Fluorinated Polyimide Films Research Articles

A novel approach for environmentally benign synthesis and solid-state polymerization of fluorinated polyimides in aqueous co-solvent

This study presents a novel approach that enables an environmentally benign water-based co-solvent synthesis of fluorinated polyimides (FPIs) using conventional fluorine-based monomers such as 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2′-bis(trifluoromethyl)benzidine (TFMB). The high surface tension inherent in fluorine-based materials, which inhibits water solubility, can be overcome by mixing water with an alcohol-based solvent. The surface tension of the co-solvent decreases proportionally with the alcohol content, facilitating synthesis from fluorine-based monomers that were previously inaccessible in water. Oligomeric fluorinated poly(amic acid) salt (FPAAS) can be rapidly synthesized in aqueous solutions containing alcohol, particularly 1-propanol (PrOH). Subsequent coating and thermal treatment processes allow high molecular weight FPI films to be produced by solid-state polymerization. A comprehensive analysis of the resulting FPI films shows excellent physical properties comparable to conventionally synthesized FPI films. The 6FDA-TFMB-based FPI exhibits remarkable thermal stability up to 570 °C (Td,5%), low yellow index of 1.37, high transparency of 92.9 % and tensile strength of 116.5 MPa. The presented synthetic strategy allows the adoption of monomers with different fluorine-based substituents, thus providing insights for future aqueous synthesis. The thermal, mechanical, and optical qualities of FPIs can be utilized to create optically clear heating devices. The transparent heater, fabricated on the FPI film utilizing a laser patterning technique to create electrodes from silver nanowires, was capable of increasing the temperature up to 100 °C under a 9 V voltage application.

Fluorinated polyimide with enhanced ultraviolet-resistant radiation via a self-sacrificial strategy

High-performance polyimide (PI) films with excellent ultraviolet (UV)-resistant radiation and low dielectric constant (k) properties are ideal spacecraft antenna substrates in space applications. However, conventional commercial PI films like Kapton® applied in the aerospace field are inevitably subjected to the harsh UV radiation environment, leading to their structural damage and performance failure. Herein, a type of “self-sacrificial” micro-branched crosslinked PI films were fabricated by employing tris(4-aminophenyl)amine (TAPA) intrinsically containing the C-N bonds to crosslink linear pure fluorinated PI (FPI), where TAPA functioned as the dual roles of crosslinker and creating “self-sacrificial” local deep traps of C-N bonds in crosslinked sites. Consequently, abundant local deep traps of C-N bonds in crosslinked sites could capture energy from UV-rays to prevent the destruction of PI molecular main chains, thus the crosslinked FPI-TAPA films exhibited better UV-resistant radiation properties than that of pure FPI films and commercial PI films. And the crosslinked film showed least k of 2.53 and least dielectric loss of 0.006 at frequency of 1 MHz owing to the introduction of micro-branched crosslinked structure. Additionally, a high breakdown strength of 522 MV/m, as well as a high tensile modulus of 3.03 ± 0.07 GPa, was achieved, much better than the value of pure FPI film. This work provides a novel and facile approach to fabricate high-performance PI films with excellent UV-resistant properties, exhibiting great potential application in aerospace and microelectronics industries.

Synthesis and characterization of fluorinated polyimide doped with NaYF4 nanocrystals for optical waveguide applications

Fluorinated polyimide materials were selected for their exceptional flexibility, high thermal stability, and minimal absorption loss. These materials were subsequently employed in the production of single-mode polymer optical waveguide devices using photolithography. In this study, a fluorinated polyimide material doped with NaYF4 nanocrystals was prepared and confirmed to exhibit low absorption loss near 1550 nm, which is within the common communication window. The refractive index of the fluorinated polyimide films was precisely adjusted by the NaYF4 doping, the adjustable ranges for the refractive index were 1.95% and 1.72% for doped and undoped, respectively. Secondly, utilizing the NaYF4 nanocrystals doped-fluorinated polyimide materials, a three-layer single-mode polymer optical waveguide device for C-band (near 1550 nm) optical interconnection was fabricated by etching the underlying cladding and employing silicon nitride as a mask. The transmission performance of the device was excellent, with a total waveguide coupling and transmission loss of 1.502 dBm.

Detection of pesticide residues on flexible and transparent fluorinated polyimide film based on surface-enhanced Raman spectroscopy technology

BackgroundExcessive pesticide residues will seriously endanger human health. The complexity and lag of the current popular analytical methods hinder the timeliness of food safety analysis. Surface-enhanced Raman scattering (SERS) was an ultra-sensitive vibration spectroscopy technology with the advantages of less time cost, non-destructive and semi-quantitative detection, which has attracted much attention in the rapid field detection of pesticide residue. It was clear that we need an efficient and convenient substrate for pesticide residue detection based on SRES technology, which needs to be portable, flexible, transparent and easy to detect irregular object surfaces. ResultsA novel SERS sensor was designed to detect single and multi-component pesticide residues on irregular fruit and vegetable surfaces by in-situ growth of silver nanoparticles on a flexible and transparent fluorinated polyimide (FPI) substrate. Among them, Ag NPs were synthesized by liquid phase reduction method (AgNO3-PVP and NaBH4). The results showed that the detection limit of 1–4 BDT was down to 10−10 mol L−1, the enhancement factor (EF) was up to 1.57 × 107, and relative standard deviation (RSD) was 7.49 %. By this method, tricyclazole solution at a concentration of 0.01 mg L−1 was still detectable by the FPI@Ag SERS substrate. The linear quantification was achieved in the range from 100 mg L−1 to 0.01 mg L−1. Two mixed pesticides, tricyclazole and imazalil, were also successfully distinguished. SignificanceThis represents the formation of a flexible, foldable and transparent substrate for rapid on-site detection. Results can be obtained in <5 min by attaching the substrate to the substance to be tested. And the SERS substrate prepared with high sensitivity, stability, portable and convenient analysis, which provided new ideas for efficient and rapid household food safety detection.

Study on the triboelectric performance of porphyrin- and phthalocyanine-crosslinked enhanced fluorinated polyimide films for lateral sliding-mode triboelectric nanogenerator

• Two fluorinated polyimide films crosslinked by TAPP or TAPc were prepared. • The PI/TAPP and PI/TAPc films showed higher dielectric constant than neat PI. • The PI/TAPP and PI/TAPc exhibited smaller charge decay than neat PI in LS-TENGs. • The PI/TAPP and PI/TAPc showed higher friction coefficient stability than neat PI. In order to improve the charge retention, anti-decay ability and durability of traditional triboelectric materials in lateral sliding-mode triboelectric nanogenerators (LS-TENGs), two fluorinated polyimide films crosslinked by porphyrin tetra-amino phenyl porphyrin (TAPP) and tetra-amine phthalocyanine (TAPc) were synthesized, and their contact angles, dielectric properties, output performances and tribological properties were studied in detail. The results showed that the polyimide films crosslinked by TAPP (PI/TAPP) and TAPc (PI/TAPc) with lower surface energies had higher dielectric constants compared with neat PI and Kapton. In addition, TAPP and TAPc not only improved the electrical output with a small decay of charge density, but also reduced the wear of PI films during the whole triboelectrification process, which is attributed to the high permittivity and the crosslinked effect of PI with TAPP or TAPc. Thus, PI films with TAPP and TAPc hold great promise for dielectric research and LS-TENG applications.

Characteristics and electrical properties of polyimide films fluorinated for different durations

Surface fluorination of polyimide films was conducted for different durations (30, 60, and 90 min) in a laboratory vessel using an F2/N2 gas mixture containing 12.5 % F2 by volume. The differences in the structural, morphology, wettability, surface free energy, and electrical properties of the fluorinated polyimide films were systematically studied to assess the effects of fluorination and fluorination time, and to investigate the relationship between the surface electrical properties and surface physicochemical properties. The obtained results indicated that fluorination cracked the film surface, with the number of cracks increasing with increasing fluorination time. Fluorination also enhanced the surface wettability and polarity. Surface conductivity and surface potential decay measurements consistently showed that the surface-fluorinated samples had a higher surface conductivity than unfluorinated samples, and that the surface potential rapidly decayed because the surface conductivity increased with enhanced water adsorption on the surface. The increased occurrence of surface cracks, as well as enhanced polarity and surface conductivity of the films, were mainly attributed to the increase in the degree of chain scission that occurred with increasing fluorination time.

Synthesis of fluorinated polyimide towards a transparent triboelectric nanogenerator applied on screen surface

A fluorinated polyimide film is synthesized toward the transparent triboelectric nanogenerator applied on touch screen surface to convert the mechanical energy into electrical energy.

Laser Scribing of Fluorinated Polyimide Films to Generate Microporous Structures for High-Performance Micro-supercapacitor Electrodes

Laser-induced graphene (LIG) typically exhibits a mesostructure with a small specific surface area, which is detrimental to the electrochemical performance of micro-supercapacitors (MSCs). Herein, ...

Thermal degradation kinetics of transparent fluorinated poly(imide siloxane) copolymers

Fluorinated polyimide films are widely used in the field of flexible display because of their excellent optical transmittance. Based on previous studies, the adhesion to other substrates of fluorinated polyimide films have been improved by incorporating GAPD into the macromolecular chains, but their heat resistance is not yet very clear. In this study, thermal behaviors of fluorinated polyimide films (PIs) with and without GAPD were studied in N2 ambient and atmosphere by TG-DTG analysis under non-isothermal conditions. Activation energies (Eas) of PIs were calculated by Flynn-Wall-Ozawa method, Kissinger-Akahira-Sunose method and Kissinger method. In addition, mechanisms of thermal decomposition reaction were determined by Coats-Redfern method. By comparison, the Eas of PIs in the same atmosphere were similar and the thermal reaction mechanisms were essentially the same, indicating that adhesion of fluorinated polyimide can be improved by adding appropriate amount of GAPD, while the excellent optical permeability and heat resistance of fluorinated polyimide can be maintained, further expanding its application in flexible display and other fields.

Influence of Aliphatic and Aromatic Fluorine Groups on Gas Permeability and Morphology of Fluorinated Polyimide Films

Partially fluorinated polymers often exhibit exceptional membrane-based separation performance for a variety of gas pairs. While many gas transport studies focus on the incorporation of aliphatic f...

Influence of Imidization Method on Properties of Fluorinated Polyimide Films

Influence of Imidization Method on Properties of Fluorinated Polyimide Films

Effect of direct fluorination on surface and electrical properties of polyimide thin films

The influences of direct fluorination on the structural, morphological, surface free energy, thermal and electric properties of polyimide films were systematically investigated by ATR-IR, SEM, contact angles, thermo-gravimetric analysis, surface conductivity and potential decay, respectively. The results indicate that the fluorination leads to substantial changes in surface composition and structure, and a modification of the surface morphology. It is also observed that the fluorination also gave rise to an increase in surface hydrophilicity and a decrease in surface free energy. The thermal stability of fluorinated polyimide film seems to slightly decrease. The intrinsic increase in surface electrical conduction is considered to be a result of decrease in depth of charge traps.

Highly transparent, strong, and flexible fluorographene/fluorinated polyimide nanocomposite films with low dielectric constant

Transparent and flexible fluorinated polyimide films with loading of well-dispersed fluorographene exhibit low dielectric constants.

Optical properties of polyimides films treated by nanosecond pulsed electrical discharges in water

Fluorinated polyimide films containing cobalt chloride based on hexafluoroisopropylidenediphthalic dianhydride and 4,4′-diamino-3,3′-dimethyl diphenylmethane were treated by nanosecond pulsed electrical discharges generated in distilled water. The polyimide films have been characterized by Fourier transform infrared (FTIR) spectra and contact angle measurements, optical transmission spectroscopy, and fluorescence spectroscopy. Significant changes in some intrinsic fluorescence features, such as the intensity and position of the emission peak, have been observed during exposure to water plasma. These effects have been considered to correlate with the development of specific chemical interactions between the liquid and the macromolecules, including the formation of hydrogen bridges. A slight increase in surface hydrophobicity was observed after plasma treatment. FTIR spectra showed a decrease in the intensity of the absorption band and an opening of the imide ring, depending on the treatment time.

Correlation of stress and optical properties in highly transparent polyimides for future flexible display

High transmittance and low birefringence are desirable optical properties in polyimide films which are promising flexible substrates in next generation display devices. However, thermal processes for the fabrication of polyimide films can cause anisotropic changes in the optical properties due to its rod-like molecular structure. Here we report the changes in optical retardation in transparent fluorinated polyimide films with sub-nanometer resolution and dimensional stability induced by deformation at high temperatures. As deformation is increased, the optical retardation is changed much prominently with enhancing thermo-dimensional stability. During thermal strain, in-plane molecular orientation is preferentially improved and stress-optical coefficient that quantifies the change in out of plane optical retardation is derived to be around 6×10–6 m2/N, which is higher compared to conventional plastic optical films. The experimental findings suggest that optimized process conditions for display substrates should be determined to address both changes in the optical and thermal stabilities. We suggest that this study can be useful information for large-scale film process to be further utilized in fabrication of the transparent polyimide films.

Controllable porous fluorinated polyimide thin films for ultralow dielectric constant interlayer dielectric applications

ABSTRACTIn this paper, silica microspheres were used as template to prepare porous fluorinated polyimide (FPI) thin films from polyamic acid (PAA, precursor of FPI) and silica colloid solution. The strong hydrogen-bonding interaction between silica microspheres and PAA chains have improved the dispersion of silica microspheres in N,N-Dimethylformamide (DMF) solution, resulting in the high weight content of silica template in PAA/silica colloid solution, and thus giving rise to the formation of porous FPI films with maximum porosity of 35%. The interior microstructures of the resultant porous FPI thin films were investigated. It is found that the porous FPI thin films have interconnected “ink-bottle-type” porous structure, and the pore size, porosity could be precisely controlled by the diameter and weight content of silica microspheres, respectively. Although both the tensile strength and young modules declined with the increasing porosity, the high level void of the porous FPI films endowed the FPI ultralow dielectric constant of 1.84 when the porosity increased to 35%. Furthermore, the mechanical and dielectric properties of the porous FPI films were closely related to the microstructures and porosity, indicating the desired properties could be controlled to meet the application in the microelectronics.

High thermal conductivity and low absorptivity/ emissivity properties of transparent fluorinated polyimide films

Polyimide film materials are a very promising and high-performance polymer in space application. However, the deep coloration of conventional polyimide films greatly limits the wide use in areas where transparency and low solar absorptance are the essential requirement. Here, we prepared the transparent polyimide from 4,4 $$^{\prime }$$ -(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and different ratios of 2,2 $$^{\prime }$$ -bis(trifluoromethyl)-benzidine (TFB) and 2,2-bis(4-(4-aminophenoxy)-phenyl) hexafluoropropane (BAPP) with a low solar absorptance. Properties, such glass-transition temperature, thermal decomposition temperature, thermal conductivity and transmittance, were investigated, It is suggested that the introduction of fluorine into polyimide will significantly increase transmittance and in turn decrease solar absorptance, The polyimide film with fluorinated groups exhibited superior optical transparency, low absorptivity/emissivity, high thermal conductivity, and good resistance to ultraviolet radiation. The transparent polyimide exhibits a low solar absorptivity of 0.04 and infrared emissivity of 0.6.

Surface charge coupling behavior of fluorinated polyimide film under DC and pulse voltage

Polyimide (PI) films have excellent electrical, mechanical and thermal properties in aspect of resisting corona, aging and radiation. However, the pulse voltage combined with dc voltage often causes concentration of local electrical field, which makes the surface charge behaviors more complex and threatens the system. As a means of surface treatment, direct fluorination has been proved as an effective way to improve the polymer properties, without compositing the bulk characteristics. Therefore, this paper intends to reveal the effects of fluorination on surface charge coupling behaviors of the PI films under dc and pulse voltage combination. The PI samples fluorinated for 0, 15, 45 and 60 min were obtained. Surface corona discharging was stressed under the combination of dc and pulse voltage. The surface charge accumulation, decay and distribution were measured coupled with an analysis of trap distribution. The results show the surface charge dynamic behaviors are strongly correlated with the fluorination time, pulse voltage amplitude and polarities of the dc and pulse voltage combination. The trap distribution results imply that the effect of fluorination and charging condition attribute to the change of trap depth and amount. Besides, surface charge behaviors are greatly improved by appropriate fluorination.

Discharge Breakdown Characteristics With Fluorinated Polyimide Films in High-Temperature Superconducting Cable Insulation

The application of high-temperature superconducting cable now has been in the process of being implemented in power system. Polyimide (PI) film has been used as insulation in the high-temperature superconducting cable systems with the advantage of good performance in low temperature, excellent mechanical properties, and dielectric properties. However, due to the organic properties of PI films, it can be aged even brake down in the service of HTS cable. It is found that partial discharge in HTS cable can lead to insulation material degradation and finally breakdown. Our recent researches have shown that fluorination can influence the surface charge behaviors thus influence the PD characteristics of modified PI films. In this paper, PI films were fluorinated in laboratory, the relationship between the fluorination time and discharge characteristics of the films were researched. The surface topography of direct-fluorinated samples were obverted by using an Atomic force acoustic microscope. It can be found from the experiment results that the discharge times and quantity both showed decreasing tendency with the fluorination time increasing. The discharge breakdown voltage shows increasing tendency with the fluorination time from zero minutes to forty-five minutes, and then shows decreasing tendency.

Synthesis and characterization of organosoluble, transparent, and hydrophobic fluorinated polyimides derived from 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene

A novel aromatic fluorinated diamine monomer, 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene, was synthesized by coupling of 2-isopropylaniline and 4-(trifluoromethyl)benzaldehyde and its structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, and mass spectrometry, and then used to prepare a series of fluorinated polyimides (FPIs) by polycondensation reaction with various commercial dianhydrides via conventional one-step method. The obtained FPIs present excellent solubility in most organic solvents and enough to cast into tough and flexible films. All the FPI films show good optical transparency and light color with the cutoff wavelengths in range of 307–362 nm and the average transmittance above 86%. These polymer films also exhibit high glass transition temperature in range of 261–331°C and thermal stability with 10% weigh loss above 463°C under nitrogen atmosphere. Furthermore, they exhibit outstanding mechanical properties with tensile strengths of 65.9–94.3 MPa, elongation at break of 11.4–13.8%, Young’s modulus of 1.6–1.9 GPa, and low dielectric constants in range of 2.75–3.10 at 1 MHz as well as prominent hydrophobicity with the contact angle in the range of 87.3–93.9°.