Co-reporter:Qudrat Ullah Khan, Nanfang Jia, Guofeng Tian, Shengli Qi, and Dezhen Wu
The Journal of Physical Chemistry C May 4, 2017 Volume 121(Issue 17) pp:9153-9153
Publication Date(Web):April 17, 2017
DOI:10.1021/acs.jpcc.7b01732
We design two novel solution processable polyimides (PIs), NH-Por-6FDA and Zn-Por-6FDA, with 5,15-bis(4,-aminophenyl)-10,20-diphenylporphyrin (trans-DATPP) (electron donor) and 4,4′-(hexafluoroisoprpoylidine)diphthalic anhydride (6FDA) (electron acceptor) as the building blocks for polymer memory applications. The chemical structures of the two polymers are mostly identical with the only difference lying in the zinc ion (Zn2+) insertion into the porphyrin core in the Zn-Por-6FDA. Electrical characterization indicates that the NH-Por-6FDA possesses bidirectional nonvolatile write once read many times (WORM) memory behavior, while the Zn-Por-6FDA shows vastly different volatile static random access memory (SRAM) behavior. Both polymer memory devices show high ON/OFF current ratio up to 106 and exhibit excellent long-term operation stability in 108 read cycles and retention time of 4000 s with no current degradation. The charge transfer (CT) and function of the donor/acceptor moiety in the polymers related with the electrical switching effect are elucidated on the basis of optical, electrochemical measurement, and quantum simulation results. The inserted zinc ion in the porphyrin is suggested to form an internal electrode and act as a bridge during the electronic transition process, which facilitates both the CT and back CT, consequently triggering the WORM/SRAM conversion upon Zn complexation. The results observed here indicate the significance of metal-complexation on the memory effects, and will attract the attention of the researchers to use noble transition metals for the suitable expecting memory devices.
Co-reporter:Nanfang Jia;Guofeng Tian;Xiaodong Wang
Journal of Electronic Materials 2017 Volume 46( Issue 4) pp:2011-2020
Publication Date(Web):2017 April
DOI:10.1007/s11664-016-5086-0
For producing polymer based electronics with good memory behavior, a series of functional copolyimides were designed and synthesized in this work by copolymerizing 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA) with (9,9′-bis(4-aminophenyl)fluorene) (BAPF) and N,N-bis(4-aminophenyl) aminopyrene (DAPAP) diamines. The synthesized copolyimides DSDA/(DAPAP/BAPF) were denoted as coPI-DAPAPx (x = 100, 50, 20, 10, 5, 1, 0), where x% represents the molar fraction of the DAPAP unit in the diamines. Characterization results indicate that the coPI-DAPAPx exhibits tunable electrical switching behaviors from write once read many times (WORM, nonvolatile, coPI-DAPAP100, coPI-DAPAP50, coPI-DAPAP20, coPI-DAPAP10) to the static random access memory (SRAM, volatile, coPI-DAPAP5, coPI-DAPAP1) with the variation of the DAPAP content. Optical and electrochemical characterization show gradually decreasing highest occupied molecular orbital levels and enlarged energy gap with the decrease of the DAPAP moiety, suggesting decreasing charge-transfer effect in the copolyimides, which can account for the observed WORM–SRAM memory conversion. Meanwhile, the charge transfer process was elucidated by quantum chemical calculation at B3LYP/6-31G(d) theory level. This work shows the effect of electron donor content on the memory behavior of polymer electronic materials.
Co-reporter:Nanfang Jia, Guofeng Tian, Shengli Qi, Xiaodong Wang, Dezhen Wu
European Polymer Journal 2017 Volume 95(Volume 95) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.eurpolymj.2017.08.012
•Novel polyimides containing saturated aliphatic chain have been synthesized.•Polyimide based memories with widely tunable memory behaviors were achieved.•Electronic structure and property variations were explored by quantum calculation.•The memory variation is ascribed to the acceptor effect and spacer effect.Four novel functional polyimides (PIs) for electrical memory applications, DATP6Cz-DSDA, DATP2Cz-DSDA, DATP6Cz-NTDA, and DATP2Cz-NTDA, were synthesized through condensation polymerization of two diamines, N,N-bis(4-amino)phenyl-6-(9-carbazol)-hexamine (DATP6Cz) and N,N-bis(4-amino)phenyl-2-(9-carbazol)-ethylamine (DATP2Cz), with two dianhydrides, diphenylsulfone-3,3′,4,4′-tetracarboxylic dianhydride (DSDA) and 1,4,5,8-Naphthalenetetracarboxylic dianhydride (NTDA). The ethyl and hexyl spacer were intentionally inserted into the diamines to alter the spatial position of the electron donor in the PIs and then to elucidate the effect on the memory behavior. Experimental results show that DATP6Cz-DSDA and DATP2Cz-DSDA exhibit nonvolatile WORM memory behavior, while DATP6Cz-NTDA and DATP2Cz-NTDA exhibit volatile SRAM and DRAM behavior, respectively. Simulation results indicate much stronger charge-trapping effect of the sulphone moiety in DSDA than that of the carbonyl moiety in NTDA, accounting for the nonvolatile feature of the DSDA-based PI memories and the volatile feature of the NTDA-based PI memories. Meanwhile, spatial position effect was observed in the NTDA-based PIs. The spacer of varied length between carbazole group and diphenyl amino group in DATP6Cz and DATP2Cz, i.e., hexyl vs. ethyl, has significantly altered the spatial position of the electron donor and the charge transportation path in the PIs, resulting in different retention time and corresponding SRAM and DRAM behavior. The present strategy is expected to be applied in material design in future information technology.Download high-res image (91KB)Download full-size image
Co-reporter:Nanfang Jia, Jiacong Guo, Guofeng Tian, Shengli Qi, Xiaodong Wang, Dezhen Wu
Dyes and Pigments 2017 Volume 146(Volume 146) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.dyepig.2017.06.059
•Organic based memory devices with tunable memory behaviors from nonvolatile WORM to volatile SRAM were achieved.•The frontier orbitals, corresponding energy levels, and energy gaps were explored by quantum calculation.•The conduction models of the devices were confirmed according to the fitted lines of current-voltage curves.•The influence of charge-trapping depth of functional moieties on the memory behavior was explored and demonstrated.In this work, two functional imides were designed and synthesized to elucidate the influence of charge trap depth on the memory behavior. Two dianhydrides, 3,3′,4,4'-diphenylsulfonetetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride were selected as the electron acceptor considering their functional moieties of different charge-trapping depth and electron-withdrawing ability. Electrical characterization indicated that the memory devices based on the two imides exhibited nonvolatile write once read many times (WORM) memory behavior and volatile static random access memory (SRAM) behavior. Mechanisms associated with the distinct memory effect were demonstrated based on the molecular simulation. Analysis results indicated that charge trapping process is responsible for the electrical bistability and the different depth of charge-trapping sites in the two imides accounts for the distinct memory behavior of corresponding memory devices. Meanwhile, the two memory devices both show excellent long term operation stability. This paper not only reports two novel memory materials but also provided some guiding principle to the design of organic based memory devices.Download high-res image (220KB)Download full-size image
Co-reporter:Nanfang Jia;Guofeng Tian;Junhao Cheng;Xiaodong Wang;Dezhen Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 38) pp:23550-23559
Publication Date(Web):2017/04/27
DOI:10.1039/C7RA03454G
To elucidate the influence of spatial structure on memory behavior, three isomeric polyimides (PIs), PI-3,6-DAPCz-6FDA, PI-3,4′-DAPCz-6FDA, and PI-2′,4′-DAPCz-6FDA, for electrical memory applications are designed and synthesized. Current–voltage characteristics indicate that the three isomeric PIs display vastly deviating memory effects. PI-3,6-DAPCz-6FDA and PI-3,4′-DAPCz-6FDA both show volatile static random access memory (SRAM) behavior, while PI-2′,4′-DAPCz-6FDA exhibits a non-volatile write once read many times (WORM) memory characteristic. The mechanisms associated with the memory effect were analyzed based on molecular simulation results. PI-3,6-DAPCz-6FDA possesses the best structural coplanarity, which greatly facilitates its charge transfer (CT) and back CT process, leading to the volatile SRAM feature. However, PI-2′,4′-DAPCz-6FDA exhibits more torsional structures, which consequently prohibits the back CT process, explaining its non-volatile behavior. Additionally, the three isomeric PIs show fast transient responses. The results show the importance of the spatial structure on polymer memory and the viability of adjusting memory types by isomerization.
Co-reporter:Nanfang Jia, Shengli Qi, Guofeng Tian, Xiaodong Wang, and Dezhen Wu
The Journal of Physical Chemistry C 2016 Volume 120(Issue 46) pp:26217-26224
Publication Date(Web):November 4, 2016
DOI:10.1021/acs.jpcc.6b09044
In this work, three functional polyimides, in which the diaminophenylaminoanthracene (DAPAA) group served as the electron donor and 4,4′-hexafluoroisopropylidene dianhydride (6FDA) served as the electron acceptor, were synthesized and denoted as 1-DAPAA-6FDA, 2-DAPAA-6FDA, and 9-DAPAA-6FDA. The only difference between the three polyimides was that the anthracene group in DAPAA was attached to the nitrogen atom through different tethering positions (1-, 2-, and 9-). Characterization results indicate that the 1-DAPAA-6FDA and 9-DAPAA-6FDA based memory devices exhibit nonvolatile write once read many times memory (WORM) behavior, while the 2-DAPAA-6FDA based memory device exhibits volatile static random access memory (SRAM) behavior. Quantum chemical calculation results indicate that a lower dihedral angle between the anthracene group and the molecular backbone of 2-DAPAA-6FDA caused better coplanar structure for charge transfer (CT) and back CT processes, which accounts for the observed volatile SRAM memory performance. All of the polyimides possess excellent long-term operational stability. This work reveals the possibility of tuning memory behavior by elaborately adjusting the spatial conformation of the electron donor, providing feasible guidance for the design of polymer memory materials.
Co-reporter:Hebo Ye, Guofeng Tian, Lei Shi, Shengli Qi, Dezhen Wu
European Polymer Journal 2015 Volume 63() pp:45-57
Publication Date(Web):February 2015
DOI:10.1016/j.eurpolymj.2014.12.001
•Polymer memories with widely tunable memory effects were achieved based on co-PNIs.•The memory behavior was modulated from non-conducting, to SRAM and to WORM.•Electronic structure and property variations were explored by quantum calculation.•The memory conversion is ascribed to enhanced ability to form stable CT complexes.For producing flexible memory materials with controlled memory characteristics, functional copolynaphthalimides (co-PNIs), with varied composition of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 4,4′-(9-fluorenylidene) dianiline (BAPF) and 4,4′-diaminotriphenylamine (DATPA), were designed and synthesized in this work. Optical and electrochemical measurements on the synthesized co-PNIs, denoted as co-PNI-TPAx (where x = 0, 1, 2, 5, 10 for the molar ratio of the DATPA-containing unit in the co-PNIs), indicate gradually enhanced HOMO and continually degraded band gap with increasing DATPA unit, as further approved by molecular simulation. What is more, electrical characterization on the ITO | thin co-PNI active layer | Al sandwich devices witnesses a wide alteration of the memory behaviors from no electrical bistability (NULL, co-PNI-TPA0 and co-PNI-TPA1), to static random access memory (SRAM, co-PNI-TPA2 and co-PNI-TPA5), and then to the write-once read-many times memory (WORM, co-PNI-TPA10), implying the significance of composition control on determining the memory characteristics. Mechanisms associated with the switching effect and the charge transfer in the co-PNIs were analyzed based on the optical, electrochemical results and the B3LYP/6–31G(d) calculations. The conversion of the memory effect from NULL, to volatile SRAM, and then to nonvolatile WORM is suggested to result from the gradually increased ability of the synthesized co-PNIs to form stable charge transfer complexes with the increased electron-donating DATPA species. The fine memory tuning achieved here reveals the particular availability of the copolymerization strategy in designing functional polyimides with controlled performances for practical memory applications.
Co-reporter:Qingrong Sun;Tianxiang Chen;Wei Hu;Yong Chen;Dezhen Wu;Riguang Jin
Journal of Applied Polymer Science 2014 Volume 131( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/app.39977
ABSTRACT
Aiming for X-ray astronomy applications, we prepared large-area submicrometer polyimide (PI) films [diameter (Φ) = 8 cm] with great thickness uniformity via the spin-coating technique by using a PI precursor, poly(amic acid) (PAA) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, and p-phenylenediamine as the starting materials. The effects of the spinning speed, apparent viscosity of the PAA solution (η), and spinning time on the PI film thickness and its uniformity, as characterized by the measurement of the film thickness every 0.5 cm along the diameter direction, were investigated. By optimizing the spin-coating conditions, we prepared final submicrometer PI films with average thicknesses in the range of 200–850 nm and with film thickness fluctuations of less than 1.3%. The pressure bulge test results indicate that at a thickness of 805 nm and an inside test aperture diameter of 2.64 cm, the prepared PI films reached a final burst pressure of 20.2 KPa; this suggested excellent mechanical performances in the self-standing submicrometer PI film. This study makes a contribution by providing a typical example and opening the way for the preparation of robust self-standing submicrometer PI films with great thickness uniformities for X-ray astronomy applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39977.
Co-reporter:Lei Shi;Nanfang Jia;Lushi Kong;Dezhen Wu
Macromolecular Chemistry and Physics 2014 Volume 215( Issue 23) pp:2374-2388
Publication Date(Web):
DOI:10.1002/macp.201400441
Co-reporter:Lei Shi, Guofeng Tian, Hebo Ye, Shengli Qi, Dezhen Wu
Polymer 2014 Volume 55(Issue 5) pp:1150-1159
Publication Date(Web):10 March 2014
DOI:10.1016/j.polymer.2013.12.046
A functional polyimide (6F/CzTPA PI), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)/ 4,4′-diamino-4″-N-carbazolyltriphenylamine (DACzTPA), was synthesized in our present work for electrical resistive memory device applications. Semiconductor parameter analysis on the polyimide memory devices indicates that the synthesized polyimide possesses a volatile static random access memory (SRAM) characteristic with an ON/OFF current ratio of about 105 at the threshold voltage of around 1.5 V and −1.8 V. In addition, the device using the 6F/CzTPA PI as the active layer reveals excellent long-term operation stability with the endurance of reading cycles up to 108 under a voltage pulse and retention times for at least 8 h under constant voltage stress (−1 V). The charge transfer mechanisms and the roles of the donor and acceptor components in the PI macromolecules associated with the electrical switching effect are elucidated on the basis of the experimental and quantum simulation results.Volatile static random access memory behavior is observed on a functional polyimide bearing hexafluoroisopropylidene-diphthalimide parts as the electron acceptor and carbazole-tethered triphenylamine moieties as the electron donor with an ON/OFF current ratio of 105 and a switching time less than 20 ns. Molecular simulation is conducted to clarify the carrier transport process and memory mechanisms in this electroactive polyimide.
Co-reporter:Lei Shi, Hebo Ye, Wenlu Liu, Guofeng Tian, Shengli Qi and Dezhen Wu
Journal of Materials Chemistry A 2013 vol. 1(Issue 44) pp:7387-7399
Publication Date(Web):16 Sep 2013
DOI:10.1039/C3TC31369G
Two novel functional aromatic polyimides (PIs), 6F-αNA PI and 6F-βNA PI, in which the hexafluoroisopropylidene-diphthalic anhydride (6FDA) serves as the electron-accepting unit and the diphenylnaphthylamine (DPNA) functions as the electron-donating species, were synthesized for memory device applications. The 6F-αNA PI shows distinct electrical bistable states with an ON/OFF current ratio up to 106, and can be switched on bi-directionally with no polarity, which could be applied as the nonvolatile write-once read-many times (WORM) memory. Whereas, the 6F-βNA PI-based memory device exhibits flash type memory characteristics with a switching-on voltage at ca. 1.1 V and an ON/OFF ratio of 104. Both polyimides exhibit good long-term operation stability, survive up to 108 reading cycles with no current degradation, and show ultrafast switching with a response time less than 20 ns. Mechanisms associated with the electrical switching behaviors are discussed on the basis of the experimental and quantum simulation results. The electric-field-induced electronic transition from diphenylnaphthylamine units to hexafluoropropylidene phthalimide units and the subsequent formation of charge-transfer complexes are supposed to be responsible for the observed electrical memory effects. Molecular simulation suggests that α-tethering of the naphthyl group results in more non-coplanar conformation of the DPNA species in the 6F-αNA PI, as compared to that of the β-tethering in the 6F-βNA PI, therefore producing a higher energy barrier that prevents the back charge transfer processes, consequently leading to the WORM vs. flash memory behaviors. The 6F-αNA PI differs from 6F-βNA PI only in the substitution position of the naphthyl group, i.e., α-tethering vs. β-tethering. The distinct memory effects observed here suggest the significance of the electron-donating structures on the memory effects, and the tailorability of the memory characteristics through fine structure adjustment.
Co-reporter:Enlin Han, Yue Wang, Xue Chen, Gongping Shang, Wenxiao Yu, Hongqing Niu, Shengli Qi, Dezhen Wu, and Riguang Jin
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 10) pp:4293
Publication Date(Web):April 17, 2013
DOI:10.1021/am4005094
Herein, we report our success on the large-scale online preparation of surface-silver-metallized polyimide (PI) fibers by utilizing silver ammonia complex cation ([Ag(NH3)2]+) as the silver (Ag) precursor and pyromellitic dianhydride/4,4′-oxidianiline (PMDA/4,4′-ODA)-based polyimide as the matrix via a direct ion-exchange self-metallization process integrated within a consecutive fiber-spinning procedure. The method works by using the online freshly prepared PMDA/4,4′-ODA-based poly(amic acid) (PAA) fibers as the starting material to perform an ion-exchange reaction in aqueous silver(I) solution to load silver(I) into the PAA precursor fibers, followed by a programmed stepwise thermal treatment process to convert PAA to its final imide form with the concomitant silver(I) reduction and the subsequent aggregation, producing the surface-silvered polyimide hybrid fibers. The influence of thermal cycles on the formation of silver nanostructures, and the variation of surface morphologies and fiber properties during the heating process were investigated. Experimental results indicate that the PI–Ag fibers were produced with good mechanical and thermal properties. In addition, bioassessment suggests that the hybrid fibers exhibit superior antibacterial activities (99.99% in 24 h toward E. coli). Outstanding electrical conductive properties of a certain length of the PI–Ag hybrid fiber (electrical resistance: ca. 0.1 Ω cm–1) could also be realized on the composite fibers but with severe destructions in the final mechanical properties. The fibers were also characterized by FTIR, ICP, XRD, SEM, and TEM.Keywords: fiber; ion exchange; polyimide; silver;
Co-reporter:Dr. Shengli Qi;Dr. Hiroki Iida;Dr. Lili Liu; Stephan Irle; Wenping Hu; Eiji Yashima
Angewandte Chemie 2013 Volume 125( Issue 3) pp:1083-1087
Publication Date(Web):
DOI:10.1002/ange.201208481
Co-reporter:Dr. Shengli Qi;Dr. Hiroki Iida;Dr. Lili Liu; Stephan Irle; Wenping Hu; Eiji Yashima
Angewandte Chemie International Edition 2013 Volume 52( Issue 3) pp:1049-1053
Publication Date(Web):
DOI:10.1002/anie.201208481
Co-reporter:Dr. Shengli Qi;Dr. Hiroki Iida;Dr. Lili Liu; Stephan Irle; Wenping Hu; Eiji Yashima
Angewandte Chemie International Edition 2013 Volume 52( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/anie.201209492
Co-reporter:Dr. Shengli Qi;Dr. Hiroki Iida;Dr. Lili Liu; Stephan Irle; Wenping Hu; Eiji Yashima
Angewandte Chemie 2013 Volume 125( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/ange.201209492
Co-reporter:Enlin Han, Dezhen Wu, Shengli Qi, Guofeng Tian, Hongqing Niu, Gongping Shang, Xiaona Yan, and Xiaoping Yang
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 5) pp:2583
Publication Date(Web):April 20, 2012
DOI:10.1021/am300248c
This paper reports our works on the preparation of the silver-nanoparticle-incorporated ultrafine polyimide (PI) ultrafine fibers via a direct ion exchange self-metallization technique using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and pyromellitic dianhydride (PMDA)/4,4′-oxidianiline (4,4′-ODA) polyimide as the matrix. The polyimide precursor, poly(amic acid) (PAA), was synthesized and then electrospun into ultrafine fibers. By thermally treating the silver(I)-doped PAA ultrafine fibers, where the silver(I) ions were loaded through the ion exchange reactions of the carboxylic acid groups of the PAA macromolecules with the [Ag(NH3)2]+ cations in an aqueous solution, ultrafine polyimide fibers embedded with silver nanoparticles with diameters less than 20 nm were successfully fabricated. The fiber-electrospinning process, the ion exchange process, and various factors influencing the hybrid ultrafine fibers preparation process such as the thermal treatment atmospheres and the thermal catalytic oxidative degradation effect of the reduced silver nanoparticles were discussed. The ultrafine fibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).Keywords: electrospinning; polyimide; silver ammonia; silver nanoparticles;
Co-reporter:Fei Chen, Guofeng Tian, Lei Shi, Shengli Qi and Dezhen Wu
RSC Advances 2012 vol. 2(Issue 33) pp:12879-12885
Publication Date(Web):22 Oct 2012
DOI:10.1039/C2RA21885B
An aromatic hyperbranched polyimide, poly(N,N,N′,N′-tetrakis(4-aminophenyl)benzidine-N,N- 4,4′-hexafluoroisopropylidene-diphthalimide) (6F-TEAPBD PI), was synthesized. Semiconductor parameter analysis on the sandwich devices using the synthesized polyimide as the active layer indicates that the polymer possesses distinct electrical bi-stable states with an ON/OFF current ratio of about 300 and a switching voltage at around 2.0 V, which could be applied as nonvolatile write-once read-many-times (WORM) memory. Mechanisms associated with the electrical switching effect are discussed on the basis of the experimental and quantum simulation results. It is suggested that the electric-field-induced charge transport from triphenylamine moieties to hexafluoropropylidene phthalimide units and the subsequent formation of charge-transfer complexes are responsible for the observed electrical memory effect.
Co-reporter:Guofeng Tian, Dezhen Wu, Lei Shi, Shengli Qi and Zhanpeng Wu
RSC Advances 2012 vol. 2(Issue 26) pp:9846-9850
Publication Date(Web):20 Aug 2012
DOI:10.1039/C2RA21226A
In this paper, we report our works on the synthesis of a silver-nanoparticle-embedded polyimide (PI) thin film and its electrical bistability. A soluble PI, (4,4′-(hexafluoroisopropylidene) diphthalic anhydride/4,4′-oxydianiline (6FDA/ODA), where the 6FDA part serves as an effective electron-accepting moiety, was synthesized in our current work as the polymer matrix. Silver nanoparticles (Ag NPs) with diameters less than 7 nm were subsequently generated in situ in the parent PI film via ultraviolet (UV) reduction of the (1,1,1-trifluoro-2,4-pentadionato) silver(I) complex (AgTFA) previously incorporated in the matrix. Electrical characterization results on the sandwiched device (ITO|PI (6FDA/ODA)/silver nanohybrid film|Au) indicate that the nanohybrid material possesses electrical bistability and the device exhibits two accessible conductivity states, which can be reversibly switched from the low-conductivity state to the high-conductivity state with an ON/OFF current ratio of about 102. The device with the PI (6FDA/ODA)/silver nanohybrid film as the active layer shows nonvolatile memory behavior. The high-conductivity state and the low-conductivity state of the device can be sustained after the removal of the applied voltage. Mechanisms regarding the charge transfer in the nanohybrid material were discussed.
Co-reporter:Zhi-Wei Lin;Sheng-Li Qi;De-Zhen Wu
Journal of Applied Polymer Science 2012 Volume 125( Issue 5) pp:3552-3559
Publication Date(Web):
DOI:10.1002/app.36240
Abstract
Double-surface-silvered polyimide (PI) films have been successfully fabricated via a direct ion-exchange self-metallization method using silver ammonia complex cation ([Ag(NH3)2]+) as silver resource and bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride/4,4′-oxydianiline (BPADA/ODA)-based poly(amic acid) (PAA) as the PI precursor. The alkaline characteristic of the silver precursor dramatically improves the efficiency of the ion exchange and film metallization process. By using an aqueous [Ag(NH3)2]+ solution with a concentration of only 0.01M and an ion-exchange time of only 5 min, metallized films with desirable performance could be easily obtained by simply heating the silver(I)-doped PAA films to 300°C. The strong hydrolysis effect of the basic [Ag(NH3)2]+ cations on the flexible and acidic BPADA/ODA PAA chains was observed during the ion exchange process by the quantitative evaluation of the mass loss of PAA matrix. Nevertheless, under the present experimental conditions, the final metallized film essentially retained the basic structural, thermal, and mechanical properties of the pristine PI, which make it a truly applicable material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Guofeng Tian;Dezhen Wu;Zhanpeng Wu ;Xiaodong Wang
Macromolecular Rapid Communications 2011 Volume 32( Issue 4) pp:384-389
Publication Date(Web):
DOI:10.1002/marc.201000570
Co-reporter:Lei Shi, Hebo Ye, Wenlu Liu, Guofeng Tian, Shengli Qi and Dezhen Wu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 44) pp:NaN7399-7399
Publication Date(Web):2013/09/16
DOI:10.1039/C3TC31369G
Two novel functional aromatic polyimides (PIs), 6F-αNA PI and 6F-βNA PI, in which the hexafluoroisopropylidene-diphthalic anhydride (6FDA) serves as the electron-accepting unit and the diphenylnaphthylamine (DPNA) functions as the electron-donating species, were synthesized for memory device applications. The 6F-αNA PI shows distinct electrical bistable states with an ON/OFF current ratio up to 106, and can be switched on bi-directionally with no polarity, which could be applied as the nonvolatile write-once read-many times (WORM) memory. Whereas, the 6F-βNA PI-based memory device exhibits flash type memory characteristics with a switching-on voltage at ca. 1.1 V and an ON/OFF ratio of 104. Both polyimides exhibit good long-term operation stability, survive up to 108 reading cycles with no current degradation, and show ultrafast switching with a response time less than 20 ns. Mechanisms associated with the electrical switching behaviors are discussed on the basis of the experimental and quantum simulation results. The electric-field-induced electronic transition from diphenylnaphthylamine units to hexafluoropropylidene phthalimide units and the subsequent formation of charge-transfer complexes are supposed to be responsible for the observed electrical memory effects. Molecular simulation suggests that α-tethering of the naphthyl group results in more non-coplanar conformation of the DPNA species in the 6F-αNA PI, as compared to that of the β-tethering in the 6F-βNA PI, therefore producing a higher energy barrier that prevents the back charge transfer processes, consequently leading to the WORM vs. flash memory behaviors. The 6F-αNA PI differs from 6F-βNA PI only in the substitution position of the naphthyl group, i.e., α-tethering vs. β-tethering. The distinct memory effects observed here suggest the significance of the electron-donating structures on the memory effects, and the tailorability of the memory characteristics through fine structure adjustment.
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/26700/26615-45-2.png)
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/26700/26615-45-2_b.png)
![Benzenamine, 4,4',4''-[1,3,5-benzenetriyltris(oxy)]tris-](/data/chemimg/133100/102852-92-6.png)
![Benzenamine, 4,4',4''-[1,3,5-benzenetriyltris(oxy)]tris-](/data/chemimg/133100/102852-92-6_b.png)
-1,4-PHENYLENEOXY-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/40000/39940-16-4.png)
-1,4-PHENYLENEOXY-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/40000/39940-16-4_b.png)
![POLY[OXY-1,4-PHENYLENEIMINOCARBONYL(DICARBOXYPHENYLENE)CARBONYLIMINO-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/9100/9043-05-4.png)
![POLY[OXY-1,4-PHENYLENEIMINOCARBONYL(DICARBOXYPHENYLENE)CARBONYLIMINO-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/9100/9043-05-4_b.png)
![Poly[(5,7-dihydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c']dipyrrole-2,6(1H,3H)-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25100/25036-53-7.png)
![Poly[(5,7-dihydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c']dipyrrole-2,6(1H,3H)-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25100/25036-53-7_b.png)
