Diamine Monomer Research Articles

Green, General and Low‐cost Synthesis of Porous Organic Polymers in Sub‐kilogram Scale for Catalysis and CO2 Capture

AbstractPorous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large‐scale production. Herein, we report the synthesis of imine and aminal‐linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta‐diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub‐kilogram quantities at a relatively low cost. Proof‐of‐concept studies demonstrate that the POPs can be used as high‐performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost‐effective approach for large‐scale synthesis of various POPs.

Green, General and Low-cost Synthesis of Porous Organic Polymers in Sub-kilogram Scale for Catalysis and CO2 Capture.

Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large-scale production. Herein, we report the synthesis of imine and aminal-linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta-diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub-kilogram quantities at a relatively low cost. Proof-of-concept studies demonstrate that the POPs can be used as high-performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost-effective approach for large-scale synthesis of various POPs.

Enhancing the Toughness of Free-Standing Polyimide Films for Advanced Electronics Applications: A Study on the Impact of Film-Forming Processes.

High-quality and free-standing polyimide (PI) film with desirable mechanical properties and uniformity is in high demand due to its widespread applications in highly precise flexible and chip-integrated sensors. In this study, a free-standing PI film with high toughness was successfully prepared using a diamine monomer with ether linkages. The prepared PI films exhibited significantly superior mechanical properties compared to PI films of the same molecular structure, which can be attributed to the systematic exploration of the film-forming process. The exploration of the film-forming process includes the curing procedures, film-forming substrates, and annealing treatments. Additionally, the thickness uniformity and surface homogeneity of free-standing films were crucial for toughness. Increasing the crystallinity of the PI films by eliminating residual stress also contributed to their high strength. The results demonstrate that by adjusting the above-mentioned factors, the prepared PI films possess excellent mechanical properties, with tensile strength and elongation at break of 194.71 MPa and 130.13%, respectively.

Synthesis and gas separation performance of Tröger's base-containing polyimides derived from 9,9-Bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride

Two imide-containing diamine monomers were prepared using 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride (6FcDA) and 2,6-dimethylaniline or 2,6-diisopropylaniline as the starting materials. Two polyimides of intrinsic microporosity (PIM-PIs), i.e., 6FcDA-Me2NH2-TB and 6FcDA-iPr2NH2-TB, were then synthesized via TB polymerization of imide-containing diamines and dimethoxymethane in trifluoroacetic acid. The surface areas, fractional free volumes, and interchain distances of the PIM-PIs were in the range of 555–569 m2 g−1, 0.16–0.20, and 0.60–0.67 nm, respectively. These values followed the order of 6FcDA-Me2NH2-TB < 6FcDA-iPr2NH2-TB owing to the larger size of isopropyl substituents relative to methyl groups. Furthermore, 6FcDA-Me2NH2-TB exhibited obvious π-π stacking interactions as evidenced by the diffraction peaks at ∼ 26 ° in wide angle X-ray diffraction patterns. Consequently, 6FcDA-Me2NH2-TB showed higher perm-selectivity but lower gas permeability as compared to 6FcDA-iPr2NH2-TB. Particularly, both polymers had a CO2 permeability of > 2900 Barrer and a CO2/CH4 selectivity of > 10, located between the 1991 and 2008 Robeson’s upper bound for CO2/CH4 separation.

Rational design and coloration mechanism of soluble intrinsic black polyimide with high comprehensive performance for black flexible copper clad laminates

With the development of flexible printed circuit boards (FPCBs) and photoelectric devices, the demand for black polyimide (BPI) is increasing, but the existing BPIs have some problems, such as poor electrical properties, mechanical performance, masking ability and solubility. To solve these problems, a novel diamine monomer (TPCPOHPDA) containing tetraphenylcyclopentadienone (TPCP) grafted with hydroxyl groups and benzene rings was customized, and then TPCPOHPDA was polymerized with 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to obtain polyimide (TPCPOHPPI). TPCP had a broad UV–visible light absorption range (250–600 nm). Appending benzene rings and auxochrome (hydroxyl groups) on the TPCP skeleton extended the conjugated π-electron system and enhanced the mobility of electrons in the large π bonds, respectively. These structural modifications further extended its light absorption range, and the resulting TPCPOHPPI was dark black with a cutoff wavelength (λcut) of 680 nm and Commission International Eclairage (CIE) lab color parameter L* of 0.7. Simulation calculations indicated that the visible-light absorption that caused the black appearance of TPCPOHPPI was mainly due to the electron transition from HOMO to LUMO occurring within the TPCP-containing diamine moieties, in which the charge mainly transferred from the aryl moieties in positions 2 and 5 to the central cyclopentadienone core. Further investigation showed that TPCPOHPPI had excellent thermal, electrical and mechanical performances and high solubility. The TPCPOHPPI-based two-layer black flexible copper clad laminate (2L-FCCL) possessed good dip soldering resistance and peeling strength. This work provides a new idea for the design and synthesis of soluble intrinsic black polyimide with excellent comprehensive performance.

Synthesis and characterization of azodianiline covalent organic frameworks intended for energy storage

Two covalent organic frameworks (COFs), a subgroup of porous organic polymers, based on diamine and trialdehyde monomers were synthesized to explore the effect of the building block structure on final electrochemical energy storage properties. One was synthesized from azodianiline (AZO) and tris (4-formyl phenyl) amine (TFPA) precursors and the other was prepared from AZO and 1,3,5-tris (p-formyl phenyl) benzene (TFPB). The former COF (TFPA-AZO-COF) and the latter one (TFPB-AZO-COF) were then evaluated by various characterization techniques. Specific surface area of 987 m2g−1 was found for TFPB-AZO-COF, while 425 m2g−1 was estimated for TFPA-AZO-COF. Specific capacity of 450 Fg−1, energy density of 24.6 W hkg−1, and power density of 8500 Wkg−1 were measured for TFPB-AZO-COF, while 160 Fg−1, 9.8 Whkg−1, and 8600 Wkg−1 were obtained for TFPA-AZO-COF. Stronger resonance in TFPB-AZO-COF accounted for better performance in terms of electrochemical energy storage.

Dynamic covalent bond enabled strong Bio-based polyimide materials with Thermally-driven Adaptivity, healability and recycling

Developing new sustainable materials as plastic replacement has become an urgent task for the rapid accumulation of non-degradable petroleum-based waste plastics. Herein, we report that catalyst-free dynamic reversible exchange operated at room-temperature by Schiff base reaction between dialdehyde cellulose nanofibrils (DACNF) and plant oil-based aliphatic long-chain diamine monomers (LCD). The dynamic imine polymer films are formed using a simple method similar to wet pressing in papermaking, which exhibits excellent mechanical properties and thermally processability for the synergistic of hydrogen bond and dynamic imine bond. The tensile strength and Young's modulus reaches 83.74 MPa and 3.90 GPa, which are significantly higher than those of most traditionally commercial plastics. In addition, the number of hydrogen bonds and dynamic imine bonds from cellulose and dynamic imine polymers are evaluated by molecular dynamics (MD) simulation to gain further insights into the intermolecular interaction. By exploring the mechanism involved in the reversible exchange of dynamic imine bonds and its application in self-healing and recycling, a sustainable adaptive material is expected to be structured. More importantly, the dynamic imine polymers also exhibits excellent water barrier properties, solvent resistance and complete biodegradability, which offers a new strategy for reducing the application of non-degradable plastics.

Structural engineering on 6FDA-Durene based polyimide membranes for highly selective gas separation

In this work, four diamine monomers, selected based-on steric hindrance and affinity with gas to be separated, were separately introduced into 6FDA-Durene to prepare co-polyimides. The influences of incorporating diamine monomer geometry on free volume elements (FFV, FAV, cavity size distribution, surface area and cavity connectivity) and gas transport properties (solubility and diffusion) of synthesized co-polyimide membranes were systematically investigated. The introduction of second amino monomer can increase gas selectivity, however leaded to lower gas permeability. Gas solubility and solubility selectivity of membrane remained almost stable with introduction of different amino monomer. While the gas diffusion changed remarkably, and the diffusion selectivity increased by about 170%. The FDDA membrane with crown ether structure displayed the highest gas selectivity (increased by 122%, 121%, 158%, 115% and 115% for H2/N2, H2/CH4, O2/N2, CO2/N2 and CO2/CH4, respectively, compared to 6FDA-Durene membrane), whose selectivity was relatively high among the PI-based membranes. This can be explained that the crown ether group granted the membrane with largest FAV ratio of specific gas pair, as well as the smallest pore size that would cause stronger size sieving effect. These results indicated that gas separation property of polyimide membranes can be effectively adjusted via tuning monomer structure, which is easily synthesized or has been commercialized, to realize the industrial application of membrane-based gas separation.

Double-decker-shaped phenyl-substituted silsesquioxane (DDSQ)-based nanocomposite polyimide membranes with tunable gas permeability and good aging resistance

Membrane-based gas separation technique shows great potential in CO2 elimination from natural gas and N2 enrichment from compressed air. In this study, a double-decker-shaped phenyl-substituted silsesquioxane (DDSQ)-based diamine monomer, that is, DDSQ-diamine, was synthesized and subsequently copolymerized with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) in combination with 4,4′-oxydianiline (ODA) to fabricate a series of DDSQ-based polyimide membranes with intrinsic microporosity (PIM-PIs). The resulting membranes showcase desirable mechanical robustness, satisfactory heat resistance and good organo solubility. Owing to the inherent internal nanometer-sized cavity of DDSQ cage, DDSQ-based membranes are more nanoporous than DDSQ-free sample, accordingly exhibiting decreasing membrane density and increasing gas permeability. Among all membranes, DDSQ-25 and DDSQ-50 show more desirable overall gas separation performance, which almost achieve the 1991 Robeson upper bound. Additionally, DDSQ-25 demonstrates good plasticization resistance and CO2/CH4 mixed-gas separation properties when measured with 50:50 CO2/CH4 binary gas mixture at upstream pressure up to 20 bar. Despite physical aging at ambient conditions for 300 days, the resultant DDSQ-based polyimide membranes still have stable gas permeability and almost constant selectivity, showcasing satisfactory anti-aging characteristic.

Safer Polyurethane Foams with Cyclic Carbonates.

Polyurethanes (PUs) are a class of materials usually synthesized from isocyanates, diols, and water. Water is essential for producing carbon dioxide (CO2 ) which is used for the self-blowing of the foams. Due to safety concerns with the production of isocyanates, alternative chemistries have been evaluated and cyclic carbonate systems have shown great promise. In a recent advancement by Bourguignon, Grignard, and Detrembleur, a cyclic carbonate and diamine system is capable of generating CO2 for self-blowing through hydrolysis of the carbonate-based monomer. The authors demonstrate that with a simple variation of the diamine monomer a wide range of physical and thermo-mechanical properties were achievable. This work represents a significant step towards safer and more environmentally friendly PUs.

Safer Polyurethane Foams with Cyclic Carbonates

AbstractPolyurethanes (PUs) are a class of materials usually synthesized from isocyanates, diols, and water. Water is essential for producing carbon dioxide (CO2) which is used for the self‐blowing of the foams. Due to safety concerns with the production of isocyanates, alternative chemistries have been evaluated and cyclic carbonate systems have shown great promise. In a recent advancement by Bourguignon, Grignard, and Detrembleur, a cyclic carbonate and diamine system is capable of generating CO2 for self‐blowing through hydrolysis of the carbonate‐based monomer. The authors demonstrate that with a simple variation of the diamine monomer a wide range of physical and thermo‐mechanical properties were achievable. This work represents a significant step towards safer and more environmentally friendly PUs.

Synthesis and characterization of nanocomposites based on polyimide bearing benzimidazole side groups filled with titania nanoparticles

ABSTRACT This study reports on the fabrication and property investigation of nanocomposites based on polyimide (PI) containing benzimidazole pendant groups reinforced with titania nanoparticles (TiO2 NPs) via the in-situ thermal imidization approach. This method involves the formation of poly(amic acid) (PAA), as the precursor of PI, by polycondensation of an equimolar amount of dianhydride, pyromellitic dianhydride (PMDA), with a benzimidazole-containing diamine monomer, 5-(2-benzimidazole)-1,3-bis(4-aminophenoxy)benzene (BIDA), in dimethylacetamide (DMAc) solvent, followed by embedding various weight percentages (3, 5, and 8 wt%) of amine-functionalized titania nanoparticles (NH2-TiO2 NPs) in PAA media, and subsequent thermal imidization to be converted to PI/TiO2 nanocomposite films. The structural, morphological, and thermal properties of the obtained neat PI and its nanocomposite films were studied by various methods, such as FT-IR spectroscopy, X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The data resulted from TGA analysis indicated that the incorporation of NH2-TiO2 NPs into the PI matrix show higher thermal stability when compared to the neat PI. The SEM images revealed that the dispersion of titania NPs was uniformly done in PI matrix, with a particle size of around 42 nm.

Achieving both low thermal expansion and low birefringence for polyimides by regulating chain structures

The synthesis of polyimides (PIs) with both low coefficient of thermal expansion (CTE) and low birefringence still faces a big challenge. In this study, we prepared a new kind of PI (PI-c-P), derived from a diamine monomer (cis-diamine-DBCOD) that contains dibenzocyclooctadiene (DBCOD) units, which exhibits near-zero thermal expansion with a CTE value of 1.5 ppm/K in the temperature range of 0–150 °C due to the unique conformation transition of DBCOD unit. The increase in chain rigidity and cis-diamine-DBCOD content could effectively reduce the CTE values by promoting conformation transition. Cross-linking could restrict chain conformation transition and impair thermal contraction, leading to higher CTE values. Unlike the conventional low CTE PIs with high orientation or crystallization, the birefringence of DBCOD-containing PI films was in the range of 0.0021 ∼ 0.0094, showing both low birefringence and low thermal expansion, this property is extremely important for its application in optical and electronic devices.

Reducing the Permittivity of Polyimides for Better Use in Communication Devices

Recent studies have shown that introducing fluorinated groups into polyimide (PI) molecules can effectively reduce the dielectric constant (Dk) and dielectric loss (Df) of PIs. In this paper, 2,2'-bis[4-(4-aminophenoxy) phenyl]-1,1',1',1',3,3',3'-hexafluoropropane (HFBAPP), 2,2'-bis(trifluoromethyl)-4,4'-diaminobenzene (TFMB), diaminobenzene ether (ODA), 1,2,4,5-Benzenetetracarboxylic anhydride (PMDA), 3,3',4,4'-diphenyltetracarboxylic anhydride (s-BPDA) and 3,3',4,4'-diphenylketontetracarboxylic anhydride (BTDA) were selected for mixed polymerization to find the relationship between the structure of PIs and dielectric properties. Firstly, different structures of fluorinated PIs were determined, and were put into simulation calculation to learn how structure factors such as fluorine content, the position of fluorine atom and the molecular structure of diamine monomer affect the dielectric properties. Secondly, experiments were carried out to characterize the properties of PI films. The observed change trends of performance were found to be consistent with the simulation results, and the possible basis of the interpretation of other performance was made from the molecular structure. Finally, the formulas with the best comprehensive performance were obtained respectively. Among them, the best dielectric properties were 14.3%TFMB/85.7%ODA//PMDA with dielectric constant of 2.12 and dielectric loss of 0.00698.

Design, synthesis and characterization of novel fluorinated polyimide membranes with bulky pendant for gas transport

AbstractThree novel fluorinated polyimides (PIs) were synthesized via one‐step solution polycondensation from a new diamine monomer, 4‐(3‐methoxy‐4‐(difluoromethoxy)phenyl)‐2,6‐bis(4‐aminophenyl)pyridine, and three commercially available aromatic dianhydrides. The solubility, thermal, optical, hydrophobic and gas transport properties of the obtained PIs were investigated. The results demonstrated that these polymers present good solubility in dimethylformamide, N‐methylpyrrolidone, dimethylsulfoxide, dimethylacrylamide, CHCl3, tetrahydrofuran and CH2Cl2 at room temperature or upon heating. Meanwhile, they displayed excellent thermal properties with glass transition temperature of 261–345 °C, weight loss temperatures at 10% of 518–523 °C as well as char yield of 60–62% at 800 °C in nitrogen atmosphere. Furthermore, the PI membranes have good hydrophobic properties with water contact angle value in the range 90.1–92.0°. Moreover, they show excellent optical properties, with cut‐off wavelength (λcut‐off) values of 368–381 nm and wavelength values at 80% transmittance (λ80%) of 421–462 nm. The pure gas permeabilities of He, CO2, O2 and N2 of the PI membranes were measured by the method of constant volume–variable pressure. The PI containing 4,4′‐(hexafluoroisopropyl)diphthalic anhydride moiety exhibits the largest molecular chain spacing and free volume, giving the best gas transport performance in this work. Molecular simulation results show that the introduction of fluorine‐containing structure and bulky pendant into polymer backbones is beneficial for gas transport. © 2023 Society of Industrial Chemistry.

Tuning interchain cavity of fluorinated polyimide by DABA for improved gas separation performance

Fluorinated polyimides with biphenyl structure and –CF3 with rigid chain structure exhibit great potential in membrane-based gas separation. However, the comprehensive separation performance of this type polyimides is not competitive as a gas separation material. Structure regulation is of great significance to improve the separation performance of polymer membrane. Few studies systematically investigated structure-property relationships in fluorinated polyimide structure. In this study, carboxylic groups are introduced into a fluorinated polyimide(6FDA-TFMB) via copolymerization with DABA diamine monomer. The hydrogen bond between –CF3 group in TFMB and –COOH group in DABA is proposed to enhance chain segment rigidity and optimize polymer chain arrangement. WAXD results and FFV data indicate that inter-chain cavity of fluorinated polyimide could be finely tuned by adjusting molar ratio of TFMB and DABA in the copolyimide. The resulted copolyimide membranes thus demonstrate tunable gas permeation properties. Gas permeability of 6FDA-TFMB/DABA firstly increases and then decreases, and ideal gas selectivity continuously increases with increasing DABA molar ratio. Among the polyimides, 6FDA-TFMB/DABA(6:4) membrane demonstrated superior separation performance, e.g. CO2 permeability of 135.6 Barrer and CO2/CH4 ideal selectivity of 31.6, surpassing the commercial cellulose acetate and Matrimid membrane. Attributed to the optimized interchain interaction, the 6FDA-TFMB/DABA (6:4) membrane displays an optimized CO2 plasticization resistance and physical aging in comparison with 6FDA-TFMB membranes. This study provides a guideline for controlling and optimize the performance of biphenyl fluorinated polyimide gas separation membrane.

Intrinsic-designed polyimide dielectric materials with large energy storage density and discharge efficiency at harsh ultra-high temperatures.

Polymer dielectric materials with excellent temperature stability are urgently needed for the ever-increasing energy storage requirements under harsh high-temperature conditions. In this work, a novel diamine monomer (bis(2-cyano-4-aminophenyl)amine) was successfully synthesized to prepare a series of cyano-containing polyimides (CPI-1-3), which possessed excellent dielectric properties and high thermostability. The maximum dielectric permittivity was up to 5.5 at 102 Hz for CPI-3, being 2.5 times higher than that of commercially used BOPP. In comparison, the CPI-1 exhibited an outstanding breakdown strength of 433 MV m-1 and a high energy density of 2.5 J cm-3 even at 250 °C, which was the highest value reported under the same conditions. The synthesized CPIs through such an intrinsic approach are potential candidate materials for energy storage and even other applications under simultaneously harsh electrical and thermal conditions.

Colorless and transparent poly(amide imide) nanocomposites containing organically modified hectorite.

Polyamic acid (PAA) was synthesized using the diamine monomer N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]bis(4-aminobenzamide) and dianhydride monomer 4,4'-oxydiphthalic anhydride. Colorless and transparent poly(amide imide) (CPAI) hybrid films were prepared via multi-step thermal imidization of PAA in which various contents of nano-filler were dispersed. The CPAI hybrid films were prepared by dispersing organoclay STN, which was obtained by organically modifying hectorite, in CPAI by solution intercalation with various contents ranging from 1 to 7 wt%. The thermomechanical properties, morphologies, and optical transparencies of the obtained CPAI hybrid films were investigated based on the dispersed STN content, and the results were compared. Some of the clay in the CPAI hybrid film were agglomerated, which was observed using a transmission electron microscope; however, most clays were well-dispersed, with a nano-size of less than 10 nm. The best thermomechanical properties of the CPAI hybrid film were exhibited with an STN content of 3 wt%, but these properties decreased above the critical content. The coefficients of thermal expansion of all the hybrid films were below 20 ppm per °C regardless of the amount of STN, and the yellow index was 1-2 even when the STN content increased to 7 wt%.

Metabolic engineering for 4-aminophenylalanine production from lignocellulosic biomass by recombinant Escherichia coli

4-Aminophenylalanine as a diamine monomer to synthesize unique biopolyimides was produced from lignocellulosic biomass by microbial fermentation. Fermentation inhibitors present in lignocellulosic hydrolysate of sorghum bagasse were identified.

Design and preparation of thermoplastic polyimides with high transmittance based on 4,4′-(4,4′-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA)

In order to prepare polyimide resins with excellent melt processing properties and high transmittance, a series of thermoplastic fluorinated polyimide resins was prepared by copolycondensation of the flexible dianhydride monomer 4,4′-(4,4′-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA) and the fluorinated diamine monomer 2,2′-bis(trifluoromethyl)benzidine (TFMB) with different contents of fluorinated dianhydride 4,4′-(hexafluoroisopropyl)diphthalic anhydride (6FDA) or cyclobutanetetracarboxylic dianhydride (CBDA) via chemical imidization. The effects of the third monomer content on the melt processing properties, optical properties, heat resistance, and mechanical properties of the polyimide resins were systematically investigated. The minimum melt viscosity of the PI resins reached 630 Pa·s below 400 °C. The transmittance at 450 nm of PI sheets prepared by compression molding reached 77%, and the color was significantly lighter than the commercial thermoplastic resin ULTEM, indicative of excellent processability and optical properties. Besides, the PI resins displayed outstanding thermal performance with glass transition temperatures ranging from 224 °C to 242 °C, 5% weight loss temperatures higher than 520 °C in a nitrogen atmosphere, and coefficients of thermal expansion of 51.45–68.97 ppm/K. Moreover, the PI sheets possessed tensile strengths of 88.4–104.7 MPa.