Characterization Of Polyimides Research Articles

Synthesis and Characterization of Polyimides with Rigid Folded Fragments

The macromolecular chain of conventional polyimide (PI) is a predominant linear extension, which is anticipated to uphold robust interchain interactions essential for preserving overall mechanical and thermal performance. This study is dedicated to the design and synthesis for the novel PIs containing folded chains, with a particular emphasis on modifying the chain conformational behavior with respect to the structure of the aggregation state and the corresponding gas separation properties. First, two unidirectional diamine monomers, dibenzo [c, g] phenanthrene-9,12-diamine (NPDA) and anthracene-1,8-diamine (ADA), were meticulously synthesized through a sequence of chemical reactions, including Witting olefination and photocyclization. These monomers possess distinctive spatial characteristics: NPDA adopts a helical conformation, while ADA maintains a planar structure. Subsequently, the corresponding folded chain-containing PIs, denoted as NPI and API, were successfully achieved by copolymerizing one of the unidirectional monomers with the 6FDA-TPDA system. API and NPI generally exhibit a propensity for enhanced molecular chain stacking, while retaining their good solubility and processability. Drawing from both experimental data and simulation results, it was ascertained that the inclusion of these two monomers produces a rearrangement of pore sizes with a decrease in large-size micropores and an increase in the percentage of ultra-micropores. Moreover, the PI membranes with the folded fragments have a much better CO2 plasticization resistance.

Development of New Polyimide/Spirulina Hybrid Materials: Preparation and Characterization

This study presents the synthesis and characterization of polyimide (PI-2) films incorporated with spirulina powder for potential biomedical applications. The synthesis of PI-2 was achieved through a two-step polycondensation reaction using N-methyl-2-pyrrolidone (NMP) as the solvent. The incorporation of spirulina was systematically varied to investigate its effects on the structural and surface properties of the hybrid materials. Scanning electron microscopy revealed a tightly bound interface between spirulina and the PI-2 matrix, indicating effective dispersion and strong interfacial adhesion. Profilometry and Raman spectroscopy confirmed the homogeneous integration of spirulina within the polymer matrix, with resulting variations in surface roughness and chemistry. Contact angle measurements demonstrated altered wettability characteristics, with increased hydrophilicity observed with spirulina incorporation. Furthermore, blood component interaction studies indicated the variations in adhesion behavior observed for red blood cells, platelets, and plasma proteins. Water uptake studies revealed enhanced absorption capacity in PI-2 films loaded with spirulina, highlighting their potential suitability for applications requiring controlled hydration. Overall, this comprehensive characterization elucidates the potential of PI-2/spirulina hybrid materials for diverse biomedical applications, offering tunable properties that can be tailored to specific requirements.

Synthesis and Characterization of Polyimides with Naphthalene Ring Structure Introduced in the Main Chain.

In this paper, a new aromatic diamine monomer 4,4'-(2,6-naphthalenediyl)bis[benzenamine]) (NADA) was synthesized and a series of modified PI films containing naphthalene ring structure obtained by controlling the molar ratio of NADA monomer, ternary polymerization with 4,4'-oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The effects of the introduction of the naphthalene ring on the free volume and various properties of PI were investigated by molecular dynamic simulations. The results show that the comprehensive properties of the modified films are all improved to some extent, with 5% thermal weight loss temperature (Td5%) of 569 °C, glass transition temperature (Tg) of 381 °C, tensile strength of 96.41 MPa, and modulus of elasticity of 2.45 GPa. Dielectric property test results show that the dielectric constant (Dk) of the film at 1 MHz is reduced from 3.21 to 2.82 and dielectric loss (Df) reduced from 0.0091 to 0.0065. It is noteworthy that the PI-1 dielectric constant is reduced from 3.26 to 3.01 at 10 GHz with only 5% NADA doping, which is expected to yield the best ratio and provide the possibility of industrial production.

Application of electrospun polyimide-based porous nano-fibers separators in ionic liquid electrolyte for electrical double-layer capacitors

This paper studies the preparation and characterization of polyimide (PI)-based porous nano-fibers as separator for supercapacitor. PI-based porous nano-fibers were fabricated by electrospinning soluble PI and polyvinyl pyrrolidone (PVP), followed by solution induced phase separation process under ultrasonic-assisted vibration. The morphology and structure of PI-based separator was investigated by means of scanning electronics microscope, pore structure and specific surface area analysis. The electrochemical performances were characterized by alternative current impedance, cyclic voltammetry and constant current charge/discharge test in an ionic liquid electrolyte. The results indicate that PI nano-fibers derived from PI: PVP mass ratio = 1: 1 electrospun fibers exhibit high specific surface area (212.4 m 2 g −1 ), wide stability electrochemical windows (0.0–4.55 V) and high electrolyte uptake (430 wt . %). The graphical abstract is about the tittle Application of electrospun polyimide-based porous nano-fibers separators in ionic liquid electrolyte for electrical double-layer capacitors. • PI-based porous nano-fibers were prepared via PI/PVP blended electrospinning and solvent induce phase separation process. • PI-based nano-fibers are suitable for the adsorption, diffusion and infiltration of ionic liquids with a large ionic size. • PI-based porous nano-fibers separators exhibit high electrolyte uptake (430 wt %), wide stability electrochemical window (0.0 V–4.55 V) in ionic liquids electrolyte.

Synthesis and characterization of polyimides containing pyridine ring

Monomer 2,2’-bis [4-(5-amino-3-methyl-2-pyridoxy) phenyl] propane was successfully synthesized by 2-chloro-3-methyl-5-nitropyridine and bisphenol A, and the structure of pyridine diamine monomer was confirmed by 1HNMR. A series of polyimides were prepared by two-step polymerization of the pyridine diamine monomer with five aromatic dianhydride monomers. The results show that the polyimide films had good thermal stability and mechanical properties. Tg was 236-300°C in DSC test and 240-299°C from DMA test, T5% and T10% weight loss at N2 were 470-492 and 499-515°C, respectively. Moreover, the polyimide films showed outstanding mechanical properties with tensile strength of 72-90MPa, tensile modulus of 1.8-2.4Pa, and breaking elongation of 5-12%. The cut-off wavelength was 338-399nm.

Tribological properties of polyimide coating filled with carbon nanotube at elevated temperatures

AbstractThis work mainly focuses on the development and characterization of polyimide (PI) based composite coatings filled with multi‐walled carbon nanotubes (MWCNT) on a steel substrate. The tribological properties of PI/MWCNT composite coatings at different temperatures ranging from room temperature (RT) to 200°C were investigated. Also, the influence of MWCNT and thermal & mechanical properties of PI composites coatings were measured. The addition of MWCNT could reduce the friction coefficient as well as wear volume at elevated temperatures. The PI/3MWCNT composites coatings show better wear‐resistant properties as compared to other composites. Also, the PI/MWCNT composites showed improved mechanical properties such as micro‐hardness and nanoindentation. Formation of an organic‐inorganic structure due to the inclusion of MWCNT, enhance the mechanical properties and reduce the thermo‐degradation of composites coatings. The glass transition temperature (Tg) of the PI/MWCNT composites was improved as the MWCNT content increases from 0.1 to 5 wt%.

Synthesis and characterization of polyimides from 4,4′-(3-(tert-butyl)-4-aminophenoxy)diphenyl ether

A novel diamine 4,4′-(3-(tert-butyl)-4-aminophenoxy)diphenyl ether (4) was synthesized from 2-tert-butylaniline and 4,4′-oxydiphenol through iodination, acetyl protection, coupling reaction and deacetylation protection. Then some polyimides (PIs) were obtained by one-pot polycondensation of diamne 4 with several commercial aromatic dianhydrides respectively. They all exhibit enhanced solubility in organic solvents (such as NMP, DMF, THF and CHCl3 etc.) at room temperature. Their number-average molecular weights are in the range of (2.1–3.7) × 104 g/mol with PDI from 2.25 to 2.74 by GPC. They can form transparent, tough and flexible films by solution-casting. The light transparency of them is higher than 90% in the visible light range from 400 nm to 760 nm and the cut-off wavelengths of UV–vis absorption are below 370 nm. They also display the outstanding thermal stability with the 5% weight loss temperature from 525 °C to 529 °C in nitrogen atmosphere. The glass transition temperatures (T g s) are higher than 264 °C by DSC. XRD results demonstrate that these PIs are amorphous polymers with the lower water absorption (<0.66%). In summary, the incorporation of tert-butyl groups and multiple phenoxy units into the rigid PI backbones can endow them excellent solubility and transparency with relatively high T g s.

Preparation and characterization of polyimides containing triaryl imidazole side groups

A novel triaryl imidazole‐containing diamine, 3,5‐diamino‐N‐(4‐(4,5‐diphenyl‐1H‐imidazol)phenyl)benzamide, was successfully synthesized via the condensation of 4‐(4,5‐diphenyl‐1H‐imidazol)benzenamine and 3,5‐dinitrobenzoyl chloride, followed by reduction of the dinitro compound. A series of new aromatic polyimides with pendent triaryl imidazole moieties were prepared from the reaction of this diamine with various tetracarboxylic dianhydrides by a conventional two‐step polymerization process via thermal and chemical imidizations. The polyimides were obtained in quantitative yields with inherent viscosities of 0.21–0.44 dL/g. All the polymers are readily soluble in polar organic solvents. Flexible and strong films of polyimides were obtained by solution casting. The glass transition temperature of these polymers was in the range of 261–264°C. They were fairly stable up to a temperature around 300°C and lost 10% weight at 408°C under nitrogen. The ultraviolet–visible absorption spectra showed that all of the polymers had absorption maxima around 320 nm with a fluorescence emission maxima around 388–407 nm in N‐methyl‐2‐pyrrolidinone solution. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.7 V. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Characterization of PI:PCBM organic nonvolatile resistive memory devices under thermal stress

In this study, we fabricated nonvolatile organic memory devices using a mixture of polyimide (PI) and 6-phenyl-C61 butyric acid methyl ester (PCBM) (denoted as PI:PCBM) as an active memory material with Al/PI:PCBM/Al structure. Upon increasing the temperature from room temperature to 470 K, we demonstrated the good nonvolatile memory properties of our devices in terms of the distribution of ON and OFF state currents, the threshold voltage from OFF state to ON state transition, the retention, and the endurance. Our organic memory devices exhibited an excellent ON/OFF ratio (ION/IOFF > 103) through more than 200 ON/OFF switching cycles and maintained ON/OFF states for longer than 104 s without showing any serious degradation under measurement temperatures up to 470 K. We also confirmed the structural robustness under thermal stress through transmission electron microscopy cross-sectional images of the active layer after a retention test at 470 K for 104 s. This study demonstrates that the operation of PI:PCBM organic memory devices could be controlled at high temperatures and that the structure of our memory devices was maintained during thermal stress. These results may enable the use of nonvolatile organic memory devices in high temperature environments.

Synthesis and characterization of highly-fluorinated colorless polyimides derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) and aromatic dianhydrides

The authors report the synthesis and characterization of a polyimide (PI) series derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) (8FBPODMA). The 8FBPODMA monomer containing a perfluorobiphenyl group with two 2,6-dimethylaniline units connected by an ether bond was synthesized and polycondensed with several aromatic dianhydrides, including 4,4′-biphthalic anhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA), pyromellitic dianhydride (PMDA), and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), by the traditional two-step imidization procedure. All PIs shows high optical transparency, higher than 80% at 500 nm for a thickness of ca. 10 μm and good thermal properties. The thermal decomposition temperatures (T10%) of the PIs are in the range of 507–527 °C and the glass transition temperatures (Tg) are in the range of 280–345 °C. In addition, the PIs have low refractive indices because of their high fluorine contents. In particular, 8FBPODMA–6FDA shows a very low refractive index (1.5389) and a low birefringence (0.0054) at 637 nm.

Synthesis and characterization of polyimides & co-polyimides derived from diol monomers

New aromatic diimide-diol monomers were synthesized from corresponding dianhydride and ethanolamine through nucleophilic substitution reaction. The structures of the monomers were characterized by FT-IR & 1H-NMR analysis. Processable polyimides (PIs) & co-polyimides (co-PIs) were synthesized from these new diol monomers and 4,4′-difluorobenzophenone through nucleophilic displacement polymerization reaction. The PIs & co-PIs were characterized by FT-IR, 1H-NMR, X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), solution viscosity, solubility test and dielectric property. The PIs & co-PIs showed good solubility due to the presence of flexible linkages. The PIs & co-PIs exhibit good thermal stability, the 10 % weight loss occurred in the range 400–425 °C in N2 atmosphere and the glass transition temperatures were in the range 181–196 °C. The dielectric constants (er) of PIs & co-PIs in the range 3.20–3.90 showed that they have excellent electrical insulation characteristics and such polymers can be used as electrical insulation materials for a system operating at high temperature for a long time.

Synthesis and characterization of high refractive index polyimides derived from 2,5-Bis (4-Aminophenylenesulfanyl)-3,4-Ethylenedithiothiophene and aromatic dianhydrides

The authors describe the synthesis and characterization of the polyimide (PI) series containing a 2,5-bis(4-aminophenylenesulfanyl)-3,4-ethylenedithiothiophene (APSEDTT) moiety in their main chain. The APSEDTT monomer with high sulfur content was prepared and polymerized with several aromatic dianhydrides such as 4,4′-[p-thio bis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4′-biphthalic anhydride (BPDA), and 4,4′-oxydiphthalic anhydride (ODPA) by the traditional two-step polycondensation procedure. All PIs exhibited high transparency, higher than 75% at 550 nm for a thickness of about 20 μm and good thermal properties such as thermal decomposition temperatures (T10%) in the range of 409–521 °C. In addition, the PIs have extraordinarily excellent optical properties in refractive index and birefringence as originally designed. In particular, the PI derived from APSEDTT and 3SDEA showed a high refractive index (1.7586), and a low birefringence (0.0087) because of their very high sulfur content (27.7%). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 944–950

Growth and Characterization of Vapor Deposited Polyimide Thin Films

In this paper, we report on the preparation and characterization of polyimide (PI) thin films through vapor deposition polymerization (VDP). PI thin films were formed by vapour co-deposition of the precursor monomers pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) following a thermal treatment at a temperature of over 300°C. The effects of the polymerization temperature on the characterization of PI films were investigated using scanning electron microscopy and Fourier transform infrared spectroscopy. The results showed that the deposited polyamic acid (PAA, a precursor of polyimide) with imidization in the temperature interval of 300-400°C are smooth, uniformly thick and form without shrinkage.

Synthesis and Characterization of Polyimide from 4,4’-Diamino diphenyl ether having Substituents at 2,2’-position

Synthesis and Characterization of Polyimide from 4,4’-Diamino diphenyl ether having Substituents at 2,2’-position

Synthesis of trisiloxane-containing alicyclic tetracarboxylic dianhydrides and the characterization of polyimides

The titular alicyclic tetracarboxylic dianhydrides were synthesized with endo- and/or exo-5-norbornene-2,3-dicarboxylic anhydride and 1,1,3,3,5,5-hexamethyltrisiloxane. The endo-structure tetracarboxylic dianhydride was reported to be a crystal, and could be divided into meso and racemic isomers. By contrast, the exo-structure tetracarboxylic dianhydride was a highly viscous liquid. Polyimides synthesized from these tetracarboxylic dianhydrides and 4,4′-oxydianiline were colorless and organosoluble. The exo-structure polyimide had better mechanical properties and higher glass transition temperatures than the endo-structure polyimides. The elongation at the break of the exo-structure polyimide increased with weight-average molecular weight (Mw) and saturated at 22% when Mw was greater than 88 000. Polyimides synthesized from the meso and racemic isomers of the endo-structure showed the same thermal properties. The endo-structure tetracarboxylic dianhydride was a crystal and could be divided into meso and racemic isomers. However, the exo-structure tetracarboxylic dianhydride was a highly viscous liquid. Polyimides derived from these tetracarboxylic dianhydrides and 4,4′-oxydianiline were colorless and organosoluble. The exo-structure polyimides had better mechanical properties and higher glass transition temperatures than the endo-structure polyimides.

Sol-gel synthesis and characterization of polyimides based on the reaction of butane-1,2,3,4-tetracarboxylic acid with 3-aminopropyltriethoxysilane

Butane-1,2,3,4-tetracarboxylic acid is reacted with hydrolyzed 3-aminopropyltriethoxysilane (APTES) at 110 and 220°C (molar ratios 1 : 1 and 1 : 2). The as-prepared materials were characterized by means of various analytical methods. FTIR measurements revealed the formation of a polyamic acid at 110°C whereas the treatment at 220°C resulted in the preparation of a polyimide. These findings were confirmed by means of SS-13C-MAS-NMR. XRPD experiments gave clear evidence for the formation of a specific periodic arrangement in the material. Thermogravimetric analysis indicated that the organic–inorganic material has improved thermal properties. All the materials obtained were insoluble in water and organic solvents. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and Characterization of Polyimides Derived from 5-Amino-2(p-aminophenyl) Benzoxazole Monomer

Polyimides prepared from 5-amino-2(p-aminophenyl) benzoxazole (AAPB) with pyromellitic dianhydride(PMDA), 2,2’3,3’-biphenyl tetracarboxylic dianhydride(i-BPDA), 4,4’-oxdiphthalic anhydride(ODPA), 1,4-bis(3,4-dicarbosyphenoxy) benzene dianhydride(HQDPA) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) were synthesized successfully via a conventional two-stage method. Their structures and properties were characterized by FT-IR, DSC, TG and XRD. The intermediate poly(amic acid)s had inherent viscosity range of 0.86~2.18 dL/g and could be thermally converted into light yellow polyimide films. The polyimides showed excellent solvent resistance and good thermal stability. The glass transition temperatures (Tg) were found to be 336oC~369 oC .The decomposition started at a temperature above 530oC in N2 atmosphere.

Synthesis and characterization of polyimides from 4‐(diphenyl phosphine oxide)phenyl pyrromellitic dianhydride

AbstractA novel rigid‐rod type dianhydride monomer with phosphine oxide moiety, 4‐(diphenyl phosphine oxide)phenyl pyrromellitic dianhydride (POPPMDA), was synthesized via the Suzuki coupling reaction of 4‐(diphenyl phosphine oxide)phenyl boronic acid (POBB) and 1‐bromo‐2,3,5,6‐tetramethyl benzene (B4MB), followed by oxidation and cyclodehydration. The monomer was characterized by FTIR, NMR, EA, and melting point analyzer and utilized to synthesize polyimides with diamines such as bis(3‐aminophenyl)phenyl phosphine oxide (mDAPPO) and p‐phenylene diamine (pPDA) by varying their ratio. The polyimides were prepared via a conventional two‐step synthesis: preparation of poly(amic‐acid), followed by solution imidization. The polyimides were characterized by FTIR, NMR, DSC, TGA, and TMA, and their solubility, intrinsic viscosity, and adhesive properties were also evaluated. The polyimides exhibited high Tg (342–362°C), good thermal stability (&gt;500°C), excellent adhesive property (134–107 g/mm), and low CTE (28–17 ppm/°C). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation and characterization of polyimide and polyethersulfone blend membrane for gas separation

ABSTRACTPolyimides (PI) have been studied as the basic materials for preparing gas separation membranes attributable to their high gas selectivity. This paper deals with the preparation and characterization of blended polyimide membranes with polyethersulfone (PES) to study separation of ethylene from nitrogen gas at different feed pressures. For improving performance of PI membranes, two procedures were used. First, using polymeric additives such as polyvinylidene fluoride (PVDF) and PES in low content and second, blending of PI casting solution with high amount of PES. Infrared spectroscopy and scanning electron microscopy (SEM) images were employed to characterize the membranes. Pyromellitic dianhydride‐co‐4, 4′‐oxy dianiline (PMDA/ODA) polyimide membranes was synthesized using polyamic acid (PAA) as precursor materials. The ideal selectivity of 100% (ethylene permeation only) was achieved at 1 bar using PMDA/ODA polyimide membranes containing 1 wt% PVDF. Addition of PES did not have any significant influence on ideal selectivity of the prepared membranes. PES‐(PMDA/ODA) polyamic acid blend membranes were prepared using different blending ratios of PES (25 wt%) and PAA (15 wt%). The blending ratio of casting solutions of PES/PAA solutions exhibited a main influence on the ideal selectivity. The ideal selectivity of 2.9 for ethylene was achieved at 3 bar using blend membranes with 0.5 wt% PAA solution. PES‐PMDA/ODA polyimide membranes were also prepared from blend casting solutions by thermal imidization. Immiscible blend membranes were obtained at different blending ratios of the casting solutions with high gas permeance and poor selectivity. © 2011 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Synthesis and Characterization of Polyimide Mixed Matrix Membranes

Polyimides of Matrimid 5218 and P84 as backbone and different fillers including silica aerosil, zeolite 4A, carbon nanotubes, and carbon molecular sieves were used to synthesize flat mixed matrix membranes (MMMs). Effects of different polymer types and concentrations, different filler types and contents, and fabrication procedure were investigated. Scanning Electron Microscopy (SEM) analysis showed acceptable connections between the two phases and the MMMs performed higher performance compared to the polymeric membranes. Thermal treatment of the MMMs, as a defect repairing technique, was found very effective. Performed pervaporation and gas permeation experiments showed better separation performances of the MMMs with respect to those of the neat polymeric membranes. The results showed up to seven and two times increment in separation factors of MMMs regarding to neat polymeric membranes for pervaporation and gas separation experiments, respectively, while permeation rates nearly remained constant indicating effectiveness of the proper filler incorporation within polymer matrices approach.