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Polyimide

A topical collection in Polymers (ISSN 2073-4360). This collection belongs to the section "Polymer Chemistry".

Viewed by 14805

Editor

Dr. Chenliang Gong

E-Mail Website
Collection Editor
State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Special Function Materials and Structure Design of Ministry of Education, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
Interests: high performance polyimide; fuel cell proton exchange membrane; POSS based hybrid polymer

Topical Collection Information

Dear Colleagues

Polyimides (PI) are an important high-performance polymer with excellent thermal stability, mechanical strength and toughness, high electric insulating properties, low dielectric constants and dissipation factors, and high radiation and wear resistance, among other properties, and they can be processed into a variety of materials, including films, fibers, carbon fiber composites, engineering plastics, foams, porous membranes, coatings and varnishes, etc. Polyimides have found widespread use in a variety of high-tech domains, including electric insulation, microelectronics and optoelectronics, the aerospace and aviation industries, etc. Dupont released the first commercial polyimide material in the late 1960s after developing an effective synthetic pathway to high-molecular-weight polyimides. Even today, however, the most popular polyimide production processes are not totally understood. This is because numerous reaction conditions, such as solvent, moisture, impurity, temperature, and others, have a considerable impact on the polymerization reaction of aromatic dianhydrides with aromatic diamines. The molecular weights of the produced polyimides can be affected by the addition mode of monomers.

In recent years, there have been many publications on polyimide materials. In order to reflect the current state of the art on the subject and to explore potential future developments, the present Special Issue welcomes submissions on all aspects of high-performance polymers, ranging from the synthesis and characterization to structural modification, processing, and new functions and applications.

Dr. Chenliang Gong
Collection Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • high-performance polymers
  • thermally stable polymers
  • aromatic polymers
  • aramids
  • polyimides and other heterocyclic polymers
  • applications

Published Papers (6 papers)

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2024

Jump to: 2023, 2022

19 pages, 10918 KiB  
Article
Polyimide Films Based on β-Cyclodextrin Polyrotaxane with Low Dielectric and Excellent Comprehensive Performance
by Xuexin Zhang, Yao Dou, Liqun Liu, Meixuan Song, Zhenhao Xi, Yisheng Xu, Weihua Shen and Jie Wang
Polymers 2024, 16(7), 901; https://doi.org/10.3390/polym16070901 - 25 Mar 2024
Cited by 2 | Viewed by 1567
Abstract
In order to prepare polyimide (PI) films with a low dielectric constant and excellent comprehensive performance, a two-step method was employed in this study to integrate β-cyclodextrin into a semi-aromatic fluorine-containing polyimide ternary system. By introducing trifluoromethyl groups to reduce the dielectric constant, [...] Read more.
In order to prepare polyimide (PI) films with a low dielectric constant and excellent comprehensive performance, a two-step method was employed in this study to integrate β-cyclodextrin into a semi-aromatic fluorine-containing polyimide ternary system. By introducing trifluoromethyl groups to reduce the dielectric constant, the dielectric constant was further reduced to 2.55 at 10 MHz. Simultaneously, the film exhibited noteworthy thermal stability (a glass transition temperature exceeding 300 °C) and a high coefficient of thermal expansion. The material also demonstrated outstanding mechanical properties, boasting a strength of 122 MPa and a modulus of 2.2 GPa, along with high optical transparency (transmittance reaching up to 89% at 450 nm). Moreover, the inherent high transparency of colorless polyimide (CPI) combined with good stretchability contributed to the attainment of a low dielectric constant. This strategic approach not only opens up new opportunities for novel electroactive polymers but also holds potential applications in flexible displays, circuit printing, and chip packaging. Full article
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2023

Jump to: 2024, 2022

20 pages, 15503 KiB  
Article
Fused-Deposition Modeling 3D Printing of Short-Cut Carbon-Fiber-Reinforced PA6 Composites for Strengthening, Toughening, and Light Weighting
by Bin Sun, Suhail Mubarak, Guocun Zhang, Kangming Peng, Xueling Hu, Qia Zhang, Lixin Wu and Jianlei Wang
Polymers 2023, 15(18), 3722; https://doi.org/10.3390/polym15183722 - 11 Sep 2023
Cited by 8 | Viewed by 3392
Abstract
Additive manufacturing of carbon-fiber-reinforced polymer (CFRP) has been widely used in many fields. However, issues such as inconsistent fiber orientation distribution and void formation during the layer stacking process have hindered the further optimization of the composite material’s performance. This study aimed to [...] Read more.
Additive manufacturing of carbon-fiber-reinforced polymer (CFRP) has been widely used in many fields. However, issues such as inconsistent fiber orientation distribution and void formation during the layer stacking process have hindered the further optimization of the composite material’s performance. This study aimed to address these challenges by conducting a comprehensive investigation into the influence of carbon fiber content and printing parameters on the micro-morphology, thermal properties, and mechanical properties of PA6-CF composites. Additionally, a heat treatment process was proposed to enhance the interlayer bonding and tensile properties of the printed composites in the printing direction. The experimental results demonstrate that the PA6-CF25 composite achieved the highest tensile strength of 163 MPa under optimal heat treatment conditions: 120 °C for 7.5 h. This corresponds to a significant tensile strength enhancement of 406% compared to the unreinforced composites, which represents the highest reported improvement in the current field of CFRP-fused deposition 3D printing. Additionally, we have innovatively developed a single-layer monofilament CF-OD model to quantitatively analyze the influence of fiber orientation distribution on the properties of the composite material. Under specific heat treatment conditions, the sample exhibits an average orientation angle μ of 0.43 and an orientation angle variance of 8.02. The peak frequency of fiber orientation closely aligns with 0°, which corresponds to the printing direction. Finally, the study explored the lightweight applications of the composite material, showcasing the impressive specific energy absorption (SEA) value of 17,800 J/kg when implementing 3D-printed PA6-CF composites as fillers in automobile crash boxes. Full article
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18 pages, 13910 KiB  
Article
Design, Synthesis and Properties of Semi-Alicyclic Colorless and Transparent Polyimide Films with High Glass Transition Temperatures and Low Retardation for Potential Applications in Flexible Electronics
by Xi Ren, Zhibin He, Zhenzhong Wang, Zhen Pan, Yuexin Qi, Shujun Han, Haifeng Yu and Jingang Liu
Polymers 2023, 15(16), 3408; https://doi.org/10.3390/polym15163408 - 14 Aug 2023
Cited by 5 | Viewed by 1917
Abstract
Polyimide (PI) optical films with high glass transition temperatures (high-Tg), high optical transparency, and low optical retardations (low-Rth) are highly desired in advanced optoelectronic applications. However, the standard PI films usually suffer from deep colors, high optical anisotropies and [...] Read more.
Polyimide (PI) optical films with high glass transition temperatures (high-Tg), high optical transparency, and low optical retardations (low-Rth) are highly desired in advanced optoelectronic applications. However, the standard PI films usually suffer from deep colors, high optical anisotropies and limited Tg values. In the current work, a series of semi-alicyclic colorless and transparent PI (CPI) films were developed from hydrogenated pyromellitic dianhydride stereoisomers, 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride, and fluorene-containing diamines, including 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(3-fluoro-4-aminophenyl)fluorene, respectively. The derived CPI films showed Tg values higher than 420 °C according to differential scanning calorimetry measurements. In addition, the fluorene-based CPI film showed optical transmittances higher than 80% at the wavelength of 400 nm, with yellow indices in the range of 0.60~1.01 and haze values below 3.0%. The CPI films showed average refractive indices from 1.5407 to 1.6309, extremely low birefringence at the level of minus fourth power of ten, and further exhibited quite low optical retardations below 10 nm. Full article
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22 pages, 6303 KiB  
Article
Isomeric Aromatic Polyimides Containing Biphenyl Moieties for Gas Separation Applications
by Laura Matesanz-Niño, David Cuellas, Carla Aguilar-Lugo, Laura Palacio, Alfonso González-Ortega, José G. de la Campa, Cristina Álvarez and Ángel E. Lozano
Polymers 2023, 15(6), 1333; https://doi.org/10.3390/polym15061333 - 7 Mar 2023
Cited by 2 | Viewed by 1947
Abstract
An optimized synthesis of the monomer 2,2′3,3′-biphenyltetracarboxylic dianhydride, iBPDA, was performed to obtain high molecular weight polymers. This monomer has a contorted structure that produces a non-linear shape, hindering the packing of the polymer chain. Aromatic polyimides of high molecular weight were obtained [...] Read more.
An optimized synthesis of the monomer 2,2′3,3′-biphenyltetracarboxylic dianhydride, iBPDA, was performed to obtain high molecular weight polymers. This monomer has a contorted structure that produces a non-linear shape, hindering the packing of the polymer chain. Aromatic polyimides of high molecular weight were obtained by reaction with the commercial diamine 2,2-bis(4-aminophenyl) hexafluoropropane, 6FpDA, which is a very common monomer in gas separation applications. This diamine has hexafluoroisopropylidine groups which introduce rigidity in the chains, hindering efficient packing. The thermal treatment of the polymers processed as dense membranes had two targets: on the one hand, to achieve the complete elimination of the solvent used, which could remain occluded in the polymeric matrix, and on the other hand to ensure the complete cycloimidization of the polymer. A thermal treatment exceeding the glass transition temperature was performed to ensure the maximum degree of imidization at 350 °C. The good mechanical properties of these materials allow for their use in high-pressure gas purification applications. Moreover, models of the polymers exhibited an Arrhenius-like behavior characteristic of secondary relaxations, normally associated with local motions of the molecular chain. The gas productivity of these membranes was high. Full article
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2022

Jump to: 2024, 2023

15 pages, 7865 KiB  
Article
Methylethynyl-Terminated Polyimide Nanofibrous Membranes: High-Temperature-Resistant Adhesives with Low-Temperature Processability
by Haoran Qi, Xi Ren, Yuang Liu, Shengwei Dai, Changxu Yang, Xiaolei Wang and Jingang Liu
Polymers 2022, 14(19), 4078; https://doi.org/10.3390/polym14194078 - 28 Sep 2022
Cited by 2 | Viewed by 2230
Abstract
As an alternative to traditional riveting and welding materials, high-temperature-resistant adhesives, with their unique advantages, have been widely used in aviation, aerospace, and other fields. Among them, polyimide (PI) adhesives have been one of the most studied species both from basic and practical [...] Read more.
As an alternative to traditional riveting and welding materials, high-temperature-resistant adhesives, with their unique advantages, have been widely used in aviation, aerospace, and other fields. Among them, polyimide (PI) adhesives have been one of the most studied species both from basic and practical application aspects. However, in the main applications of solvent-type PI adhesives, pinholes or bubbles often exist in the cured PI adhesive layers due to the solvent volatilization and dehydration reaction, which directly affect the adhesive performance. To address this issue, electrospun PI nanofibrous membranes (NFMs) were employed as solvent-free or solvent-less adhesives for stainless steel in the current work. To enhance the adhesion of PI adhesives to the metal substrates, phenolphthalein groups and flexible ether bonds were introduced into the main chain of PIs via the monomers of 4,4′-oxydiphthalic anhydride (ODPA) and 3,3-bis[4-(4-aminophenoxy)phenyl] phthalide (BAPPT). At the same time, the methylethynyl group was used as the end-capping component, and the crosslinking reaction of the alkynyl group at high temperature further increased the adhesive strength of the PI adhesives. Three kinds of methylethynyl-terminated PI (METI) NFMs with the set molecular weights of 5000, 10,000, and 20,000 g/mol were first prepared via the one-step high-temperature polycondensation procedure. Then, the PI NFMs were fabricated via the standard electrospinning procedure from the soluble METI solutions. The afforded METI NFMs showed excellent melt-flowing behaviors at high temperature. Incorporation of the methylethynyl end-capping achieved a crosslinking reaction at 280−310 °C for the NFMs, which was about 70 °C lower than those of the phenylacetylene end-capping counterparts. Using the METI NFMs as adhesive, stainless steel adherends were successfully bonded, and the single-lap shear strength (LSS) was higher than 20.0 MPa at both room temperature (25 °C) and high temperature (200 °C). Full article
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15 pages, 6322 KiB  
Article
Preparation and Properties of Intrinsically Black Polyimide Films with CIE Lab Color Parameters Close to Zero and High Thermal Stability for Potential Applications in Flexible Printed Circuit Boards
by Xi Ren, Yan Zhang, Yuang Liu, Changxu Yang, Shengwei Dai, Xiaolei Wang and Jingang Liu
Polymers 2022, 14(18), 3881; https://doi.org/10.3390/polym14183881 - 17 Sep 2022
Cited by 7 | Viewed by 2796
Abstract
Black polymer films with high thermal stability are highly desired in flexible electrical and electronic fields. Conventional black polymer films based on high-temperature resistant polymers and black inorganic dyes are usually suffered from the poor electrical and tensile properties. In the current work, [...] Read more.
Black polymer films with high thermal stability are highly desired in flexible electrical and electronic fields. Conventional black polymer films based on high-temperature resistant polymers and black inorganic dyes are usually suffered from the poor electrical and tensile properties. In the current work, a series of intrinsically black polyimide (BPI) films with International Commission on Illumination (CIE) Lab optical parameters close to zero and high thermal stability have been designed and prepared. For this purpose, an electron-rich aromatic diamine, 4,4′-iminodianiline (NDA), was copolymerized with 1,4-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (sBPDA) to afford a series of poly(amic acid) (PAA) solutions, which were then thermally dehydrated to provide the final BPI films at elevated temperatures up to 400 °C in air. The molar fraction of NDA in the total diamine monomers was 0 for BPI-0 (sBPDA-PDA), 10% for BPI-1, 20% for BPI-2, 30% for BPI-3, 40% for BPI-4, 50% for BPI-5, and 100% for BPI-6. For comparison, two referenced polyimide (PI) films, including PI-ref1 and PI-ref2, were prepared according to a similar procedure. The former was derived from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) and the latter was from PMDA and NDA. The BPI films exhibited an increasing degree of blackness with the increasing contents of NDA units in the polymer films. For example, the BPI-6 (sBPDA-NDA) film exhibited the optical transmittance of 1.4% at a wavelength of 650 nm (T650), which was obviously lower than those of PI-ref1 (T650 = 74.6%) and PI-ref2 (T650 = 3.6%). In addition, the BPI-6 film showed the CIE Lab parameters of 0.39 for L*, 2.65 for a*, 0.66 for b*, and haze of 1.83, which was very close to the criterion of “pure blackness” for polymer films (L* = a* = b* = 0). At last, incorporation of the NDA units in the rigid-rod BPI-0 (BPDA-PDA) film slightly deteriorated the high-temperature dimensional stability of the derived BPI films. BPI-6 film showed a linear coefficient of thermal expansion (CTE) value of 34.8 × 10−6/K in the temperature range of 50 to 250 °C, which was higher than those of the BPI-0 (CTE = 12.3 × 10−6/K), PI-ref1 (CTE = 29.5 × 10−6/K), and PI-ref2 (CTE = 18.8 × 10−6/K) films. Nevertheless, the BPI films maintained good thermal stability with the 5% weight loss temperatures (T5%) higher than 590 °C, and the glass transition temperatures (Tg) higher than 340 °C. Full article
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