Benzophenonetetracarboxylic Dianhydride Research Articles

Polyimides with ultra-low coefficient of thermal expansion derived from diamine containing bisbenzimidazole and bisamide

To provide polyimide (PI) with high heat resistance and ultra-low coefficient of thermal expansion (CTE) for use in flexible display substrates, a novel diamine with bisbenzimidazole and bisamide groups, namely N,N'-(1H,1'H-[5,5'-bibenzo[d]imidazole]-2,2'-diyl)bis(4-aminobenzamide) (BZBA), was designed and successfully synthesized. Several poly(benzimidazole-amide-imide) (PBIAI) films were prepared by thermal imidization with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and 4,4'-(hexafluoroisopropylindene)-diphthalic anhydride (6FDA), respectively. Among them, BZBA-BPDA has a high glass transition temperatures ( Tg = 345 °C) while achieving an extremely low coefficients of thermal expansion (CTE = 1.9 ppm K−1), meeting the processing requirements of polymer flexible substrates in OLED devices. The effects of different dianhydrides on the performance of PBIAIs were compared, providing a meaningful reference for further adjusting the PI molecular structure to meet specific requirements for industrial polymer films.

Fabrication of thermally resistant and mechanically flexible polyimide foams with anisotropic pore structures for thermal insulation and irradiation tolerance applications

Flexible polyimide foams (PIFs) demonstrate a great potential for applications in the fields of thermal insulation, flame retardancy and irradiation tolerance. In this work, mechanically flexible PIFs with anisotropic pore structure were prepared by adopting the copolymerization strategy and microwave-assisted foaming process. The copolymerization reaction was conducted to synthesize polyester ammonium salt (PEAS) precursors using 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) as dianhydride, 4,4′-diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl sulfone (DDS) as the copolymerized diamines; afterwards, PEAS powders with particle sizes ranging from 100 to 300 μm were obtained by drying, crushing and sieving treatments, which were used as the feedstock for “bottom-up” microwave-assisted foaming and thermal imidization process, thereby leading to the formation of PIFs with regular three-dimensional near-spherical pores in vertical direction (parallel to the pore growth direction) and the aligned ellipsoidal strip-like pore structure in horizontal direction. The directional growth of foam pores resulted in anisotropic mechanical flexibility and thermal insulation performance. Moreover, PIFs possessed excellent thermal stability and flame retardancy with the initial thermal degradation temperature higher than 545 °C and limited oxygen index up to 58.8%. The PIFs exhibited exceptional thermal insulation performance with thermal conductivity values ranging from 0.0276 to 0.0517 W/(m·K) between 25 and 300 °C. Additionally, the PIFs demonstrated excellent irradiation tolerance, with the mechanical and thermal stability retention rate being above 96% after the irradiation experiment (radiation dosage: 1.15 × 105 Gy) using 60Co source. Thus, lightweight PIFs with superior high temperature thermal insulation performance, flame retardancy and irradiation tolerance were successfully prepared, which showed potential applications in aerospace, medical and nuclear power sectors.

Monomer Dependence of Colorless and Transparent Polyimide Films: Thermomechanical Properties, Optical Transparency, and Solubility.

Six poly(amic acid)s (PAAs) were synthesized by reacting bis(3-aminophenyl) sulfone with various dianhydride monomers such as pyromellitic dianhydride, 4,4'-biphthalic anhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 4,4'-oxidiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride. These PAAs were then converted to polyimide (PI) films by thermal imidization at various temperatures. To obtain colorless and transparent PI (CPI), the dianhydride monomer used in this study had an overall bent structure, a structure containing a strong electron-withdrawing -CF3 substituent or an alicyclic ring. In addition, some monomers contained ether or ketone functional groups in their bent structures. The thermomechanical properties, optical transparency, and solubility of CPI films with six different dianhydride monomer structures were investigated, and the correlation between the monomer structure and CPI film properties was clarified. Overall, CPI with an aromatic main chain structure or a linear structure had excellent thermal and mechanical properties. In contrast, CPI with a bent structure containing functional groups or substituents in the main chain exhibited excellent optical transparency and solubility.

Green fabrication of carbon dioxide-based polycarbonates with durable antimicrobial properties and UV resistance

Bacterial infections pose a major threat to human health and continue to be a major challenge in medicine. In addition, the emergence of antibiotic-resistant bacteria has exacerbated the difficulty of treating such infections. To combat the spread of infections and reduce reliance on antibiotics, it is increasingly recognized as important to develop efficient antimicrobial materials. Herein, we have successfully designed and synthesized carbon dioxide-based polycarbonates containing photosensitive benzophenone groups and characterized their structures and properties. The modified polycarbonate exhibits strong UV aging resistance and also has the ability to produce reactive oxygen species through electron leaps when exposed to UV radiation. This generates oxidative stress in pathogens, resulting in their inactivation or death, thereby imparting antimicrobial properties to the material. The experimental findings demonstrate that PPCB maintains its stability in terms of both composition and surface morphology when exposed to continuous UV irradiation. The carbon dioxide-based polycarbonates, which were modified with varying amounts of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, exhibited bacteriostatic effects of 99% and 91% against the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli, respectively. This novel material may have potential applications in the development of bacteriostatic surfaces for medical devices and biomaterials.

Lightweight thermo- and heat-resistant composite materials based on polyimide foam

A prepolymer foaming composition based on 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride methyl ester and diamines: 4,4'-diaminodiphenylmethane and m-phenylenediamine for the production of high-temperature polyimide foam (PIF) is proposed. The p ossibility o f u sing P IF a s a b inder f or c omposite materials (foam composites) reinforced with carbon or organic fibers with low density (0.4–1.1 g/cm3) a s a result of foaming of the binder during the formation of the foam composite is shown. The density and mechanical properties of the foam composite can vary within a relatively wide range depending on the volume content of the fiber and air pores. The high glass transition temperature of 260°C, combined with the high thermal stability of carbon or polyimide fibers, contributes to the retention of the mechanical properties of such composites at elevated temperatures. The temperature of the start of mass loss of the foam composite must be at least 550°C, and it depends on the type of fibrous material. The combination of the excellent thermal and mechanical properties of lightweight PIF composites, together with the exceptional fire resistance of polyimide materials, may provide new applications in advanced aircraft and shipbuilding technologies.

Sunlight-induced antibacterial poly(vinyl alcohol) grafted 3,3′,4,4′-benzophenone tetracarboxylic dianhydride film for the preservation of Mongolian cheese

Mongolian cheese is a classic grassland specialty in Inner Mongolia. However, there are mildew, fat precipitation, and short shelf life phenomenon. Herein, we refabricated poly(vinyl alcohol) grafted 3,3′,4,4′-benzophenone tetracarboxylic dianhydride film (PBF) with antibacterial activity via solvent casting method. The content of the produced reactive oxygen species （ROS）by PBF was measured, and the preservation effect of PBF on Mongolian cheese was discussed. The prepared PBF has high antimicrobial efficiency (>99 %), can be recycled 3 times. Later, we characterized the microbial diversity of cheese by high-throughput DNA sequencing of 16 S rDNA libraries, and a series of quality indexes were determined for cheese. Results showed that PBF can effectively inhibited five pathogenic microorganisms and controlled the total number of bacteria on Mongolian cheese made it shelf stable for 8 days at 25 °C. The PBF was considered a potential packaging film in the protection of Mongolian cheese.

Fabrication of Lightweight Polyimide Foams with Exceptional Mechanical and Thermal Properties.

Lightweight polyimide foams (PIFs) with exceptional thermal resistance and compressive properties arefabricated by heating polyester ammonium salts (PEASs) which areprepared by copolymerizing 4, 4'-diaminobenzanilide (DABA), 4, 4'-diaminodiphenyl methane (MDA) and 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA). Hydrogen bonds areformed between CONH and CO in the PI chains due to the addition of DABA and the melt viscosity of PEAS precursors increase with increasing content of DABA, which isadvantageous to bind the foaming gases for cell expansion. The expansion ratio of PEAS precursors isincreased from 633% to 1133% when the molar ratio of MDA/DABA ischanged from 10:0 to 6:4. The compressive strength and modulus of PIFM9D1 (i.e., the molar ratio of MDA/DABA is9:1, foam density: 120.8 kg m-3 ) reach as high as 0.59 and 15.0MPa, respectively. The PIFs possess prominent thermal performance with the initial thermal degradation temperatures (under both nitrogen and air atmosphere) and glass transition temperatures (as assessed by DSC and DMA) exceeding 511 and 292°C, respectively. The thermal conductivity of PIFs islower than 0.049 W m-1 K-1 , which exhibits promising applications for serving as high-temperature thermal insulation materials in the fields of aerospace, marine, and nuclear sectors among others.

Pillared Carbon Membranes Derived from Cardo Polymers.

Carbon molecular sieve membranes (CMSMs) were prepared by carbonizing the high free volume polyimide BTDA-BAF that is obtained from the reaction of benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BTDA) and 9,9-bis(4-aminophenyl) fluorene (BAF). The bulky cardo groups prevented a tight packing and rotation of the chains that leads to high permeabilities of their CMSMs. The incorporation of metal-organic polyhedra 18 (MOP-18, a copper-based MOP) in the BTDA-BAF polymer before pyrolysis at 550 °C prevented the collapse of the pores and the aging of the CMSMs. It was found that upon decomposition of MOP-18, a distribution of copper nanoparticles minimized the collapse of the graphitic sheets that formed the micropores and mesopores in the CMSM. The pillared CMSMs displayed CO2 and CH4 permeabilities of 12,729 and 659 Barrer, respectively, with a CO2/CH4 selectivity of 19.3 after 3 weeks of aging. The permselectivity properties of these membranes was determined to be at the 2019 Robeson upper bound. In contrast, the CMSMs from pure BTDA-BAF aged three times faster than the CMSMs from MOP-18/BTDA-BAF and exhibited lower CO2 and CH4 permeabilities of 5337 and 573 Barrer, respectively, with a CO2/CH4 selectivity of 9.3. The non-pillared CMSMs performed below the upper bound.

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.

Effect of monomer moieties on the aggregate structure and gas transport properties of polyimides: Insights from experiments and simulations

AbstractTFDB‐based PIs (BTDA‐TFDB, PMDA‐TFDB and 6FDA‐TFDB) were prepared by the polymerization of 2,2′‐bis(trifluoromethyl) benzidine (TFDB) with three different dianhydrides, which contained flexible carbonyl bridged unit, rigid‐rod moiety without bridged unit, and bulky CF3 bridged unit in dianhydride moieties, respectively. The influence of dianhydride moieties on the aggregate structure and gas permeation performances of polyimide was systematically investigated in relation to their chain packing and free volumes, using the methods of molecular simulation, positron annihilation measurement and X‐ray diffractogram. Changing the dianhydride from benzophenonetetracarboxylic dianhydride (BTDA) to pyromellitic dianhydride (PMDA) and 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the gas permeation coefficients of polyimide increased, and the gas permeation selectivity (O2/N2, CO2/N2, H2/N2 and CO2/CH4) decreased. With the introduction of flexible carbonyl bridged unit into dianhydride moiety, the high rotational mobility favored tight chains packing and decreased free volumes, which in turn led to the lowest permeation coefficients of BTDA‐TFDB. The bulky CF3 bridged unit in dianhydride moiety greatly restricted chain packing and increased free volumes, thus resulting in the highest permeation coefficients of 6FDA‐TFDB. From BTDA‐TFDB to PMDA‐TFDB and 6FDA‐TFDB, the permeation selectivity decreased. This was mostly ascribed to the reduction of diffusive selectivity, which was resulted from the increase in free volumes.

Synergistic improvement of CO2/CH4 separation performance of phenolphthalein-based polyimide membranes by thermal decomposition and thermal-oxidative crosslinking

Thermal oxidative crosslinking results in the generation of oxygen bridges among polymer chains and helps regulate the membrane microstructure. Simultaneously, any strategy to increase the crosslinking sites of polyimide (PI) can improve the crosslinking efficiency and allow precise control of the pore structure of membranes. Phenolphthalein-based PIs are potentially suitable precursors for thermal oxidative crosslinking of membranes, since thermal treatment will result in the degradation of lactone ring leading to the generation of a pair of phenyl crosslinking sites. In this work, three phenolphthalein-based diamines with different structures were designed and synthesized. The three diamines were subsequently reacted with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) to prepare phenolphthalein-based PIs. The original membranes were post-treated by thermal oxidation crosslinking at 400 °C and 425 °C, respectively; the lactone ring underwent decomposition, and the imide ring opened at the same time, resulting in the generation of multiple crosslinking sites and correspondingly improving the crosslinking efficiency. The effect of the side groups (−CH3, –CF3 or unsubstituted) of phenolphthalein-based diamine and thermal treatment temperatures on the gas separation performance of phenolphthalein-based PI membranes were investigated. Wide-angle X-ray diffractometry (WAXD) and wide-angle X-ray scattering (WAXS) analysis demonstrated that the π-π stacking distance were improved. BTDA-FPP-425 had a CO2/CH4 selectivity of 37.68. This thermal degradation along with thermal oxidative crosslinking strategy provides a promising approach for fabrication of CO2/CH4 separation membrane.

Effect of phosphoric acid molarity on the structural, thermal, mechanical, and electrical properties of polyimide/polyaniline nanocomposites

In this paper, we used two monomers, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and m,m'-diaminobenzophenone (m, m’-DABP), to produce polyamide acid and then converted it to polyimide (PI). The effects of phosphoric acid (H3PO4) molarity (1, 2, and 3 M) on the structural, thermal, mechanical, and electrical characteristics of the polyimides/polyaniline (PI/PANI) nanocomposites were studied. Two sharp reflection peaks were developed by the addition of PANI to PI. When 3 M H3PO4 is added, the crystalline sharp peak loses some of its intensity. The complex formation of PI/PANI-H3PO4 was confirmed by Fourier transform infrared spectroscopy studies. The surface morphologies of the H3PO4 complex with nanocomposites were investigated by using a scanning electron microscope. From differential scanning calorimetry studies, the glass transition temperatures of nanocomposites decrease dramatically with an increase in H3PO4. Microhardness, flexural strength, and young modulus all dropped as acid molarity increased, although elongation at break increased as H3PO4 molarity increased. After the addition of H3PO4, a drop in the dielectric constant and an increase in ionic conductivity were observed.

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.

Oligoimide-Mediated Graphene Oxide-Epoxy Nanocomposites with Enhanced Thermal Conductivity and Mechanical Properties.

The current study reports the preparation of thermally conductive polymeric nanocomposites. For this purpose, two epoxy-based nanocomposites were prepared by dispersing a different type of functionalized graphene oxide (GO) nanofiller in each series. Both these GO nanofillers were functionalized by covalently bonding oligoimide chains on their surfaces. In one series, these oligoimide chains were prepared by reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with a diamine 4,4′-methylenedianiline (MDA). While in the other case, BTDA was reacted with N,N′-[((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(4,1-phenylene)]bis(4-aminobenzamide) (BDM) to mount oligoimide chains on the surface of GO. Both types of oligoimide chains have amino groups as chain-end functional groups. These modified GO nanofillers were added to the epoxy matrices separately to prepare their respective nanocomposites (MDA-B-GO-epoxy nanocomposites and BDM-B-GO-epoxy nanocomposites). The chain-end amino groups of oligoimide chains reacted with the epoxy ring developing a covalent bonding between oligoimide chains of GO and the epoxy matrix. Moreover, these oligoimide chains prevented the agglomeration of GO by acting as spacer groups leading to the uniform dispersion of GO in the epoxy matrix. Various analytical techniques were used to examine the attachment of oligoimide chains to the GO surface, and to examine the morphology, curing potential, mechanical strength, thermal stability, and thermal conductivity of the prepared nanocomposites. We demonstrated that the thermal conductivity of MDA-B-GO-epoxy nanocomposites increased by 52% and an increase of 56% was observed in BDM-B-GO-epoxy nanocomposites. Similarly, a significant improvement was observed in the mechanical strength and thermal stability of both types of nanocomposites.

Polyimide film containing sulfone groups with high dielectric properties

Polyimide dielectric film are highly demanded in the modern electronics industries and power systems at high temperature, but its low energy storage density severely limits their applications. In this paper, a kind of polyimide dielectric film was fabricated by copolymerization of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and 2-(4-amino-phenyl)-5-amino benzimidazole (BIA) with the introduction of 4,4′-diamino phenyl sulfone (DDS). With the increase of DDS contents, the dielectric constant of polyimide film could be improved to 4.45, and the dielectric loss angle remained below 5*10−3 within frequency of 1 Hz–103 Hz. The simulated molecular structure showed that the introduction of the sulfone groups could increase the chain spacing with larger free volume fraction, which facilitates a synergistic increase in dielectric constant while reducing dielectric loss. A high energy density of 3.27 J/cm3 at 380 MV/m at room temperature could be achieved by loading a small amount of 15mol% DDS. In addition, the film keeps good dielectric properties at high temperatures with the dielectric loss of 0.026 at 150 °C and 1 kHz. And the film can also maintain a high breakdown strength with an energy density of 1.14 J/cm3 at 260 MV/m and the efficiency of 74% at 150 °C, indicating its good potential for polymer film capacitors at high temperature.

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.

Fabrication of Rechargeable Photoactive Silk Fibroin/Polyvinyl Alcohol Blend Nanofibrous Membranes for Killing Bacteria.

Antibacterial materials that prevent bacterial infections and mitigate bacterial virulence have attracted great scientific interest. In recent decades, bactericidal polymers have been presented as promising candidates to combat bacterial pathogens. However, the preparation of such materials has proven to be extremely challenging. Herein, photoactive silk fibroin/polyvinyl alcohol blended nanofibrous membranes grafted with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (G-SF/PVA BNM) were fabricated by an electrospinning technique. The premise of this work is that the G-SF/PVA BNM can store photoactive activity under light irradiation and release reactive oxygen species for killing bacteria under dark conditions. The results showed that the resultant G-SF/PVA BNM exhibited the integrated properties of an ultrathin fiber diameter (298 nm), good mechanical properties, robust photoactive activity and photo-store capacity, and great photoinduced antibacterial activity against E. coli and S. aureus (99.999% bacterial reduction with 120 min). The successful construction of blended nanofibrous membranes gives a new possibility to the design of highly efficient antibacterial materials for public health protection.

Transport properties of O2, N2, and CO2 through the CMS membranes derived from tris(4‐aminophenyl)amine‐based polyimides

AbstractTwo carbon molecular sieve (CMS) membranes (XS22‐600 and XS23‐600) with closely matched pore‐size distribution were prepared via conditional pyrolysis of the hyperbranched tris(4‐aminophenyl)amine (TAPA)‐based polyimide membranes. The differentiation in their nitrogen contents comes from the dianhydride monomers, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and pyromellitic (PMDA). These CMS membranes were characterized using Fourier transform infrared, XRD, XPS, and Raman analysis. XS22‐600 with larger ultra‐micropores has a lower selectivity of 3.6 than XS23‐600 (4.1), implying the molecular sieving mechanism domains in O2/N2 separation. XS22‐600 with higher nitrogen content exhibits a higher selectivity of 19.1 than XS23‐600 (13.1) in CO2/N2 separation. The doped nitrogen atoms exhibit a beneficial effect on CO2 surface diffusing through the CMS membranes. This work provides empirical data for understanding the synergistic effect of selective surface diffusing and molecular sieving in CO2/N2 separation.

Novel high performance poly(sulfone-ether-amide-imide)s

A novel sulfone ether amide diamine was prepared through a two-step synthetic route. At first, 3,3′-((sulfonyl bis(1,4-phenylene))bis(oxy))dianiline was prepared from nucleophilic aromatic substitution reaction of 3-aminophenol with 4,4′-dichlorodiphenyl sulfone in the presence of K2CO3. In the second step, the reaction of this compound with isophthaloyl chloride resulted in the preparation of a unique aromatic diamine containing amide, ether, and sulfone groups. Then three different kinds of poly(sulfone-ether-amide-imide)s were prepared via polycondensation reaction of the synthesized diamine with different dianhydrides including pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and hexafluoroisopropylidene diphthalic anhydride. The structures of synthesized precursors, monomer, and prepared polymers were characterized using elemental analysis, 1H-NMR and FT-IR spectroscopy methods. Inherent viscosity, molecular weight, thermal behavior and stability, flame retardancy, and solubility of polymers were studied. As the polymers showed high thermal stability and also improved solubility, they can be used as heat and fire resistant materials.

Thermally cross-linked ultra-robust membranes for plasticization resistance and permeation enhancement – A combined theoretical and experimental study

This study reports enhanced flux in plasticization-resistive ultra-robust membranes by thermally cross-linking a blend of carboxylated polyimide (PI) and ladder-like amino-polysilsesquioxane (LAPSQ). A series of BTDA-Durene:DABA PIs (BTDA: 3,3′,4,4′-benzophenonetetracarboxylic dianhydride) with three different 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene):3,5-diaminobenzoic acid (DABA) molar ratios (3:2, 2:1, and 4:1) exhibited an increase in gas permeability with an increasing Durene:DABA molar ratio before and after dehydration-induced cross-linking; this indicated that the bulky Durene moiety was more critical for flux enhancement than the number of carboxylated sites post-cross-linking. More importantly, the thermally cross-linked PI/LAPSQ (80/20) membrane exhibited a significantly enhanced CO 2 permeability of 817% than that of its pre-crosslinked counterpart without sacrificing CO 2 /N 2 or CO 2 /CH 4 selectivity due to a combination of decarboxylation and amidation-induced cross-linking. Molecular dynamics simulations revealed that such a drastic increase in CO 2 permeability was due to larger and/or more interconnected cavities formed in the thermally cross-linked PI/LAPSQ (80/20) membrane. In addition, it showed a substantial increase in hardness and reduced modulus owing to the rigid double-stranded siloxane backbone of LAPSQ and plasticization resistance up to a CO 2 feed pressure of 22 bar. ● Membranes were cross-linked by decarboxylation/amidation of a hybrid polymer blend. ● Siloxane backbone in cross-linked membranes increased hardness and reduced modulus. ● CO 2 permeability of hybrid membranes increased 817% after thermal cross-linking. ● MD simulations showed cross-linking forms larger and more interconnected cavities. ● Cross-linked hybrid membranes were plasticization resistant up to 22 bar of CO 2 .