Stability of polyamic acids and polyimides

Varma, I. K.; Goel, Rakesh K.; Varma, D. S.

doi:10.1002/apmc.1977.050640109

Cited by 17 publications

(7 citation statements)

References 10 publications

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“…A reaction between the amide and carboxylic acid groups produces intermediates that can be converted back to the amic acid or to the imide. When an amide solvent like DMAc is present, these intermediates can instead undergo a cleavage reaction that cleaves the polymer backbone 45 . Because the isolated polymers need to be dried at relatively low temperature to prevent unwanted imidization, which would make the material insoluble and difficult to work with, removing all residual solvent is challenging.…”

Section: Resultsmentioning

confidence: 99%

“…When an amide solvent like DMAc is present, these intermediates can instead undergo a cleavage reaction that cleaves the polymer backbone. 45 Because the isolated polymers need to be dried at relatively low temperature to prevent unwanted imidization, which would make the material insoluble and difficult to work with, removing all residual solvent is challenging. The presence of a significant amount of residual solvent results in the reported yields above 100% for the poly(amic acids) (Table 3).…”

Section: Synthesis and Film Properties Of Multiblock Polyimidesmentioning

confidence: 99%

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Synthesis and properties of cationic multiblock polyaramides and polyimides

Biery

Knauss

2022

Journal of Polymer Science

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Poly(diallyldimethylammonium chloride) (PDADMAC) is a useful material due to its high charge density and alkaline stability, but its hydrophilic nature limits applications to those where the dissolved polymer is appropriate. To make polymers suitable for applications as films and membranes containing the diallyldimethylammonium moiety, multiblock copolymers of polyaramides (PA) and polyimides (PI), materials known for their excellent physical properties and stabilities, were synthesized. Aminophenyl difunctionalized PDADMAC oligomers were synthesized using a disulfide iniferter then counterion exchanged to the hexafluorophosphate anion to produce telechelic oligomers with good solubility in polar aprotic solvents. The oligomers were reacted in situ with the proper difunctional monomers to produce PA, polyetheraramides, PI, and polyetherimides. All the classes of copolymers were synthesized over a range of compositions at high yield and material properties were demonstrated to be a result of both the backbone chemistry and the composition. Several of the synthesized copolymers formed films with good clarity, strength, and flexibility. The copolymers containing ether linkages had increased backbone flexibility and demonstrated better film‐forming properties. The multiblock copolyaramides and copolyimides demonstrate a method to produce materials with excellent thermal stability and good strength and flexibility, making them uniquely capable of serving as water insoluble, cationic films, and membranes.

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Section: Resultsmentioning

confidence: 99%

Section: Synthesis and Film Properties Of Multiblock Polyimidesmentioning

confidence: 99%

Synthesis and properties of cationic multiblock polyaramides and polyimides

Biery

Knauss

2022

Journal of Polymer Science

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“…The preparation of high‐performance aromatic polyimide (PI) fibers was initially carried out by Japanese and Soviet researchers . Aromatic PI fibers possess various valuable properties, including high mechanical properties, good chemical and irradiation resistances, outstanding thermal stability, self‐lubricity, and excellent electrical and dielectric properties . These unique properties enable PI fibers to be one of the most promising materials using in the aircraft, car and aerospace industries, atomic energy industry, as well as in the production of heat protective clothes and others …”

Section: Introductionmentioning

confidence: 99%

Preparation of High Performance Copolyimide Fibers via Increasing Draw Ratios

Zhang

Niu

Lin

et al. 2015

Macro Materials & Eng

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High performance fibers based on copolyimide (co-PI) containing benzimidazole and ether moieties were prepared via a two-step wet spinning method. The effects of draw ratio on the structures and properties of the fibers are investigated. The mechanical properties of the co-PI fibers are improved greatly by increasing draw ratio at temperatures above 400 8C, reaching the optimum tensile strength of 2.8 GPa and modulus of 136 GPa, which is due to the development of the molecular orientation along the fiber direction. The hot drawing process roughens the fiber surface and stretches the molecules in the fibers. Moreover, the fiber structure evolutions during the drawing process were also discussed and a ''smectic A liquid crystal-like'' model was proposed.

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“…Indeed, the properties of a PAA solution play a decisive role in the final performance of the PI products [ 3 , 4 ]. However, PAA solutions are relatively unstable upon storage and exhibit undesirable variations in viscosity with different storage conditions [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Bower and Frost [ 5 ] observed a viscosity reduction of 11% DAPE-PMDA in DMAC with increasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Storage Stability of 6FDA-DMB Polyamic Acid Solution Detected by Gel Permeation Chromatography Coupled with Multiple Detectors

et al. 2023

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Polyamic acid (PAA) is the precursor of polyimide (PI), and its solution’s properties have a direct influence on the final performances of PI resins, films, or fibers. The viscosity loss of a PAA solution over time is notorious. A stability evaluation and revelation of the degradation mechanism of PAA in a solution based on variations of molecular parameters other than viscosity with storage time is necessary. In this study, a PAA solution was prepared through the polycondensation of 4,4′-(hexafluoroisopropene) diphthalic anhydride (6FDA) and 4,4′-diamino-2,2′-dimethylbiphenyl (DMB) in DMAc. The stability of a PAA solution stored at different temperatures (−18, −12, 4, and 25 °C) and different concentrations (12 wt% and 0.15 wt%) was systematically investigated by measuring the molecular parameters, including Mw, Mn, Mw/Mn, Rg, and [η], using gel permeation chromatography coupled with multiple detectors (GPC-RI-MALLS-VIS) in a mobile phase 0.02 M LiBr/0.20 M HAc/DMF. The stability of PAA in a concentrated solution decreased, as shown by the reduction ratio of Mw from 0%, 7.2%, and 34.7% to 83.8% and that of Mn from 0%, 4.7%, and 30.0% to 82.4% with an increase of temperature from −18, −12, and 4 to 25 °C, respectively, after storage for 139 days. The hydrolysis of PAA in a concentrated solution was accelerated at high temperatures. Notably, at 25 °C, the diluted solution was much less stable than the concentrated one and exhibited an almost linear degradation rate within 10 h. The Mw and Mn decreased rapidly by 52.8% and 48.7%, respectively, within 10 h. Such faster degradation was caused by a greater water ratio and less entanglement of chains in the diluted solution. The degradation of (6FDA-DMB) PAA in this study did not follow the chain length equilibration mechanism reported in literature, given that both Mw and Mn declined simultaneously during storage.

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Stability of polyamic acids and polyimides

Cited by 17 publications

References 10 publications

Synthesis and properties of cationic multiblock polyaramides and polyimides

Synthesis and properties of cationic multiblock polyaramides and polyimides

Preparation of High Performance Copolyimide Fibers via Increasing Draw Ratios

Storage Stability of 6FDA-DMB Polyamic Acid Solution Detected by Gel Permeation Chromatography Coupled with Multiple Detectors

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