Copoly(peryleneimide)s containing 1,3,4‐oxadiazole rings: Synthesis and properties

New copolyimides containing perylenediimide, oxadiazole and hexafluoroisopropylidene moieties were prepared by one‐step polycondensation reaction in solution at high temperature of aromatic diamines containing preformed oxadiazole ring with a mixture of a dianhydride having a perylene ring and another dianhydride with hexafluoroisopropylidene unit. The thermal stability and glass transition temperatures of these copolyimides were measured and compared with those of related polyimides. The solid polymers were also studied by polarized light microscopy and X‐ray diffraction which revealed a semicrystalline state consisting of face‐to‐face arranged columns of perylenediimide units. The film‐forming ability and properties of the resulting thin films were investigated by using atom force microscopy and scanning electron microscopy which showed that the films were organized into self‐assembled rod‐like structures. The UV‐Vis and photoluminescence properties in solution and in solid state were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4230–4242, 2010     

New thermally stable and organosoluble heterocyclic poly(naphthaleneimide)s

As majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene‐containing dianhydride, with hexafluoroisopropylidene‐dianhydride in the polycondensation reaction with the same diamino‐oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin‐coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd.     

COMPARED PROPERTIES OF FLUORINATED HETEROCYCLIC COPOLYIMIDES

Various new fluorinated heterocyclic copolyimides have been synthesized by a polycondensation reaction of a diacid chloride containing imide, hexafluoroisopropylidene and methylene groups with aromatic or heteroaromatic diamines containing preformed phenylquinoxaline or 1,3,4-oxadiazole rings. Other fluorinated heterocyclic copolyimides have been prepared by a polycondensation reaction of the same diacid chloride with aromatic dihydrazides, bis(o-hydroxy-amine)s or a bis(o-carboxy-amine), resulting in intermediate polyhydrazides, poly(o-hydroxy-amide)s or poly(o-carboxy-amide), respectively, which were futher cyclodehydrated to the corresponding polyoxadia zole-imide, polybenzoxazole-imide or polybenzoxazinone-imide structure. These polymers showed good solubility in polar amidic solvents, such as N-methylpyrrolidinone (NMP) and dimethylformamide (DMF), and even in less polar liquids, like tetrahydrofurane or pyridine, except for those compounds containing benzoxazole rings which were less soluble, only on heating in NMP or DMF. The weight average molecular weight measured for tetrahydrofurane-fully-soluble polymers are in the range of 12800–26700 and the polydispersity is in the range of 2–5. All these polymers exhibited good thermal stability, with decomposition temperature being above 350°C, although somewhat lower than that of related polymers prepared by using fully aromatic diacid chlorides instead of the present ones containing methylene units. The glass transition temperature is in the range of 200–300°C. The dielectric constant measured for polymer films is in the range of 3.3–3.7. Tensile strength is in the range of 35–70 MPa, elongation to break between 30–40% and tensile modulus in the range of 170–330 MPa. A study of the relation between conformational parameters and properties of some of these polymers has been carried out by using the Monte Carlo method with an allowance for hindered rotation, and the values were compared with the experimental data and discussed in relation with the rigidity of the chains. The present polymers are potential candidates for use as high performance materials.     

Synthesis and characterization of highly soluble fluorescent main chain copolyimides containing perylene units

A series of high molecular weight copolyimides containing various amount of perylene units in the main chain have been synthesized. The polymers were characterized by FT-IR, NMR, UV/Vis, fluorescence spectroscopy, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis measurements. They are highly soluble in conventional solvents such as CHCl₃, THF, cyclohexanone etc. and form optically transparent films by solution casting or spin coating. The incorporation of various amount of perylene units in the main chain allows the control of the fluorescence intensity in solution and in solid thin films. The copolyimide containing 0.28 mol% perylene units exhibits the highest solid-state fluorescence. The observed fluorescence intensities of the copolyimides in solid state film decreased with the increasing amount of perylene units in the main chain when the mole ratio of perylene units greater than 0.28 mol% indicating the aggregation of chromophores. The copolyimides are thermally stable up to 400 °C and exhibit glass transition temperatures in the range of 340-360 °C. The number average molecule weight ranges from 1.72×10⁴ to 1.25×10⁵ and the molecule weight distribution mediated between 1.9 and 2.4.     

New silicon-containing heterocyclic polyimides

New aromatic polyimides and polyamide-imides with phenylquinoxaline rings and dimethylsilane units have been synthesized by solution polycondensation reaction of aromatic diamines containing phenylquinoxaline units with bis(3,4-dicarboxyphenyl)-dimethylsilane dianhydride, or with a diacid chloride resulting from the reaction of this dianhydride with p-aminobenzoic acid. These polymers were easily soluble in organic solvents, such as N-methylpyrrolidinone and dimethylacetamide, and showed high thermal stability with decomposition temperature being above 440°C and glass transition temperature in the range of 245-285°C. Very thin coatings were deposited from polymer solutions onto silicon wafers and exhibited smooth, pinhole-free surface in atomic force microscopy investigations. Some of these polymers showed blue fluorescence in solution and films, with a maximum in the range of 415-425 nm.     

Syntheses and characterization of functionalized polynorbornene dicarboximides for flexible substrates

In this study, we synthesized polynorbornene (PNB) dicarboximides substituted by monochlorophenyl group (PMCPhNDI) and dichlorophenyl group (PDCPhNDI) via ring‐opening polymerization using a ruthenium catalyst and investigated their thermal, mechanical, and optical properties. We also discussed the performance and application of the functionalized PNB dicarboximide films as flexible substrates for organic light‐emitting devices (OLEDs). The polymer films exhibited good optical transparency with an average transmittance of around 97% in the visible light region and good thermal stability with a 5% degradation temperature of >440°C. The polymers were applied for flexible displays, which were coated on indium tin oxide (ITO) thin films using a radio‐frequency planar magnetron sputtering system with changing the deposition substrate temperatures. A flexible OLED that was fabricated on the ITO‐grown polymer substrates exhibited a performance as comparable to the corresponding ITO‐grown glass substrates. Copyright © 2012 John Wiley & Sons, Ltd.     

Blue light‐emitting poly(p‐phenylenevinylene) derivatives containing alternating conjugated segments and aliphatic spacers

Two new poly(p‐phenylenevinylene) derivatives were prepared by Heck coupling. They contained alternating conjugated segments on the basis of p‐distyrylbenzene and flexible nonconjugated spacers. The synthesized polymers P1 and P2 carried two m‐terphenyl of four tertbutyl pendants, respectively, per repeat unit. Both polymers were amorphous and exhibited satisfactory thermal stability. Polymer P1 displayed a limited solubility in common organic solvents, whereas P2 dissolved readily in these solvents. The glass‐transition temperature values were 128 °C for P1 and 37 °C for P2 . The polymers emitted blue or violet‐blue light with photoluminescent maxima at about 445 and 460 nm for solutions and thin films, respectively. The bulky pendants reduced their tendency to form aggregates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1091–1098, 2003     

Aromatic polymers with side oxadiazole rings as luminescent materials in LEDs

Aromatic polyamides and polyazomethines with side oxadiazole rings have been synthesized by using aromatic diamines containing pendent substituted oxadiazole groups and a diacid chloride having diphenylsilane or hexafluoroisopropylidene, or an aromatic dialdehyde with fluorene unit, respectively. These polymers were easily soluble in amidic solvents. Very thin films which were deposited from polymer solutions onto silicon wafers exhibited smooth, pinhole-free surface in atomic force microscopy investigations. The polymers showed high thermal stability with decomposition temperature being above 400°C. Some of them exhibited blue photoluminescence, in the range of 450-480 nm, making them promising candidates for future use as high performance materials in the construction of light emitting devices.     

Fluorenyl cardo copolyimides containing poly(ethylene oxide) segments: Synthesis,characterization, and evaluation of properties

A set of new block copolyimides containing fluorenyl cardo moieties (FR) in the polyimide blocks and poly(ethylene oxide) (PEO) sequences has been prepared using the two‐step method of polyimide synthesis. The combination of both moieties led to novel copolyimides with good solubility in a variety of solvents, which could easily be processed into films. Copolyimides with PEO content from 30 to 56 wt % were amorphous, showed good mechanical properties, and absorbed less water than other PEO‐containing polyimides previously reported. Copolyimides with higher PEO content (60 and 65%) showed crystallinity and yielded soft films. All of the copolymers showed two glass transition temperatures, the first one around ?25 °C attributed to the PEO segments, and the second one at much higher temperature, which corresponded to the polyimide domains. The thermal degradation occurred in two steps, the first one being associated with the degradation of the PEO segments and the second one with the generalized aromatic polyimide decomposition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8170–8178, 2008     

Synthesis and properties of nitrogen‐linked poly(2,7‐carbazole)s as hole‐transport material for organic light emitting diodes

A novel class of carbazole polymers, nitrogen‐linked poly(2,7‐carbazole)s, was synthesized by polycondensation between two bifunctional monomers using the palladium‐catalyzed amination reaction. The polymers were characterized by ¹H NMR, Infrared, Gel permeation chromatography, and MALDI‐TOF MS and it was revealed that the combination of the monomer structures is important for producing high molecular weight polymers. Thermal analysis indicated a good thermal stability with high glass transition temperatures, e.g., 138 °C for the higher molecular weight polymer P2 . To pursue the application possibilities of these polymers, their optical properties and energy levels were investigated by UV‐Vis absorption and fluorescence spectra as well as their electrochemical characteristics. Although the blue light emission was indeed observed for all polymers in solution, the quantum yields were very low and the solid films were not fluorescent. On the other hand, the HOMO levels of the polymers estimated from the onset potentials for the first oxidation in the solid thin films were relatively high in the range of ?5.12 to ?5.20 eV. Therefore, light emitting diodes employing these polymers as a hole‐transport layer and iridium(III) complex as a triplet emitter were fabricated. The device of the nitrogen‐linked poly(2,7‐carbazole) P3 with p,p′‐biphenyl spacer, which has a higher HOMO level and a higher molecular weight, showed a much better performance than the device of P2 with m‐phenylene spacer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3880–3891, 2009     

High‐performance laminates through chemical welding of thin liquid crystalline polymer films

A systematic study of the welding (healing) process of polymers with different chemical compositions, structures and properties was carried out. It was shown that welding can be due to a number of physical and/or chemical factors. Diffusion alone led to a relatively weak welding under the selected conditions. A jump was observed in the temperature dependence of the shear stress of polyimides. The abrupt increase in the activation energy of welding can be explained by assuming a change in the nature of the created bonds from physical to chemical ones. For the first time the chemical reactions taking place at the contacting surfaces were directly experimentally proved by electron spin resonance. In some cases, for the first time, the healing process was carried out at temperatures below the glass transition temperature. In this way, the contribution of the diffusion process to the healing may be distinguished from that of the chemical reactions. On the basis of a poly(ethylene terephthalate) copolyester containing 60 mol% p‐hydroxybenzoic acid thin liquid crystalline films (160 µm thick) are obtained by melting the polymer at 300°C and chilling at 0°C. The undrawn films have a high degree of orientation as shown by X‐ray measurements. These films have excellent mechanical properties because of the molecular orientation. In order to avoid losses in the mechanical strength due to increase in their thickness, laminates were prepared using thin liquid crystalline films. Lamination was carried out by annealing under pressure at 170°C for 6 hr, resulting in samples with excellent mechanical properties regardless of their thickness. A method is proposed that makes it possible to combine the unique mechanical properties of thin films of liquid crystalline polymers with a lamination process in order to obtain thick and very strong materials. Copyright © 1999 John Wiley & Sons, Ltd.     

Dielectric behavior of some aromatic polyimide films

Aromatic polyimides were prepared by polycondensation reaction of two aromatic diamines, such as 4,4′-diaminodiphenylmethane (DDM) and 3,3′-dimethyl-4,4′-diaminodiphenylmethane (MDDM), with aromatic dianhydrides, such as 4,4′-isopropylidene-diphenoxy-bis(phthalic anhydride) (6HDA), benzophenonetetracarboxylic dianhydride (BTDA) and hexafluoroisopropylidene-bis (phthalic anhydride) (6FDA). These polymers are soluble in polar aprotic solvents and can be cast into thin films from such solutions. The polyimides show high thermal stability, with decomposition temperature being above 430 °C in air, and high glass transition temperature being in the range of 200–287 °C. The free standing films, having the thickness of tens of micrometers, exhibited good mechanical and electrical insulating properties. The dielectric constant, molecular mobility and AC conductivity of thin films prepared from these polymers were investigated in detailed. The study of their dielectric behavior evidenced low dielectric constant values, in the range of 2.88–3.48 at 1 Hz at room temperature, and three relaxation processes (γ,β₁ and β₂) were observed at sub-glass temperatures for polyimides based on 6HDA and 6FDA and only two (γ and β) relaxations were detected for polyimides based on BTDA. The cooperativity of the molecular motions associated with the relaxation processes was discussed.     

Oriented thin films from soluble polythiophenes

The degree of orientation of thin films of eight different polymeric structures, belonging to the class of soluble polyalkylthiophenes (PATs) has been studied. Thin films of the polymers, obtained by spin coating onto glass substrates, were oriented by means of the rubbing technique. The degree of orientation is related to the regioregularity of the system: highly regioregular polymers can be oriented, while regiorandom materials are not oriented. The degree of orientation can be improved by thermal annealing of the oriented films. As a result of annealing, which was performed at different temperatures according to the thermal behavior of the polymers, it was possible to increase the polarization ratio for poly(3-decylthiophene) up to 12–13 as detected from the UV-vis spectra in polarized light. Moreover in the investigated PATs, both the key role of molecular weight and its distribution for achieving a high orientation degree has been assessed. Copyright © 2003 John Wiley & Sons, Ltd.     

New series of highly phenyl‐substituted polyfluorene derivatives for polymer light‐emitting diodes

A new series of highly phenyl‐substituted polyfluorene derivatives were synthesized and characterized. The resulting polymers were amorphous and showed excellent solubility in common organic solvents, such as chloroform, tetrahydrofuran, xylene, toluene, chlorobenzene, and so forth. All possessed satisfied thermal stability with glass‐transition temperatures (T_g's) in the range of 79–115 °C. They emitted blue light with photoluminescent (PL) maximum peaks at about 408–412 nm in thin films. The PL efficiencies of the polymer films were measured around 30–33%. The highly phenylated pendants improved the T_g of polyfluorene without forming defects in the polymers and reduced their tendency to form aggregate/excimers. Polymer light‐emitting diodes were fabricated from these polymers with the configuration of indium tin oxide/polyethylenedioxythiophene:polystyrene sulfonic acid/polymer/Ba/Al, which emitted bright blue light with maximum peaks at 418–420 nm. The maximum external quantum efficiencies of these devices were 0.41–0.6%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2985–2993, 2004     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Thermally stable antireflective coatings based on nanoporous organosilicate thin films

Thermally stable nanoporous organosilicate thin films were realized by the microphase separation of pore-generating polymers mixed with an organosilicate matrix to be antireflective coatings (ARCs), for which a thin film with a refractive index (n) of 1.23 for zero reflection is required. The refractive index of such nanoporous organosilicate films can be tuned from 1.39 down to 1.23 by incorporating nanopores within the films. With a nanoporous single layer with n approximately 1.23, the light transmittance of the glass above 99.8% was achieved in the visible range (lambda approximately 550 nm). To overcome the limitation on the narrow wavelength for high transmittance imposed by a single antireflective nanoporous thin film, bilayer thin films with different refractive indices were prepared by placing a high refractive index layer with a refractive index of 1.45 below the nanoporous thin film. UV-vis transmittance of a glass coated with the bilayer films was compared with nanoporous single-layer films and it is demonstrated that the novel broadband antireflection coatings in a wide range of visible wavelength can be easily obtained by the organosilicate bilayer thin films described in this study. Also, ARCs developed in this study demonstrate excellent AR durability owing to the hydrophobic nature of the organosilicate matrix.     

Atomic force microscopy studies on the dewetting of perfluorinated ionomer thin films

The surface structure and dewetting process of thin films of complex perfluorinated ion‐containing polymers have been studied with atomic force microscopy. These polymers, or ionomers, consist of hydrophilic, hydrophobic, and ionic groups, which are noncompatible with one another, and this results in the association of the polymers into supramolecular structures. These types of polymers have a broad range of technological uses, ranging from thin selective coatings to fuel cells in the form of polymer electrolyte membranes. As the technology calls for thinner films, the interfacial structure and dynamics (wetting/dewetting) of the films become critical in controlling the overall behavior of the polymers. The ionomer under consideration forms structured films consisting of bundles of micelles. These ultrathin films do not dewet above the glass‐transition temperatures of the polymers, contrary to what has been observed in thin diblock copolymers. Perturbing the system with a high‐ionic‐strength solution, however, results in a breakup of the primary aggregate and enhances the adhesion of the films and their stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 149–158, 2003     

FLUORINATED PHTHALAZINONE-CONTAINING COPOLYIMIDES FOR PASSIVE OPTICAL WAVEGUIDES

A series of fluorinated copolyimides containing phthalazinone moieties were prepared from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 3,3′4,4′-benzophenone-tetracarboxylic dianhydride (BPDA) and 2-(4-alninophenyl)-4-[4-(4-alninophenoxyl)phenyl]-2,3-phthalazin-1-one (DHPZ-2NH2) for making polymeric optical waveguides. The resulting copolymers containing 0-50mol% BPDA/DHPZ-2NH2 show good solubility and are soluble in some organic polar aprotic solvents. The copolyimides also present excellent thermal stability. These polymers possess high glass transition temperature higher than 603K and high decomposition temperature above 742K determined by differential scanning calorimetry and thermogravimetric analysis, respectively, under a nitrogen atmosphere. Their refractive indices could be controlled by varying the ratio of 6FDA and BPDA in the copolymer from 0.5 to 1.0, and the in-plane refractive indices (riTE) range from 1.6366 to 1.6668 and the out-of-plane refractive indices (nTM) from 1.6024 to 1.6280 at 632.8nm.The polymers birefringence (0.0342—0.0388) is almost independent of the 6FDA content of copolymer, which indicated that the phthalazinone-containing copolyimides could be suitable to fabricate optical waveguides possessing a low polarization dependent loss (PDL).     

两种高Tg非线性光学聚合物母体及掺杂,极化的研究

利用具有非线性光学活性的对硝基苯胺掺杂高玻璃化转变温度的聚芳醚砜(PES-C)和聚芳醚酮(PEK-C),得到了两种掺杂含量较高的掺杂型非线性光学聚合物体系。电晕极化表明较高的取向和较慢的松驰。     

Synthesis and Characterization of Novel Poly(Arylene Ether)s from 4,4′‐Thiodiphenol

Four novel perfluoroalkylated poly(arylene ether)s have been synthesized successfully using four perfluoroalkyl‐activated bisfluoro monomers. These polymers are synthesized through nucleophilic displacement of the fluorine atoms on the benzene ring with 4,4′‐thiodiphenol and are named as 1a, 1b, 1c and 1d, respectively. The polymers obtained by displacement of the fluorine atoms exhibit weight‐average molar masses up to 3.9×10⁴ g · mol^?1 in Gel permeation chromatography. These poly(arylene ether)s showed very high thermal stability up to 548°C for 10% weight loss in TGA under nitrogen and high glass transition temperature (T_g) up to 178°C in DSC depending on the repeat unit structures. The glass transition temperatures taken as peak in tan δ in DMA measurements are in good agreement with the DSC T_g values. All the polymers synthesized are soluble in a wide range of organic solvent such as CHCl₃, CHCl₂, THF, NMP, DMF and toluene. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 72 MPa, modulus up to 1.69 GPa with low elongation at break depending on their exact repeating unit structures. Rheological properties showed ease of processability of these polymers with no change in melt viscosity with temperature.