Synthesis,characterization, and electroluminescence of polyfluorene copolymers containing T‐shaped isophorone derivatives

We have successfully synthesized a series of new fluorene‐based copolymers, poly[(9,9‐bis(4‐octyloxy‐phenyl)fluorene‐2,7‐diyl)‐co‐[2(3{2[4(2{4[bis(bromophenyl‐4yl) amino]phenyl}vinyl)‐2,5‐bisoctyloxyphenyl]vinyl}‐5,5‐dimethyl‐cyclohex‐2‐enylidene)malononitrile] (PFTBMs), with varying molar ratios of the low‐energy band gap comonomer, 2(3{2[4(2{4[bis(4‐bromophenyl)amino]phenyl}vinyl)‐2,5‐bisoctyloxyphenyl]vinyl}‐5,5‐dimethyl‐cyclohex‐2‐enylidene)malononitrile (BTBM). To prepare BTBM (which has a T‐shaped structure) from triphenylamine, dialkoxy phenyl, and isophorone, we introduced three individual segments of an isophorone derivative containing two cyanide groups at the carbonyl position, a dialkoxy phenyl group for increased solubility, and a triphenyl amine for effective charge transfer. Furthermore, we introduced vinyl linkages between each segment to increase the length of π‐conjugation. The synthesized polyfluorene copolymers with the BTBM, PFTBMs, were synthesized via palladium‐catalyzed Suzuki coupling reactions. The photoluminescence emission spectra of the synthesized polymers in solution did not show significant energy transfer from PBOPF segments to the BTBM units. Light‐emitting devices based on these polymers were fabricated with an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/polymers/Balq/LiF/Al configuration. Examination of the electroluminescence emission of the synthesized polymers showed that the maximum wavelength shifted continuously toward long wavelengths with as the number of BTBM units in the polymer main chain was increased. In particular, a device using PFTBM 05 exhibited a maximum brightness of 510 cd/m² and a maximum current efficiency of 0.57 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 82–90, 2010     

Synthesis of alkaline‐developable,photosensitive hyperbranched polyimides through the reaction of carboxylic acid dianhydrides and trisamines

Hyperbranched polyimides (HBPI)s with high glass‐transition temperatures and excellent thermal stability were synthesized through the reaction of commercially available carboxylic acid dianhydrides with tris[4‐(4‐aminophenoxy)phenyl]ethane (TAPE). In particular, hyperbranched polyimide HBPI(TAPE‐DSDA), prepared through the reaction of TAPE with 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA), showed higher thermal stability and good solubility. Furthermore, alkaline‐developable, photosensitive HBPI(TAPE‐DSDA)‐MA‐CA was prepared through the reaction of HBPI(TAPE‐DSDA) with glycidyl methacrylate with tetrabutylammonium bromide as a catalyst in N‐methyl‐2‐pyrrolidinone (NMP) followed by the addition reaction of cis‐1,2,3,6‐tetrahydrophthalic anhydride with triphenylphosphine as a catalyst in NMP. The glass‐transition temperatures of HBPI(TAPE‐DSDA)‐MA‐CA were greater than 300 °C. A resist composed of 74 wt % HBPI(TAPE‐DSDA)‐MA‐CA, 22.2 wt % trimethylpropane triacrylate, and 3.8 wt % Irgacure 907 as a photoinitiator achieved a resolution of a 55‐μm line pattern and a 275‐μm space pattern by UV irradiation (1000 mJ/cm²). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3697–3707, 2004     

Tunable memory performances of the porphyrin terminated hyperbranched polyimides

Herein, a functional hyperbranched polyimide, denoted as ATPP‐HBPI, was synthesized by termination of polyamic acid with 5‐(4‐aminophenyl)‐10, 15, 20‐triphenylporphyrin (ATPP) and chemical imidization. Subsequently, ATPP‐HBPI was coordinated with Zn ion to give Zn‐ATPP‐HBPI. In the HBPIs, the porphyrin terminals acted as the electron donor (D) and the 6FDA moieties acted as the electron acceptor (A) to promote the electron transition. Both ATPP‐HBPI and Zn‐ATPP‐HBPI exhibited good organo‐solubility and high thermal stability. They were used as the electroactive layer to fabricate the memory device with a configuration of indium tin oxide (ITO)/HBPI/Al to evaluate their bistability. The devices exhibited different memory behaviors, WORM for ATPP‐HBPI and SRAM for Zn‐ATPP‐HBPI, respectively. Optical and electrochemical experiments and molecular simulation were carried out to illustrate this phenomenon of performance transformation. The results show that the metallization of terminal of the HBPIs provides a strategy for tailoring the memory characteristics of the devices. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1953–1961     

Syntheses,properties, and field‐effect transistors of small band gap quinoxaline‐ and thienopyrazine‐vinylene/ethynylene conjugated polymers

New conjugated copolymers of quinoxaline (AQ) and thienopyrazine (ATP) with vinylene (V) or ethynylene (E), poly[2,3‐bis(4‐(2‐ethylhexyloxy)phenyl)‐quinoxaline vinylene] (PAQV), poly[2,3‐bis(4‐(2‐ethylhexyloxy)phenyl)‐quinoxaline ethynylene)] (PAQE), poly[2,3‐bis(4‐(2‐ethylhexyloxy)phenyl)‐thieno[3,4‐b]pyrazine vinylene] (PATPV), and poly[2,3‐bis(4‐(2‐ethylhexyloxy)phenyl)‐thieno[3,4‐b]pyrazine ethynylene] (PATPE), were successfully synthesized by Stille coupling reaction. The optical band gaps of the PAQV, PAQE, PATPV, and PATPE were 1.86, 2.00, 0.88, and 0.90 eV, respectively, whereas the electrochemical band gaps were 1.99, 2.06, 1.00, and 1.06 eV, respectively. The reduced steric hindrance by the incorporation of the V or E linkage or the intramolecular charge transfer between the acceptor and the V or E linkage led to the small band gap. The AQ/ATP‐vinylene copolymers exhibited much higher vis/near infrared absorption intensity than the AQ/ATP‐ethynylene suggested the stronger π–π* transition intensity in the former and led to better charge‐transporting characteristics. The saturation field‐effect hole mobilities of the PATPV were 2.1 × 10^?3, 1.7 × 10^?2, and 1.1 × 10^?2 cm² V^?1 s^?1 on bare, octyltrichlorosilane (OTS)‐treated, and octadecyltrichlorosilane(ODTS)‐treated SiO₂, respectively, with on‐off current ratios of 35, 6.02 × 10², and 7.56 × 10². On the other hand, the estimated field‐effect transistor hole mobility of the PATPE was in the range of 1.7 × 10^?6–8.1 × 10^?4 cm² V^?1 s^?1, which was significantly smaller than those of the PATPV. The small band gaps and high charge carrier mobility of the prepared copolymers suggested their potential applications for near‐infrared electronic and optoelectronic devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 74–81, 2010     

Synthesis and characterization of organosoluble ditrifluoromethylated aromatic polyimides

Two novel diamine monomers, 1,4‐bis (4‐aminophenoxy)‐2‐[(3′,5′‐ditrifluoromethyl)phenyl]benzene and 1,4‐bis [2′‐cyano‐3′(4″‐amino phenoxy)phenoxy]‐2‐[(3′,5′‐ditrifluoromethyl)phenyl] benzene, were synthesized from (3,5‐ditrifluoromethyl)phenylhydroquinone. A series of ditrifluoromethylated aromatic polyimides derived from the diamines were prepared through a typical two‐step polymerization method. These polyimides had a high thermal stability, and the temperatures at 10% weight loss were above 507 °C in nitrogen. Most of the polymers showed good solubility in anhydrated 1‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, chloroform, and tetrahydrofuran at room temperature. All the polymers formed transparent, strong, and flexible films with tensile strengths of 63.6–95.8 MPa, elongations at break of 5–10%, and Young's moduli of 2.38–2.96 GPa. The dielectric constants estimated from the average refractive indices are 2.69–2.89. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3018–3029, 2005     

High Performance Nonvolatile Transistor Memories Utilizing Functional Polyimide‐Based Supramolecular Electrets

We report pentacene‐based organic field‐effect transistor memory devices utilizing supramolecular electrets, consisting of a polyimide, PI(6FOH‐ODPA), containing hydroxyl groups for hydrogen bonding with amine functionalized aromatic rings (AM) of 1‐aniline (AM1), 2‐naphthylamine (AM2), 2‐aminoanthracene (AM3), and 1‐aminopyrene (AM4). The effect of the phenyl ring size and composition of AM1–AM4 on the hole‐trapping capability of the fabricated devices was investigated systematically. Under an operating voltage under ±40 V, the prepared devices using the electrets of 100 % AM1–AM4/PI ratios exhibited a memory window of 0, 8.59, 25.97, and 29.95 V, respectively, suggesting that the hole‐trapping capability increased with enhancing phenyl ring size. The memory window was enhanced as the amount of AM in PI increased. Furthermore, the devices showed a long charge‐retention time of 10⁴ s with an ON/OFF current ratio of around 10³–10⁴ and multiple switching stability over 100 cycles. This study demonstrated that the electrical characteristics of the OFET memory devices could be manipulated through the chemical compositions of the supramolecular electrets.     

PCPP derivatives containing carbazole pendant as hole transporting moiety for efficient blue electroluminescence

The syntheses and characterization of poly((2,6‐(4,4‐bis(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))‐co‐(2,6‐(4,4‐bis(4‐(((9‐carbazolyl)hexyl)oxy)phenyl))‐4H‐cyclopenta[def]phenanthrene)) (BCzPh‐PCPPs) and poly((2,6‐(4,4‐bis(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))‐co‐(2,6‐(4‐(4‐(((9‐carbazolyl)hexyl)oxy)phenyl)‐4‐(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))) (CzPh‐PCPPs), with carbazole unit as pendants, are presented. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. The devices of the polymers with the configurations of ITO/PEDOT:PSS/polymers/Ca/Al generate EL emission with maximum peaks at 400–450 nm, CIE coordinates of (x = 0.11–0.29, y = 0.11–0.33), low turn‐on voltages of 4–6 V, maximum brightness of 60–810 cd/m², and luminescence efficiencies of 0.04–0.22 cd/A. The PL spectra of CzPh‐PCPPs films did not show any peak at around 550 nm, which corresponds to keto defect or aggregate/excimer formation, even after annealing for 30 h at 150 °C in air. Out of the series, CzPh‐PCPP1 (PCPP derivative with 10% of carbazole moiety as pendant) shows blue emission with the maximum brightness of 810 cd/m² at 9 V, and the highest luminescence efficiency of 0.22 cd/A at 395 mA/cm². © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1327–1342, 2009     

A facile strategy for synthesis of α,α′‐heterobifunctionalized poly (ε‐caprolactones) and poly (methyl methacrylate)s containing “clickable” aldehyde and allyloxy functional groups using initiator approach

Two new initiators, namely, 4‐(4‐(2‐(4‐(allyloxy) phenyl)‐5‐hydroxypentane 2‐yl) phenoxy)benzaldehyde and 4‐(4‐(allyloxy) phenyl)‐4‐(4‐(4‐formylphenoxy) phenyl) pentyl 2‐bromo‐2‐methyl propanoate containing “clickable” hetero‐functionalities namely aldehyde and allyloxy were synthesized starting from commercially available 4,4′‐bis(4‐hydroxyphenyl) pentanoic acid. These initiators were utilized, respectively, for ring opening polymerization of ε‐caprolactone and atom transfer radical polymerization of methyl methacrylate. Well‐defined α‐aldehyde, α′‐allyloxy heterobifunctionalized poly(ε‐caprolactones) (M_n,GPC: 5900–29,000, PDI: 1.26–1.43) and poly(methyl methacrylate)s (M_n,GPC: 5300–28800, PDI: 1.19–1.25) were synthesized. The kinetic study of methyl methacrylate polymerization demonstrated controlled polymerization behavior. The presence of aldehyde and allyloxy functionality on polymers was confirmed by ¹H NMR spectroscopy. Aldehyde‐aminooxy and thiol‐ene metal‐free double click strategy was used to demonstrate reactivity of functional groups on polymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Hydroxyl‐ and amine‐terminated hyperbranched polyurethanes using AB2‐type azide monomers: Synthesis,characterization, fluorescence,and charge‐transfer complexation studies

Novel AB₂‐type azide monomers such as 3,5‐bis(4‐methylolphenoxy)carbonyl azide (monomer 1) , 3,5‐bis(methylol)phenyl carbonyl azide (monomer 2) , 4‐(methylol phenoxy) isopthaloyl azide (monomer 3) , and 5‐(methylol) isopthaloyl azide (monomer 4) were synthesized. Melt and solution polymerization of these monomers yielded hydroxyl‐ and amine‐terminated hyperbranched polyurethanes with and without flexible ether groups. The structures of theses polymers were established using FT‐IR and NMR spectroscopy. The molecular weights (M_w) of the polymers were found to vary from 3.2 × 10³ to 5.5 × 10⁴ g/mol depending on the experimental conditions used. The thermal properties of the polymers were evaluated using TGA and DSC: the polymer obtained from monomer ( 1 ) exhibited lowest T_g and highest thermal stability and the polymer obtained from monomer ( 2 ) registered the highest T_g and lowest thermal stability. All the polymers displayed fluorescence maxima in the 425–525 nm range with relatively narrow peak widths indicating that they had pure and intense fluorescence. Also, the polymers formed charge transfer (CT) complexes with electron acceptor molecules such as 7,7,8,8‐tetracyano‐quino‐dimethane (TCNQ) and 1,1,2,2‐tetracyanoethane (TCNE) as evidenced by UV‐visible spectra. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3337–3351, 2009     

New liquid‐crystal alignment agents based on fluorinated polyimides with trifluoromethyl‐substituted benzene or diphenylether in the side chain

Fluorinated copolyimides derived from 4,4′‐oxydiphthalic anhydride (ODPA) with 4,4′‐oxydianline (ODA) and trifluoromethyl‐containing aromatic diamines have been synthesized and characterized. The trifluoromethyl‐containing diamines include 2,4‐diamino‐3′‐trifluoromethylazobenzene, 2,4‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] aniline, 3,5‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] benzamide, 3,5‐diamino‐1‐[(3′‐trifluoromethyl) phenyl] benzamide, 1,4‐bis(4′‐aminophenoxy)‐2‐(3′‐trifluoromethylphenyl) benzene, 3,5‐diaminobenzenetrifluoride, 4,4′‐diamino‐4″‐(p‐trifluoromethyl phenoxy) triphenylamine, and 4‐[(4′‐trifluoromethylphenoxy) phenyl]‐2,6‐bis(4″‐aminophenyl)pyridine. Strong and flexible copolyimide films, produced by casting the polyamic acid solution followed by thermal imidization, exhibited great thermal stability and high mechanical properties. The polyimides had an ultraviolet–visible absorption cutoff at 330–340 nm and pretilt angles as high as 20° for nematic liquid crystals, making them great potential candidates for advanced liquid‐crystal display applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1583–1593, 2002     

Fluorene based donor‐acceptor polymer electrets for nonvolatile organic transistor memory device applications

Fluorene based donor‐acceptor polyimides, including poly[bis‐(4‐aminophenyl)fluorene‐hexanediamide] [PA(BAP F‐AC)], poly[bis‐(4‐aminophenyl)fluorene‐hexafluoroisopropylidenediphthalimide] [PI(BAPF‐6FDA)], poly[bis‐(4‐aminophenyl)fluorene‐oxydiphthalimide] [PI(BAPF‐ODPA)], and poly[bis‐(4‐aminophenyl)fluorene‐1,2,4,5‐cyclohexanetetracarboxylic diimide] [PI(BAPF‐HPMDA)], as charge storage layer (electret) are employed for nonvolatile memory device applications. The polyimides are consisted of electron‐donating fluorene diamine moiety (BAPF) and neutral (AC and HPMDA) or electron‐accepting (6FDA and ODPA) moieties, respectively. The memory characteristics of these devices can be tuned from the EORM (erase once and read many times) behavior [PA(BAPF‐AC)], semi‐flash [PI(BAPF‐ODPA)], [PI(BAPF‐HPMDA)], to a flash type memory [PI(BAPF‐6FDA)]. The PI(BAPF‐6FDA) devices show the largest memory window of 77 V and a long retention time over 10⁴ s with a high I_on/I_off current ratio of 10⁸. This is attributed to the largest torsion angle of PI(BAPF‐6FDA) stabilizing charge transfer (CT) complexes. The write‐read‐erase‐read cycles were stably operated over 100 cycles. This work provides a new insight into the relationship between the CT effect and the nonvolatile memory behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 602–614     

Soluble polyimides containing 1,4:3,6‐dianhydro‐d‐glucidol and fluorinated units: Preparation,characterization, optical,and dielectric properties

Aiming to develop soluble and colorless polyimides, two novel diamines, 2,5‐bis(2‐trifluoromethyl‐4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2a) and 2,5‐bis(2‐methyl‐4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2b), were designed and synthesized by the reduction of corresponding dinitro monomer which was obtained via solvent‐free melt heating method. Polyimides (PI–(1–5)) containing 1,4:3,6‐dianhydro‐d ‐glucidol fragments were prepared from 2a and five kinds of common dianhydrides and PI–6 was synthesized from 2b and 4,4′‐(hexafluoroisopropylidene)‐diphthalic anhydride (6FDA) via a two‐step thermal imidization. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough, and transparent films with transparency as high as 87% at 450 nm. Meanwhile, PI–(1–6) exhibited unexpectedly low dielectric constants of 2.02–2.52 at 1 MHz. In addition, analogs PI–7 derived from 2,5‐bis(4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2c) and 6FDA and PI–8 derived from 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl (2d) and 6FDA were also obtained via a two‐step thermal imidization for comparision with PI–(1–6) on aspects of thermal, mechnical, optical, electrical, and morphological properties. The structure–property relationships of PI–(1–8) were discussed in detail. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3253–3265     

Electrically driven self‐healing polymers based on reversible guest–host complexation of β‐cyclodextrin and ferrocene

A multifunctional ferrocene‐modified poly(glycidyl methacrylate) (PGMA‐Fc) and a difunctional β‐cyclodextrin derivative (bis‐CD) has been prepared for the construction of an electrically driven removable and self‐healing polymeric materials based on the complexation reaction between ferrocene and β‐CD groups. The chemical structures of PGMA‐Fc and bis‐CD have been characterized with Fourier transform infrared, ¹H nuclear magnetic resonance, and X‐ray photoelectron spectroscopy. The effects of electrical voltages and medium conductivity on the decrosslinking efficiency of the crosslinked PGMA‐Fc/CD polymer have been examined. The PGMA‐Fc/CD network has shown removable feature and properties for application as a reworkable crosslinked material. Moreover, the crosslinked PGMA‐Fc/CD sample has shown electrically driven self‐healing behavior. The self‐healing performance could be enhanced with wetting the sample to increase the electrical conductivity. As a result, the material could serve as a self‐healing agent for commercial painting products. Preparation and application of a novel and efficient self‐healing polymer have been demonstrated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3395–3403     

High Tg,ambipolar, and near‐infrared electrochromic anthraquinone‐based aramids with intervalence charge‐transfer behavior

Two novel series of ambipolar and near‐infrared electrochromic aromatic polyamides with electroactive anthraquinone group were synthesized from new aromatic diamines, 2‐(bis(4‐aminophenyl)amino)anthracene‐9,10‐dione and 2‐(4‐(bis(4‐aminophenyl)amino)phenoxy)anthracene‐9,10‐dione, respectively, via low‐temperature solution polycondensation reaction. These polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with high glass‐transition temperatures (T_g) (285–360 °C). Electrochemical studies of these electrochromic polyamides revealed ambipolar behavior with reversible redox couples and high contrast ratio both in the visible range and near‐infrared region. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and memory characteristics of highly organo‐soluble hyperbranched polyimides with various electron acceptors

A series of hyperbranched polyimides (HBPIs) were synthesized by reacting a triamine monomer N ,N ′,N ″‐tris(4‐methoxyphenyl)‐N ,N ′,N ″‐tris(4‐phenylamino)?1,3,5‐benzenetriamine with various dianhydrides such as oxydiphthalic dianhydride (ODPA), 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA). The hyperbranched polyimide (6FHBPI) using 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as dianhydride monomer was also added into the discussion. All the hyperbranched polyimides exhibited excellent organo‐solubility and high thermal stability. Memory devices with a sandwiched structure of indium tin oxide (ITO)/HBPI/Al were constructed by using these HBPIs as the active layers. All these HBPIs based memory devices exhibited favorable memory performances, with switching voltages between ?1.3 V and ?2.5 V, ON/OFF current ratios up to 10⁷ and retention times long to 10⁴ s. Tunable memory characteristics from electrical insulator to volatile memory, and then to nonvolatile memory were obtained by adjusting the electron acceptors of these HBPIs. Molecular simulation results suggested that the electron affinity and the dipole moment of these HBPIs were responsible for the conversion of the memory characteristics. With the electron affinity and dipole moment of these HBPIs increasing, the memory characteristics turned from volatile to nonvolatile. The present study suggested that tunable memory performance could be achieved through adjusting the acceptor moieties of the hyperbranched polyimides. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2281–2288     

Low‐bandgap donor–acceptor copolymers with 4,6‐bis(3′‐(2‐ethylhexyl)thien‐2′‐yl)thieno[3,4‐c][1,2,5]thiadiazole: synthesis,optical, electrochemical,and photovoltaic properties

Two new low‐bandgap alternating copolymers (CEHTF and CEHTP) consisting of 4,6‐bis(3′‐(2‐ethylhexyl)thien‐2′‐yl)thieno[3,4‐c][1,2,5] thiadiazole and 9,9‐bis(2‐ethylhexyl)fluorene or 2,5‐bis(isopentyloxy)benzene were synthesized by Suzuki coupling reaction of corresponding comonomers. Their optical, electrochemical, and photovoltaic (PV) properties were studied and are reported. Both the copolymers exhibited long‐wavelength absorption covering the whole visible spectral region, which is in CEHTP thin films extended up to near infrared region, ambipolar redox properties, and electrochromism. High‐electron affinities and low‐optical bandgap values, 1.37 and 1.15 eV, were determined for CEHTF and CEHTP, respectively. PV devices with bulk heterojunction made of blends of copolymers and fullerene derivative [6,6]‐phenyl‐C⁶¹‐butyric acid methyl ester ([60]PCBM) were prepared and characterized. Effects of intramolecular charge transfer strength and side‐chain nature and length on photophysical properties are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,characterization and memory properties of novel organosoluble polyimides

Two novel series of aromatic polyimides were prepared from 2,2′‐bis(4‐amino‐3‐trifluoromethylthylphenoxy) biphenyl, 2,2′‐bis(4‐amino‐3‐methoxyphenoxy)biphenyl with 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA) via a one‐step procedure. The resulting polymers were fully characterized, and they exhibited excellent organosolubility. These polyimides are thermally stable with 5% weight loss over 430°C, and glass transition temperatures of the polyimides were found to be 225–262°C. Resistive switching devices with the configuration of Al/polymer/indium‐tin oxide were constructed from these polyimides by using conventional solution coating process. Devices with all polyimides exhibited nonvolatile and rewritable flash type memory characteristics with turn‐on voltage at ?1.1 to ?2.8 V. The ON/OFF current ratio of these devices was larger than 10⁴, and the retention times can be as long as 10⁴ s. The theoretical simulation based on the density functional theory suggested that greater distinct charge separation between the ground and charge transfer states led to a highly stable memory behavior. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel fluorinated polyimides derived from 4,4′‐[2,2,2‐trifluoro‐1‐(3‐trifluoromethylphenyl)ethylidene]diphthalic anhydride and aromatic diamines

A novel fluorinated aromatic dianhydride, 4,4′‐[2,2,2‐trifluoro‐1‐(3‐trifluoromethyl‐phenyl)ethylidene]diphthalic anhydride (TFDA) was synthesized by coupling of 3′‐trifluoromethyl‐2,2,2‐trifluoroacetophenone with o‐xylene under the catalysis of trifluoromethanesulfonic acid, followed by oxidation of KMnO₄ and dehydration. A series of fluorinated aromatic polyimides derived from the novel fluorinated aromatic dianhydride TFDA with various aromatic diamines, such as p‐phenylenediamine (p‐PDA), 4,4′‐oxydianiline (ODA), 1,4‐bis(4‐aminophenoxy)benzene (p‐APB), 1,3‐bis(4‐amino‐phenoxy)benzene (m‐APB), 4‐(4‐aminophenoxy)‐3‐trifluoromethylphenylamine (3FODA) and 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene (6FAPB), were prepared by polycondensation procedure. All the fluorinated polyimides were soluble in many polar organic solvents such as NMP, DMAc, DMF, and m‐cresol, as well as some of low boiling point organic solvents such as CHCl₃, THF, and acetone. Homogeneous and stable polyimide solutions with solid content as high as 35–40 wt % could be achieved, which were prepared by strong and flexible polyimide films or coatings. The polymer films have good thermal stability with the glass transition temperature of 232–322 °C, the temperature at 5% weight loss of 500–530 °C in nitrogen, and have outstanding mechanical properties with the tensile strengths of 80.5–133.2 MPa as well as elongations at breakage of 7.1–12.6%. It was also found that the polyimide films derived from TFDA and fluorinated aromatic diamines possess low dielectric constants of 2.75–3.02, a low dissipation factor in the range of 1.27–4.50 × 10^?3, and low moisture absorptions <1.3%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4143–4152, 2004     

Synthesis,characterization, and application of light‐emitting copolyfluorenes slightly doped with distyrylbenzene derivatives

Copolyfluorenes PFG1～PFG4 slightly doped with 0.006–0.5 mol % of 2,5‐dihexyloxy‐1,4‐bis(2‐phenyl‐2‐cyanovinyl)benzene (green chromophore) were synthesized by the Suzuki coupling reaction to be evaluated as hosts for white‐light electroluminescent (EL) devices. Their optical, thermal and electrochemical properties were almost identical to those of polyfluorene ( PF ) due to minimal chromophore content. However, the electroluminescent (EL) spectra of the PFGn were very different from photoluminescence spectra in film state. Relative intensity of green emission (ca. 521 nm) in EL spectra are much stronger than those in PL spectra, which can be attributed to charges trapping in the chromophores due to its narrow band gap (E_g ≈ 2.56 eV). The performance of EL devices [ITO/PEDOT:PSS/polymer/Ca (50 nm)/Al (100 nm)] were improved with an increase in chromophore content. The PFG4 device revealed the best performance (6790 cd/m², 1.69 cd/A), and the PFG1 and PFG2 devices exhibited comparable intensity in blue and green emissions. Blend EL devices were fabricated by using the PFGn as the hosts and a red iridium complex [Ir(piq)₂(acac)] as dopant. By controlling the amount of the iridium complex, the white‐light emitting device was achieved with PFG2 , with maximum brightness and CIE coordinate being 4120 cd/m² and (0.31, 0.28), respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 149–160, 2009     

New synthetic route for photosensitive poly(benzoxazole)

A new positive working photosensitive poly(benzoxazole) (PBO) precursor based on poly(o‐hydroxyazomethine) ( 3 ) and 1‐{1,1‐bis[4‐(2‐diazo‐1‐(2H)naphthalenone‐5‐sulfonyloxy)phenyl]ethyl}‐4‐{1‐[4‐(2‐diazo‐1(2H)naphthalenone‐5‐sulfonyloxy)phenyl]methylethyl}benzene (S‐DNQ) as a photosensitive compound was developed. 3 was prepared by the condensation of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane with isophthalaldehyde in 1‐methyl‐2‐pyrrolidinone/toluene under azeotropic conditions. The photosensitive PBO precursor containing 30 wt % S‐DNQ showed a sensitivity of 120 mJ cm^?2 and a contrast of 2.2 when it was exposed to 436‐nm light and developed with a 2.38 wt % aqueous tetramethylammonium hydroxide solution at room temperature. A fine positive image featuring 10‐μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm^?2 ultraviolet light at 436 nm by the contact mode. The positive image was successfully converted into the PBO pattern by a thermal treatment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3399–3405, 2002