Diamine Research Articles

Preparation and Properties of Intrinsically Black Polyimide Films with CIE Lab Color Parameters Close to Zero and High Thermal Stability for Potential Applications in Flexible Printed Circuit Boards.

Black polymer films with high thermal stability are highly desired in flexible electrical and electronic fields. Conventional black polymer films based on high-temperature resistant polymers and black inorganic dyes are usually suffered from the poor electrical and tensile properties. In the current work, a series of intrinsically black polyimide (BPI) films with International Commission on Illumination (CIE) Lab optical parameters close to zero and high thermal stability have been designed and prepared. For this purpose, an electron-rich aromatic diamine, 4,4′-iminodianiline (NDA), was copolymerized with 1,4-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (sBPDA) to afford a series of poly(amic acid) (PAA) solutions, which were then thermally dehydrated to provide the final BPI films at elevated temperatures up to 400 °C in air. The molar fraction of NDA in the total diamine monomers was 0 for BPI-0 (sBPDA-PDA), 10% for BPI-1, 20% for BPI-2, 30% for BPI-3, 40% for BPI-4, 50% for BPI-5, and 100% for BPI-6. For comparison, two referenced polyimide (PI) films, including PI-ref1 and PI-ref2, were prepared according to a similar procedure. The former was derived from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) and the latter was from PMDA and NDA. The BPI films exhibited an increasing degree of blackness with the increasing contents of NDA units in the polymer films. For example, the BPI-6 (sBPDA-NDA) film exhibited the optical transmittance of 1.4% at a wavelength of 650 nm (T650), which was obviously lower than those of PI-ref1 (T650 = 74.6%) and PI-ref2 (T650 = 3.6%). In addition, the BPI-6 film showed the CIE Lab parameters of 0.39 for L*, 2.65 for a*, 0.66 for b*, and haze of 1.83, which was very close to the criterion of “pure blackness” for polymer films (L* = a* = b* = 0). At last, incorporation of the NDA units in the rigid-rod BPI-0 (BPDA-PDA) film slightly deteriorated the high-temperature dimensional stability of the derived BPI films. BPI-6 film showed a linear coefficient of thermal expansion (CTE) value of 34.8 × 10−6/K in the temperature range of 50 to 250 °C, which was higher than those of the BPI-0 (CTE = 12.3 × 10−6/K), PI-ref1 (CTE = 29.5 × 10−6/K), and PI-ref2 (CTE = 18.8 × 10−6/K) films. Nevertheless, the BPI films maintained good thermal stability with the 5% weight loss temperatures (T5%) higher than 590 °C, and the glass transition temperatures (Tg) higher than 340 °C.

Thermal and UV Curable Formulations of Poly(propylene glycol)-Poly(hydroxyurethane) Elastomers toward Nozzle-Based 3D Photoprinting.

In this work, isocyanate-free formulations for poly(propylene glycol) polyurethane elastomers are studied. These formulations are based on poly(propylene glycol) end-capped by CO2-sourced cyclic carbonate (bisCC PPG) macromonomers able to react with amines leading to poly(hydroxyurethane)s. In order to obtain covalent networks, two curing approaches are studied. First, the direct thermally activated cross-linking of bisCC PPG with a mixture of various aliphatic or aromatic diamines and a triamine is investigated, and in particular the nature of the diamine on the mechanical properties. In the second approach, UV-activated formulations are developed by reacting bisCC PPG with allylamine followed by the addition of a trithiol by photoactivated thiol-ene reaction. The swelling tests show that both systems provide highly cross-linked polymer networks and complementary characterizations highlighted excellent mechanical properties. Thanks to the fast curing and adapted viscosity of the developed photoactive formulation, the latter was found suitable for use as a photoresin for 3D printing as demonstrated by printing a vaginal ring by a nozzle-based photoprinter.

Synthesis and Properties of Optically Transparent Fluoro-Containing Polyimide Films with Reduced Linear Coefficients of Thermal Expansion from Organo-Soluble Resins Derived from Aromatic Diamine with Benzanilide Units.

Wholly aromatic polyimide (PI) films with good solution processability, light colors, good optical transparency, high storage modulus, and improved heat resistance were prepared and characterized. For this purpose, a multi-component copolymerization methodology was performed from a fluoro-containing dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), a rigid dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and a fluoro-containing diamine, 2,2′-bis(trifluoromethyl)-4,4′-bis [4-(4-amino-3-methyl)benzamide]biphenyl (MABTFMB). One homopolymer, FPI-1 (6FDA-MABTFMB), and five copolymers, FPI-2~FPI-6, containing the BPDA units from 10 mol% to 50 mol% in the dianhydride moieties, were prepared, respectively. The derived PI resins showed good solubility in the polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). The flexible PI films obtained by the solution casting procedure showed good optical properties with the transmittances higher than 74.0% at the wavelength of 450 nm. The PI films exhibited excellent thermal properties, including 5% weight loss temperatures (T5%) over 510 °C, together with glass transition temperatures (Tg) over 350.0 °C according to the peak temperatures of the loss modulus in dynamical mechanical analysis (DMA) measurements. The FPI-6 film also showed the lowest linear coefficient of thermal expansion (CTE) value of 23.4 × 10−6/K from 50 to 250 °C according to the thermomechanical analysis (TMA) measurements, which was obviously lower than that of FPI-1 (CTE = 30.6 × 10−6/K).

Intrinsically Negative Photosensitive Polyimides with Enhanced High-Temperature Dimensional Stability and Optical Transparency for Advanced Optical Applications via Simultaneous Incorporation of Trifluoromethyl and Benzanilide Units: Preparation and Properties

Negative photosensitive polyimides (PSPIs) with the photo-patterned ability via the photocrosslinking reactions induced by the i-line (365 nm) and h-line (426 nm) emitting wavelengths in high-pressure mercury lamps have been paid increasing attention in semiconductor fabrication, optical fiber communications, and other advanced optoelectronic areas. In the current work, in view of the optical and thermo-mechanical disadvantages of the currently used negative PSPIs, such as the intrinsically photosensitive or auto-photosensitive systems derived from 3,3’,4,4’-benzophenonetetracarboxylic dianhydride (BTDA) and the ortho-alkyl- substituted aromatic diamines, a series of modified negative PSPIs with the enhanced optical transparency in the wavelength of 365~436 nm and apparently reduced coefficients of linear thermal expansion (CTE) were developed. For this purpose, a specific aromatic diamine with both of trifluoromethyl and benzanilide units in the molecular structures, 2,2’-bis(trifluoromethyl)-4,4’-bis[4-(4-amino-3-methyl)benzamide]biphenyl (MABTFMB) was copolymerized with BTDA and the standard 3,3’,5,5’-tetramethyl-4,4’-diaminodiphenylmethane (TMMDA) diamine via a two-step chemical imidization procedure. As compared with the pristine PI-1 (BTDA-TMMDA) system, the new-developed fluoro-containing PSPI systems (FPI-2~FPI-7) exhibited the same-level solubility in polar aprotic solvents, including N-methyl-2-pyrrolidone (NMP) and N,N- dimethylacetamide (DMAc). The FPI films cast from the corresponding FPI solutions in NMP showed the optical transmittances of 78.3–81.3% at the wavelength of 436 nm (T436, h-line), which were much higher than that of the PI-1 (T436 = 60.9%). The FPI films showed the CTE values in the range of 40.7 × 10−6/K to 54.0 × 10−6/K in the temperature range of 50 to 250 °C, which were obviously lower than that of PI-1 (CTE = 56.5 × 10−6/K). At last, the photosensitivity of the FPI systems was maintained and the micro-pattern with the line width of 10 μm could be clearly obtained via the standard photolithography process of FPI-7 with the molar ratio of 50% for MABTFMB in the diamine moiety.

Plant oil-based non-isocyanate waterborne poly(hydroxyl urethane)s

With the increasingly depletion of the petroleum resources and awareness of the importance of environmental issues, a quest for a newer, safer and greener route for plant oil-based non-isocyanate waterborne polyurethanes is becoming one of the major challenges in the polyurethanes industry. In this study, the carbonated linseed oil (CLSO) was prepared from epoxy linseed oil, which was used to polymerize with different diamines and hydrophilic moiety to produce green and safety cationic, anionic and nonionic plant oil-based non-isocyanate waterborne poly(hydroxyl urethane)s (NIWPUs). Meanwhile, aromatic diamines, aliphatic diamines and polyether diamines were used as chain extenders to tailor the performance of the resulting plant oil-based NIWPUs, which also further evaluate the robustness of the proposed preparation route. The results showed that all the NIWPU dispersions exhibited excellent storage stability. The cationic NIWPU films showed good mechanical properties (the highest tensile property was more than 9 MPa and the highest elongation at break was more than 200 %) and antibacterial properties (antibacterial efficiency toward Staphylococcus aureus and Escherichia coli above 98 %), anionic NIWPU films exhibited good mechanical properties (the highest tensile property was more than 8 MPa and the highest elongation at break was more than 300 %) and coating performance (the highest pencil hardness was 7H and the highest crosshatch adhesion was 5B), and nonionic NIWPUs showed tailorable cloud points. The technique reported here offers a number of advantages, including low cost, easy performance, environmentally friendly and economical process, opening new platform for the production of NIWPUs prepared from plant oil.

A 4‐Arm Small Molecule Acceptor with High Photovoltaic Performance

AbstractManipulating the backbone of small molecule acceptors (SMAs) is of particular importance in developing efficient organic solar cells (OSCs). The common design is constructing 2‐arm SMAs with linear or curved backbones. Herein, we report an acceptor 4A‐DFIC with a 4‐arm backbone unexpectedly generated in the reaction of an electron‐rich aromatic diamine and hexaketocyclohexane. Single‐crystal X‐ray diffraction analysis indicates the rigid and twisted molecular plane and the effective molecular stacking of 4A‐DFIC in solid state. 4A‐DFIC shows a low band gap of 1.40 eV and excellent light‐harvesting capability from visible to near‐infrared region. Binary and ternary OSCs based on 4A‐DFIC gave power conversion efficiencies (PCEs) of 15.76 % and 18.60 % (certified 18.1 %), respectively, which are the highest PCEs for multi‐arm SMA‐based OSCs to date.

A 4-Arm Small Molecule Acceptor with High Photovoltaic Performance.

Manipulating the backbone of small molecule acceptors (SMAs) is of particular importance in developing efficient organic solar cells (OSCs). The common design is constructing 2-arm SMAs with linear or curved backbones. Herein, we report an acceptor 4A-DFIC with a 4-arm backbone unexpectedly generated in the reaction of an electron-rich aromatic diamine and hexaketocyclohexane. Single-crystal X-ray diffraction analysis indicates the rigid and twisted molecular plane and the effective molecular stacking of 4A-DFIC in solid state. 4A-DFIC shows a low band gap of 1.40 eV and excellent light-harvesting capability from visible to near-infrared region. Binary and ternary OSCs based on 4A-DFIC gave power conversion efficiencies (PCEs) of 15.76 % and 18.60 % (certified 18.1 %), respectively, which are the highest PCEs for multi-arm SMA-based OSCs to date.

The cyclotriphosphazene-based covalent organic frameworks constructed entirely by flexible building blocks for adsorping and fluorescence sensing iodine

A series of flexible cyclotriphosphazene-based COFs, we call them fully flexible cyclotriphosphazene-based COFs (HDADE, HBAPB and HBPDA), were prepared by means of reversible Schiff base polycondensation reactions for the first time, which were constructed entirely by flexible building blocks, not only hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP–6–CHO) as a flexible knot but also aromatic ether diamine as flexible linkers. The fully flexible cyclotriphosphazene-based COFs are crystalline porous materials. Their crystallinity and BET specific surface areas increase with the length of the linkers, and are higher than that of the corresponding COFs constructed by the rigid linkers. HDADE, HBAPB and HBPDA can absorb iodine in both gas or liquid phase. The adsorptive capacities are 5.22, 4.55, and 3.86 g g−1, respectively, which are higher than the corresponding COFs formed by rigid linkers. The fully flexible cyclotriphosphazene-based COFs can fluorescently sense iodine with high sensitivity. Their quenching constants (KSV) are 2.22 × 104, 7.07 × 104, and 1.04 × 104 L mol−1. Their LODs are 1.35 × 10−10, 4.24 × 10−11, and 2.88 × 10−10 mol L−1, respectively. The fluorescence quenching of iodine to the fully flexible cyclotriphosphazene-based COFs has both photo-induced charge transfer and resonant energy transfer processes.

Formation of Nano-Fibrous Patterns on Aluminum Substrates via Photolithographic Fabrication of Electrospun Photosensitive Polyimide Fibrous Membranes.

The formation of polymeric micro-patterns on various substrates via a photolithography procedure has been widely used in semiconductor fabrication. Standard polymer patterns are usually fabricated via photosensitive polymer varnishes, in which large amounts of potentially harmful solvents with weight ratios over 50 wt% have to be removed. In the current work, a novel pattern-formation methodology via solvent-free electrospun photosensitive polymeric fibrous membranes (NFMs) instead of the conventional photosensitive solutions as the starting photoresists was proposed and practiced. For this purpose, a series of preimidized negative auto-photosensitive polyimide (PSPI) resins were first prepared via the two-step chemical imidization procedure from the copolymerization reactions of 3,3′,4,4′-benzophenonetetracarboxylic- dianhydride (BTDA) and two ortho-methyl-substituted aromatic diamines, including 3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane (TMMDA) and 3,7-diamino-2,8-dimethyl- dibenzothiophene sulfone (TSN). The derived homopolymer PI-1 (BTDA-TMMDA) and the copolymers, including SPI-2~SPI-6, with the molar ratio of 5~25% for TSN in the diamine units, showed good solubility in polar solvents. Then, a series of PSPI NFMs were fabricated via standard electrospinning procedure with the developed PSPI solutions in N,N-dimethylacetamide (DMAc) with a solid content of 25 wt% as the starting materials. The derived PSPI NFMs showed good thermal stability with 5% weight loss temperatures higher than 500 °C in nitrogen. Meanwhile, the derived PSPIs showed good photosensitivity to the ultraviolet (UV) emitting wavelengths of i-line (365 nm), g-line (405 nm) and h-line (436 nm) of the high-pressure mercury lamps in both forms of transparent films and opaque NFMs. Fine micro-patterns with a line width of around 100 μm were directly obtained from the representative SPI-4 NFM via standard photolithography procedure.

Self-toughening of epoxy resin by introduction of highly crosslinked thermoset epoxy microspheres

The theories and technologies concerning polyolefin toughening with rubber or inorganic rigid particle have been studied comprehensively, the results indicated that the toughening with rubber always lowers the modulus and heat resistance of materials. Also, toughening with inorganic rigid particle is not good because of its low dispersion and miscibility with epoxy resin. Monodisperse epoxy microspheres (EMs) with high crosslinking density were prepared with Polypropylene glycol with molecular weight of 600 as the reaction solvent and trifunctional epoxy resin (TDE-85) and aromatic diamine (DETDA) as the precursors. The formation of EMs was investigated in detail. The crosslinked microspheres were used as toughening agent to realize DGEBA/DDS system self- toughening. When adding 5wt% epoxy microspheres, the impact strength improved by 87% and Tg increased more than 6 °C. The results show that the prepared epoxy microspheres with high crosslinking density can not only greatly improve the toughness of epoxy resin, but also improve its heat resistance.

Preparation of aromatic polyamide with ultra-high intrinsic breakdown strength via layered stacking structure induced by coplanar monomer

Dielectric polymers with high breakdown strength (Eb) and high retention rate of breakdown strength at elevated temperature have important application potential in advanced electrical insulation devices. Herein, the aromatic heterocyclic diamine monomer, 5-amino-2-(2-hydroxy-4-aminobenzene)-benzoxazole (HBOA), was synthesized. Theoretical calculation and single crystal date demonstrated fully the formation of intramolecular H-bond of OH⋯N]C between benzoxazole and benzene ring in HBOA, which endows the monomer a coplanar geometry. Moreover, the aromatic polyamide films were prepared by polycondensation of HBOA, and the in-plane orientation of films increases with increasing the coplanar HBOA content, which reduces the orientation confusion and cavity of chains packing. When the HBOA content is over 70%, the films exhibit dense-layered stacking structure with high crystallinity. It is found that the dense-layered stacking structure can prevent the films breakdown and failure effectively, which endows the homopolymerization (HBOA-100) film with Eb of 771 kV/mm. Moreover, the Eb of the HBOA-100 film is still as high as 634 kV/mm at 150 °C, and its retention rate of Eb reaches 82% in high temperature environment. In addition, tensile strength of the HBOA-100 film is nearly 343 MPa, glass transition temperature is about 334 °C and the thermal stability up to 487 °C. • HBOA and BOA single crystals were obtained, suggesting that the intramolecular hydrogen bond leads to coplanar geometry. • The HBOA monomer and its model compound present layered stacking pattern arising from the coplanar structure. • The dense-layered stacking structure can be constructed in the aromatic polyamide film by the coplanar monomer. • The intrinsic breakdown strength of the homopolymerization film reaches 771 kV/mm and still as high as 634 kV/mm at 150 °C. • This work provides a promising strategy of molecular structure design for high-temperature dielectric polymers.

Preparation of semi-alicyclic homo- and blended polyimide membranes using alicyclic dianhydrides with kink structures and their gas separation properties

Aromatic polyimides are promising membrane materials for gas separation due to their excellent gas separation properties. Herein, two soluble semi-alicyclic polyimides were synthesized via a one-step thermal imidization process with two semi-alicyclic dianhydrides possessing kink structures: bicyclo[2,2,2] oct-7ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) and 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA), and a flexible aromatic diamine: 4,4′-Oxydianiline (ODA). Their homo- and blended membranes were prepared in various mixing ratios (100/0, 75/25, 50/50, 25/75, and 0/100) and their gas permeation properties were investigated for five gases (H2, CO2, O2, N2, and CH4) and selectivity for five gas pairs (H2/CH4, H2/N2, CO2/CH4, CO2/N2, and O2/N2). The homopolyimides (BCDA-ODA, DOCDA-ODA) exhibited amorphous structure without crystallinity and good solubilities in the casting solvents. BCDA-ODA showed larger d-spacing/FFV values, higher gas diffusivities/gas solubilities than DOCDA-ODA, resulted in higher gas permeabilities and lower gas selectivity, which were remarkably affected by feed temperature. Also, the gas permeability and selectivity of the blended membranes were dependent upon the BCDA/DOCDA mole ratio. The good gas separation performances of homo- and blended membranes were observed for H2/CH4, H2/N2, CO2/CH4, and O2/N2, which are comparable to those of commercial membrane materials such as P84®, PSF, CA, Matrimid®, etc.

Hydrazide-hydrazone-modified polyamide as reinforcement and dispersion aid for poly(lactic acid)/hydroxyapatite nanocomposites

Hydrazide-hydrazone based polyamide (HHPA) was synthesized from an aromatic diamine containing hydrazide-hydrazone group and dodecanedioic acid via direct polycondensation. The surface modified hydroxyapatite (SMHA) was prepared using a modification process of hydroxyapatite nanoparticles (HAN) with imine functionalized polyethyleneimine (FPEI). The new pol(ylactic acid) (PLA)/HAN/HHPA nanocomposites with increased heat and combustion resistance, and improved mechanical and gas barrier properties were fabricated using solution casting method. The structure and morphology of the prepared PLA nanocomposites were evaluated using FTIR, FE-SEM, and XRD techniques. The synergistic effect of SMHA and HHPA was studied on the heat and combustion resistance, gas barrier properties, and mechanical strength of PLA. The findings exhibited that HAN was homogeneously dispersed in the PLA polymeric network, due to the excellent interfacial interactions. The TGA results of nanocomposites revealed that PLA containing 3 mass% of each SMHA and HHPA additives, named PHP6, offers more heat resistance, in both N2 and air environment, compared to the neat PLA. According to the MCC results, the heat release rate peaks reduced from 555 W/g to 357 W/g for PLA containing 6 mass% of each SMHA and HHPA additives, named PHP12. From mechanical test, the tensile strength of PHP6 was obtained 88.27 MPa, which was 48 MPa higher than the neat PLA. Furthermore, the gas barrier studies for CO2 and N2 indicated that the incorporation of both HHPA and SMHA results in reduced permeability and solubility coefficients compared to the neat PLA, where PHP2 and PHP6 samples outperform other samples.

Cleavable epoxy networks using azomethine-bearing amine hardeners

This work is a proof-of-concept of the use of azomethine-bearing diamines as novel hardeners of standard epoxy compounds to yield cleavable and thermoformable covalent adaptable networks (CANs), with functional properties otherwise comparable to conventional epoxy networks. A suitable aromatic diamine (TPA-o-PD) was synthesised at acceptable purity for the intended use and successfully reacted with DGEBA. The resulting azomethine-bearing cured epoxy networks exhibited glass transition temperature values and a thermal stability profile similar to conventional epoxy network counterparts. In contrast to their conventional counterparts however, the azomethine-bearing networks were shown to dissolve in mixtures of chloroform and methanesulfonic acid, due to acid hydrolysis of at least some of the azomethine bonds of the network. The resulting recyclate material after evaporating the solvent was consistent with the profile of a thermoplastic polymer of high molecular weight, suggesting limited depolymerisation/network cleavage during dissolution in the chloroform/methanesulfonic acid mixture. The recyclates were soluble in polar aprotic solvents and showed good thermal stability, high Tg and molecular weight values, consistent with the attributes of engineering thermoplastics. Lastly, the cured networks were shown to be thermoformable at 200 °C, yielding self-standing films with only minor reduction of properties.

Dispersion of graphene oxide nanolayers in novel heat-stable poly(benzimidazole-amide) by ultrasonic irradiation route: synthesis and characterization

ABSTRACT Poly(benzimidazole-amide) (PBIA) nanocomposites containing 5, 10, and 15 wt.% of graphene oxide were successfully prepared. A new PBIA was prepared via polymerization of 1,3-bis(5-amino-1H-benzimidazole-2-yl)benzene, as an aromatic diamine, and 5-hydroxy isophthalic acid in the presence of molten tetra-n-butyl ammonium bromide and triphenyl phosphite as a green and environmentally friendly method. To prevent agglomeration of graphene in the PBIA matrix, graphene oxide was prepared by hummer’s method. Then, different PBIA/graphene oxide nanocomposites were synthesized via interaction of pure PBIA and graphene oxide using ultrasonic technique. TEM and FE-SEM images certified that the graphene oxides were uniformly dispersed in the PBIA matrix.

The effects of hydrogen incorporation in modified atmosphere packaging on the formation of biogenic amines in cold stored rainbow trout and horse mackerel

The formation of biogenic amines (BAs) in fish products during storage forms a serious challenge to producers and is generally related to the growth of decarboxylase-producing microorganisms. Controlling the formation of BAs is a serious challenge for the fishery industry. This study evaluates the impact of incorporating molecular hydrogen (H2) in a modified atmosphere packaging on the formation of BAs in both freshwater and seawater fish, i.e., rainbow trout and horse mackerel, respectively, stored at + 4 °C for 15 days. Fish samples were packaged in modified atmosphere packaging [MAP1 (50% CO2/50% N2) and MAP2 (60% CO2/40% N2)], reducing atmosphere packaging [RAP1 (50% CO2/46% N2/4% H2) and RAP2 (60% CO2/36% N2/4% H2)], and under air (control). The amount of BAs, except spermidine and spermine, significantly increased during storage in all treated samples. Both MAPs and RAPs showed significant restrictive effects on the formation of heterocyclic, aromatic, and aliphatic di-amines (histamine, tyramine, putrescine, cadaverine) in both fish species, with a more potent effect seen in RAP rather than MAP. Reduction rates of BAs ‎were about two folds higher in RAPs than that of MAPs. This shows the advantage of hydrogen incorporation in the package atmosphere on the inhibition of biogenic amine formation, especially in the presence of a high level of CO2. Therefore, RAP may be proposed as a promising technology for limiting the BA formation in fishery products.

Low‐temperature processable glass fiber reinforced aromatic diamine chain extended bismaleimide composites with improved mechanical properties

AbstractThe synthesis of 4,4′‐bismaleimido diphenylmethane (BMIM) and modified BMIM by its chain extension using commercially available aromatic diamines like 4,4′‐diamino diphenyl methane (DDM), 4,4′‐diaminodiphenyl sulphone (DDS), and 4,4′‐diamine diphenyl ether (DDE) was done. The synthesized materials have been characterized for structural aspects using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The structure of BMIM was confirmed due to the presence of specific bands at ~1400 and 1705 cm−1 responsible for CC and OCNCO groups, respectively. The reduction in the heat of fusion and enthalpy of curing for chain extended bismaleimides/modified BMIM shows the influence of the swivel group in diamine during curing. The curing window has broadened for BMIM_M and BMIM_E by ~40°C and narrowed for BMIM_S by ~100°C. The mechanical properties and the chemical resistance were studied for the composites made from the BMIM and modified BMIM based composites. Fiber‐enhanced modified bismaleimide resin has improved mechanical properties.

Effects of monomer rigidity on microstructures and properties of novel polyamide thin-film composite membranes prepared through interfacial polymerization for pervaporation dehydration

In this study, thin-film composite (TFC) membranes were produced through interfacial polymerization between diamine and trimesoyl chloride on a polyetherimide (PEI) support. The TFC membranes with different diamines, 4,4′-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))dianiline (BAPP), 4,4′-((methylene bis(4,1-phenylene))bis(oxy))dianiline (MPDA), and 6,6′-bis(4-aminopheoxy)-4,4,4′,4′,7,7′-hexamethyl-2,2′-spirobichroman (SBC), were denoted as TFCPEI/B, TFCPEI/M, and TFCPEI/S, respectively. These three aromatic diamines have different central moieties that affect reactivity during the interfacial polymerization reaction. The crosslinking degree of the TFC membranes increased in the following order: TFCPEI/S < TFCPEI/M < TFCPEI/B. Positron annihilation lifetime spectroscopy analysis also unveils that TFCPEI/B had the lowest free volume. These results reveal that the appropriate steric structure of the diamine molecules can create less compact structure without impeding the formation of the crosslinked polyamide selective layer. Moreover, the TFCPEI/B membrane had a flux of approximately 705 ± 46 g∙m−2 h−1, and the water concentration in the permeate was maintained at approximately 99.8 wt% at 25°C during the 70 wt% isopropanol solution dehydration. Furthermore, the TFCPEI/B membrane can be operated under broad operating conditions and possesses high long-term stability.

Investigation of thermal, antibacterial and heavy metal ion removal behavior of polyamide/polyimide iron oxide nanocomposites

In this study, a newly-designed diamine (DA) containing pyridine and carbazole groups was synthesized and the relevant polyamides (PAs) and polyimides (PIs) were prepared by polymerization reaction between the DA monomer and terephthalic acid, adipic acid, and pyromellitic dianhydride. In addition, polymer nanocomposites were prepared through a combination of the synthesized polymers with modified magnetite iron oxide nanoparticles. The synthesized compounds were fully characterized by hydrogen nuclear magnetic resonance (1HNMR), fourier-transform infrared (FTIR), field emitting scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), Transmission electron microscopy (TEM), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) analyses. All of the synthesized properties of compounds such as thermal stability, viscosity, elimination capability of heavy metals ions adsorption, and antibacterial activity were investigated. Polyamides and PI showed good solubility in aprotic solvents and the viscosity was in the range of 0.72–0.89 dL/g. Also, the glass-transition temperature (Tg) of synthetic polymers was in the range of 214–273°C and 10% weight loss temperatures (T10%) for the synthesized compounds were in the temperature range of 280–492°C in N2, and the percentage of residual ash between 61 and 74%. The adsorption rate of Hg2+, Co2+, Pb2+, Cr2+, and Cd2+ metal ions by PA containing terephthalic acid (PAT) and its nanocomposite (NCPAT) showed that nanocomposite has a better performance compared to PAT. The highest and lowest removal efficiency was related to Hg2+ and Pb2+ ion, respectively. Finally, antibacterial test results against Gram-positive and Gram-negative bacteria showed favorable inhibitory effects of all the synthesized polymers.

Computational mechanistic studies on persulfate assisted p-phenylenediamine polymerization.

p-Phenylenediamine (p-PDA) is a monomer of many important polymers such as kevlar, twaron, poly-p-PDA. Most of the noticed polymers formation is initiated by a free-radical, but their polymerization mechanism is not elucidated computationally. The proposed study helps to fully understand the frequently utilized initiator/oxidant, potassium persulfate (K2 S2 O8 ) role in the aromatic diamines polymerization, which support experimental protocols, and a polymer scope. The formation of the poly-p-PDA is studied with the density functional theory (DFT) B3LYP-D3 functional using experimental polymerization parameters (0°C and aqueous media). K2 S2 O8 initiated free-radical polymerization of p-PDA is studied in detail, taking into account sulfate free-radical (SO4 - )· , SFR, persulfate anion (S2 O8 )2- , PA and K2 S2 O8 cluster, PP. The reaction mechanism is calculated as the conversion of p-PDA to free-radical, the p-PDA free-radical attack to the next p-PDA (dimerization), ammonia extrusion from the dimer adduct, the dimer adduct conversion to the free-radical (completion of p-PDA polymerization cycle) for the polymer chain elongation. Calculations show that the dimerization step is the rate-limiting step with a 29.2kcal/mol energy barrier when SFR initiates polymerization. In contrast, the PA-assisted dimerization energy barrier is only 12.7kcal/mol. PP supported polymerization is calculated to have very shallow energy barriers completing the polymerization cycle, i.e., dimerization (TS2K, ∆G‡ = 11.6kcal/mol) and ammonia extrusion (TS3K, ∆G‡ = 6.7kcal/mol).