Diamine Research Articles

One-pot aqueous-phase synthesis of polyimides from typical monomers

One-pot aqueous-phase synthesis of polyimides (PIs) offers great economic and environmental benefits and improves the hydrolytic stability of the precursor (polyamic acid) obviously. However, this method is only suitable for the polymerization of very limited dianhydride and diamine monomers up to now. In this study, the most commonly used dianhydrides and diamines for the preparation of commercially available PI products were selected for one-pot aqueous-phase synthesis of various polyamic acid salts (PAAS). The effects of the structure of monomers, the reaction temperature and the adding process of the organic base on the polymerization reaction were explored by rotational rheology, nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. The polymerization products obtained via the aqueous-phase route show high molecular weight when the reaction conditions have been optimized. Various PI films prepared by the thermal imidization of corresponding PAAS demonstrate good optical transparency, excellent thermal stability, and outstanding mechanical and electrical properties. This work proposes the reaction mechanism of PAAS via one-pot aqueous-phase route and utilizes this novel polymerization strategy to synthesize high-molecular-weight PIs from typical aromatic dianhydride and diamine monomers.

Coordinative Polyimides‐Ln3+ for Full‐Spectrum Luminescence with Applications in PLEDs and Acid‐Responsive Data Encryption

AbstractControllable coordination and efficient sensitization of rare earth ions in polymer materials are key to achieving high‐performance optoelectronic polymers. By designing aromatic diamines, polyimides are synthesized with 1,10‐phenanthroline benzimidazole groups (PBG) in the polymer backbone. Utilizing the coordination between PBG and rare earth ions (Eu3⁺, Tb3⁺), polyimide‐rare earth complexes are formed and precisely characterized their structures. The unique coordination allows PBG to effectively sensitize Eu3⁺, resulting in efficient, long‐lived red emission. Furthermore, PBG maintains excellent coordination with Eu3⁺ in acidic environments, granting acid‐responsive color changes for data encryption. Importantly, PBG sensitization of Tb3⁺ enabled full‐spectrum emission (CIE coordinates: (0.31, 0.35)) within a single rare earth‐polyimide complex, due to electron transfer among the ions, ligands, and polymer. This leads to the design of a multi‐layer PLED device with an optimal external quantum efficiency of 0.43% for white light emission (CIE coordinates: (0.28, 0.34)). Through comparative theoretical and experimental analysis, the photophysical behavior of these coordinated polyimides is explained and explored their photoluminescent and electroluminescent properties. This research integrates the advantages of rare earth elements and polyimides, creating novel luminescent polymers with diverse optical applications, providing a new strategy for designing luminescent coordination polymers.

Three-Component Synthesis of 1-Substituted 5-Aminotetrazoles Promoted by Bismuth Nitrate.

A nontoxic bismuth-promoted multicomponent synthesis of 5-aminotetrazoles and bistetrazoles is reported. The reaction of phenyl isothiocyanate, NaN3, and amine (primary aliphatic, aromatic, and aliphatic diamine) promoted by Bi(NO3)3·5H2O under microwave heating affords good yields, short reaction times, simple workup, and purification without column chromatography. A set of diagnostic 1H NMR signals was identified as a guide for quickly elucidating the exclusive (or main) regioisomer formed, with the stronger electron donor group located at heterocyclic nitrogen 1. This regioselectivity is strongly dependent on the electronic density of the amine. It is opposite to that obtained by several thiourea desulfurization methods promoted by thiophilic metals and metal-free protocols.

Flammability of Novolac epoxy cured with aromatic diamines

The modification of Novolac epoxy with the organophosphorus compound 9,10-dihydro-9-oxa-10-phosphaphenanthren-10-oxide (DOPO) to reduce flammability and its influence on curing reactions has been investigated. Three aromatic diamine curing agents were used, namely 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulphone (DDS), and diethyltoluenediamine (DETDA). The thermal stability and dynamic-mechanical behaviour of the cured resin depend on interactions of the curing agent with DOPO. The onset degradation temperature decreased with increasing phosphorus content, indicating the influence of DOPO on thermal stability. The DDM 3 %P sample exhibited the highest glass transition (Tg) of 136 °C, while DDS-crosslinked simples displayed the highest Tg of 147 °C among all samples. An improvement in the reaction of Novolac epoxy to fire was achieved by incorporating DOPO compound, as indicated by cone calorimetry results, showing up to a 67 % reduction in the peak heat release rate (pHRR) and 53 % reduction in total heat release (THR) for DDM 3 %P. The modified samples containing DOPO presented a self-extinguishing performance, displaying a UL-94 V-0 rating and a limiting oxygen index (LOI) values reached a maximum of 37.1 % for DDM 3 %P, with less flame propagation than for neat Novolac epoxy.

Design and Evaluation of a Reprocessable Bismaleimide Thermoset: Enhancing Functionality and Sustainability Compatibility.

Bismaleimide (BMI) resins are high-performance thermosets that are primarily used in aerospace because of their exceptional heat resistance and physical properties. However, their growing demand has led to significant environmentally unfriendly waste. To address this, our research proposes a reprocessable BMI system using a newly synthesized BMI vitrimer (BMIV) with functional groups that form covalent adaptable networks (CANs). To enhance the properties, a symmetrical BMI with two ester groups introduced into the rigid rod molecule was designed as a CAN component. After confirming the structure using various spectroscopic techniques, BMIV was coupled with aromatic diamines via an additional aza-Michael reaction to obtain the cured resins. Subsequently, the mechanical properties and reprocessing behavior of the thermally stable and optimized thermosetting material with the best performance were evaluated, and the evidence, mechanism, and activation energy of the topology rearrangement are reported in detail.

Bio-based liquid crystal epoxy resins: Toughening and strengthening of conventional epoxy resins with strategically extended spacer layers

Liquid crystal epoxy resin, as an ideal toughening agent, combines the features of liquid crystal ordering and network cross-linking, which can effectively optimize the comprehensive performance of blended epoxy resins and achieve an ideal balance of rigidity and toughness. Here we successfully synthesized rigid and flexible bio-based liquid crystal epoxy resin (THBR-EP) by finely tuning the length of alkyl side chains. Using aromatic diamine as curing agent, a homogeneous network without phase separation was constructed by taking advantage of the different activity but good compatibility with ordinary epoxy resins, which significantly improved the toughness of the blended system. Specifically, only a small amount of THBR-EP(2.5 wt%) was required to exhibit a maximum impact strength of 48.8 kJ/m2. Moreover, the increase in system toughness was accompanied by a benign improvement in flexural strength, modulus and thermal stability. The ordered structure of the liquid crystals and their good compatibility with the resin matrix enhanced the ability to inhibit crack extension and energy dissipation. The feasibility to simultaneously achieve effective toughening and other property improvements of common resins broadens the application of resins under various demanding scenarios.

Carbonized Polymer Dots: Influence of the Carbon Nanoparticle Structure on Cell Biocompatibility.

Carbonized polymer dots (CPDs) were obtained by using microwave irradiation under the same conditions. However, different carbogenic precursors were used, such as aromatic diamine molecules, ortho-phenylenediamine (o-OPDA), and 3,4-diaminobenzoic acid (3,4-DABA). Both carbon nanoparticles showed different structural results based on Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and atomic force microscopy analyses. However, there are similar spectroscopic (UV-visible and fluorescence emission) profiles. The photophysical results, like quantum yield (QY) and fluorescence lifetime, were not identical; CPDs-OPDA has a higher QY and fluorescence lifetime than CPDs-3,4-DABA. CPDs-3,4-DABA presents a more hydrophobic character than CPDs-OPDA and has a more negative superficial charge. Cell viability studies in both standard and tumor lines demonstrated higher cytotoxicity from CPDs-OPDA than that from CPDs-3,4-DABA. The oxidative stress identified in cells treated with CPDs-OPDA was based on reactive oxygen species and associated with nitric oxide production. CPDs-3,4-DABA showed more DPHH inhibition than CPDs-OPDA, indicating the antioxidant activity of CPDs.

An investigation of the enzymatic oligomerization of nitro-substituted phenylene diamine: Thermal and fluorescence properties

2-nitro-p-phenylenediamine, an aromatic diamine, was studied for its oxidative oligomerization with H2O2 using enzyme-catalyzed oligomer synthesis. Characterization of molecular structures was performed utilizing ultraviolet-visible (UV-Vis) spectrophotometer, Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) techniques, identifying phenazine-bridged oligomer resulting from the enzymatic oligomerization process. Based on the results of gel permeation chromatography (GPC) analysis, the synthesized compound was identified as being in an oligomeric form. Conversely, the number of repeating units, as determined by Mw, was found to be 28. The solvent effect on the optical features of the synthesized oligomer in polar solvents was analyzed. The degradation of phenazine-type structures in the oligomer occurred at higher temperatures than that of the monomer. Under visible light excitation, the oligomer exhibited green light emission with a quantum yield (QY) of 6.2% in N,N-dimethylformamide (DMF). 2-nitro-p-phenylenediamine was readily oxidized into an oligomer with ortho-coupled constitutional units, having a lower electrochemical band gap than the monomer, via the enzymatic oligomerization route. Scanning electron microscopy revealed that enzyme-catalyzed oxidation of monomers exhibited a spongy morphology with some pores

Building High-Density Polar Hybrid Perovskites via Intercalation of Cs+ and Aromatic Diamine for Passive X-ray Detection.

2D organic-inorganic hybrid perovskites (OIHPs) have shown great promise in direct X-ray detection. The development of high-performance passive X-ray detectors in 2D OIHPs calls for an increase in material density while maintaining structural polarity, which is becoming quite challenging. Here, a high-density, polar 2D alternating-cation-intercalated (ACI) perovskite, (4-AP)Cs2Pb2I8 (B, 4-AP = 4-amidinopyridinium), capable of addressing this problem is successfully constructed by introducing heavy Cs+ into the interlayer space of an aromatic Dion-Jacobson (DJ) perovskite (4-AP)PbI4 (A). Through such a DJ-to-ACI design, the newly developed 2D OIHP B not only significantly increases its density to 4.23 g cm-3 (even higher than that of 3D MAPbI3) but also crystallizes in a polar space group (Ama2), which further leads to enhanced X-ray attenuation and an obvious polar photovoltage (1.1 V) under X-ray irradiation. As a result, X-ray detectors fabricated by high-quality single crystals of B exhibit excellent and stable detection performance under self-powered mode with a high sensitivity of 107 μC Gy-1 cm-2 and a low detection limit of 289 nGy s-1. This work provides implications for the future exploration and regulation of novel ACI OIHPs for high-performance photoelectronic devices.

Synthesis of Polyimide-PEO Copolymers: Toward thermally stable solid polymer electrolytes for Lithium-Metal batteries

The rapid pace of technological advancement in field of electric vehicles and need in sustainable energy sources calls for new, high-performance energy storage technologies. Lithium metal batteries (LMBs) based on solid polymer electrolyte represent a promising battery technology to increase energy density of conventional batteries while enhancing safety, eliminating dendrite formation, and providing mechanical flexibility. In this study, we developed novel polyimide-poly(ethylene oxide) (PI-PEO) copolymers and employed them as solid polymer electrolytes for LMBs. Copolymers with 5, 15, and 30 mol% of PEO-containing diamine were synthesized by reacting with aromatic dianhydride and diamine, using a facile and eco-friendly method in a benzoic acid melt. Chemical structures were confirmed using NMR and IR spectroscopy. Glass transition temperatures varied from 24 °C to 195 °C, increasing with a decrease in the PEO/PI moiety ratio. All copolymers demonstrated good thermal stability up to T5% > 345 °C with a two-step degradation and favorable mechanical properties below the glass transition temperature, as observed by DMA measurements. Solid polymer electrolytes with 70 wt% of LiTFSI exhibited an ionic conductivity of 1.4 × 10−4 S cm−1 at 70 °C, with a transference number of 0.7. The polymer electrolyte exhibited non-flammable properties and the potential for utilization in lithium metal batteries, indicating the promising application of these new polymers for high-safety battery systems.

Investigating Cross-Linking Parameters and Molecular Arrangement in Liquid Crystalline Epoxy Monomer with Aromatic Diamine: DSC-TOPEM® and WAXS Analysis.

This study presents the characterization of cross-linking parameters of a liquid crystalline epoxy monomer with an aromatic diamine as a curing agent. The mixture tested consisted of bis [4-(10,11-epoxyundecanoyloxy)benzoate] p-phenylene (LCEM) and 1,3-phenylenediamine (1,3-PDA). This paper focuses on the structural characterization of such systems using X-ray analysis. To investigate this, a comprehensive analysis was conducted using Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray Scattering (WAXS). Through DSC analysis, the curing behavior and transition temperature of the liquid crystal epoxy system were established. To fully characterize the cross-linking of the system, a novel technique called DSC-TOPEM® was employed. The use of this technique enabled real-time monitoring of the curing process and provided precise information on the cross-linking energy, which resulted in the finding that the mixture was cross-linking faster than expected. WAXS analysis was performed to assess the structural changes formed during the cross-linking. The results of this analysis confirm that lower cross-linking temperatures of the mixture cause better ordering of mesogens than higher ones.

Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures

Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures

Synthesis, electro‐optic properties, and performance of novel fluorinated polyurethaneimide

AbstractUrethane imide anhydride oligomers with terminal groups as anhydride groups were designed and synthesized using second‐order nonlinear optical chromophore molecule, bisphenol AF‐type diethylidene dianhydride, and toluene diisocyanate as monomers. Polyurethaneimide (PUI) second‐order nonlinear optical polymers with the structure of imide and amino ester chain segments were then synthesized by the polycondensation reaction between urethane imide anhydride oligomers and aromatic diamine monomers. The glass transition temperature (Tg) of PUI reached 186°C, and the 5% heat‐loss decomposition temperature was 320°C. The corona‐polarized PUI had an electro‐optic (EO) coefficient (γ33) of 82 pm/V tested by the reflection method. The loss of light transmission of the polymer waveguide prepared with PUI as electro‐optical material was 1.13 dB/cm at 1550 nm. Mach–Zehnder type polymer waveguide electro‐optical modulators have been prepared based on the properties of the electro‐optic material PUI. The fabricated polymer EO modulators had favorable electro‐optic modulation response performance for low‐frequency electrical signals. The good modulation characteristics of the manufactured electro‐optical modulators proved that the synthesized PUI was a waveguide polymer material with good comprehensive performance.Highlights Electro‐optic fluorinated polyurethaneimide was synthesized. Polyurethaneimide as core material, polymer waveguide EO modulators were fabricated. The prepared modulators had good electro‐optic modulation performance.

Functionalization of Carbon Nanofibers with an Aromatic Diamine: Toward a Simple Electrochemical-Based Sensing Platform for the Selective Sensing of Glucose.

Despite a variety of glucose sensors being available today, the development of nonenzymatic devices for the determination of this biologically relevant analyte is still of particular interest in several applicative sectors. Here, we report the development of an impedimetric, enzyme-free electrochemical glucose sensor based on carbon nanofibers (CNFs) functionalized with an aromatic diamine via a simple wet chemistry functionalization. The electrochemical performance of the chemically modified carbon-based screen-printed electrodes (SPCEs) was evaluated by electrical impedance spectroscopy (EIS), demonstrating a high selectivity of the sensor for glucose with respect to other sugars, such as fructose and sucrose. The sensing parameters to obtain a reliable calibration curve and the selective glucose sensing mechanism are discussed here, highlighting the performance of this novel electrochemical sensor for the selective sensing of this important analyte. Two linear trends were noted, one at low concentrations (0-1200 μM) and the other from 1200 to 5000 μM. The limit of detection (LOD), calculated as the (standard error/slope)*3.3, was 18.64 μM. The results of this study highlight the performance of the developed novel electrochemical sensor for the selective sensing of glucose.

Reactivity, processability, and thermal stability of tetrafunctional glycidyl ether cyclic siloxane epoxy hybrid networks

AbstractA low viscosity tetra‐functional cyclosiloxane epoxy resins (TGTS) is synthesized via a one‐step hydrosilylation reaction and cured separately with four different aromatic diamines to explore the reaction kinetics, network development, and thermal resistance. The hardeners used are 1,3‐phenylenediamine (PDA), diethyl toluene diamine (DETDA), 4,4‐diaminodiphenylmethane (DDM), and 1,3‐bis(4‐aminophenoxy) benzene, because of their availability and aromaticity. During cure with TGTS they all display autocatalytic behavior, but when compared to a traditional organic epoxy resin, diglycidyl ether of bisphenol A (DGEBA) cured with DDM however, the rate constants are about 3 times slower and less exothermic. The DETDA hardener in particular exhibits significantly slower rates of cure when compared to the other amines, being about an order of magnitude slower compared to the PDA curative. This is attributed to higher steric hindrance, compounded by reduced miscibility. The TGTS‐DDM carbon fiber composite displays the most thermal resistance after extended exposure to 220°C, producing the least mass loss and after combustion of about 12% compared to 20% for the DGEBA cured with DDM. The results presented here, illustrate that a tetrafunctional cyclic siloxane epoxy resin, can exhibit excellent processability, evidenced by very low viscosities and long gelation times, whilst also displaying excellent thermal resistance, whether at elevated temperature, or during combustion.

Study on the curing characteristics and properties of phthalonitrile resin cured with organic guanidine

Bisphenol A-based phthalonitrile resin was synthesized by nucleophilic substitution reaction from bisphenol A and 4-nitrophthalonitrile, and then the obtained resin was cured with sulfaguanidine as a novel curing agent. The curing characteristics, kinetics, thermal stability and dynamic mechanical property were studied by standard thermal analysis techniques including DSC, TGA, and DMA. The peak temperature of exothermic peak ( Tp) and apparent activation energy ( Ea) of sulfaguanidine cured phthalonitrile resin were 263.20°C and 76.6 kJ·mol−1 respectively, much lower than those of traditional aromatic diamine cured resin. Moreover, the resin cured by sulfaguanidine showed excellent thermomechanical properties and thermal stability. The glass transition temperature ( Tg) was 284.8°C, the initial thermal decomposition temperature ( Td,5%) was 439.6°C, and the char yield at 800°C was 62.1% in nitrogen atmosphere. To sum up, organic guanidine cured phthalonitrile resin exhibits excellent curing characteristics (low Tp and Ea) and high thermal properties, which provides a promising approach to preparing phthalonitrile resin with high comprehensive performance.

Urea-formaldehyde resin room temperature phosphorescent material with ultra-long afterglow and adjustable phosphorescence performance

Organic room-temperature phosphorescence materials have attracted extensive attention, but their development is limited by the stability and processibility. Herein, based on the on-line derivatization strategy, we report the urea-formaldehyde room-temperature phosphorescence materials which are constructed by polycondensation of aromatic diamines with urea and formaldehyde. Excitingly, urea-formaldehyde room-temperature phosphorescence materials achieve phosphor lifetime up to 3326 ms. There may be two ways to enhance phosphorescence performance, one is that the polycondensation of aromatic diamine with urea and formaldehyde promotes spin-orbit coupling, and another is that the imidazole derivatives derived from the condensation of aromatic o-diamine with formaldehyde maintains low levels of energy level difference and spin-orbit coupling, thus achieving ultra-long afterglow. Surprisingly, urea-formaldehyde room-temperature phosphorescence materials exhibit tunable phosphorescence emission in electrostatic field. Accordingly, 1,4-phenylenediamine, urea, and formaldehyde are copolymerized and self-assembled into phosphorescence microspheres with different electrostatic potential strengths. By mixing 1 wt% 1,4-phenylenediamine polycondensation microspheres with 1,4-phenylenediamine free microspheres, phosphor lifetime of the composite could be regulated from 27 ms to 123 ms. Moreover, vulcanization process enables precise shaping of urea-formaldehyde room-temperature phosphorescence materials. This work not only demonstrates that urea-formaldehyde room-temperature phosphorescence materials are promising candidates for organic phosphors, but also exhibits the phenomenon of electrostatically regulated phosphorescence.

Multicomponent Polymerizations of Elemental Sulfur, CH2Cl2, and Aromatic Amines toward Chemically Recyclable Functional Aromatic Polythioureas.

The exploration of new polymer materials required the development of efficient, economic, robust, and scalable synthetic routes, taking energy consumption, environmental benefit, and sustainability into overall consideration. Herein, through retro-polymerization analysis of functional aromatic polythioureas, a multicomponent reaction of elemental sulfur, CH2Cl2, and aromatic amines was designed with the assistance of fluoride, and efficient, economic, and robust multicomponent polymerizations (MCPs) of these three abundantly available cheap monomers, elemental sulfur, CH2Cl2, and aromatic diamines, were developed to realize scalable conversion directly from sulfur to a series of functional aromatic polythioureas with high molecular weights (Mn up to 50,800 g/mol) in excellent yields (up to 98%). The synergistic cooperation of the strong and selective coordination of thiourea with gold ions and the redox property of aromatic polythiourea enable in situ reduction of Au3+ to elemental gold under a normal bench condition. Furthermore, the functional aromatic polythiourea could be chemically recycled through aminolysis with NH3·H2O to afford a diamine monomer in 83% isolated yield. The development of elemental sulfur-based MCP has brought the opportunity to access cost-effective and sustainable sulfur-containing functional polymer materials, which is anticipated to provide a solution for the utilization of sulfur waste and making profitable polymer materials.

Reactions of Diaminonaphthalenes with a Cage‐Opened C60 Derivative

AbstractThe reactions of cage‐opened C60 derivatives with aromatic diamines are known to cause an orifice‐enlargement in association with incorporating extended π‐systems. The present work focuses on 1,2‐, 2,3‐, and 1,8‐diaminonaphthalenes for the synthesis of a series of naphthalene‐fused fullerene derivatives. For the former two, orifice enlargement proceeded by cleaving two C=C bonds to afford an opening with a ring‐atom count of 20, in which the naphthalene moiety was fused by a pyrazine ring. For the reaction with 1,8‐diaminonaphthalene, only one C=C bond was cleaved to give a 17‐membered‐ring opening where the diaminonaphthalene moiety was fused by a pyrimidine ring.

Hybrid Siloxane Materials Based on a Mutually Reactive Epoxy–Amine System: Synthesis, Structure, and Thermal Stability Investigations

Hybrid siloxane materials based on a mutually reactive epoxy–amine system are organic-inorganic hybrid materials synthesized via the sol–gel reaction of siloxane precursors, followed by the polymerization of organo-functionalized oligosiloxanes. Therefore, using a new hybrid system as the reaction product resulting from the reaction between 1,3-bis(3-glycidoxypropyl)-l, 1,3,3-tetramethyldisiloxane—C16H34O5Si2—(gp-DS) and p-phenylenediamine—C6H4(NH2)2—(PPD), an aromatic diamine, was obtained. The chemical structure of the synthesized hybrid siloxane material was confirmed via Fourier Transform Infra-Red (FTIR) spectroscopy, mass spectrometry (MS), and 1H-NMR spectroscopy. The morphology and surface chemical composition was highlighted via scanning electron microscopy (SEM) equipped with an EDX elemental analysis system. Further, the thermal stabilities of the prepared hybrid siloxane and its precursors have been investigated via thermogravimetric analysis (TGA), proving the modification of epoxy-functional disiloxanes with a paraphenylenediamine reagent that made it possible to produce hybrid siloxane materials with very good thermal stabilities and dual weak hydrophilic/hydrophobic surfaces.