Organic memory effect from donor-acceptor polymers based on 7-perfluorophenyl-6H-[1,2,5]thiadiazole[3,4-g]benzoimidazole

Article abstract of DOI:10.1039/c5ra15059k

A novel D-A conjugated polymer (PIBT-BDT) with 7-perfluorophenyl-6H-[1,2,5]thiadiazole[3,4-g]benzoimidazole is synthesized by the Stille coupling reaction. A memory device with PIBT-BDT as the active layer shows a large on/off ratio (>10⁵), good endurance (>100 cycles), and long retention (>10⁴ s). Through simulating the I-V curves and analysing energy barriers in the device structure, we suggest that the memory effect of Au/PIBT-BDT/ITO originates from the charge transfer between the strong acceptor (IBT) units and the donor BDT units.

Full text of DOI:10.1039/c5ra15059k

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Novel Organic Memory Effect from Donor-Acceptor Polymers based
on 7-Perfluorophenyl-6H-[1,2,5]thiadiazole[3,4-g]benzoimidazole
Received 00th January 20xx,
Accepted 00th January 20xx
Benlin Hu, a Chengyuan Wang,a Jing Zhang,a Kai Qian, a Pooi See Lee,a Qichun Zhang*ab
DOI: 10.1039/x0xx00000x
A novel D-A conjugated polymer (PIBT-BDT) with 7-perfluorophenyl-6H-[1,2,5]thiadiazole[3,4-g]benzoimidazole has been
synthesized through the Stille coupling reaction. The memory device with PIBT-BDT as an active layer shows a large
on/OFF ratio (> 105), good endurance (> 100 cycles), and long retention (>104 s). Through simulating the I-V curves and
analysing energy barriers in the device structure, we suggest that the memory effect of Au/PIBT-BDT/ITO is originated
from the charge transfer between the strong acceptor (IBT) units and the donor BDT units.
www.rsc.org/
polymers usually need to further be modified by other electron-
withdraw groups. The fluorination for polymers has received
numerous attentions in materials science due to the interesting
Introduction
Over the last 50 years, resistive switching, referring to the physical
phenomena where a dielectric sharply changes its resistance under
the effect of a strong electric field or current, has attracted
numerous attentions for its charmingly potential application in
memories, logic calculation and artificially neuromorphic
synapses.1-8 Especially, the resistance memory, i.e. resistance
random access memory (RRAM), has advantages of simple
structure, mass storage, high operation speed, and being
compatible with traditional CMOS technology.9-15 Since the
Ag/Pr0.7Ca0.3MO3(PCMO)/YBa2Cu2O7-x(YBCO) sandwiched structure
was firstly explored as RRAM,16 a large number of inorganic and
organic materials have been explored as RRAM materials, such as
complex oxides, binary oxides, amorphous silicon, organic small
improvements of the properties of materials by introducing fluorine
atoms into the structure, such as better solubility, high oxidative
stability and degradation resistance.40-43 Especially, conjugated
fluoropolymers used in organic electronics have been reported to
possess lower LUMO energy levels, better electrode interface to the
injection of charge carriers, and high stability to the ambient
species (O2/H2O) since the fluorine atom is the most
electronegative element. In fact, conjugated fluoroligomers and
conjugated fluoropolymers have been demonstrated to show
excellent performances in OFETs, OPVs and OLEDs .34-37,39
In this contribution, a new D-A conjugated polymer (PIBT-BDT,
see scheme 1) based on novel acceptor with a strong electron-
deficient
pentafluorophenyl
group,
7-perfluorophenyl-6H-
molecules,
conjugated
polymers,
functional
polyimides,
[1,2,5]thiadiazole[3,4-g]benzoimidazole (IBT), incorporated into the
BT unit to enhance the electron-withdrawing ability has been
designed and synthesized. The as-synthesized polymer has high
molecular weight (Mn) of 14 Ka by means of gel permeation
chromophores pendent polymers and polymer nanocomposites
(blended with carbon nanomaterials and metal nanoparticles).17-33
Compared with inorganic materials and most organic small
molecules,4,6,25 polymers show more interests in the application as
RRAM due to their unique characteristics of high scalability, highly
tailorable, easy solution processability, flexibility, high mechanical
strength and three-dimensional stacking capability.17,19,22,25
Donor-acceptor polymers based on 2,1,3-benzothiadiazole (BT)
have been widely explored as optic-electrical materials, such as
organic field-effect transistor (OFET), organic photovoltaic device
(OPV) and organic light-emitting diode (OLED).34-39 However, less
effort about D-A polymers based on BT units was reported with
memory effect. Moreover, because the electron-withdrawing ability
of the BT unit is not strong enough, BT units as acceptors in
chromatography (GPC) analysis against
a linear polystyrene
standard. The polymer is readily soluble in common organic
solvents, such as toluene, chloroform, tetrahydrofuran and
chlorobenzene. The sandwiched device of Au/ PIBT-BDT /ITO shows
an excellent nonvolatile memory effect, such as high ON/OFF ratio,
good endurance and long retention. The memory effect is derived
from the charge transfer between of IBT units and BDT units.
EXPERIMENTAL
Materials and methods
4,7-Dibromo-5,6-diaminobenzothiadiazole44 (4) and M239,45,46
(Scheme 1) were prepared according to the reported procedures.
All starting chemicals, unless otherwise specified, were purchased
from Alfa Aesar or Sigma-Aldrich and used as received.
a.School of Materials Science and Engineering, Nanyang Technological University,
Singapore 639798, Singapore. Email: qczhang@ntu.edu.sg.
b.Division of Chemistry and Biological Chemistry, School of Physical and
Mathematical Sciences, Nanyang Technological University, Singapore 637371,
Singapore
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Scheme 1. The synthesis of the monomer (M1) and the polymer (PIBT-BDT)
1H Nuclear Magnetic Resonance (1H NMR) spectra were differential refractive index (DRI) and Ultraviolet (UV)
measured at 300 MHz on a Bruker 300 AVANCE detectors using THF as the eluent and linear polystyrenes as
spectrometer with chloroform (CDCl3) or dimethyl sulfoxide the molecular weight standards. Cyclic voltammetry (CV)
(DMSO-d6) as solvents. UV-Vis absorption spectra were measurements were carried out with CHI 604E
Ⅲ
a
recorded on a Shimadzu 2501 PC spectrophotometer at room Electrochemical Workstation (CH Instruments, Shanghai
temperature. The film for UV-Vis test was fabricated by Chenhua Instrument Corporation, China) under an argon
dropping the polymer solution (CHCl3) onto glass plates and atmosphere. The polymer film coated on a Pt plate (working
dried before tested. Thermogravimetric analysis (TGA) was electrode) was scanned at 10 mV/s in an anhydrous
performed on a TA Instrument Q500 instrument under a dichloromethane
nitrogen atmosphere with a gas-flow rate of 50 mL/min and a hexafluorophosphate (n-Bu4NPF6, 0.1 M), with a Pt wire and
heating rate of 10 /min. Differential scanning calorimetry platinum gauze as the reference and counter electrodes,
solution
of
tetrabutylammonium
℃
(DSC) measurements were carried out on a Mettler Toledo DSC respectively. The thickness of the polymer film was measured
system under a nitrogen atmosphere with a gas-flow rate of 50 by a KLA Tencor Alpha-Step Surface Profiler.
mL/min and a heating rate of 20 °C/min. Glass transition
temperature was recorded as the temperature at the middle
of the thermal transition in the second heating scan. Gel
permeation chromatography (GPC) traces of the samples were
Synthesis of monomer and polymer
4,7-Dibromo-5-(N-entaphenylmethylene)-6-aminobenzothiadiazole
(6)
monitored on an Agilent 1260 GPC-MDS system fitted with
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Figure 1. The 1H NMR spectrum of 6 and M1
2,3,4,5,6-Pentafluorobenzaldehyde (5) (784.2 mg, 4 mmol) and
compound 4 (1296 mg, 4 mmol) were thoroughly mixed in DMF (20
mL), and p-methylbenzenesulfonic acid (60 mg) was added. the
resulted solution was stirred overnight. The reaction mixture was
poured into water and extracted with EtOAc (3 ×100 mL), and
washed with brine (3 ×100 mL). After dried by MgSO4, the organic
solvent was evaporated under reduced pressure. The crude product
was purified through column chromatography (eluent: DCM/hexane
Figure 2. TGA (a) and DSC (b) curves of PIBT-BDT under argon
atmosphere.
1
= 1:4) to yield 6 as a pale solid (1.6065 g, 80 %). H NMR (300 MHz,
83 %). 1H NMR (300 MHz, CDCl3): δ (ppm): 10.64 (s), 9.66 (s), 9.15-
8.69 (m), 7.63-7.36 (m), 7.18 (d), 7.08 (d), 6.90 (s), 6.36 (s), 4.51
(br), 4.22 (s), 1.28 (br), 0.91-0.82 (m).
DMSO-d6): δ (ppm) 8.51 (s, 1H, CH=N), 6.91 (s, 2H, NH2). 19F NMR
(282 MHz, DMSO-d6): δ (ppm), -145.66 (dd, 2F, J = 25.2 Hz, 8.4 Hz), -
153.22 (t, 1F, J = 23.7 Hz), -162.23 (td, 2F, J = 24.9, 11.2 Hz)
4,7-Dibromo-2-(2,3,4,5,6-pentafluorophenyl)-5H-imidazo[4,5-f]-2,1,
3-benzothiadiazole (M1).
Fabrication and characterization of memory devices
The ITO glasses were washed with ethanol, isopropanol and
acetone sequentially in an ultrasonic bath for 20 min, respectively.
A 0.1 mL chlorobenzene solution of the polymer PIBT-BDT was spin-
coated onto the ITO substrates at a spinning speed of 400 rpm for
12 s and then 2000 rpm for 40 s, followed by a vacuum-drying at
100 °C for 8 h. Before spin-coating, the solution was filtered
through polytetrafluoroethylene (PTFE) membrane micro-filters
with a pore size of 0.45 μm. The thickness of the polymer film is ~97
nm, as measured by spectroscopic ellipsometer (model M2000DI,
Woollam). To construct the Au/PIBT-BDT/ITO structures, Au top
electrodes with a diameter of 100 μm and thickness of 100 nm were
deposited at room temperature by thermal evaporation with a
metal shadow mask. The current–voltage (I–V) characteristics of the
Au/PIBT-BDT/Pt devices were measured in an ambient atmosphere
on Keithley 4200 SCS semiconductor characterization system in
voltage sweeping mode. The sweeping step is 0.01 V.
Compound 5 (502 mg, 1 mmol) was dissolved into DMF (10 mL),
and FeCl3·6H2O (200 mg) was added into the mixture. And the
stirred solution was then heated at ca. 80 °C for 3h (monitored by
TLC). After the reaction mixture was allowed to cool to room
temperature and then added dropwise into a vigorously stirred 0.05
M aq. Na2CO3 (100 mL). The reaction mixture was poured into
water and extracted with DCM (3 ×50 mL), and washed with brine
(3 ×50 mL). After dried by MgSO4, the organic solvent was
evaporated under reduced pressure. The crude product was
purified through column chromatography (eluent: DCM/hexane =
1
1:4) to yield M1 as a brightly yellow solid (460 mg, 92 %). H NMR
(300 MHz, DMSO-d6): δ (ppm), 14.02 (s, 1H, NH). 19F NMR (282
MHz, DMSO-d6): δ (ppm), -138.23 (d, 2F, J = 26.7 Hz), -148.81 (t, 1F,
J = 24.3 Hz), -161.03 (t, 2F, J = 24.9Hz).
PIBT-BDT
The equimolecular amounts of M1 and M2 (0.15 mmol), and
Pd(PPh3)4 (∼1.6 mol%) were dissolved in anhydrous toluene. Argon
was bubbled through the solution for 30 min and then the mixture
was vigorously stirred at 110 °C under an argon atmosphere for 48
h. After cooling to room temperature, the mixture was poured into
methanol. After washed with methanol, oligomers and catalyst
residues were removed by hexane through a Soxhlet apparatus for
24 h. Then, the product was extracted by tetrahydrofuran (THF) for
another 24 h. The THF extraction was concentrated and the product
was precipitated by methanol, and collected by filtration and dried
in vacuum overnight. Deeply blue powders (129 mg, yield
RESULTS AND DISCUSSION
Characterization of polymer structures
The synthetic route for the monomer and polymer is shown in
Scheme 1. The monomer M1 was synthesized by the condensation
and cyclization of 4,7-dibromo-5,6-diaminobenzothiadiazole 4 and
2,3,4,5,6-pentafluorobenzaldehyde 5. The intermediate product 6
was obtained by the condensation reaction between compounds 4
and 5 in the presence of p-TsOH as a catalyst. Although several
other organic acid and hydrochloric acid have been tried as
catalysts for this reaction, only p-TsOH as a catalyst gave the best
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UV-Vis absorption spectrum of PIBT-BDT in CHCl3 shows a
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maximum absorption peak at ~355 nm with a shoulder peak at ~410
nm, which can be ascribed to the π–π* transition of the conjugated
polymer backbone. A broad bands in the range of 500-800 nm can
be observed with a maximum absorption peak at ~712 nm, and this
peak is due to the coupling between the n–π* and π–π* transitions of
imidazole units, as well as the intramolecular charge-transfer (CT)
interaction of PIBT-BDT as a dilute solution in chloroform.47 As
expected, both absorption bands of PIBT-BDT film are obviously
broader than those of PIBT-BDT dilute solution. The red shifts of
maximum absorption peaks are Δλ=9 nm and Δλ=45 nm,
respectively, indicating that the polymer chains are stacked more
tightly to be extended π–π stacking between the D and A moieties.48
As increasing the polarity of the studied solvents, the absorption
maxima of π–π* transition show slightly redshifts, whereas these of
n–π* and π–π* transitions exhibit significant blue shift, which
suggests that the energy barrier of π–π* transition in the polymer
mainchain did not change very much by the polarity of solvents,
however, the energy barrier of n–π* and π–π* transitions is enlarged
by increasing the polarity of the solvents, especially the formation of
the hydrogen bonds between solvents and imidazole units.
To further investigate the optical properties of this novel IBT-
including polymer, we measured the photoinduced intramolecular
charge transfer by the fluorescence spectra in different organic
solvents. As shown in Figure 3b, the emission spectrum of PIBT-
Figure 3. a) UV/Vis absorption spectra of PIBT-BDT in solution and
as films; b) Photoluminescence spectra of PIBT-BDT in solution, and BDT in toluene shows strong emission bands at λmax=396, 423 and
the insets are the PL spectra of polymer in DMF (10-5 M) and as
films.
444 nm. Interestingly, when the polarity of the organic solvents
increased, no obvious change of maximum emission bands was
investigated, which suggests the π–π* transition is not affected by
the polarity of the solvents very much, and agrees with the UV-Vis
result . Note that compound 6 cannot be converted to M1 without
the oxidant agents even heated to 80 °C in the DMF for two days
results. It is noticeable that the concentration of PIBT-BDT in toluene
under air. The intermediate product 6 and monomer M1 were
and chloroform solution is ~ 10-5 M for the fluorescence testing, but
the fluorescence spectrum of a solution of the PIBT-BDT in DMF
solution with a concentration of 10-5 M shows overflow in the range
of 384-500 nm (see the inset of Figure 3b). The fluorescence
spectrum in Figure 3b for the PIBT-BDT in DMF was recorded after
diluting the PIBT-BDT in DMF solution to 10-7 M, which is still
stronger than that in toluene and chloroform solution with a
concentration of 10-5 M.
characterized by 1H and 19F NMR spectra. As shown in Figure 1, two
1
peaks at 8.51 and 6.91 ppm are observed in the H NMR spectrum
of 6, which are typical peaks for the proton from imide bonds
(CH=N) and amino group with strong electron-withdrawn units.
After cyclization, only one peak at 14.02 ppm can be found in the 1H
NMR spectrum of the product M1. In addition, the 19F NMR results
can agree with the chemical structures of 6 and M1 very well. D-A
polymer P1 was synthesized through the Stille coupling
polymerization between M1 and M2. The chemical structure of the
1
as-synthesized polymer PIBT-BDT can be confirmed by the H NMR
spectrum. The molecular weight and polydispersity index (PDI) were
characterized by GPC with calibration against polystyrene standards
and THF as an eluant. The weight-average molecular weight of
PIBT-BDT is 14 kDa and the polydispersity index is 1.76 by GPC
analysis. PIBT-BDT exhibits good solubility in common organic
solvents, such as DMF, THF, chloroform and chlorobenzene.
Thermal properties
The thermal properties of the as-synthesized polymer PIBT-BDT
were evaluated by TGA and DSC under nitrogen atmosphere. As
shown in Figure 2, PIBT-BDT was found to have a degradation
temperature (Td10%) of 276 °C and a glass transition temperature
(Tg) of 106 °C. The results suggest that this polymer is a thermally
stable polymer, which can be used in the microelectronics industry.
Optical and electrochemical properties
Figure 4. Cyclic voltammograms of PIBT-BDT films.
The UV-vis absorption spectra of the polymer PIBT-BDT in solution
and thin film state are shown in Figure 3a. It can be found that the
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Figure 7. Retention of an Au/PIBT-BDT/ITO device.
Figure 5. I–V characteristics of ITO/ PIBT-BDT /Ag memory cells; the
inset is a schematic configuration of the Au/PIBT-BDT/ITO devices
Memory device characteristics of the polymer.
Figure 4 shows the cyclic voltammogram of PIBT-BDT films with
Au/PIBT-BDT/ITO memory device was fabricated and the device
structure is shown as the insert of Figure 5. The initial resistance of
the as-fabricated device is 92.5 MΩ and this state can be named as
platinum plate electrodes using
a
0.1
M
solution of
tetrabutylammonium hexafluorophosphate
(n-Bu4NPF6) in
anhydrous acetonitrile. According to the equation of OFF stated or high resistance stated (HRS). The bottom electrode
HOMO/LUMO=−[Eox/red−Eox.(ferrocene)]−4.8,49 the HOMO/LUMO values
(ITO) was grounded during the I-V sweeping. The typical I-V curves
of the Au/PIBT-BDT/ITO memory device are employed to depict the
memory effect process, as shown in Figure 5. The current increases
gradually and slowly from ~100 pA to ~25 nA when the applying
positively-biased voltage sweeps from 0 to 1.23 V. And the current
increase abruptly at 1.24 V with further increasing the sweeping
voltage, which suggests that the state of this device has switched
from a HRS to a low resistance state (LRS or ON state). This
transition from OFF state to ON state is defined as a “Write” or
“SET” process. Generally, a compliance current (1 mA in this work)
is usually required in the “SET” process to prevent a permanent
breakdown of the device. During the sweeping voltage from 1.24V
to 2V, and 2 V to -0.51 V, the device keeps the ON state (sweeps 2
and 3), indicating the non-volatile characteristic of this memory
device. However, the current drops sharply once the voltage
exceeds –0.51 V, and this process is generally defined as “Erase” or
“RESET” process. This HRS can be kept until the next “Read” process
(sweep 4). The ON/OFF ratio of as high as 2.5 × 105 can be achieved,
which leads to a low misreading possibility for the memory
application
of the samples can be experimentally calculated form the onset of
the redox potentials by employing the known reference level for
ferrocene, 4.8 eV below the vacuum level. Ferrocene showed an
onset oxidation of 0.32 V versus Ag/AgCl in our electrochemical
experiments. The first oxidation (Eox) for PIBT-BDT is 0.32 V versus
Ag/AgCl, whereas the first reduction potential (Ered) is -1.03 V versus
Ag/AgCl. Therefore, the HOMO of PIBT-BDT is -4.83 eV and the
LUMO is -3.45 eV.
Cyclic switching operations are used to investigate the endurance
performance of the Au/PIBT-BDT/ITO memory devices. Figure 6a
exhibits the evolution of the resistance of the two well-resolved
states more than 100 cycles. The resistance values are read out at
0.1 V in each sweep. The resistances in the OFF states show no
obvious distribution in the endurance testing, whereas the
resistances distribution of the ON state can be seen with a slight
fluctuation. Generally, the resistance rations are kept more than
five orders of magnitude during RS cycles. The evolution of the
switching voltages of SET and RESET of the Au/PIBT-BDT/ITO
devices shows large fluctuation compared to the resistance of the
ON and OFF states, as shown in Figure 6b. The range of the SET
voltages is 0.90~1.49 V, and the range of RESET voltages is -0.65~-
0.35 V. In some senses, the endurance measurement suggests that
.
Figure 6. The distribution of resistances (a) and programming
voltages (b) during the endurance testing.
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the memory effect of this device is controllable, reversible and
reproducible.
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Figure 7 shows the retention performance of the typical Au/PIBT-
BDT/ITO device under 0.1 V readout voltage. The readout is
nondestructive. The readout measurement was carried out in
ambient atmosphere at room temperature. After more than 104 s,
both the variation of the resistance distribution LRS and HRS states
of the device is very small without external electrical power supply,
confirming the nonvolatile nature of the device.
The I-V curves of the SET process were replotted in a log-log
scale, as shown in Figure 8 to understand the conduction and
switching mechanisms of Au/PIBT-BDT/ITO devices. The I-V curve of
the ON state can be satisfactorily fitted with the Ohmic conduction
model, however, the fitting of conduction mechanisms of the OFF
state faces more difficulty. The fitting results suggest that the
charge transport behavior is in good agreement with a classical
trap-controlled space charge limited current (SCLC), which consists
of three portions: the Ohmic region (I ∝ V), and the Child’s law
region (I ∝ V2).6 Therefore, the dominant conduction mechanism of
the OFF state is trap-controlled SCLC. The total different conduction
behaviors in ON and OFF states suggest that the memory effect may
be resulted from the forming/rupturing of the filament, which is
composed with the charge transfer complex between the donors
and acceptors in the polymer chains.
Figure 8. Experimental and fitted I–V curves of an Au/PIBT-BDT/ITO
memory device in both the ON and OFF states during the SET
process.
layer and the interface may be resulted from the excessive current
flow. The heat and Coulomb repulsion will lead to the rupture of
the filament formed in the SET process, which will switch the device
back to its initial OFF state.
In the polymer chain, BDT moieties are electron donors and act
as nucleophilic sites, whereas the IBT moieties are electron
acceptors and act as electrophilic sites. The energy level diagram of
Au/polymer/ITO device is shown in Figure 9. The energy barrier for
the hole injection from the Au to the HOMO of the polymer is
estimated to be 0.27 eV, whereas the energy barrier for the
electron injection from the ITO to the LUMO of the polymer is 1.35
eV. Therefore, the energy barrier for the hole injection from Au
electrodes to the HOMO of the polymer is much lower than that for
electron injection from the ITO to the LUMO of the polymer. Thus,
the conduction process in the devices is dominated by the hole
injection. When applying an increasing positive-biased voltage,
holes are injected from the ITO into the HOMO of the polymer
gradually. The injected holes are mobilizable by a hopping process
among the polymer chains. Charge trapping sites among the
polymer chains can lead to a charge accumulation and then a
redistribution of the electric field in the polymer layer. When the
sweeping voltage increases to the threshold voltage, there will form
a conductive path, where almost all the BDT moieties are injected
with holes, and then the holes have high mobility to form a
conductive filament from the Au electrode to ITO electrode. The
current can flow through the filament and sustain the ON state.
When the current increases over the compliance current, a large
number of charges will flow through the previous formed filament
and this process can produce excess heat. In addition, the injected
charges into the HOMO of the polymer also increase, and the
charges can be trapped in the polymer layer and the interface
between the polymer and electrodes. When the applied voltage
increases over a certain value (RESET voltage), the injected charges
will exceed the capacity of the filament. Excessive current flow will
also generate much heat. In the same time, repulsive Coulomb
interactions among the trapped charges gathering in the polymer
CONCLUSIONS
The D-A polymer PIBT-BDT with
a
novel acceptor, 7-
perfluorophenyl-6H-[1,2,5]thiadiazole[3,4-g]benzoimidazole, was
designed and synthesized. The as-synthesized PIBT-BDT shows high
molecular weight of 14 kDa, strong absorption in the range of 300-
800 nm, strong fluorescence in the range of 400-500 nm, and a
HOMO/LUMO energy level of -4.83/-3.45 eV. The memory device
based on PIBT-BDT exhibit large OFF ratio of more than 105, good
endurance of more than 100 cycles, and long retention of more
than 104 s. The memory effect is originated from the charge
transfer between the strong acceptor (IBT) units and the donor BDT
units. Our results could provide a new horizon to modify the BT unit
and design new D-A polymers based on BT units used in organic
electronics with excellent device performance.
Figure 9. Energy level diagram of Au/PIBT-BDT/ITO device.
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20. C. Wang, G. Liu, Y. Chen, S. Liu, Q. Chen, R.VLieiw, ABrt.iclZehOannlinge,
DOI: 10.1039/C5RA15059K
21. J. Yao, L. Zhong, D. Natelson, J. M. Tour, Sci. Rep. 2012, 2, 242.
Acknowledgements
The authors thank Mr. Kai Wang for the GPC testing. Q.Z.
ChemPlusChem 2014, 79, 1263-1270.
acknowledges the financial support AcRF Tier 1 (RG 16/12 and 22. B. Hu, F. Zhuge, X. Zhu, S. Peng, X. Chen, L. Pan, Q. Yan, R.-W. Li,
J. Mater. Chem. 2012, 22, 520-526.
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DOI: 10.1039/C5RA15059K
Journal Name
ARTICLE
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Novel Organic Memory Effect from Novel Donor-Acceptor Polymers based on 7-Perfluorophenyl-6H-
[1,2,5]thiadiazole[3,4-g]benzoimidazole
Benlin Hu, Chengyuan Wang, Jing Zhang, Kai Qian, Pooi See Lee, Qichun Zhang
A novel D-A polymer is designed for resistance memory devices with large OFF ratio, good endurance and long
retention time.
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