Diamine Research Articles

Synchronous Proton-Hydride Transfer by a Pyrazole-Functionalized Protic Mn(I) Complex in Catalytic Alcohol Dehydrogenative Coupling.

A series of Mn(I) complexes Mn(L1)(CO)3Br, Mn(L2)(CO)3Br, Mn(L1)(CO)3(OAc) and Mn(L3)(CO)3Br [L1 = 2-(5-tert-butyl-1H-pyrazol-3-yl)-1,8-naphthyridine, L2 = 2-(5-tert-butyl-1H-pyrazol-3-yl)pyridine, L3 = 2-(5-tert-butyl-1-methyl-1H-pyrazol-3-yl)-1,8-naphthyridine] were synthesized and fully characterized. The acid-base equilibrium between the pyrazole and the pyrazolato forms of Mn(L1)(CO)3Br was studied by 1H NMR and UV-vis spectra. These complexes are screened as catalysts for acceptorless dehydrogenative coupling (ADC) of primary alcohols and aromatic diamines for the synthesis of benzimidazole and quinoline derivatives with the release of H2 and H2O as byproducts. The protic complex Mn(L1)(CO)3Br shows the highest catalytic activity for the synthesis of 2-substituted benzimidazole derivatives with broad substrate scope, whereas a related complex [Mn(L3)(CO)3Br], which is devoid of the proton responsive β-NH unit, shows significantly reduced catalytic efficiency validating the crucial role of the β-NH functionality for the alcohol dehydrogenation reactions. Control experiments, kinetic and deuterated studies, and density functional theory (DFT) calculations reveal a synchronous hydride-proton transfer by the metal-ligand construct in the alcohol dehydrogenation step.

Metal-Free Photocatalyst with Redox Center and Lewis Acid Site for Selective Synthesis of Mono- and Disubstituted Benzimidazoles via Alcohol and Aromatic Diamine Cross-Dehydrocoupling

Metal-Free Photocatalyst with Redox Center and Lewis Acid Site for Selective Synthesis of Mono- and Disubstituted Benzimidazoles via Alcohol and Aromatic Diamine Cross-Dehydrocoupling

Reprocessing and shape recovery of polybenzoxazine-polydimethylsiloxane networks enabled with incorporation of dynamic diselenide bonds

In this contribution, we reported the synthesis of linear polybenzoxazine-polydimethylsiloxane (PBZ-PDMS) multiblock copolymers with diselenide bonds (Se–Se) in the main chains. First, bis(4-aminophenyl)diselenide (BAPDS) was synthesized via the reaction of p-bromoaniline with selenium, which was catalyzed with copper (II) oxide nanoparticles. The aromatic diamine bearing a diselenide bond was used for Mannich polycondensation with 4,4′-dihydroxyldiphenylisopropane and para-formaldehyde to obtain the linear PBZ. To synthesize the multiblock copolymer, α,ω-diaminopropyl-terminated polydimethylsiloxane (denoted NH2-PDMS-NH2) was used as a macromolecular diamine and added to perform the Mannich copolycondensation. It was found that the PBZ-PDMS multiblock copolymers readily underwent the self-curing (or crosslinking) at elevated temperature. Compared to linear PBZ only bearing static covalent bonds, the introduction of diselenide bonds significantly decreased the activation energy (Ea) of curing reaction. For the curing of the PBZ-PDMS multiblock copolymers, the Ea's increased with raising the contents of PDMS. The morphological investigation showed that the PBZ-PDMS networks were microphase-separated. Depending on the contents of PDMS, the PBZ-PDMS networks displayed the thermomechanical properties from glassy to rubbery polymers. The introduction of PDMS component endowed the networks with enhanced surface hydrophobicity compared to the control PBZ network. More importantly, the PBZ-PDMS networks are reprocessable. The exchange of the dynamic covalent bonds (viz. diselenide bonds) is responsible for the reprocessing behavior. In addition, the PBZ-PDMS networks displayed shape memory properties, which can be modulated with the contents of PDMS. Furthermore, the original shapes were re-configurable by taking advantage of the metathesis of dynamic diselenide bonds.

Structure and Properties of Urethane-Containing Elastomers Based on Adipic Acid Polyester and Ethylene Glycol, Isophorone Disocyanate, and Aromatic Diamine

Structure and Properties of Urethane-Containing Elastomers Based on Adipic Acid Polyester and Ethylene Glycol, Isophorone Disocyanate, and Aromatic Diamine

Synthesis and Characterization of Organo-Soluble Polyimides Based on Polycondensation Chemistry of Fluorene-Containing Dianhydride and Amide-Bridged Diamines with Good Optical Transparency and Glass Transition Temperatures over 400 °C.

Polymeric optical films with light colors, good optical transparency and high thermal resistance have gained increasing attention in advanced optoelectronic areas in recent years. However, it is somewhat inter-conflicting for achieving the good optical properties to the conventional thermal resistant polymers, such as the standard aromatic polyimide (PI) films, which are well known for the excellent combined properties and also the deep colors. In this work, a series of wholly aromatic PI films were prepared via the polycondensation chemistry of one fluorene-containing dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (FDAn) and several aromatic diamines with amide linkages in the main chain, including 9,9-bis [4-(4-aminobenzamide)phenyl]fluorene (FDAADA), 2,2'-bis(trifluoromethyl)-4,4'-bis[4-(4-aminobenzamide)] biphenyl (ABTFMB), and 2,2'-bis(trifluoromethyl)-4,4'-bis[4-(4-amino-3-methyl)benzamide] biphenyl (MABTFMB). The derived FLPI-1 (FDAn-FDAADA), FLPI-2 (FDAn-ABTFMB) and FLPI-3 (FDAn-MABTFMB) resins showed good solubility in the polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO). The solution-processing FDAn-PI films exhibited good optical transmittance over 80.0% at a wavelength of 500 nm (T500), yellow indices (b*) in the range of 1.01-5.20, and haze values lower than 1.0%. In addition, the FDAn-PI films showed low optical retardance with optical retardation (Rth) values in the range of 31.7-390.6 nm. At the same time, the FDAn-PI films exhibited extremely high glass transition temperatures (Tg) over 420 °C according to dynamic mechanical analysis (DMA) tests. The FDAn-PI films showed good dimensional stability at elevated temperatures with linear coefficients of thermal expansion (CTE) in the range of (31.8-45.8) × 10-6/K.

Efficient Synthesis of Benzimidazole and Quinoline Derivatives Catalyzed by Functionalized Amidato Ruthenium Complexes in Water via Acceptorless Dehydrogenative Coupling Strategy

AbstractTransition‐metal‐catalyzed acceptorless dehydrogenative coupling (ADC) has emerged as a sustainable synthetic strategy for the construction of N‐heteroaromatics. Herein, a series of water‐soluble amidato Ru catalysts were designed, synthesized, and utilized in the selective synthesis of 2‐substituted benzimidazoles from the aromatic diamines and primary alcohols, as well as 2‐substituted quinolines from the substituted 2‐aminobenzyl alcohols and acetophenones via the ADC strategy in water. Catalyst 1 d bearing a strong electron‐donating hydroxyl group on the ligand exhibited the best catalytic activity. The catalytic system demonstrated remarkable efficiency and versatility, allowing for the application of over 40 substrates in two ADC reactions with good to high yields. Based on control experiments and density functional theory (DFT) calculations, a plausible mechanism was proposed, highlighting the significant role of functionalized amidato Ru complexes in catalyzing alcohol dehydrogenation via an outer‐sphere pathway.

Rapid and selective removal of aromatic diamines from the polyurethane bio-hydrolysate by β-cyclodextrin appended hyper-cross-linked porous polymers

During the degradation and recycling process of polyurethane (PU) through biotechnology, it is essential to remove toxic and hazardous aromatic diamines (4,4′-methylene dianiline (MDA), 2,4-toluene diamine (TDA)) selectively and rapidly before the biorefinery of residues in the PU hydrolysate. In this study, β-cyclodextrin (β-CD) appended hyper-cross-linked polymers (HCPs) with high porosity were constructed via the Friedel-Crafts alkylation reaction. In particular, with partial hydroxyl groups on β-CD units, the hydrophilicity of HCP-BCDOH was drastically improved, contributing to fast adsorption equilibrium for TDA (1 min) and MDA (15 min). Besides, the isothermal experiments demonstrate high maximum theoretical adsorption capacities of HCP-BCDOH upon MDA (2.27 mmol·g−1) and TDA (1.53 mmol·g−1). Moreover, spectral analysis and thermodynamic experiments revealed the adsorption mechanism of aromatic diamines by HCP-BCDOH, which is mainly controlled by weak interactions, involving “host–guest” interaction, hydrophobic interaction, and π-π stacking. These interactions endow HCP-BCDOH with high selectivity and removal efficiencies towards MDA and TDA. Owing to the exceptional adsorption properties and high reusability of HCP-BCDOH, it may offer a promising and efficient adsorbent for the removal of aromatic amines from the PU bio-hydrolysate.

Autocatalytic one-step high-temperature synthesis of carboxylated polyimides for in-situ high performance applications

Carboxylated polyimides (CxPIs) represent a great potential for gas separation membranes, highly thermostable coatings and fibers, ion-conducting materials, aerogels, (nano)composites, etc. However a prolonged and expensive two-stage method proceeding through the formation of an unstable poly(amic acid) and subsequent thermal or chemical imidization is traditionally used for the synthesis of CxPIs. Herein a new strategy consisting in one-step high-temperature synthesis of CxPIs based on 3,5-diaminobenzoic acid (DABA), the carboxyl groups of which provide an autocatalytic effect, in N-methyl-2-pyrrolidone (NMP) is presented. The effect of DABA content on the formation and properties of CxPIs is studied. It is established that high-molecular-weight CxPIs (Mw = 158–356 kDa) with five- and more stable six-membered imide rings from various dianhydrides of aromatic tetracarboxylic acids and diamines as comonomers are synthesized within 1–4 h of the reaction even with 25 mol% of DABA content. Additional catalyst-free synthesis of CxPIs in NMP allows to use the solutions obtained in situ for the production of various materials. In particular, CxPI-varnishes form the primary protective coating of the optical fiber superior to the commercial analogue in terms of its manufacturing technology, thermal and hydrolytic stability, which provides more reliable and long-term operation.

Preparation and Characterization of Light-Colored Polyimide Nanocomposite Films Derived from a Fluoro-Containing Semi-Alicyclic Polyimide Matrix and Colloidal Silica with Enhanced High-Temperature Dimensionally Stability.

Light-colored and transparent polyimide (PI) films with good high-temperature dimensional stability are highly desired for advanced optoelectronic applications. However, in practice, the simultaneous achievement of good optical and thermal properties in one PI film is usually difficult due to the inter-conflicting molecular design of the polymers. In the present work, a series of PI-SiO2 nanocomposite films (ABTFCPI) were developed based on the PI matrix derived from hydrogenated pyromellitic anhydride (HPMDA) and an aromatic diamine containing benzanilide and trifluoromethyl substituents in the structure, 2,2'-bis(trifluoromethyl)-4,4'-bis [4-(4-aminobenzamide)]biphenyl (ABTFMB). The inorganic SiO2 fillers were incorporated into the nanocomposite films in the form of colloidal nanoparticles dispersed in the good solvent of N,N-dimethylacetamide (DMAc) for the PI matrix. The derived ABTFCPI nanocomposite films showed good film-forming ability, flexible and tough nature, good optical transparency, and good thermal properties with loading amounts of SiO2 up to 30 wt% in the system. The ABTFCPI-30 film with a SiO2 content of 30 wt% in the film showed an optical transmittance of 79.6% at the wavelength of 400 nm (T400) with a thickness of 25 μm, yellow index (b*) of 2.15, and 5% weight loss temperatures (T5%) of 491 °C, which are all comparable to those the pristine ABTFCPI-0 matrix without filler (T400 = 81.8%; b* = 1.77; T5% = 492 °C). Meanwhile, the ABTFCPI-30 film exhibited obviously enhanced high-temperature dimensional stability with linear coefficients of thermal expansion (CTE) of 25.4 × 10-6/K in the temperature range of 50 to 250 °C, which is much lower than that of the AMTFCPI-0 film (CTE = 32.7 × 10-6/K).

In-situ formed aryl acid-triggered intramolecular dehydrative cyclization whilst supported Pd-catalyzed carbonylative synthesis of 2-aryl benzimidazoles

Herein, polystyrene supported palladium (Pd@PS) nanoparticles (NPs) catalyzed carbonylative synthesis of 2-aryl benzimidazoles from aryl iodides and aromatic diamines has been introduced. In-situ formed aryl carboxylic acid was revealed as a catalyst for dehydrative cyclization of secondary (2°) and tertiary (3°) amides formed via aminocarbonylation between aryl iodides and aromatic diamines. Herein, oxalic acid acts as carbon monoxide (CO) and carbon dioxide (CO2) gases source plausibly leading to aminocarbonylation via CO gas as major pathway and carboxylation of aryl iodides via CO2 as minor pathway. The Pd@PS catalyst was found to be easily separable, air/moisture stable and recyclable under the targeted reaction conditions. In addition, the present protocol requires only catalytic amount of inorganic base (K2CO3) to achieve the highest yields of desired products.

Synthesis and Characterization of Electro-Optic Polyurethaneimide-Polyimide Copolymers

Polyurethaneimide prepolymer was synthesized using the synthesized chromophore C containing tricyanofuran, hexafluorodianhydride and phenyl diisocyanate as monomers. Polyimide prepolymers were synthesized using fluorinated aromatic diether dianhydride and fluorinated aromatic diamine as monomers. Polyurethaneimide-polyimide (PUI-FPI) copolymers were then synthesized by a polycondensation reaction of the polyimide and polyurethaneimide prepolymers. The electro-optic (EO) PUI-FPI copolymers had a special segment structure and concentrate the advantages of polyurethaneimide and polyimide. The copolymers exhibited good film-forming properties, high glass transition temperature (Tg =196 °C), and high thermal stability (Td up to 358 °C). The copolymers possessed a high EO coefficient (γ33 =72 pm/V) at the 1550 nm wavelength, good long-term electro-poled orientation stability, and low optical propagation loss (1.2–1.4 dB/cm) at 1550 nm. Mach-Zehnder interferometric electro-optic modulators were designed and fabricated using the synthesized copolymer as the waveguide material. The prepared polymer optical waveguide EO modulators showed a good low-frequency electro-optic modulation response. The results showed that the synthesized polyurethaneimide-polyimide copolymers meeted the performance requirements for the preparation of polymeric optical waveguide devices and were suitable as polymeric electro-optic waveguide materials.

Synthesis of highly thermoplastic polyamide-imides with high transparency and low coefficient of thermal expansion

With the applications of injection molding optical components, higher requirements are put forward for thermoplastic polyimides (TPIs) in terms of transparency and coefficient of thermal expansion (CTE). Two series of thermoplastic polyamide-imides (PAIs) derived from 2,2'-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(1,3-dioxoisoindoline-5-carbonyl chloride) (CT-TFDB) and rigid/flexible aromatic diamines with specific groups were prepared at room temperature, which both exhibited moderate glass transition temperatures (Tgs) in the range of 251–274 °C, excellent dimensional stability with CTE values of 17–34 ppm/K, high transmittance (T450nm ≥ 59%) and good thermoplasticity with -d logE'/dT values of 0.08–0.34. Among them, PAI-2a exhibited the best comprehensive performances, especially for the high thermoplasticity (-d logE'/dT = 0.34), low CTE (28 ppm/K), and high transmittance (T450nm = 84%), which provides a new strategy for the research on thermoplastic PAI materials in optical field.

Molecular design of soluble poly(amide-imide) with high char yield for flame retardant epoxy resin

Abstract In this study, a noncoplanar diimide diacid monomer (DIDA) was synthesized by direct condensation of trimellitic anhydride (TMA) with m-tolidine. The noncoplanar unit was incorporated into poly(amide-imide)s (PAIs) main chain by Yamazaki-Higashi phosphorylation of DIDA with various aromatic diamines. Encouragingly, all of the PAIs show good solubility in some common solvents such as N,N-Dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP), and m-cresol. In addition, the soluble PAIs show good optical transmittances of beyond 85 % at 500 nm due to the decreased crystallization ability. On the other hand, PAIs possess good mechanical properties with tensile strengths of 72–90 MPa and tensile moduli beyond 2 GPa. Meanwhile, the designed PAIs also exhibit excellent thermal properties: their glass transition temperatures (T g) range from 278 to 314 °C, initial decomposition temperatures (5 % weight loss temperatures, T 5wt%) are beyond 470 °C, coefficients of thermal expansion (CTE) are below 10 ppm/°C. The excellent mechanical and thermal properties are due to the strengthened hydrogen bonding interaction among the amide groups. Therefore, it is believed that incorporating noncoplanar unit and amide group into the polymer main chain at the same time can simultaneously improve processability, optical transparency, mechanical and thermal properties. Furthermore, it is worth noting that the char of PAI at 800 °C is as high as 72.5 %, which is one of the highest known values. When PAI was incorporated into epoxy resin, the blend passed UL94 V-0 rating due to the high charring capability of PAI.

Preparation and Properties of High-Temperature-Resistant, Lightweight, Flexible Polyimide Foams with Different Diamine Structures.

Polyimide foam (PIF) is a rising star in high-end applications such as aerospace thermal insulation and military sound absorption. However, the basic rule on molecular backbone design and uniform pore formation of PIF still need to be explored. In this work, polyester ammonium salt (PEAS) precursor powders are synthesized between alcoholysis ester of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDE) and aromatic diamines with different chain flexibility and conformation symmetry. Then, a standard "stepwise heating" thermo-foaming approach is used to prepare PIF with comprehensive properties. A rational thermo-foaming program is designed based on in situ observation of pore formation during heating. The fabricated PIFs have uniform pore structure, and PIFBTDA-PDA shows the smallest size (147 μm) and narrow distribution. Interestingly, PIFBTDA-PDA also presents a balanced strain recovery rate (SR = 91%) and mechanical robustness (0.051 MPa at 25% strain) and its pore structure maintains regularity after 10 compression-recovery cycles, mainly due to high rigidity of the chains. Furthermore, all the PIFs possess lightweight feature (15-20 kg∙m-3), good heat resistance (Tg at 270-340 °C), thermal stability (T5% at 480-530 °C), thermal insulation properties (λ = 0.046-0.053 W∙m-1K-1 at 20 °C, λ = 0.078-0.089 W∙m-1K-1 at 200 °C), and excellent flame retardancy (LOI > 40%). The reported monomer-mediated pore-structure control strategy can provide guidelines for the preparation of high-performance PIF and its industrial applications.

High performance imide oligomers and thermosets derived from 9,9-bis (3,4-dicarboxyphenyl)fluorene dianhydride

In this work, a new class of imide oligomers and thermosets with improved overall properties was developed by exploiting the steric effects of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). First, a model compound was prepared from BPAF and aniline. This model compound possessed a twisted architecture, with two dihedral angles between fluorene ring and phthalimide segments of around 75°. Then, an array of phenylethynyl-endcapped imide oligomers was synthesized from BPAF, 4-phenylethynyl phthalic anhydride (4-PEPA), and aromatic diamines (4,4′-oxydianiline (4,4′-ODA), 2,2′-bis(trifluoromethyl)benzidine (TFMB), m-phenylenediamine (m-PDA)). The BPAF-derived imide oligomers exhibited improved organic solvents solubility and higher melt viscosity compared to those based on 2,3,3′,4′-biphenyltetracarboxylic dianhydride (3,4′-BPDA), due to their bulky, twisted, and sterically hindered cardo architectures. The imide oligomers under pressure were converted into thermosets by the thermal crosslinking of phenylethynyl at 370 °C for 2 h. The BPAF-derived thermosets exhibited much higher glass transition temperature (Tg) (＞ 404 °C), 5% weight-loss temperature (T5%) (＞ 549 °C) in an air environment, and more excellent high-frequency dielectric properties from 30 to 45 GHz (dielectric constant as low as 2.85 and dielectric loss factor as low as 0.0037) while possessing comparable or even better mechanical properties relative to the 3,4′-BPDA-derived polymers. Therefore, these polymers based on BPAF may have potential applications as matrix resins for heat-resistant, structural and functional composites.

Upcycling Waste Polycarbonate to Poly(carbonate imine) Vitrimers with High Thermal Properties and Unprecedented Hydrolytic Stability

The global market for polycarbonate (PC) increases steadily because of its heat resistance, toughness, and optical transparency. To achieve sustainability, the waste polycarbonate (WPC) should be recycled. This work reports a 100% atom-efficiency upcycling of WPC to a WPC-derived aldehyde (WPC-CHO). Then, poly(carbonate imine) vitrimers (PCIs) based on the WPC-CHO and two aromatic diamines were prepared. Generally, polyimines can cleave in mild acidic conditions such as 0.1 M HCl(aq) and seldom show good thermal and tensile properties. The PCIs in this work showed good thermal and tensile properties and an unprecedented resistance toward acid hydrolysis. They can survive even immersing in a 5 M H2SO4 THF/H2O solution for 6 months. This unusual resistance toward acid hydrolysis expands the application of PCIs in an acidic environment. Small pieces of PCIs can be compression-molded into a newly formed polymer film at 240 °C. This thermal reprocessability demonstrates the vitrimer characteristic of the PCIs. The PCIs can be degraded through simultaneous aminolysis of carbonate and transimination of imine by hexylamine (HA) in a catalyst-free mild condition. Based on the aminolysis and transimination, we degraded the cross-linking network in the PCI-based carbon fiber-reinforced polymer (CFRP) and recovered undamaged carbon fiber. This environmentally friendly work will attract the attention of researchers who are interested in sustainability and circularity.

Study of kinetics of thermal degradation and to determine the activation energies of polyamides based on s-triazine

A series of ten polyamides was prepared by the high-temperature polycondensation of 4,6-bis(N-(4-(benzoylchloride)amino))-2-(N-phenyl- piperazin-1-yl)-1,3,5-triazine with different aromatic and aliphatic diamines. The synthesized polyamides were analyzed by physico-chemical properties such as solubility, density, viscosity etc. The structure of prepared polyamides was evaluated by 1H NMR and FTIR spectrum. Thermogravimetric analysis used to study the kinetics of thermal degradation of some synthesized polyamides. Broido, Horowitz & Metzger, Coats Redfern and Chan et al. models were applied to respective thermograms to determine the activation energy (Ea). Activation energy data shows that the polyamides obtained from aromatic diamine has greater stability than the polyamides obtained from aliphatic amine.

Unidirectional Fracturing of Super Engineering Plastic Films

Polyamideimides and polyimides are prepared based on chemical imidization using aromatic diamine, diacid anhydride, and diacid chloride as monomers, with the precursor polyamic acid remaining in part, to produce mechanically unique films through convection drying. The resulting films are colorless and transparent and exhibit unidirectional fracture behavior. These films do not break when bent in the direction of the air contact surface but easily break when bent in the opposite direction. A cross‐sectional electron microscope image of the broken film shows that the film consists of a double layer. After examining both sides of the film through various spectroscopic and gel permeation chromatography analyses, it is found that the residual polyamic acid undergoes both hydrolytic and thermal decomposition, exclusively on the air contact surface. Later, the polymer film is laminated with two sheets of glass through UV curing of commercial acryl resin. Because of the unidirectional fracture characteristics of the film, the laminated glass does not completely break when subjected to bending toward the air contact surface but easily breaks (without fragments) in the opposite direction, indicating its potential application in safety glasses suitable for emergency escapes.

SYNTHESIS AND PROPERTIES OF POLYIMINES BASED ON DIALDEHYDES OF THE FURAN SERIES AND VARIOUS DIAMINES

In this work, the reactions of 2,5-diformylfuran (DFF) with various aromatic and aliphatic diamines were studied, and the physicochemical properties of the resulting polyimines were studied. Research on the synthesis of electro-conductive polymers and the study of their physicochemical properties attracts great interest in modern polymer science. A class of electrically conductive polymers that has been particularly attractive for research in the last half century are aromatic polyimines, which are also known as polyimines or Schiff-based polymers. DFF-based polymers are little studied due to the high cost of the monomer, which limits its synthetic application. The availability of DFF is made both by the development of economical methods for its production, the oxidation of 5-hydroxymethylfurfural (5-HMF), and by the provision of sustainable access to 5-HMF from biomass. Polyimines containing furan fragments were synthesized by low-temperature polycondensation of DFF, available from plant materials, and various aromatic diamines in ethanol. The resulting polymers were high-melting thermoplastics from yellow to orange. The polymers showed typical absorption bands characteristic of the stretching vibrations of the C=N group (about 1620 cm-1) in the infrared spectra and had high glass transition temperatures of more than 200 °C. The ionic conductivity of polyimines has been characterized by electrochemical impedance spectroscopy. The conductivity value for polyimines, doped with I2, reaches 1.24·10-4 S cm-1 (at 298 K and 100% relative humidity), which is one of the highest values of proton conductivity for polyimines doped without using metals or their salts. The resulting polymers can be used to manufacture composites with various fillers. For citation: Kataria Y.V., Klushin V.A., Kashparova V.P., Sokolova V.A., Smirnova N.V. Synthesis and properties of polyimines based on dialdehydes of the furan series and various diamines. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 6-12. DOI: 10.6060/ivkkt.20236606.6763.

Heat-Resistant Polymers with Intense, Visible Photoluminescence Functionality and Fluorescence Probing Application

Heat-resistant polymers with an intense, visible photoluminescence (PL) functionality are presented. A polybenzoxazole (PBO) containing hexafluoroisopropylidene (HFIP) side groups exhibited an intense purple PL with a quantum yield, ΦPL, of 0.22 (22%), owing to the effectively disturbed concentration quenching (CQ) in the fluorophore units by the bulky HFIP side groups. The chain ends of a wholly cycloaliphatic polyimide (PI), derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 4,4′-methylenebis(cyclohexylamine) (MBCHA), were modified with conjugated monoamines. The PI derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-NTDA) and MBCHA exhibited a very high glass transition temperature (Tg = 376 °C) and purple fluorescence from the S1(π,π*) state. However, its ΦPL value was lower than expected. A pronounced effect of fluorophore dilution using CBDA on the PL enhancement was observed. This is closely related to the planar structure of the 2,3,6,7-NTDA-based diimide units. By contrast, the counterpart using an 2,3,6,7-NTDA isomer, 1,4,5,8-NTDA, was virtually non-fluorescent, despite its sufficient dilution using CBDA. The PI film obtained using 3,3″,4,4″-p-terphenyltetracarboxylic dianhydride (TPDA) with a non-coplanar structure and MBCHA exhibited an intense blue fluorescence spectrum (ΦPL = 0.26) peaking at 434 nm. The dilution approach using CBDA enhanced its fluorescence up to a high ΦPL value of 0.41. Even when TPDA was combined with an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB), the intense blue fluorescence was observed without charge-transfer fluorescence. A semi-cycloaliphatic PI derived from TFMB and a novel cycloaliphatic tetracarboxylic dianhydride, which was obtained from a hydrogenated trimellitic anhydride derivative and 4,4′-biphenol, was used as another host polymer for 9,10-bis(4-aminophenyl)anthracene (BAPA). The BAPA-incorporating PI film resulted in a significant PL enhancement with a considerably high ΦPL of 0.48. This PI film also had a relatively high Tg (265 °C). A reactive dye, N,N′-bis[4-(4-amino-3-methylbenzyl)-2-methylphenyl]-3,4,9,10-perylenetetracarboxydiimide, was harnessed as a fluorescence probe to explore transamidation between polyimide precursors in solution.