Octa(aminophenyl)silsesquioxane Research Articles

Hybrid Dendrimer Network based on Silsesquioxane and glycidyl methacrylate for Enhanced Adsorption of Iodine and Dyes in Environmental Remediation.

A novelhybrid network was synthesized in two steps: the first step involved the attachment of glycidyl methacrylate (GMA)to octa(aminophenyl) silsesquioxane (OAPS) through a ring-opening reaction, forming a hybrid dendrimer structure, and the second stepinvolved the cross-linking of hybrid dendrimer using an azobisisobutyronitrile initiator to create the final hybrid network of OAPS-GMA. The synthesized hybrid material was comprehensively characterized using fourier transform infrared Spectroscopy (FTIR), nuclear magnetic resonance ((1H,13C, and 29Si NMR) spectroscopy, thermogravimetric Analysis (TGA), and scanning electron microscopy (SEM). The BET surface area was found to be 25.44 m²/g, and significant 2.341 cm³/g of total pore volume was observed. The TGA analysis shows that the material is highly stable up to 450 oC. The synthesized network demonstrated remarkable adsorption capacities for iodine and dyes. It exhibited an iodine adsorption capacity of 3.4g/g from vapors and 874mg/g from solution. Additionally, it showed significant adsorption capacities for Rhodamine B and Congo red, with values of 762mg/g and 517mg/g, respectively. This study not only provides a novel method for preparing GMA-functionalized silsesquioxane-based porous hybrid polymers but also contributes to advancing solutions for environmental pollution issues.

Molecular‐level fabrication strategies for the POSS cross‐linked polybenzoxazines

AbstractIn order to study the dispersion and compatibility of polysilsesquioxane (POSS) with different functional groups in benzoxazine resin, four different polysilsesquioxane/polybenzoxazine (POSS/PBZ) composites are prepared based on 3‐phenyl‐3,4‐dihydro‐2H‐benzoxazine (PHa), unreactive Octaphenylsilsesquioxane (OPS), Mercaptopropyl‐isobutyl silsesquioxane (SPOSS) containing one reactive sulfhydryl group, Aminopropyl‐isobutylsilsesquioxane (NPOSS) containing one reactive amino group and Octa (aminophenyl) silsesquioxane (OAPS) containing eight reactive amino groups, respectively. Scanning electron microscope (SEM), transmission electron microscope (TEM), and transmission electron microscope with probe corrector (AC‐TEM) are used to investigate compatibility. The results indicate that OAPS have very good compatibility and interaction with benzoxazine in the molecular level based on the microstructure. Besides, molecular and mesoscopic dynamic simulations (MesoDyn) also confirms OAPS and PHa have the best compatibility based on the micro and mesoscopic aspects. Then their properties of thermal stability and glass transition temperature (Tg) are identified by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. While OAPS is beneficial to increase the initial decomposition temperature (T5%) of PBZ by 26 °C and the Tg by 16 °C, comparing with pure PHa. However, NPOSS and SPOSS aggregate into micron‐sized silicon spheres, and OPS precipitates and deposits on the bottom of the resin, which could weaken the property of their thermal stability.

A Hidden Relaxation Process in Poly(2-vinylpyridine) Homopolymers, Copolymers, and Nanocomposites

In broadband dielectric spectroscopy experiments, we find that introducing an air gap between the top electrode and the polymer sample reduces DC conductivity substantially, allowing the study of low-frequency relaxations, whose signal would otherwise be hidden by the DC conductivity signal. An extra process slower than the α-relaxation process is observed in poly(2-vinylpyridine) (P2VP), consistent with some earlier reports. This “slower process” was studied in two heterogeneous systems to examine the interaction between the 2VP and other species to elucidate the mechanism behind the slower process signal. In a random copolymer of styrene and 2VP, the relaxation strength of the slower process relative to the α-process increases substantially at low 2VP mole fractions. Additionally, in a composite of P2VP and octa(aminophenyl) silsesquioxane (OAPS), the presence of OAPS increases both the strength and timescale of the slower process, leaving the α-relaxation process relatively unchanged. This suggests that the slower process could be caused by cooperative polymer relaxation coupled to the transport of heterogeneous components and impurities. Further studies are needed to probe the molecular-level mechanism of this slower process and its effect on interfacial properties.

Identifying the meta, para and ortho isomers in octa(aminophenyl)silsesquioxane (OAPS) from joint experimental characterizations and theoretical predictions of the IR and NMR spectra

Polyhedral oligomeric silsesquioxane (POSS) compounds are defined by the chemical formula (RSiO3/2)8 with R being an organic fragment. They display versatile features due to the combination of both their stable Si-O-Si inorganic cores and the large number of possible organic groups that can be attached to them. The present work aims at characterizing a highly-thermoresistant POSS, the octa(aminophenyl)silsesquioxane (OAPS). This siloxane-based cage has three different isomers depending on the meta, ortho and para positions of the amines with respect to the phenyl groups and can be obtained using two synthesis routes. However, the presence of the isomers depends on the synthesis route and remains up to now an open question.Experimental characterizations including pycnometry, infrared spectroscopy (IR), 1-dimensional and 2-dimensional nuclear magnetic resonance (NMR) have been performed for a commercial OAPS containing all three isomers and a controlled OAPS containing only the para and meta isomers. The density is found to be insensitive to the nature of the isomers, unlike the IR, 13C NMR and 1H NMR spectra that are isomer-dependent. To better identify the isomers, the experimental IR and NMR spectra were compared to predictions from Density Functional Theory (DFT) quantum mechanical methods and by machine-learning analyses. Within this context, quantum mechanical methods were found to be clearly superior to machine-learning methods, despite being computationally much more expensive. As a result, several peaks in the IR spectra and each peak in both the 13C NMR and 1H NMR spectra could be assigned to a specific OAPS isomer.

Molecular Characterization of Membrane Gas Separation under Very High Temperatures and Pressure: Single- and Mixed-Gas CO2/CH4 and CO2/N2 Permselectivities in Hybrid Networks.

This work illustrates the potential of using atomistic molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations prior to experiments in order to pre-screen candidate membrane structures for gas separation, under harsh conditions of temperature and pressure. It compares at 300 °C and 400 °C the CO2/CH4 and CO2/N2 sieving properties of a series of hybrid networks based on inorganic silsesquioxanes hyper-cross-linked with small organic PMDA or 6FDA imides. The inorganic precursors are the octa(aminopropyl)silsesquioxane (POSS), which degrades above 300 °C, and the octa(aminophenyl)silsesquioxane (OAPS), which has three possible meta, para or ortho isomers and is expected to resist well above 400 °C. As such, the polyPOSS-imide networks were tested at 300 °C only, while the polyOAPS-imide networks were tested at both 300 °C and 400 °C. The feed gas pressure was set to 60 bar in all the simulations. The morphologies and densities of the pure model networks at 300 °C and 400 °C are strongly dependent on their precursors, with the amount of significant free volume ranging from ~2% to ~20%. Since measurements at high temperatures and pressures are difficult to carry out in a laboratory, six isomer-specific polyOAPS-imides and two polyPOSS-imides were simulated in order to assess their N2, CH4 and CO2 permselectivities under such harsh conditions. The models were first analyzed under single-gas conditions, but to be closer to the real processes, the networks that maintained CO2/CH4 and CO2/N2 ideal permselectivities above 2 were also tested with binary-gas 90%/10% CH4/CO2 and N2/CO2 feeds. At very high temperatures, the single-gas solubility coefficients vary in the same order as their critical temperatures, but the differences between the penetrants are attenuated and the plasticizing effect of CO2 is strongly reduced. The single-gas diffusion coefficients correlate well with the amount of available free volume in the matrices. Some OAPS-based networks exhibit a nanoporous behavior, while the others are less permeable and show higher ideal permselectivities. Four of the networks were further tested under mixed-gas conditions. The solubility coefficient improved for CO2, while the diffusion selectivity remained similar for the CO2/CH4 pair and disappeared for the CO2/N2 pair. The real separation factor is, thus, mostly governed by the solubility. Two polyOAPS-imide networks, i.e., the polyorthoOAPS-PMDA and the polymetaOAPS-6FDA, seem to be able to maintain their CO2/CH4 and CO2/N2 sieving abilities above 2 at 400 °C. These are outstanding performances for polymer-based membranes, and consequently, it is important to be able to produce isomer-specific polyOAPS-imides for use as gas separation membranes under harsh conditions.

Effect of polyhedral oligomeric silsesquioxane on combustion performance of HTPB propellants

HTPB-based (hydroxyl‑terminated polybutadiene) propellants containing aluminum and ammonium perchlorate (AP) were prepared with 1 wt% polyhedral oligomeric silsesquioxanes (POSS) and Fe2O3, respectively. The influences of POSS compounds on combustion performance of HTPB propellants were investigated. Four POSS compounds, octa (phenyl) silsesquioxane (OPS), octa (nitrophenyl) silsesquioxane (ONPS), octa (dinitrophenyl) silsesquioxane (ODNPS) and octa (aminophenyl) silsesquioxane (OAPS) were used. Their compatibility with the HTPB propellant components were tested by DSC analysis. Their combustion heats of and sensitivities were measured by oxygen bomb calorimeter and friction and impact tests, respectively. The results show that ODNPS and ONPS belong to low sensitive energetic compounds. The POSS compounds have good compatibility with the components of HTPB propellant. The burning rates of the HTPB propellants were measured in combustion chamber with transparent window under pressure. The combustion behaviors of the propellants under atmospheric pressure were recorded using high-speed camera. The condensed-phase combustion products were collected and studied through the SEM observation, XRD analysis and particle size measurements. The POSSs can increase the burning rates of HTPB propellants. With the ODNPS, the burning rate of HTPB propellant is similar to that of Fe2O3. The addition of the OPS, OAPS and Fe2O3 reduces the combustion heats of propellants, while with ONPS and ODNPS, the combustion heats are close to that of the HTPB propellant. POSS compounds can promote the combustion of aluminum in the propellants, inhibit the agglomeration of aluminum particles in the combustion process, and reduce the size of condensed phase products. These should correlate to the formation of the nano carbon layers from the POSS compounds in combustion of the propellants.

POSS/PDMS composite pervaporation membranes for furfural recovery

In this work, polyhedral oligomeric silsesquioxane (POSS) with two different functional groups, octa(nitrophenyl)silsesquioxane (ONPS) and octa(aminophenyl)silsesquioxane (OAPS), was incorporated with polydimethylsiloxane (PDMS), forming composite membranes for furfural recovery via pervaporation process. The addition of POSS had enhanced the hydrophobicity of the PDMS and improved the affinity of furfural with membranes. At the same filler loading, OAPS/PDMS membrane showed a superior separation factor to the bare PDMS and the ONPS/PDMS composite. The effects of OAPS loading on property and pervaporation performance of the membrane were also investigated. The loading at 15 wt% was found to be the optimum value that could improve water contact angle to 116° and furfural affinity to achieve over 20% improvement in both furfural flux and separation factor. The PDMS membrane with 15 wt% of OAPS could provide 7-fold concentrated furfural solution compared to the feed. The newly developed OAPS/PDMS membrane showed great potential for furfural recovery as the alternative separation method with improved energy-effectiveness and low chemical footprint.

Porous polymers from octa(amino-phenyl)silsesquioxane and metalloporphyrin as peroxidase-mimicking enzyme for malathion colorimetric sensor

Rapid and efficient pesticide detection methods are particularly important due to the growing problems of pesticide residues. Here, a new azo-based porous organic polymer, Azo(Fe)PPOP, was prepared from octa(amino-phenyl)silsesquioxane (OAPS) and iron(III) 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (FeTPP(NO2)4) via a simple coupling reaction without the participation of metal catalysts. The inorganic cage units of OAPS endowed Azo(Fe)PPOP a porous framework, high surface area, favorably thermal and chemical stability. In Azo(Fe)PPOP, iron(III) porphyrin units were individually isolated in a fixed location, which could effectively avoid dimerization or self-oxidation as happens as in the case of porphyrin monomers. Such a unique structure made Azo(Fe)PPOP exhibit an excellent peroxidase-like catalytic performance in the presence of H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB). Because of these advantages, we established a selective, facile, and sensitive colorimetric platform for direct detection of malathion within a very short time (3 min) with a low detection limit (8.5 nM). In addition, the recognition mechanism between Azo(Fe)PPOP and malathion was verified using X-ray photoelectron spectroscopy spectra. The practicality of the constructed platform was further executed by the detection of the pesticide in soil and food samples.

Molecular characterization of polyOAPS-imide isomer hyper-cross-linked membranes: Free-volume morphologies and sorption isotherms for CH4 and CO2

PolyPOSS-imides are hybrid hyper-cross-linked networks based on inorganic octa(aminopropyl)silsesquioxane (POSS) cages covalently bonded via organic imide bridges. They were initially developed for separations under harsh conditions, but they cannot be used above 300 °C due to the decomposition of their –(CH2)3– propyl linkers. Replacing the aliphatic-arm POSS with its phenyl-arm derivative, octa(aminophenyl)silsesquioxane (OAPS), should thus increase their resistance. However, OAPS has three possible isomers depending on the meta, para or ortho position of the –NH2 group on the phenyl ring. To pre-screen the most interesting structures before attempting synthesis, molecular dynamics (MD) simulations were recently used to compare twenty-two model networks based on the OAPS isomers, the initial POSS and several imide precursors at high temperatures. Six phenyl-arm polyOAPS-PMDA and polyOAPS-6FDA and two aliphatic-arm polyPOSS-PMDA and polyPOSS-6FDA were selected for further analyses of their CH4 and CO2 sorption isotherms at 35 °C. All of them have an average number of ~5 links per cage and cross-linking densities of ~3.8. In terms of connectivities and free-volume morphologies, both the metaOAPS and paraOAPS networks are found to be open structures with many low-energy sites and high penetrant solubilities. On the other hand, the ortho functionalization leads to denser morphologies associated to lower solubilities, which makes it closer to the POSS networks. Differences are enhanced when the inorganic precursor is associated to a rigid organic linker such as PMDA.The iterative GCMC (Grand Canonical Monte Carlo)-MD sorption-relaxation technique was used to predict the single-gas uptakes of CH4 and CO2 in the networks over an extended 0–60 bar pressure range at 35 °C. The sorption capacities varied in the order paraOAPS > metaOAPS > orthoOAPS > POSS for the inorganic precursor, and PMDA > 6FDA for the organic precursor (except for the orthoOAPS). All correlate directly to the accessible free-volume, but the CO2/CH4 ideal sorption selectivities remained essentially the same over the whole pressure range. Compared to POSS, OAPS showed less swelling at equivalent penetrant concentrations in the matrix. It is also more resistant to other mechanical deformations such as isotropic dilation or uniaxial tension. This confirms that the polyOAPS-imides can indeed be used under harsher conditions than the current polyPOSS-imides, without loss of the CO2/CH4 sorption selectivities.

The significant effect of octa(aminophenyl)silsesquioxane on the electrospun ion-selective and ultra-strong poly-m-phenyleneisophthalamide separator for enhanced electrochemical performance of lithium-sulfur battery

In this paper, a novel ion-selective and ultra-strong poly-m-phenyleneisophthalamide (PMIA)-based gel polymer electrolyte (GPE) containing fluorinated emulsion and octa(aminophenyl)silsesquioxane (OAPS) nanoparticles is rationally designed for lithium-sulfur batteries by electrospinning. Under the significant effect of OAPS, the PMIA-based GPE acts as a multi-functional separator with exceedingly high electrolyte uptake, exceptionalthermalstability and robust mechanical strength. Particularly, the -NH2 groups of OAPS provide an electronegative environment, which facilitate the lithium ions migration while inhibit the negative polysulfide anions transfer. Thus, the PMIA-based GPE exhibits an effective electrostatic shielding effect to restrain lithium polysulfide on cathode side, while vigorously stimulating the transmission of lithium ions. As a great result, the lithium ions migration, the interface impedance and the reversible rate capacity of the assembled lithium-sulfur battery obtain a marked improvement. Meantime, the cell with the PMIA-based separator, adopting conventional sulfur-carbon black as cathode materials, delivers a high initial capacity of 851.1 mAh·g−1 with capacity retention of 458.3 mAh·g−1 after 800 cycles at 0.5 C rate, accompanied by a low capacity decay of 0.057% per cycle. Therefore, the prepared PMIA separator imbedding with OAPS can be deemed as an extraordinary potential candidate for the application in high-performance lithium-sulfur cells.

Fluorinated polyimide nanocomposites for low K dielectric applications

A novel fluorinated amine compound prepared was characterized by 1H NMR, 19F NMR and FTIR. Subsequently, polymerized with pyromellitic dianhydride results in the formation of neat fluorinated polyimide matrix (PI). In addition, three different nanomaterials such as of graphene oxide (GO), Octa (aminophenyl) silsesquioxane (OAPS) and graphene oxide blended with Octa (aminophenyl) silsesquioxane (GO-OAPS) were reinforced separately with PI in varying weight percentages. The developed composites were studied for their thermal, dielectric and hydrophobic behaviour and compared. Comparatively the 7% OAPS-GO/PI exhibits lower dielectric constant (k = 2.1) than that of neat PI, GO/PI and OAPS/PI composites. The OAPS grafted onto the GO surface contributes for lower polarity due to its porous caged structure and contributes for higher insulation behaviour. Further, the 7% OAPS-GO/PI also exhibits higher contact angle (107°) due to the less polar nature of the composites which in turn contributes to enhanced hydrophobic behaviour. The data obtained from morphological, surface and dielectric studies indicate that the OAPS-GO/PI composites exhibited substantially improved hydrophobic and dielectric properties than that of GO/PI and OAPS/PI.

Preparation of cellulose insulating paper of low dielectric constant by OAPS grafting

This study aims to decrease the dielectric constant of cellulose insulating paper by octa(aminophenyl)silsesquioxane (OAPS) grafting. OAPS was grafted onto the primary hydroxyl group of cellulose molecules via amino groups and epichlorohydrin. The dielectric constant and dielectric loss of insulating paper before and after modification were investigated. Relative to the unmodified paper, the dielectric constant of 15 wt% OAPS-grafted paper decreased from 5.27 to 4.28, and the dielectric loss decreased by 37.5% at 50 Hz. The movement and orientation polarization of the cellulose chains could be restricted due to the porous macromolecular structure and nano quantum interface effect produced by OAPS, thereby resulting in the reduction of cellulose polarizability. Moreover, the OAPS grafting modification does not degrade the other properties of cellulose insulation, i.e., its thermal stability, mechanical performance, fire-resistant properties, and electrical strength. OAPS grafting has promising potential application for preparing low dielectric constant insulating paper.

Multifunctional behavior of POSS-reinforced imidazole core polyimide nanocomposites

A new imidazole core unsymmetrical diamine monomer (4, 4′ (4, 5-diphenyl-1H-imidazol-1, 2-diyl) dianiline) was successfully synthesized and used as precursor to develop polyimide (PI). In addition, different weight percentages of octaaminophenyl silsesquioxane (NH2-POSS) were reinforced to form, respective, POSS–PI nanocomposites. The formation of polyimides and composites was confirmed by various spectral analyses in addition to their morphology studies by scanning electron microscopy and high-resolution transmission electron microscope. Further, the developed neat PI and POSS–PI nanocomposites were studied for their thermal, optical, dielectric and antimicrobial properties. Data resulted from different studies indicated that the incorporation of 10 wt% NH2-POSS into the PI matrix show higher glass transition temperature, higher thermal stability and better UV shielding behavior when compared to the neat PI matrix as well as other POSS–PI composites. Dielectric studies infer that the value of dielectric constant was decreased with increasing the weight percentages of NH2-POSS reinforcement and the lowest value of dielectric constant (k = 2.1) was obtained for 10 wt% POSS–PI hybrid nanocomposites in addition to its better antimicrobial behavior. Thus, the current study promises that the developed PI and POSS–PI can be used as a multifunctional composite in various high-performance applications.

Octa(aminophenyl)silsesquioxane derived nitrogen-doped well-defined nanoporous carbon materials: Synthesis and application for supercapacitors

Development of nitrogen-doped carbon materials with well-defined nanoporous structure is critical due to their versatile applications for the electrochemical energy conversion and storage devices. In this work, we report a new and facile strategy for the synthesis of N-doped nanoporous carbon materials (NNC) with adjustable nitrogen content (3.63–5.37%), large surface area (1942m2g−1), uniform and well-defined nanopores (∼0.85–1nm) and high nanopore volume (0.53–0.88cm3g−1) derived from octa(aminophenyl)silsesquioxane (OAPS). OAPS is miscible with phenolic resol, forming an uniformly distributed and self-templated and cross-linked copolymer of OAPS and resol and NNC materials after carbonization and removal of monodispersed silica domains. The symmetric supercapacitor assembled by the electrodes with OAPS to resol ratio of 95:5 in 1M H2SO4 electrolyte exhibits the high specific capacitance of 230Fg−1at 1Ag−1 due to the pseudocapacitive contribution of the N-groups, and delivers a high energy density of 5Whkg−1 with a power density of 1445Wkg−1 and high stability with performance loss of less than 5% over 10,000 cycles at 50mVs−1.

Synthesis and characterization of flexible and high-temperature resistant polyimide aerogel with ultra-low dielectric constant

A polyimide (PI) aerogel with excellent combined thermal and dielectric properties was successfully prepared by the polycondensation of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 5-amino-2-(4-aminophenyl)benzoxazole (APBO) and octa(amino-phenyl)silsesquioxane (OAPS) crosslinker, followed by a supercritical carbon dioxide (scCO2) drying treatment. The developed PI aerogel exhibited an ultra-low dielectric constant (k) of 1.15 at a frequency of 2.75 GHz, a volume resistivity of 5.45·10 14 Ω·cm, and a dielectric strength of 132 kV/cm. The flexible PI aerogel exhibited an open- pore microstructure consisting of three-dimensional network with tangled nanofibers morphology with a porosity of 85.6% (volume ratio), an average pore diameter of 19.2 nm, and a Brunauer-Emmet-Teller (BET) surface area of 428.6 m 2 /g. In addition, the PI aerogel showed excellent thermal stability with a glass transition temperature (Tg) of 358.3 °C, a 5% weight loss temperature over 500 °C, and a residual weight ratio of 66.7% at 750 °C in nitrogen.

Synthesis and characterization of optically active polyimides and their octa(aminophenyl)silsesquioxane nanocomposites

New optically active diamine (3,5-diaminophenyl)((R)-3,4-dihydro-1-phenylisoquinoline-2(1H)-yl)methanone was successfully prepared. Optically active polyimides (PIs) were synthesized by reacting the prepared diamine with the aromatic tetracarboxylic dianhydrides, namely, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride/pyromelltic dianhydride by thermal imidization method and characterized using Fourier transform infrared and nuclear magnetic resonance spectral techniques. Additionally, PI nanocomposites were also prepared by incorporating amino-functionalized polyhedral oligomeric silsesquioxane named as octa(aminophenyl)silsesquioxane (OAPS). The cut-off wavelengths of PIs and their nanocomposites were found to be less than 350 nm, indicating that the PIs are transparent. The PIs and their nanocomposites were found to have glass transition temperature between 204°C and 269°C (differential scanning calorimetric analysis). The 10% weight loss temperature and char yield were found to be 319.5–420.3°C and 26.3–62.7%, respectively. The PIs were found to be amorphous as indicated by X-ray analysis. The scanning electron microscopic images of the nanocomposites also reveal uniform distribution of the nanoparticles in the nanocomposite. PIs and PI/OAPS nanocomposites were found to have low dielectric constant in the range of 2.59–3.36.

Intrinsically Atomic-oxygen-resistant POSS-containing Polyimide Aerogels: Synthesis and Characterization

Abstract A series of polyimide aerogels with intrinsically atomic-oxygen-resistant features have been synthesized. For this purpose, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) was copolymerized with 2,2′-dimethylbenzidine (DMBZ) and a polyhedral oligomeric silsesquioxane (POSS)-containing aromatic diamine, N-[(heptaisobutylPOSS)propyl]-3,5-diaminobenzamide (DA-POSS), with octa(aminophenyl)silsesquioxane (OAPS) as the crosslinker via sol–gel procedures followed by supercritical carbon dioxide (scCO2) drying treatments.

Solution processable octa(aminophenyl)silsesquioxane covalently cross-linked sulfonated polyimides for proton exchange membranes

In this work, a series of octa(aminophenyl)silsesquioxane(OAPS) covalently cross-linked sulfonated polyimides (SPIs) were fabricated for improving their mechanical and chemical stability, reducing fuel crossover and improving proton conductivity as proton exchange membranes. The content of OAPS cross-linkers was modified from 0.2 to 1.6mol% to control the degree of cross-linking. The resulting OAPS cross-linked membranes were solution processable and exhibited higher strength, superior thermal and chemical stabilities, and lower methanol permeability compared with the linear SPI membrane. Compared with Nafion 117, all of the cross-linked membranes exhibited comparable proton conductivity from 20 to 80°C and at 100% relative humidity. Moreover, when the content of OAPS was 0.4mol%, the cross-linked SPI exhibited the highest proton conductivity (0.111S/cm).

Effect of octa(aminophenyl) polyhedral oligomeric silsesquioxane functionalized graphene oxide on the mechanical and dielectric properties of polyimide composites.

An effective method is proposed to prepare octa(aminophenyl) silsesquioxane (OAPS) functionalized graphene oxide (GO) reinforced polyimide (PI) composites with a low dielectric constant and ultrastrong mechanical properties. The amine-functionalized surface of OAPS-GO is a versatile starting platform for in situ polymerization, which promotes the uniform dispersion of OAPS-GO in the PI matrix. Compared with GO/PI composites, the strong interfacial interaction between OAPS-GO and the PI matrix through covalent bonds facilitates a load transfer from the PI matrix to the OAPS-GO. The OAPS-GO/PI composite film with 3.0 wt % OAPS-GO exhibited an 11.2-fold increase in tensile strength, and a 10.4-fold enhancement in tensile modulus compared with neat PI. The dielectric constant (D(k)) decreased with the increasing content of 2D porous OAPS-GO, and a D(k) value of 1.9 was achieved.

Hierarchical porous polyaniline–silsesquioxane conjugated hybrids with enhanced electrochemical capacitance

We prepared multi-armed polyaniline–silsesquioxane conjugates (PANI–SQ) with hierarchical porous structure by introducing various amounts of octa-aminophenylsilsesquioxane (OASQ). A rapid-mixing-dilute polymerization reaction was used to synthesize PANI–SQ. PANI–SQ conjugates were characterized by a set of methods, including FTIR, UV-vis, N2 adsorption measurement, wide-angle X-ray diffraction (WXRD), TEM and field-emission scanning electron microscopy (FE-SEM). These conjugates exhibited a high surface area (122.69 m2 g−1) and an average pore width of 1.6 nm, which was significantly lower than that of the pure PANI (29.1 nm). By increasing the mass of OASQ, a decrease in crystallinity and in electrical conductivity can be observed. For PANI–SQ conjugates, FE-SEM and TEM images revealed that interconnected porous nanofiber networks have been formed with a nanofiber diameter of 10–30 nm because of the incorporation of OASQ onto the skeleton. The as-synthesized PANI–SQ conjugate exhibited excellent specific capacitance and stability, suggesting its potential use as electrode material.