Preparation Of Polyimides Research Articles

Soluble polyimides with ultralow dielectric constant and dielectric loss and high colorless transparency based on spirobisindane-bis (aryl ester) diamines

With the emergence of 5G technology, the traditional polyimide with a relatively high dielectric constant (Dk) and dielectric loss (Df) are not suitable the requirements of ultra-high transmission and ultra-low loss. In particular, reducing the Df value of polyimide has become a significant difficulty in science and engineering. Herein, an elaborate design was proposed for the preparation of polyimide with both low Dk and low Df, based on a pair of diamine isomer containing two esters and a spiro-bis-indene structure (p-SBI2EA and m-SBI2EA), and their polymerization with 4,4′-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA). The resultant polyimide films showed an exceptional dielectric property, with Dk values of 2.83 and 2.88, and Df values of 0.0043 and 0.0048 for p-SBI2EA-6FDA and m-SBI2EA-6FDA, respectively, at high frequencies (40 GHz). Interestingly, introducing the spirobisindane structure significantly displayed preeminent solubility in both high-boiling-point and low-boiling-point solvents. Furthermore, the PI films exhibited perfect optical performance, with cutoff wavelengths (λcut-off) of 315 and 321 nm, transmittance exceeding 86 % and 89 % at 450 nm, and yellowing indices (YI) as low as 1.72 and 1.63, respectively. The features of the PIs render them auspicious candidate materials for applications in 5G high frequency communication and optical fields.

Exploring The Impact of Blend And Graft of Quinoline Derivative in Low-temperature Curable Polyimides.

The utilization of accelerators has been a common approach to prepare low-temperature curable polyimide (PI). However, the accelerators have gradually fallen out of favor because of their excessive dosages and negative effect on the properties of PI. In this work, a new strategy of introducing accelerators by grafting to eliminate these disadvantages is presented. A novel quinoline derivative named NQLwasdesigned for this purpose, and an ultra-low dosage of only 2.5 mol%wassufficient to prepare low-temperature curable PI. The favorable low-temperature curing effect of NQLwasattributed to its strong alkalinity (pKa = 18.47) and electron-donating ability (HOMO = -6.22eV). At a curing temperature of 200°C, the PI with 2.5 mol% NQL showed outstanding properties (Young's modulus of 5.73GPa, elongation of 37.3%, tensile strength of 237MPa and coefficient of thermal expansion of 16ppm/K). In particular, NQLcouldeven lower the curing temperature to 180°C and the ultra-low temperature curable PI film still retained excellent properties. These results demonstrate that introducing low-temperature curable accelerators by partial grafting instead of blending is a promising way to furnish low-temperature curable PI, and provide insights into the preparation of polyimide with high performance in advanced packaging. This article is protected by copyright. All rights reserved.

Synthesis and characterization of adamantane-based copolyimides with high transparency

In this work, a copolyimide (Co-PI) film with high transparency was prepared by the copolymerization of hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,2′-Bis(trifluoromethyl)benzidine (TFMB) and adamantane-1,3-diamine (DAA). The effects of DAA monomers on the optical, thermal, and mechanical properties of the co-PIs were discussed in detail. We found that the preparation of polyimide (PI) based on the combination of two dianhydrides and two diamines could obtain the co-PI film with excellent comprehensive performance due to the synergy between the -CF3 group, the aliphatic ring and the aromatic structure. Through the structure and composition optimization, the co-PI film with 1.30% DAA (Q3) has a Tg of 374oC, T5 higher than 530oC, T430 of 82% and the tensile strength higher than 145 MPa. These results indicate that the Co-PI films can be successfully utilized in the development of novel heat-resistant plastic substrates for the optoelectronic engineering applications.

The effect of poor solvent on the microstructures and thermal insulation performance of polyimide aerogels

The sol–gel process is essentially a process of phase separation between micelles and solvent, so the influence of solvent composition on the result of phase separation will further affect the wet gel and the structure of the aerogel made by it. In this study, during the preparation of polyimide (PI) aerogels, poor solvents were introduced into the reagent during the synthesis of PI aerogel precursor, polyamic acids. The pore structure and thermal insulation performance changes of the PI aerogels caused by this behavior were studied. With the addition of poor solvent, submicron-scale pores were found inside the aerogel. In addition, the introduction of a small amount of poor solvent improved the thermal insulation performance of the prepared PI aerogel.

Preparation of two-component hybrid polyimide film for atomic oxygen erosion resistance

Searching for a method for simple and low-cost preparation of polyimide (PI) composite film and exploring their atomic oxygen (AO) erosion resistance properties are highly important. For the first time we studied the AO erosion resistance of SiO2–Al2O3 doped composite PI film, and the associated sol–gel method and physical blending method were compared. After exposure to AO, all the nanocomposite film shows enhanced AO erosion resistance. Especially, a loading of 7.5 wt% SiO2–2.5 wt% Al2O3 can decrease the AO induced mass loss by 81% when compared to the pure PI, i.e. the AO resistance was increased by 4–5 times. It is found that with the same doping content, the AO resistance of the two-component (SiO2–Al2O3) hybrid PI film is notably higher than that of the single component one. The mechanism could be attributed to the SiO2–Al2O3 synergistic effect which induces a more stable protective layer on the material surface. The two-component PI composite film with enhanced AO resistance shows promise in the space applications where AO erosion has to be avoided.

Multilayer polyimide nanocomposite films synthesis process optimization impact on nanoparticles dispersion and their dielectric performance

AbstractThe preparation of polyimide (PI)/nanocomposite films and their thickness are a complex process with some ambiguous variables that are involved in the synthesis process. Therefore, it is crucial to understand those variables and reveal the chemistry behind them. Several methods have been probed until an optimal synthesis process was found. A detailed synthesis process optimization is described in this article to understand all variables, which can influence the molecular weight of polyamic acide (PAA) solution, the thickness of films, and nanoparticles dispersion. The spin coating technique was used to control the thickness of single and multilayer PI/nanocomposite films, which reveals that the thickness of the casted PI film depends on several factors, such as the viscosity, molecular weight of the PAA solution, and the spin speed of spin coater. Factors, which can influence the molecular weight of PAA solution, are discussed in detail. After completing the synthesis process, the single and multilayer PI nanocomposite films are characterized experimentally. The results reveal that using a thin layer of nanocomposite on PI film in the form of a multilayer structure improves the nanoparticles dispersion and thereafter its dielectric properties.

Polyimides prepared without the use of toxic amidic solvents

Polyimides and their modified forms (e.g., poly(imide-siloxanes)) are an important class of unique polymers. Their typical two-step preparation includes the preparation of a solution of the polyimide precursor in an amidic solvent (e.g., N-methyl-2-pyrrolidone, N,N-dimethylacetamide). Currently, these solvents are classified as toxic, and there is a strong demand to limit their use. Therefore, this study addresses the preparation of polyimides by nontoxic γ-butyrolactone as a solvent and the synthesis of polyimides and poly(imide-siloxanes) in the presence of an enzyme without the use of a solvent. The ability of these products to form self-standing films (membranes) and their thermal and mechanical properties have been found, at least partly, to be comparable to those of the products prepared by using traditional amidic solvents.

Performance of high-temperature thermosetting polyimide composites modified with thermoplastic polyimide

The preparation of polyimide (PI) resin with high heat resistance and toughness is a significant challenge. In this study, thermoplastic PI (TPI) was used to toughen thermosetting PIs, and toughened PI (TPI/PI) blends were prepared. The modified PI resin system exhibited good thermal stability, excellent heat resistance, and high toughness. The results indicated that the TPI/PI blends maintained the curing behavior and characteristics of the PI oligomer. The Tg of the cured TPI/PI blend exceeded 395 °C, and the T5% values were in the range of 533–563 °C, suggesting excellent thermal stability and heat resistance. The maximum impact strength was increased by 46% compared with that of pure PI, indicating the excellent toughening effect of the TPI. Carbon fiber-reinforced PI composites were prepared using the toughening system as a matrix. The compression-after-impact values of the carbon fiber-reinforced PI composites were up to 190 MPa, indicating the excellent toughness of the materials.

Preparation of Polyimide with Pendant Glycidyl Groups for Cationic Electrodeposition Coatings and Evaluation of Their Properties

Preparation of Polyimide with Pendant Glycidyl Groups for Cationic Electrodeposition Coatings and Evaluation of Their Properties

New hydrogen-bonded comblike polyimides with mesogenic side chains for stable orientation and fast switching of liquid crystals

ABSTRACTNew supramolecular comblike polyimides with mesogenic side chains for stable homeotropic orientation and fast electro-optical switching of liquid crystals (LCs) have been prepared through selective intermolecular hydrogen bonding between 4-(4-heptylphenyl)benzoic acid (4HPB) and host polyimide. A low concentration of 4HPB as the mesogenic guest molecule was hydrogen-bonded to polyimide backbone leading to the self-assembled comblike polyimide with enhanced homeotropic orientation properties. The electro-optical characteristics of the LC device containing hydrogen-bonded comblike polyimide exhibited better performance than those of LC cell with conventional polyimide. Because the conventional covalent approach for preparation of polyimides requires considerable synthetic efforts to achieve new functionality in polyimide materials, the proposed noncovalent method is a simple one and highly cost effective. Our controlled methodology should find wide application for the fabrication of functional alignment materials requiring high orientation ability.

Synthesis of highly transparent and thermally stable copolyimide with fluorine‐containing dianhydride and alicyclic dianhydride

ABSTRACTThe development of optical films is highly desirable for applications in flexible displayers. In this work, a copolyimide (co‐PI) film with high thermal stability and high transparency was prepared by the copolymerization of 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminodiphenyl ether, cyclobutanetetracarboxylic dianhydride, and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). The effects of aliphatic dianhydride and fluorine dianhydride monomers on the optical, thermal, and mechanical properties of the co‐PIs were discussed in detail based on the experimental results and theoretical simulations. We found that the preparation of polyimide (PI) based on the combination of two dianhydrides could obtain the PI film with excellent comprehensive performance due to nonconjugated structure and strong electron‐withdrawing effect. Through the structure and composition optimization, a PI film of PI‐6FDA‐70 with Tg of 300 °C, Td10% more than 500 °C, the average transparency of 90% and the elongation at the breakage more than 8% was prepared. Such molecular design provides a practical approach to develop high‐performance colorless PI films. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48603.

Preparation of Polyimide Fiber/Thermoplastic Resin Composites with Improved Mechanical Properties

Preparation of Polyimide Fiber/Thermoplastic Resin Composites with Improved Mechanical Properties

Preparation and Properties of Rigid Polyimides from Dianhydrides Having Various Number of Phenylene Units and <i>p</i>-Phenylenediamine

Rigid aromatic polyimides PI-PP-m (m = 0, 1, 2, 3, 4) were synthesized from p-phenylenediamine and dianhydride DA-m having various numbers (m) of phenylene units, 3,3’4,4’-biphenyltetracarboxylic dianhydride (DA-0), 3,3’’4,4’’-p-terphenyltetracarboxylic dianhydride (DA-1), 3,3’’’4,4’’’-p-quarterphenyltetracarboxylic dianhydride (DA-2), 3,3’’’’4,4’’’’-p-quinquephenyltetracarboxylic dianhydride (DA-3), and 3,3’’’’’4,4’’’’’-p-sexiphenyltetracarboxylic dianhydride (DA-4), by a conventional two-step procedure that included ring-opening polymerization and subsequent thermal cyclic dehydration. The PI-PP-m (m = 0, 1, 2, 3) films were characterized by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetry (TG), dynamic mechanical analysis (DMA), and stress-strain curves. The properties were compared on the basis of the number (m) of phenylene units. The glass transition temperatures (Tg) were observed at 270-280 ℃ as tan δ peak temperatures of DMA, and the values did not depend on m. The decrement of storage modulus at the Tg was smaller with increasing m. The thermal properties of PI-PP-0 were compared with those previously reported for Upilex-S type polyimides prepared from p-phenylenediamine and DA-0.

Preparation of Polyimides with Anionic Electrodeposition Coating Ability and Properties of their Deposition Coatings

Preparation of Polyimides with Anionic Electrodeposition Coating Ability and Properties of their Deposition Coatings

Aqueous solution blending route for preparing low dielectric constant films of polyimide hybridized with polytetrafluoroethylene

High performance polymer materials with low dielectric constant, good thermal stability and excellent mechanical property are on demand in the next generation integrated circuit devices as the interlayer dielectrics. This study reports the preparation of polyimide hybridized with polytetrafluoroethylene (PI/PTFE hybrid) films with low dielectric constant, excellent thermal stability and mechanical strength by a facile approach. The PI/PTFE hybrid films were prepared by an aqueous solution blending method, that a synthesized water soluble poly(amic acid) ammonium salt was blended with a PTFE aqueous emulsion, followed with spin-coating and thermal imidization. The PI hybrid film (40 wt% PTFE) showed a lowest dielectric constant of 2.25 (at 1 kHz). Meanwhile, the PI/PTFE hybrid films exhibited good thermal stability of the 5% weight loss temperatures (T5%) higher than 520 °C, and glass transition temperatures (Tg) higher than 285 °C; as well as excellent mechanical properties of the tensile stress, modulus, and elongation at break being 84–127 MPa, 0.94–1.86 GPa, and 56–118%, respectively.

One-pot solvothermal synthesis of robust ambient-dried polyimide aerogels with morphology-enhanced superhydrophobicity for highly efficient continuous oil/water separation

In this study, using a sequential polyamic acid (PAA) gelation and solvothermal imidization, we demonstrate a scalable one-pot solvothermal approach for the preparation of polyimide (PI) aerogels having a three-dimensional network composed of uniform microspheres. PI aerogels prepared by this approach were mechanically robust can be directly dried in oven without considerable contraction. More importantly, the PI aerogels showed morphology-enhanced water droplet contact angles from 98° to as high as 146°, which makes them nearly superhydrophobic. Such hydrophobic/oleophilic monolithic aerogels could rapidly and continuously separate oil from oil/water mixtures and even from water-in-oil emulsions.

Preparation of polyimide from melamine and pyromellitic dianhydride by microwave irradiation

Under microwave irradiation, the reaction time of PMDA and melamine in DMSO was shortened to just 30 minutes. Structure of the obtained polyimide was characterized by FTIR, and its thermal stability was confirmed by TGA analysis. The longer reaction time in DMSO solution up to 30 h at high temperature was required.

Polyimide nanocomposites with novel functionalized‐graphene sheet: thermal property, morphology, gas permeation, and conductivity

4‐Amino‐N‐hexadecylbenzamide‐graphene sheets (AHB‐GSs), used in the preparation of polyimide (PI) nanocomposite films, were synthesized by mixing a dispersion of graphite oxide with a solution of the ammonium salt of AHB. The atomic force microscopy image of the AHB‐GSs on mica and a profile plot revealed the average sheet thickness to be ~3.21 nm. PI films were prepared by reacting 4,4'‐biphthalic anhydride and bis(4‐aminophenyl) sulfide. PI nanocomposite films containing different amounts of AHB‐GS (0–10 wt%) were compared for their morphologies, thermal properties, gas permeation, and electrical and thermal conductivities. The graphenes, for the most part, were well dispersed in the polymer matrix despite some agglomeration. However, micrometer‐scale particles were not detected. The average thickness of the particles was less than 10 nm, as revealed from the transmission electron microscope images. Only a small amount of AHB‐GS was required to improve the coefficient of thermal expansion, gas permeation, and electrical and thermal conductivities. In contrast, the glass transition temperature and initial decomposition temperature of the PI hybrid films continued to decrease with increasing AHB‐GS content up to 10 wt%. Copyright © 2015 John Wiley & Sons, Ltd.

Preparation of Polyimide–Cellulose Composite Using Oligoimide with Ethynyl Terminals

Abstract A soluble imide oligomer (IO) (repeating number; 2 and 4) having N-phenylated melamine units and phenylethynyl terminals was prepared, and the application to polyimide composites with cellulose (CEL) crystals derived from pulp (CELp) or Halocynthia (CELh) with or without a modifier was investigated. The CELh additive up to 0.5 wt % was easily dispersed in IO matrix in solution, and thermostable (glass-transition temperature, ca. 285 °C) transparent tough film (tensile strength, ca. 169 MPa; elongation at break, ca. 8.9%; tensile modulus, ca. 4.6 GPa) was obtained, while the addition of a modifier such as cetyltrimethylammonium bromide and poly(ethylene glycol) derivatives was necessary to obtain a similar tough film for the CELp additive.

High glass transition of organo-soluble copolyimides derived from a rigid diamine with tert-butyl-substituted triphenylpyridine moiety

A new diamine with a tert-buty-substituted triphenylpyridine unit was synthesized and used in the preparation of polyimides via a one-step polymerization. The polyimides are completely amorphous and exhibit good solubility in organic solvents. As a result of the presence of bulky substituents and rigid triphenylpyridine units, the final polyimide products have high glass transition temperatures (up to 365 °C) and good thermal stability with 10% weight loss temperatures in the range 538–563 °C. Triphenylpyridine units and tert-butyl groups might play a key role in improving the solubility of the polyimides while maintaining high glass transition temperatures and good thermal stability. The polyimide films had good mechanical properties.