Diamine Monomer Research Articles

N-doping of β-ketoenamine based covalent organic frameworks for catalytic conversion of CO2 to cyclic carbonate and Knoevenagel condensation

Covalent organic frameworks (COFs) based on β-ketoenamine structure are obtained through the irreversible enol-to-keto tautomerization, resulting in a highly stable and crystalline skeleton structure. Herein, N-doped β-ketoenamine based COFs (TP-BD-COF, TP-PD-COF, TP-PMD-COF) were successfully constructed between C2-symmetric diamine monomers containing different amounts of nitrogen atoms (0 N, 1 N and 2 N) and C3-symmetric 1,3,5-Triformylphloroglucinol (TP) monomer. The as-prepared COFs containing both the –NH– unit and pyridine nitrogen atom on the backbone of COFs could provide hydrogen bond and Lewis base double active sites for catalytic application. Studies showed that TP-BD-COF containing 0 N atom exhibited highest catalytic efficiency (99 %) for the cycloaddition reaction between carbon dioxide and styrene oxide, while TP-PD-COF (1 N) and TP-PMD-COF (2 N) showed the catalytic efficiency only with 87 % and 85 %, respectively. However, for Knoevenagel condensation of benzaldehyde and malononitrile, the order of catalytic efficiency is TP-PD-COF (99 %) > TP-PMD-COF (92 %) > TP-BD-COF (70 %), the recycled number and the possible catalytic mechanism were also investigated. This research provides theoretical guidance for the rational construction of non-metallic heterogeneous catalysts based on β-ketoenamine COFs.

Nanochannel regulation of graphene quantum dots composite membranes via electrospray assisted self-assembly method

Nanochannel construction and regulation of graphene-based composite films are critical to the efficient separation performance. We report on a novel approach to preparing porous graphene-based composite films based on electrospray assisted self-assembly method by intercalating diamine monomers between graphene quantum dots (GQDs) nanosheets. Four kinds of diamine monomers were chosen as the bridging agents to fine tune the nanochannels between GQDs nanosheets. The physicochemical structures of as-prepared GQDs composite membranes were further optimized by post-crosslinking. The results showed that the covalent reactions of GQDs nanosheets with diamine monomers were occurred simultaneously between parallel and perpendicular GQDs nanosheets in the membrane preparation process, which constructed the three-dimensional space architecture of the GQDs composite membrane. The diamine monomers with different structures and molecular weights could change the loose structures of the separation layers, which endowed the GQDs composite membranes with the adjustable pore size and better hydrophilicity, further affecting their dye desalination performance. With the increase of the molecular weight of diamine monomers, the pore size of GQDs composite membranes increased slightly from 3.4 nm (GQDs-EDA) to 3.8 nm (GQDs-PPD), while the dye rejection decreased slightly. This study provided an insight into the uniform self-assembly of GQDs into nanofilms to fine tune the nanochannel structure.

New Fluorine-Containing Diamine Monomers for Potentially Improved Polyimides.

Two new fluorine-containing diamine monomers were designed with the goal of reducing charge transfer complex (CTC) interactions between neighboring chains in polyimides (i.e., high transparency/low color) while hopefully maintaining the well-known thermal stability and flexibility generally associated with polyimides. The proposed diamines have been prepared through (1) the functionalization of 1,3-bis[(pentafluorobenzyl)oxy]benzene with 4-aminophenol and (2) the addition of 2-chloro-5-nitrobenzotrifluoride to 4,4'-bicyclohexanol followed by reduction of the resulting dinitro compound. The new compounds have been characterized by multinuclear NMR and IR spectroscopy and high-resolution liquid chromatography-mass spectrometry as well as single-crystal X-ray diffraction on the new diamine prepared from 4,4'-bicyclohexanol. Not only was the structure of the proposed new diamine confirmed, but another interesting example of hydrogen bonding between an N-H proton and the π-system of an aromatic ring was observed and documented. Initial polymerizations have been carried out via the two-step imidization process.

Novel polyimides with improved adhesion to smooth copper and low coefficient of thermal expansion

Polyimides (PIs) have been extensively developed as interlayer dielectrics in electronic package industry due to their excellent comprehensive properties. However, the insufficient adhesion between PI and copper wires usually led to delamination and thus compromising the reliability of applications. In this work, a diamine monomer (SPMNH2) that contained pyrimidine side groups and ether bonds was synthesized, and a series of its copolyimides (SPI) were prepared by copolycondensation with 2-(4-aminophenyl)-1H-benzimidazol-5-amine (APBI) and pyromellitic dianhydride (PMDA). The incorporation of pyrimidine rings, along with the presence of benzimidazole rings promoted the adhesion between PI and copper (1.3805 N/3 mm of SPI-4). In addition, a desired coefficient of thermal expansion (15.28 ppm/K of SPI-4) close to that of copper was obtained, facilitating the adhesion of the interface during high-temperature processes. Moreover, SPI-4 exhibited exceptional mechanical (the elongation at break of 44.02% and tensile strength of 191.64 MPa) and thermal properties (Tg = 363.70 °C, T5% = 519.33 °C). Therefore, the high-performance SPI films showed great potential in advanced packaging.

PI@TB blend membranes containing amorphous carbon for gas separation

This study employs the same diamine monomer to synthesize polyimide (PI) and Tröger’s Base-based polymers of intrinsic microporosity (TB), which exhibit infinite miscibility due to like-dissolves-like phenomenon. The TB and PI exhibit significantly different thermal decomposition temperatures, enabling the partial carbonization of TB at a lower temperature while retaining the favorable mechanical properties of PI. Consequentially, This work propose a novel method to prepare blend membranes with a partial amorphous carbon structure. These membranes have excellent gas separation performance, similar to that of carbon membranes, while also retaining the machinability of traditional polymer membranes. The molecular structure of the material is characterized using 1H NMR and FTIR spectra, while the microscopic morphology is observed through scanning electron microscopy. Molecular dynamics simulations confirm the compatibility of both polymers and explain the improved properties. Gas transportation measurement confirms that PI@TB blend membranes demonstrate significant improvement in gas separation performance compared to original membranes. Specifically, enhancements in the gas separation performance of CO2/CH4, H2/CH4, and O2/N2 systems have been observed, with the CO2/CH4 pair demonstrating the most remarkable improvements, surpassing the 2019 Robeson upper limit. This design strategy can be applied to produce blend membranes containing amorphous carbon that exhibit great potential for high-performance separation processes in the future.

Furan-derived Schiff base covalent adaptable thermosets with recyclability and anti-flammability

Conventional thermosetting polymers, mostly derived from nonrenewable petroleum resources, are not reprocessable and recyclable due to their highly cross-linked three-dimensional networks and face the disadvantage of high flammability. To solve these issues, in this study, we synthesized a novel Schiff base covalent adaptable thermoset from a furan-derived tri-aldehyde monomer (TMFP) and a furan-derived di-amine monomer (DFDA). The as-prepared TMFP-DFDA-Vitrimer exhibited superior anti-flammability with a high limiting oxygen index (LOI) of 35.0% and a UL-94 V-0 rating, which was attributed to the excellent charring ability. Additionally, TMFP-DFDA-Vitrimer could also be conveniently recycled by chemical decomposition under a mixed hydrochloric acid/tetrahydrofuran (HCl/THF) solution. After recycling for 5 times, the thermal, mechanical, and flame retardant properties of the recycled TMFP-DFDA-Vitrimer retained almost unchanged compared to the original one. This work provides a prime instance to develop advanced thermosetting polymers from abundant furan-based compounds.

Crosslinked polyimides with bulky side-group polyhedral silsesquioxanes: Towards lower dielectric constant and better mechanical property

The synthesis of a low dielectric constant polyimide (PI) with a polyhedral oligomeric silsesquioxane (POSS) cross-linked structure is presented. A non-planar conjugated diamine monomer (FSNH2) with two -CH=CH2 reactive groups was first synthesised in a two-step process, and then two polyimides were synthesized by PSS-Octavinyl (OVPOSS) substituted, FSNH2 and dianhydride. OVPOSS cross-linked polyimides have good thermal stability and low dielectric constant. 6FDA-FSNH2-OVPOSS(6FPI-3) can reach a minimum dielectric constant of 2.08 (108 Hz) and a dielectric loss of 0.008 (108 Hz). In addition, the cross-linked structure of the OVPOSS and polyimide chains prevents the agglomeration of OVPOSS to a certain extent and improves the tensile strength and elongation at break of the polyimides, which has great application potential in large-scale integrated circuits.

Accelerated Design of Ultra-High-Performance Aramid Copolymers via a High-Throughput Screening Approach.

Developing advanced materials, such as functional polymers, poses a significant challenge as a result of the vastness of the material space that needs to be explored, which could potentially be infinite in principle. We propose a data-driven high-throughput screening approach coupled with molecular dynamics (MD) simulations to address this issue in the design of high-performance co-polymerized aramid fibers. We aimed to identify diamine monomers that could replace 3,4'-oxydianiline in Technora from a large-scale set (1 920 304) of possible monomers that were prepared from the PubChem database. We initially screened these monomers using a cheminformatics-based approach, considering four criteria: complexity, neutrality, linearity, and gyration radius of the molecule. Then, we performed subsequent screening based on MD simulations to estimate interchain interaction energies under both stretched and melted conditions and tensile strength simulations. Our screening approach successfully identified 31 promising and novel diamine monomers for aramid copolymers. This demonstrates the potential and effectiveness of our approach as a promising protocol for exploring targeted chemical spaces in designing novel monomers for high-performance aramid fibers and possibly other advanced polymers.

Semi aromatic colorless polyimide coatings for dual electrochromic and electrofluorochromic displays and its potential for information encryption

Based on the concept of minimizing the charge transfer complex effect, the diamine monomer which contains amide bond bridged adamantane group and triarylamine unit was synthesized. Subsequently, two colorless polyimides with excellent electrochemical stability and high fluorescence quantum yield were prepared by polycondensation of the aforementioned diamine monomer with 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride and 4,4'-hexafluoroisopropylidene)-diphthalic anhydride, respectively. CPIs coatings ranging from colorless to oxidized blue exhibit excellent electrochromic behaviors and optical transmittance of 80 %, which is 60 % after 15,000 s electrochemical cycles. Interlayer electrochromic displays constructed through a simple strategy can display tailored patterns during electrochemical process. The color contrast between neutral state and oxidized state is strong, which can be used for encrypted transmission of information. Furthermore, the CPI synthesized from HPMDA (PI-HPMDA) demonstrated remarkable electrofluorescence performance, with the fluorescence of the film being controlled by applying voltage. The solution of PI-HPMDA exhibited a fluorescence quantum efficiency of 32.5 %, and the fluorescence intensity of PI-HPMDA could be reduced in the presence of Fe3+. he responsiveness of PI-HPMDA to Fe3+ is expected for specific ion probes.

Self-assembly-dominated hierarchical porous nanofibrous membranes for efficient high-temperature air filtration and unidirectional water penetration

Increasingly-severe air pollution problem dominated by various air pollutants makes the development of air filtration materials a hotspot. A multi-functional air filter with high efficiency and high temperature resistance was produced using a co-electrospinning method combined with subsequent impregnation treatment. Herein, Cu-MOF was assembled onto polyimide (PI) nanofibers to construct a hierarchical porous structure. Diamine monomers containing amide bonds were copolymerized in the PI skeleton to activate the surface sluggishness of PI. β-cyclodextrin (β-CD) was used as PI fiber inducer to achieve the self-assembly of Cu-MOF crystals via hydrogen bonding. On one hand, PI/CD-MOF nanofiber filter possesses an excellent PM0.3 filtration efficiency (99.85%) and a low pressure drop (136 Pa), which are attributed to high specific surface area of the nanofibrous filter. On the other hand, the filter demonstrates the optimal performance in terms of CO2 adsorption due to the outstanding open metal sites of Cu-MOF. In particular, Janus double-layer composite nanofibrous membrane, which consists of PI/CD-MOF and PI membranes, has unique unidirectional water permeability performance and long-term filtration stability. Base on the above studies, this preparation strategy could provide idea for the development of multifunctional air purifiers.

Flexible Backbone Effects on the Redox Properties of Perylenediimide-Based Polymers.

Organic electrode materials are appealing candidates for a wide range of applications, including heterogeneous electrocatalysis and electrochemical energy storage. However, a narrow understanding of the structure-property relationships in these materials hinders the full realization of their potential. Herein, we investigate a family of insoluble perylenediimide (PDI) polymers to interrogate how backbone flexibility affects their thermodynamic and kinetic redox properties. We verify that the polymers generally access the highest percentage of redox-active groups with K+ ions (vs Na+ and Li+) due to its small solvation shell/energy and favorable soft-soft interactions with reduced PDI species. Through cyclic voltammetry, we show that increasing the polymer flexibility does not minimize barriers to ion-insertion processes but rather increases the level of diffusion-limited processes. Further, we propose that the condensation of imides to iminoimides can truncate the imide polymer chain growth for certain diamine monomers, leading to greater polymer solubilization and reduced cycling stability. Together, our results provide insight into how polymer flexibility, ion-electrode interactions, and polymerization side reactions dictate the redox properties of PDI polymers, paving the way for the development of next-generation organic electrode materials.

A new dip-coating approach for plasticization-resistant polyimide hollow fiber membranes: In situ thermal imidization and cross-linking of polyamic acid

Polymeric hollow fiber membranes (HFMs) are in high demand for gas separation due to their superior processability and cost-effectiveness, despite exhibiting high vulnerability to plasticization. In this study, we present a new dip-coating technique for fabricating defect-free and plasticization-resistant polyimide HFMs on a cross-linked polyimide/polysilsesquioxane hollow fiber support. This is achieved through an in situ process involving thermal imidization and cross-linking of a polyamic acid (PAA) precursor solution. The use of a thermally stable cross-linked nanoporous hollow fiber support ensures the coating of various glassy PAA solutions prepared by different dianhydrides and diamine monomers without disturbing its internal pore structure. The resulting polyimide hollow fiber membranes enhanced CO2/CH4 separation performance compared to as-synthesized polyimide solution-coated counterpart. It is because in situ thermal imidization and cross-linking of PAA solutions induced the formation of more imine linkages, possibly generating larger free volume elements due to the disturbance of intersegmental chain packing while maintaining sufficient chain rigidity. Additionally, the membrane’s practical applicability was confirmed as the hollow fibers demonstrated resistance to plasticization when subjected to an equimolar CO2/CH4 mixed feed of approximately 50 bar. Our simple but versatile dip-coating approach allows for the formation of highly plasticization-resistant polyimide HFMs.

High flux nanofiltration membrane via surface modification using spirocyclic quaternary ammonium diamine for efficient antibiotics/salt separation

Efficiently separating antibiotics from monovalent salt is a practical challenge in the pharmaceutical industry. In this study, a novel spirocyclic quaternary ammonium diamine monomer (SBI) was synthesized and used as a surface modifier of polyamide (PA)-based nanofiltration membrane to enhance antibiotic separation. The SBI monomer was reacted with the residual acyl chloride groups and successfully grafted into the PA film. The rigid spirocyclic structure of SBI increased the molecular weight cut-off (MWCO) of the membrane from 348 Da to 382 Da, which loosened the selective layer and reduced the water transport resistance. The SBI-modified membrane had an excellent pure water permeance of 33.4 L·m−2·h−1·bar−1, 2.5 times as high as the pristine one. Moreover, the introduction of quaternary ammonium moieties partially neutralized the surface negative charge of the membrane, reducing the Donnan exclusion. The resulting modified membrane demonstrated high antibiotic rejection and low NaCl rejection. The erythromycin ERY/NaCl selectivity was 20.7 in 10 g·L−1 NaCl solution, and ERY was concentrated from 100 to 419 ppm in 7 h. This study indicates that the surface modification using the SBI monomer is a potential method to improve the antibiotics/salt separation.

Fluorinated polyimide with triphenyl pyridine structure for 5G communications: Low dielectric, highly hydrophobic, and highly transparent

With the rapid development of 5G communications, the traditional interlayer dielectric material polyimide (PI) requires modification due to its intrinsically high dielectric constant (Dk), high dielectric loss (Df), and high moisture absorption, which make it difficult to meet the needs of the high-frequency communications industry. In this paper, a new strategy for the preparation of novel PI with intrinsically low Dk and Df is proposed from the perspective of molecular structure design, the modification effect of superimposing bulky triphenyl pyridine structures and strong electronegativity groups, combined with long-chain anhydride to reduce the density of the imide structure. Therefore, three bulk diamine monomers (BPAB, PBAB3F, PBAB6F) containing triphenyl pyridine structures were designed in this paper and polymerized with 4,4′-(4,4′-isopropyldiphenoxy) phthalic anhydride (BPADA) to obtain three new PIs (PI-H, PI-CF3, PI-2CF3) with different fluorine contents, focusing on the relationship between structure and properties, especially the effect of fluorine content on dielectric properties. The results of the study show that the dielectric and hygroscopic properties of PI improve with increasing fluorine content. Among them, PI-2CF3 has the best overall performance, showing low dielectric (Dk = 2.72@10 GHz & Df = 0.00233@10 GHz), high transparency (Cut-off wavelength (λ0) = 389 nm, Maximum transmittance (Tvia) = 89%) and low hygroscopicity (Water absorption (Ma) = 0.246%, Contact angle (Ca) = 111°).

Investigations on thermomechanical and structure properties of pure and wet polyimine networks by molecular dynamics simulations

Polyimine polymer is a kind of covalent adaptable networks with excellent reprocessing and self-healing properties. It has attracted wide attentions in recent years because it can release stress by reversible bond exchange reactions without using catalysts. Since polyimines containing -NH- groups are strongly hydrophilic, the influence of water content on their thermomechanical and structure properties is significant. In this study, we establish atomic models involving diamine and dialdehyde monomers combined with triamine cross-linkers to investigate the thermomechanical and structure properties of polyimine networks. Furthermore, different amounts of water molecules are added into networks to explore the interaction between polyimines and water molecules in aqueous polyimine systems. It is concluded that the increase of cross-linking density and conversion degree will improve the thermomechanical properties of polyimines. The water molecules in the aqueous polyimine systems will reduce glass transition temperature and enhance plasticity. Moreover, the diffusion coefficient is found to positively correlate with water content and temperature. Further researches on the structure of polyimines shows that the radius of gyration of polyimines and the radial distribution function of water molecules around the polyimines are also sensitive to temperature and water content. This investigation provides comprehensive information on different factors affecting the thermomechanical properties of pure and wet polyimine networks and contributes toward predicting the evolution of properties of polyimines under different circumstances.

Low dielectric post-cured benzocyclobutene-functionalized fluorine-containing polyimide material

Low dielectric constant (Dk) polyimide polymer materials are one of most attractive materials for their importance in microelectronic industries, such as high speed communication field. Herein, a novel benzocyclobutene (BCB) and trifluoromethyl functionalized diamine monomer (BFDA) was synthesized and used to prepare a series of co-polyimides with different BCB content (PI-BFs). Both trifluoromethyl and BCB structure can facilitate to low down Dk and dissipation factor (Df). For the cured PI-BFs, dielectric property test showed that the dielectric constant decreased significantly with the increase of BCB content, and the dielectric constant of PI-BF40% could reach 2.72 at 1 MHz. Besides, BCB can also contribute to improve glass transition temperature and initial storage modulus of PI-BFs. The Tg of PI-BF40% was 360 °C, and the initial storage modulus reached 2.83 GPa. Meanwhile, TMA test indicates that the post-curing by BCB group contributes to enhance the thermo-size stability. Moreover, PI-BFs show excellent thermal stability (Td5 > 499 °C), good transparency and low water uptake.

Triarylamine-based polyamide containing adamantane group as Fe3+ probe and electrochromic smart devices

A new triarylamine-based polyamide was synthesized from 1,4-cyclohexanedicarboxylic acid and diamine monomer containing adamantane group (PA-CA), which exhibits high fluorescence quantum up to 46.1% and excellent electrochromic behaviors. The photoluminescence of PA-CA was quenched by coordination and internal filtration effect to realize Fe3+ response. Neutral colorless PA-CA film was converted to the oxidized blue in the electrochemical oxidation process and the maximum transmittance reached 80%, and the transmittance still exceeded 55% after 10,000 s. A Sandwich structure electrochromic device with PA-CA as the active layer was constructed with a simple strategy and different contents were displayed through patterned customization. Electrofluorochromic performance was regulated and decoding information was customized by applying voltage changes of the light and dark for PA-CA film. The applications of multifunctional integrated PA-CA responding to stimulus have broad prospects in the field of Fe3+ fluorescence sensors, photodetectors and multicolor electrochromic display devices.

Light‐absorbing copolymers of polyimides as efficient photothermal materials for solar water evaporation

AbstractPolyimide (PI), an important engineering polymer with a rigid chemical structure, readily has excellent chemical stability, heat resistance, and electrical insulation but lacks broadband photothermal properties. Herein, we design and synthesize PI copolymers that embrace intrinsic photothermal properties by using two diamine monomers of (Z)‐2,3‐bis(4‐aminophenyl) acrylonitrile (CNDA) and 4,4‐diphenyldiamine (NDA) with strong ultraviolet (UV), and near‐infrared (NIR) absorption capabilities, respectively. Tuning the molar ratio of the two diamines can modulate UV and NIR light absorption and regulate the intrinsic photothermal properties of PIs. After condensation with pyromellitic dianhydride, the resulting PI‐0.5 with a unit molar ratio of CNDA:NDA = 1 shows the best photothermal efficiency. PI‐0.5 is used to construct 3D steam generators with vertically dried channels by a freeze‐drying method. The 3D steam generators show a good water evaporation rate and continuously operate with excellent stability under varying salinity and pH conditions. The synthetic design herein suggests that PI can be molecularly engineered to be intrinsic photothermal materials, expanding the properties and applications of existing PIs.

A Transparent, Healable and Recyclable Alicyclic Poly(ether-b-amide) Multiblock Copolymer with Ultrahigh Toughness.

Self-healing polyamide multiblock copolymer with robust mechanical properties is highly desired. Here, an alicyclic diamine monomer, isophoronediamine (IPDA), with asymmetric structure and substantial steric hindrance was incorporated into the backbone of poly(ether-b-amide) multiblock copolymer. Based on the phase-lock effect, the mechanical properties and segmental mobility of copolymers can be modulated on a large scale via adjusting the molecular weight of hard segments. An extraordinary tensile strength of 32.0 MPa and an excellent elongation at break of 1881 % were simultaneously achieved, which leaded to a record-high toughness of 328.9 MJ m-3 for self-healable polyamide elastomers. The synergism between the dynamic H-bonding networks and the diffusion of polymer chains contributed to a balance between the mechanical performance and self-healing efficiency of copolymers. Due to the adjustable mechanical performance, rapid scratch self-healing ability and superior impact resistance, the resultant copolymers showed great potential in the fields of protective coatings and soft electronics.

Comprehensive treatment of aroma chemicals industrial effluent with substantial COD content by a novel PVP/polyamide composite hydrophilized RO membrane

A hydrophilized polyvinyl pyrrolidone/polyamide composite high rejection reverse osmosis (HPA-HR RO) membrane was used for the treatment of aroma chemicals containing effluent coming as multiple effect evaporators (MEE) condensate at UK Aromatics Pvt. Ltd., Boisar, Maharashtra. The unique membrane has an active composite layer of polyamide prepared by interfacial polymerization of high diamine (3%) and acid chloride (0.2%) monomer concentrations, which is further coated with polyvinyl pyrrolidone (PVP) to enhance hydrophilicity and chemical inertness. The plant provides removal of total dissolved solids (TDS) from 2500 to 3500 ppm in the feed to a value of 50–100 ppm in the permeate water indicating a rejection of more than 95% of the dissolved solids, with a high water recovery of 80% in permeate. Similarly, complete rejection of color was observed from dark brown to colorless (transparent), whereas the COD content was brought down from 3000 to 5000 mg/L in the MEE condensate to around 1000 mg/L indicating removal of 60 % to 80% depending upon the pressure applied to overcome the high osmotic pressure of the effluent. Physicochemical interactions between the PVP and polyamide skin layers of the composite membrane make the separating barrier durable and highly hydrophilic. Water would have greater sorption due to high affinity with the membrane and higher diffusion coefficient from its smaller size, while the less polar esters that constitute most of the COD would have low interaction and their larger molecular sizes make them less diffusive. The recovered permeate water has been reused in various internal industrial applications like cooling towers, cleaning, etc. at UK Aromatics.