Dipolar Aprotic Solvents Research Articles

Poly(arylene sulfide)s via nucleophilic aromatic substitution reactions of halogenated pyromellitic diimides

AbstractNucleophilic aromatic substitution (SNAr) reactions are exploited to prepare poly(arylene sulfide)s (PAS's) via the reaction of bis‐thiolates and dibrominated pyromellitic diimide (PMDI) derivatives. Small‐molecule model studies reveal the reaction is well‐defined and proceeds in quantitative yield in practical times at room temperature. Variation in comonomer feed ratios allowed some control over target polymer molecular weights in the step polymerization, but control was likely limited by the relatively poor polymer solubility in the dipolar aprotic solvents typically employed to promote SNAr reactions. One substitution pattern produces a steric “pocket” around the PMDI units, inducing a peculiar solubility trend in halogenated solvents; that is, greatly reduced solubility in CHCl3 relative to CH2Cl2 and C2H2Cl4. One example small‐molecule readily dissolves in CHCl3 at room temperature, then rapidly grows poorly soluble crystals revealed by single‐crystal XRD to contain CHCl3 molecules in the steric pockets. Finally, the recently demonstrated depolymerization of phthalonitrile‐based PAS's via ipso substitution with monothiolates as chain scission agents yields quantitative molecular weight reduction to monomeric species from the polymers reported here.

Towards potentiometric detection in nonaqueous media: Evaluation of the impacts of organic solvents on polymeric membrane ion-selective electrodes

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in various fields including clinical diagnosis, environmental monitoring and industrial analysis. Although most samples of analytical interest measured by the ISEs are aqueous solutions, the applications of these electrodes in nonaqueous media are often inevitable. Unfortunately, so far, little has been known about the extent to which the properties of the ISEs could be affected by the organic solvents. Herein, the feasibility for the applications of the polymeric membrane ISEs in nonaqueous media has been investigated. A polymeric membrane Ca2+-ISE is chosen as a model of potentiometric sensors. Four typical water miscible organic solvents (three protic solvents: ethanol, acetic acid, and methanol, and one aprotic dipolar solvent: acetonitrile) are used as the representative examples. Experiments show that the aprotic solvent acetonitrile has the strongest destructive ability towards the sensing performance of the ISE in terms of Nernstian slope and selectivity coefficient. Moreover, the effect on the sensing performance depends on the kind of the protic solvent, the immersion time and the polarity of the membrane plasticizer. We believe that the obtained results could promote further applications of the polymeric membrane ISEs in the organic solvent-containing samples, which could significantly extend the application scope of the ISEs.

Prediction of acid pKa values in the solvent acetone based on COSMO-RS.

In this contribution we extent the use of the conductor-like screening model for realistic solvation (COSMO-RS) to the prediction of pKa values in acetone, a commonly used dipolar aprotic solvent. For this, we calculated the Gibbs free energy of dissociation of 120 organic acids (nine acrylic acids, 87 benzoic acids, nine phenols, and 15 benzenesulfonamides) using COSMO-RS at the two levels BP-TZVP and BP-TZVPD-FINE and determined the parameters for a linear free energy relation for the prediction by performing linear fits to experimental values. Our results suggest that the data set dissects into two groups, with the phenols being different from the other three subsets. The acrylic and benzoic acids and the sulfonamides can be treated together and yield an excellent linear correlation ( ) with an RMSD of only ~0.3. The slope is found to be significantly smaller than the theoretical value ( ), only 45% of it, which is in accordance with findings in the literature. The phenols, however, while similarly well correlated in their own subset with an RMSD of 1.7-1.9, exhibit a slope larger than one. We discuss both a higher uncertainty in the reference values as well as physical origins as possible reasons.

Replacement of Less-Preferred Dipolar Aprotic and Ethereal Solvents in Synthetic Organic Chemistry with More Sustainable Alternatives.

Dipolar aprotic and ethereal solvents comprise just over 40% of all organic solvents utilized in synthetic organic, medicinal, and process chemistry. Unfortunately, many of the common “go-to” solvents are considered to be “less-preferable” for a number of environmental, health, and safety (EHS) reasons such as toxicity, mutagenicity, carcinogenicity, or for practical handling reasons such as flammability and volatility. Recent legislative changes have initiated the implementation of restrictions on the use of many of the commonly employed dipolar aprotic solvents such as dimethylformamide (DMF) and N-methyl-2-pyrrolidinone (NMP), and for ethers such as 1,4-dioxane. Thus, with growing legislative, EHS, and societal pressures, the need to identify and implement the use of alternative solvents that are greener, safer, and more sustainable has never been greater. Within this review, the ubiquitous nature of dipolar aprotic and ethereal solvents is discussed with respect to the physicochemical properties that have made them so appealing to synthetic chemists. An overview of the current legislative restrictions being imposed on the use of dipolar aprotic and ethereal solvents is discussed. A variety of alternative, safer, and more sustainable solvents that have garnered attention over the past decade are then examined, and case studies and examples where less-preferable solvents have been successfully replaced with a safer and more sustainable alternative are highlighted. Finally, a general overview and guidance for solvent selection and replacement are included in the Supporting Information of this review.

Solvent-Resistant UV-Cured Polysulfone Support Membranes Using a Green Solvent.

Solvent-resistant UV-cured supports consisting of a semi-interpenetrating network of polysulfone (PSf) and cross-linked poly-acrylate were successfully synthesized for the first time using an alternative, non-reprotoxic, and biodegradable solvent. Tamisolve® NxG is a high-boiling, dipolar aprotic solvent with solubility parameters similar to those of dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP), making it an eco-friendly alternative. The support membranes, prepared via UV-curing followed by non-solvent-induced phase inversion, can serve as a universal solvent-resistant support for the synthesis of a broad set of membranes, for which the selective layer can be deposited from any solvent. Parameters such as UV irradiation time and intensity, as well as the concentrations of PSf, penta-acrylate, and photo-initiator in the casting solution were varied to obtain such supports. The characteristics of the resulting supports were investigated in terms of separation performance, hydrophobicity, porosity, degree of acrylate conversion, and pure water flux. The resulting membranes showed improved chemical resistance in solvents such as ethyl acetate, NMP, tetrahydrofuran (THF), and toluene. Solvent-resistant supports with different pore sizes were synthesized and used for the preparation of thin film composite (TFC) membranes to demonstrate their potential. Promising separation performances with Rose Bengal (RB) rejections up to 98% and water permeances up to 1.5 L m−2 h−1 bar−1 were reached with these TFC-membranes carrying a polyamide top layer synthesized via interfacial polymerization.

Carvone and its eutectic mixtures as novel, biodegradable, and tunable solvents to extract hydrophobic compounds in substitution for volatile toxic solvents

Finding safe solvents with low viscosities has been in great demand in extraction processes. Herein, R-(-)-carvone, a natural monoterpenoid rich in spearmint, was mixed with naturally occurring fatty acids and terpenes. Most eutectic mixtures presented a wide liquid window in the solid-liquid equilibrium phase diagrams. Carvone mixtures at the ideal eutectic points were characterized for physicochemical properties. Despite varying properties, all the tested solvents were immiscible with water and displayed low viscosity with reasonable biodegradability. Sigma potentials of the mixtures were applied to machine learning algorithms, suggesting carvone mixtures as substitutes for polar protic and dipolar aprotic solvents. Carvone mixtures could be successfully applied to liquid-liquid extraction of a red algae called laver, which is rich in natural hydrophobic and hydrophilic pigments of high value. This study proposes carvone as a new bio-based source of hydrophobic solvents and the eutectic mixtures as biodegradable and tunable solvents to extract hydrophobic compounds.

Surface architecture and proton conduction in SPVDF-co-HFP based nanocomposite membrane for fuel cell applications: Influence of aprotic solvent mixture

In the present study, the prime focus is to study the effect of a new solvent mixture on the formation of PVDF-co-HFP based nanocomposite membrane by solution casting method and their applicability to perform as a proton conducting membrane for fuel cell applications. A definite proportion two dipolar aprotic solvent mixture N-Methyl-2-pyrrolidone (NMP) and Acetonitrile (ACN) was used as the solvent mixture and it has been observed that the use of these solvents results in a porous structure with smaller micro domains within it, as evidenced from the FESEM micrographs. The mechanical resistance of the membranes also significantly improved with the change of solvent resulting in the formation of a ductile membrane. Incorporation of in-situ synthesized silanized silica nanoparticles into the polymer backbone following the sulfonation of the membranes using chlorosulfonic acid, also contributed in the improved physicochemical and the electrochemical properties with respect to higher water retention, better ion exchange capability (0.98 meq. g−1) and proton conductivities. Additionally, the silanized silica nanoparticles showed improved dispersibility within the polymer membrane thereby resulting in absorption of more sulfonic acid groups and shortened interchain separation distance which has been confirmed from XRD analysis. Thus, an interconnected proton conduction pathway which was formed, enhanced the proton conductivity to 0.113 S cm−1. Further, the barrier properties of the silica nanoparticles additionally suppressed the methanol crossover as compared with Nafion, while improving the membrane selectivity (3.65 × 104 S.scm−3).

Circular Aqueous Fmoc/t-Bu Solid-Phase Peptide Synthesis.

Circular economy and aqueous synthesis are attractive concepts for sustainable chemistry. Here it is reported that the two can be combined in the universal method for peptide chemistry, fluorenylmethoxycarbonyl(Fmoc)/t-Bu solid-phase peptide synthesis (SPPS). It was demonstrated that Fmoc/t-Bu SPPS could be performed under aqueous conditions using standard Fmoc amino acids (AAs) employing TentaGel S as resin and 4 : 1 mixture of water with inexpensive green solvent PolarClean. This resin/solvent combination played a crucial dual role by virtue of improving resin swelling and solubility of starting materials. In a model coupling, TCFH and 2,4,6-collidine afforded a full conversion at only 1.3 equiv. AA, and these conditions were used in SPPS of Leu enkephaline amide affording the model peptide in 85 % yield and 86 % purity. A method to recycle the waste by filtration through a mixed ion exchange resin was developed, allowing reusing the waste without affecting quality of the peptide. The method herein obviates the use of unconventional or processed AAs in aqueous SPPS while using lower amounts of starting materials. By recycling/reusing SPPS waste the hazardous dipolar aprotic solvents used in SPPS were not only replaced with an aqueous medium, solvent use was also significantly reduced. This opens up a new direction in aqueous peptide chemistry in which efficient use of inexpensive starting materials and waste minimization is coupled with the universal Fmoc/t-Bu SPPS.

Solvent and moleculer structure effects on acidity strength in non-aqueous medium

The acidic properties of ten 3-alkyl(aryl)-4-[3-hydroxy-4-methoxy benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives were investigated. In this study, isopropyl alcohol and tert‐butanol were used as an amphiprotic solvent. Aceton and N,N‐ dimethylformamide (DMF) were preferred as a dipolar aprotic solvent. Compounds were titrated with tetrabuthylamonnium hydroxide (TBAH) in isopropyl alcohol and titrimetric analyses were used potentiometric method determining the end-points, half-neutralization method determining acidity. Typical S-shaped titration graphs excepted were determined. The acidity strengths of 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives in amphiprotic and dipolar aprotic solvents were calculated using tables and graphs. The pKa values obtained in the solvents were found to be differentiated. The effects of solvent, molecular structure, autoprotolysis constant dielectric constant, and leveling‐differentiation effects of the solvents upon acidity strength of the compounds were discussed.

Densities, heat capacities, viscosities, 1H- and 13C-NMR spectra, and solvatochromic parameters of binary mixtures of 1,3-dimethyl-1,3-diazinan-2-one (DMPU) and water

The compound 1,3-dimethyl-1,3-diazinan-2-one (N,N’-dimethylpropyleneurea, DMPU) is a dipolar aprotic solvent with very strong electron-donating abilities but which is much less toxic and less carcinogenic than similar solvents such as the widely used HMPA (hexamethylphosphorictriamide). This paper reports densities and viscosities of the binary mixtures of (DMPU + water) in the temperature range (293.15 to 353.15) K at 5 K intervals, over the whole composition range. Isobaric heat capacities of these mixtures were measured by flow calorimetry at 298.15 K. The 1H- and 13C-NMR spectra as well as the solvatochromic parameters (polarizability, π*, hydrogen-bond acceptor basicity, β, and hydrogen-bond donor acidity, α) of the mixtures were also determined. The densities and viscosities were sensitive to traces of water in the organic-rich region while the heat capacities were not. Excess molar volumes were strongly negative, showing an extremum at mole fraction xDMPU ≈ 0.40. The variation of viscosity with mixture composition was similar to the density with a sharp maximum at xDMPU ≈ 0.35. Apparent molar volumes, Vϕ, of the mixtures show that the water-DMPU interactions have a larger effect on Vϕ of water than on DMPU. While the standard isobaric molar heat capacity of DMPU in water is much higher than that of DMPU itself, the corresponding value for water in DMPU was not much influenced by the presence of DMPU. The 1H-NMR spectra show that the chemical shift of the water protons is more influenced by mixture composition than those of the DMPU protons. A de-shielding of the DMPU carbonyl carbon resonance was observed in the 13C-NMR spectra at low xDMPU, indicative of H-bonding between the water protons and the non-bonding electrons of the carbonyl oxygen.

NOVEL NON-AQUEOUS ELECTROLYTES BASED ON COORDINATION BORON COMPOUNDS

The review provides a classification of electrolytes for modern chemical power sources, supercapacitors, sodium and lithium-ion batteries depending on changes in the physicochemical properties of salts and the products of their interaction with the solvent. A comparative analysis of physicochemical properties of salts depending on the structure of the cation and anion, and the influence of these properties on the properties of final solutions of electrolytes on the example of different classes of ionic liquids and chelatoborates of alkali metals and ammonium was conducted. The dependence of the physicochemical properties of electrolytes (solubility, electrical conductivity of solutions and the range of potentials of electrochemical stability) on the nature of the chelate ligand, electron donor and electroacceptor substituents in the bis (chelate) borate anion is analyzed. The electrical conductivity of salt solutions and ranges of potentials of electrochemical stability of the corresponding electrolytes containing other anions and used for a long time in chemical current sources are carried out. The advantages and disadvantages of using liquid electrolytes compared to solid and polymer electrolytes in terms of similarity of their structures have been detected. It is shown that the nature of the chelate ligand, electro-donor and electro-acceptor substituents in the bis (chelato) borate anion is an important factor in regulating the interaction with aprotic dipolar solvents. Mixed salts with two different chelate ligands typically combine the best characteristics of the corresponding monochelate compounds, but the methods for their preparation and purification are technologically significantly more complex compared to monochelate compounds. The analysis of the mechanism of formation of a protective film on a surface of electrode materials, dependence of potential on its formation and on the chemical nature of ligands is made. It is noted that bis (chelato) borate salts are more environmentally friendly compared to fluorine-containing complex salts. Emphasis is placed on the physicochemical properties of solutions of the most promising chelatoborate salts for use in lithium and sodium ion batteries, supercapacitors and electrolytic capacitors, and it is shown that bis (oxalate) borates and bis (salicylate gold) borates occupy ) borates in terms of electrical conductivity, solubility and potential range of electrochemical stability.

Li-Nafion Membrane Plasticised with Ethylene Carbonate/Sulfolane: Influence of Mixing Temperature on the Physicochemical Properties.

The use of dipolar aprotic solvents to swell lithiated Nafion ionomer membranes simultaneously serving as electrolyte and separator is of great interest for lithium battery applications. This work attempts to gain an insight into the physicochemical nature of a Li-Nafion ionomer material whose phase-separated nanostructure has been enhanced with a binary plasticiser comprising non-volatile high-boiling ethylene carbonate (EC) and sulfolane (SL). Gravimetric studies evaluating the influence both of mixing temperature (25 to 80 °C) and plasticiser composition (EC/SL ratio) on the solvent uptake of Li-Nafion revealed a hysteresis between heating and cooling modes. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the saturation of a Nafion membrane with such a plasticiser led to a re-organisation of its amorphous structure, with crystalline regions remaining practically unchanged. Regardless of mixing temperature, the preservation of crystallites upon swelling is critical due to ionomer crosslinking provided by crystalline regions, which ensures membrane integrity even at very high solvent uptake (≈200% at a mixing temperature of 80 °C). The physicochemical properties of a swollen membrane have much in common with those of a chemically crosslinked polymer gel. The conductivity of ≈10−4 S cm−1 demonstrated by Li-Nafion membranes saturated with EC/SL at room temperature is promising for various practical applications.

Electrical Conductivities of DBU-Based Ionic Liquid in Its Binary Solutions with Nonaqueous Molecular Solvents

A protic ionic liquid (IL) [DBUH][Triz], prepared from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (Triz), has been synthesized in this work. Then, the concentration-dependent electrical conductivity (κ) of binary solutions of [DBUH][Triz] with six molecular solvents, including four polar protic solvents (methanol, ethanol, isopropanol and n-butanol) and two dipolar aprotic solvents (dimethyl sulfoxide, DMSO and N,N-dimethylformamide, DMF), respectively, have been measured at temperatures ranging from 298.15 to 313.15 K. In addition, the electrical conductivities κ have been well correlated using the Castell–Amis equation with satisfying results. It has been found that within the solvent-rich range, the electrical conductivity κ first increased with increasing mole fraction of IL due to solvent–IL interactions. Afterwards, κ values of solutions gradually decreased due to the predomination of a strong electrostatic force between ions and enhancement of the viscosities of the solutions in the [DBUH][Triz]-rich region. Furthermore the maximum value of the electrical conductivity in [DBUH][Triz]/alcohol systems is in the following order: methanol > ethanol > isopropanol > n-butanol, which is consistent with the dielectric constants of the alcohols, indicating that an alcohol with higher dielectric constant can more readily promote the dissociation of [DBUH][Triz]. However, the electrical conductivity of the [DBUH][Triz]/DMF system is obviously larger than that of the [DBUH][Triz]/DMSO system although the dielectric constant of DMF is smaller than that of DMSO, implying that the viscosity could play the major role in determining the electrical conductivity of solutions of the IL with aprotic solvents.

Can Greener Cyrene Replace NMP for Electrode Preparation of NMC 811 Cathodes?

N-methyl-2-pyrrolidone (NMP) is the normally used solvent for cathode processing in lithium battery field. However, its high toxicity attracted more and more environmental scrutiny and was restricted by many chemical legislations in industry applications. So, it is necessary to find a greener and safer alternative to replace it. Dihydrolevoglucosenone (Cyrene), a newly reported green dipolar aprotic solvent, has very similar solvent properties as NMP, making it a very attractive candidate. The possibility to use Cyrene to replace NMP for NMC 811 cathode fabrication was studied. Although PVDF binder has very poor solubility in Cyrene at room temperature, increasing temperature can significantly change this. High temperature (above 80 °C) electrode processing with Cyrene gives promising performance, which is comparable to the conventional NMP fabricated electrode. A proof of principle was provided: Cyrene can be a good green alternative to replace NMP. The positive results reported here may also lead to a search for more Cyrene-like green solvents that have a higher solubility for PVDF, or of PVDF-like binders that are more soluble in Cyrene, to help making the electrode processing much greener.

Green Solvents as an Alternative to DMF in ZIF-90 Synthesis.

The use of green solvents as an alternative to dimethylformamide (DMF) in the synthesis of zeolitic imidazolate framework-90 (ZIF-90) was investigated. Two biobased aprotic dipolar solvents CyreneTM and γ-valerolactone (GVL) proved to successfully replace DMF in the synthesis at room temperature with a high product yield. While the CyreneTM—based product shows reduced porosity after activation, the use of GVL resulted in materials with preserved crystallinity and porosity after activation, without prior solvent exchange and a short treatment at 200 °C. The primary particles of 30 nm to 60 nm in all products further form agglomerates of different size and interparticle mesoporosity, depending on the type and molar ratios of solvents used.

Environmentally Benign Route for Scalable Preparation of 1-Imino-3-thioisoindolines-The Key Building Blocks for the Synthesis of Dithio- and Diamino-β-isoindigo Derivatives.

A one-step, gram-scale protocol for the preparation of 1-imino-3-thioisoindolines and a novel one-pot two-step methodology of the synthesis of dithio- or diamino-β-isoindigo derivatives starting from phthalonitriles and sodium hydrosulfide in an aprotic dipolar solvent have been developed. It was demonstrated that the electronic properties of the substituent(s) in the phthalonitrile core play a critical role in β-isoindigo synthesis resulting either in the selective formation of dithio- or diamino-β-isoindigo chromophores. The N-acylated 1-imino-3-thioisoindolines can be used for the direct, easily scalable, and chromatography-free procedure for the preparation of a new class of N,N'-diacylamino-β-isoindigoid compounds. Properties of the monomeric as well as J-aggregated forms of dithio- and diamino-β-isoindigo were probed by the absorption and fluorescence spectroscopies. It was demonstrated that the tetracyano-diamino-β-isoindigo 3f can form a J-aggregate that absorbs at 793 nm and fluoresces at 824 nm. This aggregate is stable in N,N-dimethylformamide solution; however, it slowly dissociates in tetrahydrofuran or under sonication conditions. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were employed to elucidate the electronic structures, spectroscopic properties, and aggregation of new dithio- and diamino-β-isoindigo derivatives.

Green alternative cosolvents to N-methyl-2-pyrrolidone in water polyurethane dispersions.

N-Methyl-2-pyrrolidone is a toxic dipolar aprotic solvent widely used in the synthesis of polyurethane dispersions (PUD). Since legislation strongly restricts this substance, green alternatives are essential. Dihydrolevoglucosenone and gamma valerolactone demonstrate comparable performance to that of NMP as cosolvent in the synthesis and the film forming process of PUD.

Systematic study on solubility of chrysin in different organic solvents: The synergistic effect of multiple intermolecular interactions on the dissolution process

The solubility of chrysin in N, N-dimethylformamide (DMF), acetone, ethyl acetate (EA), n-butanol, isopropanol, n-propanol, ethanol, methanol, n-hexane, and water was measured by using the static equilibrium method or the dynamic method at temperatures ranging from 293.2 to 333.2 K. Chrysin shows the easiest solvation in the dipolar aprotic solvents, followed by the polar protic solvents (alcohols), and shows poor solvation in the apolar aprotic solvents (hexane) and the strong polar water. The solubility of chrysin increases with rising temperature. The inherent microscopic solvation mechanisms were investigated qualitatively and quantitatively using a combination of the KAT-LSER model as well as σ-profile theory and molecular interaction energies calculated by COSMO–RS model. The results show the solvation process of chrysin in the different solvents is a complex process which depends on the synergistic effects of multiple molecular interactions between the solute and solvent together with the solvent and solvent. Moreover, the experimental solubility data in all solvents could be reasonably correlated by the modified Apelblat equation, λh equation, van't Hoff equation, Wilson model, and NRTL model, whereas the NRTL model and the modified Apelblat equation showed the most satisfactory fitting results. The dissolution thermodynamic properties, including enthalpy, entropy and Gibbs energy of chrysin in the dissolution process were evaluated using the van't Hoff equation. Moreover, the overall dissolution trend and the temperature-dependence of experimental solubility of chrysin in the different classes of solvents can be predicted correctly by the COSMO–RS model.

SYNTHESIS OF SUCROSE ESTERS WITH STEARIC, PALMITIC AND OLEIC ACIDS

The esterification of sucrose with stearic, palmitic and oleic acids yields the corresponding esters. Effective methods have been developed for carrying out the esterification reaction at temperatures of 150–170℃ in high-boiling aprotic dipolar solvents.

Synthesis of novel aromatic polyamides containing cardo groups and triphenylphosphine oxide structures by a heterogeneous palladium-catalyzed carbonylation and condensation reaction

New aromatic polyamides containing cardo groups and triphenylphosphine oxide structures were synthesized by a heterogeneous palladium-catalyzed carbonylation and condensation of bis(4-(3-iodophenoxy)phenyl)phenylphosphine oxide (BIPPO), aromatic diamines bearing cardo groups, and carbon monoxide. Polycondensations were carried out in N,N-dimethylacetamide under 1 atm of CO at 120 °C in the presence of a magnetically recyclable heterogeneous palladium catalyst and 1,8-diaza-bicyclo[5,4,0]-7-undecene (DBU) and afforded novel aromatic polyamides with inherent viscosities between 0.72 and 0.76 dL/g. All the polyamides were quite soluble in dipolar aprotic solvents and pyridine and could be converted into transparent, flexible, and tough polyamide films by casting from DMAc solutions. These polymers exhibited high thermal and thermooxidative stability with the glass transition temperatures of 237 °C–256 °C, the temperatures at 5% weight loss of 448 °C–465 °C in air. All the phosphorus-containing polyamides self-extinguished as soon as the flame was removed, and the limited oxygen indices (LOIs) of these polymers were in the range of 39%–44%. The polymer films also showed good mechanical properties and high optical transparency.