Photosensitive fluorinated polyimides with a low dielectric constant based on reaction development patterning

Constructing a Novel Electroluminescent Device with High-Temperature and High-Humidity Resistance based on a Flexible Transparent Wood Film

Plastic-based electroluminescent devices generally suffer from thermal expansion owing to the high coefficient of thermal expansion (CTE) of the plastic substrate, which reduces the service lifetime of the electroluminescent device. In this study, we employed a delignified veneer synergistically reinforced with epoxy resin as a low-cost substrate for alternating current electroluminescent (ACEL) devices. In brief, the natural interconnected porous structure of wood had a good antideformation capacity to restrict the volume expansion of the epoxy resin under thermal conditions. Furthermore, the impregnation of epoxy resin dramatically improved the optical transmittance of delignified veneer. Considering its low CTE and antideformation capability, the intrinsically high-temperature and high-humidity resistance device based on transparent sliced veneer (TSV) was constructed. Remarkably, the TSV-ACEL device exhibited excellent stability and maintained good luminescence performance even at a high temperature (100 °C, 30 min; as a reference, the poly(ethylene terephthalate)-based ACEL device has stopped operating), completely submerged in water (30 min), or under high-temperature and high-humidity conditions (90 °C, relative humidity: >90%, 30 min). These results pave the way for the realization of flexible and high-temperature resistance ACEL devices.

Polyimide/mica hybrid films with low coefficient of thermal expansion and low dielectric constant

Polyimide (PI)/mica hybrid films were successfully prepared by in situ condensation polymerization method, in which the mica particles were modified by coupling agent γ-aminopropyltriethoxy silane (APTS) to strengthen the interaction between the mica particles and PI matrix. The morphology, structure, thermal and mechanical properties as well as dielectric properties of PI films were systematically studied via Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR spectrometer), Thermal gravimetric analysis (TGA), tensile experiments, Thermal mechanical analyzer (TMA), impedance analyzer, etc. The results indicated that the mica particles were dispersed homogeneously in PI matrix, leading to an improvement of the mechanical property, thermal stability and hydrophobicity. It was novel to notice that hybrid films exhibited low coefficient of thermal expansion (CTE) and low dielectric constant simultaneously. The CTE and dielectric constant of hybrid film dropped to 25.36 ppm/k and 2.42 respectively, in the presence of 10 wt% mica into polyimide matrix.

Poly(ether–imide)s with flexible linkages and kinks

Four new aromatic diimide–diol monomers were synthesized from bisphenol A dianhydride and hydroxyamines. The poly(ether–imide)s (PEI-1 to PEI-4) were synthesized from these diols and 4,4′-difluorobenzophenone-IV via carbonyl-activated aromatic nucleophilic fluoro displacement reaction. The chemical structures of the monomers and PEIs were confirmed by Fourier transform infrared spectrometer and proton nuclear magnetic resonance spectroscopies. The PEIs synthesized here were amorphous and soluble in polar aprotic solvents and low-boiling organic solvents. The PEIs had good thermal stability, 10% weight loss occurred in the temperatures range of 400–448°C, and char yields at 800°C under nitrogen atmosphere was in the range of 14–22%. The limiting oxygen index values of PEIs were in the range of 23.1–26.3, and such PEIs can be used as self-extinguishing polymers. The dielectric constants of the PEIs were in the range of 3.30–4.00, and such PEIs can be used as electrical insulation materials for systems operating at high temperature for long time.

Synthesis of diol monomers and organosoluble fluorinated polyimides with low dielectric

Four diimide–diol monomers were synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride and aminophenol/aminonaphthol. The structures of the monomers were characterized by spectroscopic analysis. A series of fluorinated polyimides (FPI-1 to FPI-8) were synthesized from these new diols and 4,4′-difluorobenzophenone/4,4′-dichlorodiphenyl sulphone, through nucleophilic displacement reaction. The FPIs were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, thermogravimetry, differential scanning calorimetry, solution viscosity, solubility test, and dielectric properties test. FPIs were amorphous and showed good solubility due to the presence of >C(CF3)2 unit and flexible groups in the polyimides backbone. These FPIs also showed good thermal stability and the 10% weight loss occurred in the range 353–505°C. The limiting oxygen index values of FPIs were in the range of 31.5–39.1 and such FPIs can be used as self-extinguishing polymers. These FPIs have a dielectric constant in the range of 3.10–4.23 and can be used as high temperature electrical insulation materials.

Rationally designed polyimides for high-energy density capacitor applications

Development of new dielectric materials is of great importance for a wide range of applications for modern electronics and electrical power systems. The state-of-the-art polymer dielectric is a biaxially oriented polypropylene (BOPP) film having a maximal energy density of 5 J/cm(3) and a high breakdown field of 700 MV/m, but with a limited dielectric constant (∼2.2) and a reduced breakdown strength above 85 °C. Great effort has been put into exploring other materials to fulfill the demand of continuous miniaturization and improved functionality. In this work, a series of polyimides were investigated as potential polymer materials for this application. Polyimide with high dielectric constants of up to 7.8 that exhibits low dissipation factors (<1%) and high energy density around 15 J/cm(3), which is 3 times that of BOPP, was prepared. Our syntheses were guided by high-throughput density functional theory calculations for rational design in terms of a high dielectric constant and band gap. Correlations of experimental and theoretical results through judicious variations of polyimide structures allowed for a clear demonstration of the relationship between chemical functionalities and dielectric properties.

A new polymer with low dielectric constant based on trifluoromethyl-substituted arene: preparation and properties

A polymer based on trifluoromethyl-substituted arene was synthesized with high molecular weight (M_n) of 62 000 by the Scholl reaction. The polymer film showed low dielectric constants of about 2.56 in a range of frequencies from 1 to 25 MHz. Moreover, the polymer revealed high thermostability and good mechanical properties, suggesting that the polymer had potential applications in the electronics industry.

Synthesis of poly(amide-imide)s from new diacid monomers

Two new diacid monomers 4,4′-bis[5-(trimellitimido)napthyloxy]diphenyl sulfone and 4,4′-bis[5-(trimellitimido)napthyloxy]benzophenone were synthesized and characterized by spectroscopic analysis. A series of poly(amide-imide)s (PAIs) were prepared from these diacids and aromatic diamines through phosphorylation reaction. The structures of the PAIs were characterized by infrared and 1H-NMR. The PAIs were characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, electrical properties, solution viscosity and solubility test. The flexible linkages and pendant groups in the PAIs chain will disturb chain–chain packing and their effects on solubility, thermal stability and electrical properties were investigated. PAIs showed excellent thermal stability and good solubility. The dielectric constants of the PAIs were in the range 4.15–4.77. The PAIs have electrical insulation character and the film can be used in insulation of electrical items operating at elevated temperatures.

1,1,1,3,3,3-Hexafluoro-2,2-bis[4-(4-nitrophenoxy)phenyl]propane

In the title compound, C₂₇H₁₆F₆N₂O₆, the nitro groups are almost coplanar with the aromatic rings to which they are attached [dihedral angles = 3.5 (5) and 6.2 (3)°]. The dihedral angles between adjacent aromatic rings are 78.07 (8) and 71.11 (8)° for nitro­phen­yl/phenyl and 69.50 (8)° for phen­yl/phenyl. An inter­molecular C—H⋯π inter­action seems to be effective in the stabilization of the structure.