions for implementing PIs in LIBs are outlined.展开更多
Polyimides (PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some...Polyimides (PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some epoxy resins at room temperature. These PIs can be incorporated in the absence of organic solvent into epoxy resin E51 with the loading below 2 wt% forming EP-PI composites. No phase separation is observed by SEM on cryogenically fractured surfaces of EP-PI composites. The PI can improve mechanical properties, especially impact strength. Adding 2 wt% PI-1.5W, the impact strength reaches to 55 kJ/m^2 with the increase in tensile and flexural strengths by 14% and 3%, respectively. SEM analyses for the fracture surface suggest that PI reduces the crosslink density, improves the plasticity of epoxy resin and changes the mode of fracture from fragile to ductile. Moreover, the glass transition temperature of EP-PI composites was found to increase to a significant extent.展开更多
Two highly soluble aromatic polyimides were synthesized successfully from a diamine with two tert-butyl groups (MBTBA) and dianhydrides with a thioether or sulfone moiety (DTDA and DSDA). Both of them showed excel...Two highly soluble aromatic polyimides were synthesized successfully from a diamine with two tert-butyl groups (MBTBA) and dianhydrides with a thioether or sulfone moiety (DTDA and DSDA). Both of them showed excellent solubility in common solvents such as chloroform, tetrahydrofuran and dioxane at the room temperature. The numberaverage molecular weight was 6.0× 10^4 and 8.3 ×10^4 according to gel permeation chromatography relative to a polystyrene standard, and the polydispersity index was 1.80 and 1.82 respectively. The glass-transition temperatures of them were 286℃ and 314℃ (or 315℃ and 358℃) respectively, as measured by differential scanning calorimetry (or dynamic mechanical analysis). The 5% weight loss temperature of both was near 490℃ in N2 by therrnogravimetric analysis. These results indicated that the tert-butyl pendent groups reduced the interactions among polymer chains and the thioether or sulfone moiety was flexible which may improve their solubility in conventional organic solvents without the loss of thermal stability. Transparent and flexible films of the two polyimides were obtained via solution casting. The MBTBA-DTDA membrane had higher storage moduli than those of the MBTBA-DSDA membrane.展开更多
The recent development of flexible display technology raised additional requirements for optical and electric properties of polyimides,accelerating the structure and property tunning of transparent polyimides.The uniq...The recent development of flexible display technology raised additional requirements for optical and electric properties of polyimides,accelerating the structure and property tunning of transparent polyimides.The unique electronic effect and steric hindrance effect of fluorine substitutions make fluorine-containing polyimides occupy an important position in the transparent polyimide family.In this work,a series of transparent aromatic polyimides were prepared from a fixed 4,4’-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)and biphenyl diamines with different substitute groups at the 2,2’,6,6’-positions.We systematically studied the effects of pendant groups on the thermal,mechanical,optical and dielectric properties of these 6FDA-based polyimides with the aid of density function theory(DFT)calculation.In particular,we paid special attention to the simple but compact fluoro group substitution.The simple fluoro substitution brought the advantages of maintaining the linearity of the backbone and dense polymer chain packing,which would minimize the weakening of polyimides’inherent thermal,dimensional and mechanical properties.Comparing with trifluoromethyl substituted polyimides with the best optical transparency,polyimides containing fluoro substitutes exhibited slightly decreased optical transparency,but increased thermal and dimensional stability and higher mechanical strength.These results could shed light on the ultimate transparent polyimide film development toward the application in extreme working condition,e.g.,the colorless polyimide substrate film for the flexible display technology.展开更多
The monomer 2,6,12-triaminotriptycene was synthesized and the structure was confirmed by IR and 1H NMR spectra. Hyperbranched polyimides modified with different terminal groups were obtained from precursors, anhydride...The monomer 2,6,12-triaminotriptycene was synthesized and the structure was confirmed by IR and 1H NMR spectra. Hyperbranched polyimides modified with different terminal groups were obtained from precursors, anhydride- and aminoterminated hyperbranched poly(amic acid)s from polymerization of A2 + B3 system. From gel permeation chromatograrn (GPC) characterization, representative products had high molecular weight. All polymers had good solubility in CHCl3, DMF and tetrahydrofuran (THF), and performed no detective Tgs in the range of 50-300 ℃ and high Tds above 455 ℃ when 5% weight loss.展开更多
A kind of highly organsoluble polyimide and copolyimides were successfully synthesized from bicyclo(2.2.2)-oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA), the commercial diamine 4,4'-methylenedianiline (...A kind of highly organsoluble polyimide and copolyimides were successfully synthesized from bicyclo(2.2.2)-oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA), the commercial diamine 4,4'-methylenedianiline (MDA) and the designed diamine 4,4'-methylenebis-(2-tert-butylaniline) (MBTBA). The polyimide from BCDA and MBTBA is highly soluble in conventional low boiling point solvents (such as chloroform, tetrahydrofuran) at room temperature. But the solubility of the copolyimides in conventional solvents decreased with the molar ratio of MBTBA and MDA decreased. When the molar ratio of MBTBA and MDA was larger than 7/3, the copolyimides can be soluble in low boiling point solvents at room temperature to form a transparent, flexible, tough film by solution casting. When the molar ratio of MBTBA and MDA was between 7/3 and 1/9, they can only be soluble in hot dipolar aprotic solvents (such as DMF, NMP etc.) and form films too. The copolyimide was only soluble in m-cresol when the molar ratio of MBTBA and MDA was lower than 1/9. The number-average molecular weights of the soluble copolyimides were larger than 5.8 × 1064 g/mol by GPC and their polydispersity indices were higher than 1.4. Only one glass transition temperature of these copolyimides was detected around 400℃ by DMA. The copolyimides did not show appreciable decomposition up to 430℃ in N2.展开更多
A series of sulfonated polyimide copolymers as novel proton exchange materials were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), sulfonated diamine based on pyridine...A series of sulfonated polyimide copolymers as novel proton exchange materials were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), sulfonated diamine based on pyridine group and diamine containing N-phenyl-1,2,4-triazole moiety. Flexible, transparent and tough membranes with high thermal stability and good mechanical properties were obtained. They exhibited good stability in boiling water and Fenton's reagent at 80 ℃. More interestingly, a nonlinear relationship between proton conductivities of the resulting membranes and the degree of sulfonation (DS) was observed. The membrane with 50% DS exhibited the maximum proton conductivity, which was due to the combinational contributions of sulfonic acid and N-pheny-1,2,4-triazole groups. Thus, the N-phenyl-l,2,4- triazole moiety in this study not only can depress water absorption but also increase proton conductivity, especially at low DS.展开更多
The development of optical films with high transparency,high thermal resistance and low birefringence remains a challenge in the flexible display industry.In this work,we designed and synthesized a series of fluorinat...The development of optical films with high transparency,high thermal resistance and low birefringence remains a challenge in the flexible display industry.In this work,we designed and synthesized a series of fluorinated colorless polyimides(CPIs)materials using 2,5-substituted m-phenylenediamine diamine monomers and 1,2,4,5-cyclohexanetetracarboxylic dianhydride(CHDA).We systematically studied the effects of fluorinated group substitutions on the thermal,mechanical,optical and dielectric properties of CPI films.The introduction of alicyclic CHDA dianhydride affords high transparency and low yellowness,while the 2,5-substituted m-phenylenediamine diamines offer the CPIs with quite low birefringence as well as high glass transition temperatures.A particular CHDA/o3FBDA film with simple chemical structure stands out,exhibiting well-balanced overall properties.展开更多
Five novel near-infrared electrochromic aromatic polyimides (PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4"-(1-benzylbenzimidazol-2-yl)triphenylamine (named as DBBT) with five diff...Five novel near-infrared electrochromic aromatic polyimides (PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4"-(1-benzylbenzimidazol-2-yl)triphenylamine (named as DBBT) with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π* transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry (CV) test. A new absorption peak emerged at 847 nm in near-infrared (NIR) region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), in the range of-5.17 eV to -5.20 eV and -2.14 eV to -2.26 eV (versus the vacuum level) determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.展开更多
A diamine was synthesized by two successive reactions. Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid. Then reaction of this compound with 1,8...A diamine was synthesized by two successive reactions. Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid. Then reaction of this compound with 1,8-diamino-3,6- dioxaoctane via Yamazaki method resulted in preparation of diamine named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester. After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane. Characterization of polymers was achieved by common methods and their physical properties including inherent viscosity, thermal behavior, thermal stability, crystallinity and solubility were studied. Prepared polyimides showed improved solubility and good thermal stability.展开更多
Some novel polyimides containing bisthiazole rings were prepared by reacting 2,2'-diamino-4, 4'-bisthiazole (DART) with different aromatic dianhydride. The polyimides obtained had inherent viscosities of 0.37-...Some novel polyimides containing bisthiazole rings were prepared by reacting 2,2'-diamino-4, 4'-bisthiazole (DART) with different aromatic dianhydride. The polyimides obtained had inherent viscosities of 0.37-0.82 dl/g. Thermogravimetric analysis of the polyimides showed good thermal stability, the temperature at 5% weight loss being from 450 degrees to 560 degrees C. The permeability of two polymer membranes to H-2, O-2 and N-2 was determined, respectively. Three kinds of polyimide films were converted into electrical conductor by pyrolysis at high temperature in nitrogen atmosphere. The maximum room temperature conductivity as high as 3.9x10(2) S/cm for PI him pyrolyzed at 1200 degrees C for 10 min was obtained, and it was very stable in air.展开更多
An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride (ONA), was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was al...An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride (ONA), was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant (PMR) type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td (ca. 580℃) and glass transition temperature, Tg (330℃) of the novel resin (PI-20), prepared trader optimum process conditions, compare favorably with the Td (ca. 620℃) and Tg (ca. 348℃) of the state-of-the-art resin (PI'-20), respectively.展开更多
A rigid aromatic diamine monomer containing di-tert-butylbenzene and dimethyl groups,3,3'-dimethyl-4,4'-diaminophenyl-3",5"-di-tert-butyltoluene,was successfully synthesized by a simple coupling reac...A rigid aromatic diamine monomer containing di-tert-butylbenzene and dimethyl groups,3,3'-dimethyl-4,4'-diaminophenyl-3",5"-di-tert-butyltoluene,was successfully synthesized by a simple coupling reaction using 3,5-di-tert-butylbenzaldehyde and o-toluidine as starting materials.A series of novel polyimides(PI 3a-3c)with large pendant groups were prepared with the obtained diamine monomer and three different commercial aromatic dianhydrides(3,3',4,4'-biphenyltetracarboxylic dianhydride,4,4'-oxydiphthalic anhydride,and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride)by one-step high temperature polycondensation.The prepared polyimides exhibited high solubility and good membrane forming ability:they could be dissolved not only in some high boiling solvents such as DMF,NMP,DMAc,and m-Cresol at room temperature,but also in some low boiling solvents such as CHCl3,CH2Cl2,and THF.Their solubility in most solvents could exceed 10 wt%,and the flexible membranes could be obtained by casting their solutions.The prepared membranes exhibited good gas separation properties.The permeability coefficients of PI 3c for CO2 and O2 were up to 124.6 and 42.8 barrer,respectively,and the selectivity coefficients for CO2/CH4 and O2/N2 were 14.7 and 3.3,respectively.The membranes had light color and good optical transmission.Their optical transmittance at 450 nm wavelength was in the range of 67%-79%,and the cutoff wavelength was in the range of 310-348 nm.They also had good thermal properties with glass transition temperature(Tg)values in the range of 264-302℃.In addition,these membranes possessed good mechanical properties with tensile strength ranging between 77.8-87.4 MPa,initial modulus ranging between 1.69-1.82 GPa,and elongation at break ranging between 4.8%-6.1%.展开更多
Two soluble isomerized polyimides(PIs) synthesized from 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) with either 2,2'-dimethylbenzidine(2,2'-DMB) or 3,3'-DMB were investigated by means ...Two soluble isomerized polyimides(PIs) synthesized from 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) with either 2,2'-dimethylbenzidine(2,2'-DMB) or 3,3'-DMB were investigated by means of size-exclusion chromatography coupled with multi-angle laser light scattering,a viscometer and a refractive index detector in tetrahydrofuran(THF) with tetrabutylammonium bromide(TBAB) at 35 ℃.The corresponding parameters related to conformations α and ν,evaluated from the scaling relationships [η]=K η M α and R g =K g M ν,respectively,were 0.66±0.01 and 0.55±0.02 for poly(6FDA/3,3'-DMB),and 0.67±0.01 and 0.56±0.01 for poly(6FDA/2,2'-DMB),indicating a random coil conformation for both the samples in this mobile system.The persistence length l p and shift factor M L(relative molecular weight per unit contour length) were estimated from the relationship between intrinsic viscosity and molecular weight for the wormlike cylinder model proposed by Bohdanecky.Both l p and M L showed that the two PIs in THF are flexible chains and exhibit some local rigidity to some extent.展开更多
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the financial support provided by the National Natural Science Foundation of China (nos. U21A20170 [X. He], 22279070 [L. Wang], and 52206263 [Y. Song])the Ministry of Science and Technology of China (no. 2019YFA0705703 [L. Wang])the “Explorer 100” cluster system of Tsinghua National Laboratory for Information Science and Technology for their facility support
文摘Lithium-ion batteries(LIBs)have helped revolutionize the modern world and are now advancing the alternative energy field.Several technical challenges are associated with LIBs,such as increasing their energy density,improving their safety,and prolonging their lifespan.Pressed by these issues,researchers are striving to find effective solutions and new materials for next-generation LIBs.Polymers play a more and more important role in satisfying the ever-increasing requirements for LIBs.Polyimides(PIs),a special functional polymer,possess unparalleled advantages,such as excellent mechanical strength,extremely high thermal stability,and excellent chemical inertness;they are a promising material for LIBs.Herein,we discuss the current applications of PIs in LIBs,including coatings,separators,binders,solid-state polymer electrolytes,and active storage materials,to improve high-voltage performance,safety,cyclability,flexibility,and sustainability.Existing technical challenges are described,and strategies for solving current issues are proposed.Finally,potential directions for implementing PIs in LIBs are outlined.
基金financially supported by the Shanghai key R&D Program(No.DZ1100105)
文摘Polyimides (PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some epoxy resins at room temperature. These PIs can be incorporated in the absence of organic solvent into epoxy resin E51 with the loading below 2 wt% forming EP-PI composites. No phase separation is observed by SEM on cryogenically fractured surfaces of EP-PI composites. The PI can improve mechanical properties, especially impact strength. Adding 2 wt% PI-1.5W, the impact strength reaches to 55 kJ/m^2 with the increase in tensile and flexural strengths by 14% and 3%, respectively. SEM analyses for the fracture surface suggest that PI reduces the crosslink density, improves the plasticity of epoxy resin and changes the mode of fracture from fragile to ductile. Moreover, the glass transition temperature of EP-PI composites was found to increase to a significant extent.
基金supported by the National Basic Research Program(No.2009CB930400)National Natural Science Foundation of China(Nos.50873058,50633010)Shanghai Leading Academic Discipline Project(No.B202)
文摘Two highly soluble aromatic polyimides were synthesized successfully from a diamine with two tert-butyl groups (MBTBA) and dianhydrides with a thioether or sulfone moiety (DTDA and DSDA). Both of them showed excellent solubility in common solvents such as chloroform, tetrahydrofuran and dioxane at the room temperature. The numberaverage molecular weight was 6.0× 10^4 and 8.3 ×10^4 according to gel permeation chromatography relative to a polystyrene standard, and the polydispersity index was 1.80 and 1.82 respectively. The glass-transition temperatures of them were 286℃ and 314℃ (or 315℃ and 358℃) respectively, as measured by differential scanning calorimetry (or dynamic mechanical analysis). The 5% weight loss temperature of both was near 490℃ in N2 by therrnogravimetric analysis. These results indicated that the tert-butyl pendent groups reduced the interactions among polymer chains and the thioether or sulfone moiety was flexible which may improve their solubility in conventional organic solvents without the loss of thermal stability. Transparent and flexible films of the two polyimides were obtained via solution casting. The MBTBA-DTDA membrane had higher storage moduli than those of the MBTBA-DSDA membrane.
基金financially supported by the Key-Area Research and Development Program of Guangdong Province(No.2020B010182002)the Recruitment Program of Guangdong(No.2016ZT06C322)the Major Program of National Natural Science Foundation of China(No.51890871)。
文摘The recent development of flexible display technology raised additional requirements for optical and electric properties of polyimides,accelerating the structure and property tunning of transparent polyimides.The unique electronic effect and steric hindrance effect of fluorine substitutions make fluorine-containing polyimides occupy an important position in the transparent polyimide family.In this work,a series of transparent aromatic polyimides were prepared from a fixed 4,4’-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)and biphenyl diamines with different substitute groups at the 2,2’,6,6’-positions.We systematically studied the effects of pendant groups on the thermal,mechanical,optical and dielectric properties of these 6FDA-based polyimides with the aid of density function theory(DFT)calculation.In particular,we paid special attention to the simple but compact fluoro group substitution.The simple fluoro substitution brought the advantages of maintaining the linearity of the backbone and dense polymer chain packing,which would minimize the weakening of polyimides’inherent thermal,dimensional and mechanical properties.Comparing with trifluoromethyl substituted polyimides with the best optical transparency,polyimides containing fluoro substitutes exhibited slightly decreased optical transparency,but increased thermal and dimensional stability and higher mechanical strength.These results could shed light on the ultimate transparent polyimide film development toward the application in extreme working condition,e.g.,the colorless polyimide substrate film for the flexible display technology.
基金the National Natural Science Foundation(No.50673031)of China and authors would like to extend thanks to Professor Yongming Chen at CAS.
文摘The monomer 2,6,12-triaminotriptycene was synthesized and the structure was confirmed by IR and 1H NMR spectra. Hyperbranched polyimides modified with different terminal groups were obtained from precursors, anhydride- and aminoterminated hyperbranched poly(amic acid)s from polymerization of A2 + B3 system. From gel permeation chromatograrn (GPC) characterization, representative products had high molecular weight. All polymers had good solubility in CHCl3, DMF and tetrahydrofuran (THF), and performed no detective Tgs in the range of 50-300 ℃ and high Tds above 455 ℃ when 5% weight loss.
基金This work was financially supported by the National Basic Research Program (No. 2007CB808000)the Foundation of Chinese Academy of Sciences (Nos. 50633010, 50503012)the Zhejiang Provincial Natural Science Foundation of China (Nos. Y405500, Y405411)
文摘A kind of highly organsoluble polyimide and copolyimides were successfully synthesized from bicyclo(2.2.2)-oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA), the commercial diamine 4,4'-methylenedianiline (MDA) and the designed diamine 4,4'-methylenebis-(2-tert-butylaniline) (MBTBA). The polyimide from BCDA and MBTBA is highly soluble in conventional low boiling point solvents (such as chloroform, tetrahydrofuran) at room temperature. But the solubility of the copolyimides in conventional solvents decreased with the molar ratio of MBTBA and MDA decreased. When the molar ratio of MBTBA and MDA was larger than 7/3, the copolyimides can be soluble in low boiling point solvents at room temperature to form a transparent, flexible, tough film by solution casting. When the molar ratio of MBTBA and MDA was between 7/3 and 1/9, they can only be soluble in hot dipolar aprotic solvents (such as DMF, NMP etc.) and form films too. The copolyimide was only soluble in m-cresol when the molar ratio of MBTBA and MDA was lower than 1/9. The number-average molecular weights of the soluble copolyimides were larger than 5.8 × 1064 g/mol by GPC and their polydispersity indices were higher than 1.4. Only one glass transition temperature of these copolyimides was detected around 400℃ by DMA. The copolyimides did not show appreciable decomposition up to 430℃ in N2.
文摘A series of sulfonated polyimide copolymers as novel proton exchange materials were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), sulfonated diamine based on pyridine group and diamine containing N-phenyl-1,2,4-triazole moiety. Flexible, transparent and tough membranes with high thermal stability and good mechanical properties were obtained. They exhibited good stability in boiling water and Fenton's reagent at 80 ℃. More interestingly, a nonlinear relationship between proton conductivities of the resulting membranes and the degree of sulfonation (DS) was observed. The membrane with 50% DS exhibited the maximum proton conductivity, which was due to the combinational contributions of sulfonic acid and N-pheny-1,2,4-triazole groups. Thus, the N-phenyl-l,2,4- triazole moiety in this study not only can depress water absorption but also increase proton conductivity, especially at low DS.
基金supported by the Natural Science Foundation of Guangdong Province(No.2022A1515010125)the Key-Area Research and Development Program of Guangdong Province(No.2020B010182002)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110543)the R&D Program of Guangzhou(No.2023A04J1577)the Major Program of National Natural Science Foundation of China(No.51890871)the Recruitment Program of Guangdong(No.2016ZT06C322)the 111 Project(No.B18023)Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application at Soochow University.
文摘The development of optical films with high transparency,high thermal resistance and low birefringence remains a challenge in the flexible display industry.In this work,we designed and synthesized a series of fluorinated colorless polyimides(CPIs)materials using 2,5-substituted m-phenylenediamine diamine monomers and 1,2,4,5-cyclohexanetetracarboxylic dianhydride(CHDA).We systematically studied the effects of fluorinated group substitutions on the thermal,mechanical,optical and dielectric properties of CPI films.The introduction of alicyclic CHDA dianhydride affords high transparency and low yellowness,while the 2,5-substituted m-phenylenediamine diamines offer the CPIs with quite low birefringence as well as high glass transition temperatures.A particular CHDA/o3FBDA film with simple chemical structure stands out,exhibiting well-balanced overall properties.
基金financially supported by the National Natural Science Foundation of China(Nos.51373049,51372055,21372067,21206034,51303045 and 51473046)Doctoral Fund of Ministry of Education of China(Nos.20132301120004 and 20132301110001)Reserve Talented Person of Harbin(No.2015RAXXJ015)
文摘Five novel near-infrared electrochromic aromatic polyimides (PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4"-(1-benzylbenzimidazol-2-yl)triphenylamine (named as DBBT) with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π* transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry (CV) test. A new absorption peak emerged at 847 nm in near-infrared (NIR) region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), in the range of-5.17 eV to -5.20 eV and -2.14 eV to -2.26 eV (versus the vacuum level) determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.
文摘A diamine was synthesized by two successive reactions. Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid. Then reaction of this compound with 1,8-diamino-3,6- dioxaoctane via Yamazaki method resulted in preparation of diamine named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester. After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane. Characterization of polymers was achieved by common methods and their physical properties including inherent viscosity, thermal behavior, thermal stability, crystallinity and solubility were studied. Prepared polyimides showed improved solubility and good thermal stability.
基金This project was supported by the National Natural Science Foundation of China
文摘Some novel polyimides containing bisthiazole rings were prepared by reacting 2,2'-diamino-4, 4'-bisthiazole (DART) with different aromatic dianhydride. The polyimides obtained had inherent viscosities of 0.37-0.82 dl/g. Thermogravimetric analysis of the polyimides showed good thermal stability, the temperature at 5% weight loss being from 450 degrees to 560 degrees C. The permeability of two polymer membranes to H-2, O-2 and N-2 was determined, respectively. Three kinds of polyimide films were converted into electrical conductor by pyrolysis at high temperature in nitrogen atmosphere. The maximum room temperature conductivity as high as 3.9x10(2) S/cm for PI him pyrolyzed at 1200 degrees C for 10 min was obtained, and it was very stable in air.
基金financially supported by the Research Foundation of State Key Laboratory of Applied Organic Chemistry
文摘An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride (ONA), was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant (PMR) type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td (ca. 580℃) and glass transition temperature, Tg (330℃) of the novel resin (PI-20), prepared trader optimum process conditions, compare favorably with the Td (ca. 620℃) and Tg (ca. 348℃) of the state-of-the-art resin (PI'-20), respectively.
基金This work was finanially supported by the Key Research Project of Jiangsu Province(No.BE2017645)Scientifc Research and Innovation Project for Graduate Students in Jiangsu Province(No.KYCX19-1757)。and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions of China。
文摘A rigid aromatic diamine monomer containing di-tert-butylbenzene and dimethyl groups,3,3'-dimethyl-4,4'-diaminophenyl-3",5"-di-tert-butyltoluene,was successfully synthesized by a simple coupling reaction using 3,5-di-tert-butylbenzaldehyde and o-toluidine as starting materials.A series of novel polyimides(PI 3a-3c)with large pendant groups were prepared with the obtained diamine monomer and three different commercial aromatic dianhydrides(3,3',4,4'-biphenyltetracarboxylic dianhydride,4,4'-oxydiphthalic anhydride,and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride)by one-step high temperature polycondensation.The prepared polyimides exhibited high solubility and good membrane forming ability:they could be dissolved not only in some high boiling solvents such as DMF,NMP,DMAc,and m-Cresol at room temperature,but also in some low boiling solvents such as CHCl3,CH2Cl2,and THF.Their solubility in most solvents could exceed 10 wt%,and the flexible membranes could be obtained by casting their solutions.The prepared membranes exhibited good gas separation properties.The permeability coefficients of PI 3c for CO2 and O2 were up to 124.6 and 42.8 barrer,respectively,and the selectivity coefficients for CO2/CH4 and O2/N2 were 14.7 and 3.3,respectively.The membranes had light color and good optical transmission.Their optical transmittance at 450 nm wavelength was in the range of 67%-79%,and the cutoff wavelength was in the range of 310-348 nm.They also had good thermal properties with glass transition temperature(Tg)values in the range of 264-302℃.In addition,these membranes possessed good mechanical properties with tensile strength ranging between 77.8-87.4 MPa,initial modulus ranging between 1.69-1.82 GPa,and elongation at break ranging between 4.8%-6.1%.
基金Supported by the National Natural Science Foundation of China(No.20674085)the Funds for Creative Researth Groups of China(No.50921062)the Project of Bureau of Science and Technology of Jilin Province,China(No.20101535)
文摘Two soluble isomerized polyimides(PIs) synthesized from 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) with either 2,2'-dimethylbenzidine(2,2'-DMB) or 3,3'-DMB were investigated by means of size-exclusion chromatography coupled with multi-angle laser light scattering,a viscometer and a refractive index detector in tetrahydrofuran(THF) with tetrabutylammonium bromide(TBAB) at 35 ℃.The corresponding parameters related to conformations α and ν,evaluated from the scaling relationships [η]=K η M α and R g =K g M ν,respectively,were 0.66±0.01 and 0.55±0.02 for poly(6FDA/3,3'-DMB),and 0.67±0.01 and 0.56±0.01 for poly(6FDA/2,2'-DMB),indicating a random coil conformation for both the samples in this mobile system.The persistence length l p and shift factor M L(relative molecular weight per unit contour length) were estimated from the relationship between intrinsic viscosity and molecular weight for the wormlike cylinder model proposed by Bohdanecky.Both l p and M L showed that the two PIs in THF are flexible chains and exhibit some local rigidity to some extent.