Glycidyl Polyhedral Oligomeric Silsesquioxane Research Articles

Multi-technique characterization and thermal degradation study of epoxy modified resins designed for multifunctional applications

Tetraglycidyl methylene dianiline (TGMDA) was mixed with 1,4-Butanediol diglycidyl ether (BDE) (in a 4:1 mass ratio) and with a stoichiometric amount of the curing agent diaminodiphenyl sulfone which was solubilized at 120 °C for 20 min in the liquid mixture TGMDA + BDE. The so obtained unfilled epoxy resin matrix, denoted as ER, was blended with glycidyl polyhedral oligomeric silsesquioxane and carbon nanotubes in suitable proportions to obtain binary and ternary mixtures. Characterization of the formulated materials was performed using different experimental techniques, such as Dynamic mechanical analysis, Thermogravimetry (TG), Field emission scanning electron microscopy. Furthermore, the investigation of the flame behavior was carried out by the limiting oxygen index and mass loss calorimeter measurements. Direct current measurements and investigation by Tunneling atomic force microscopy of the conductive nanodomain map allowed the evaluation of the electrical properties of the developed nanofilled systems. The TG data related to thermal decomposition of ER and its binary and ternary mixtures were processed according to isoconversional kinetic analysis by assuming a non-Arrhenian behavior of the temperature function, and lifetime prediction was estimated at suitable relatively low temperatures and possible relation between the thermal stability and the presence of each component was discussed. This method of kinetic analysis paves the way for the possibility of evaluating in a more realistic way, on the basis of thermal stability, the potential application of structural resins with primary load functions in contact with hot areas of aeronautical aircraft engines.

Construction of an Interfacial Layer of Aramid Fibers Grafted with Glycidyl POSS Assisted by Heat Treatment and Evaluation of Interfacial Adhesion Properties with Epoxy Resin.

The surface of para-aramid fibers (AFs) was modified via air-assisted heat pretreatment and solution impregnation by varying the glycidyl polyhedral oligomeric silsesquioxane (POSS) content. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed an ester group, confirming the graft reaction between glycidyl POSS and oxidized AFs. The mechanical properties of AFs could be altered by varying the glycidyl POSS content. The modified AFs exhibited an optimal tensile strength after embedding 5 wt % glycidyl POSS on the fiber surface. The thermal stability of the modified fibers decreased; however, no obvious changes in crystallinity were observed by varying the glycidyl POSS content. Moreover, the tensile strength of monofilament increased from 23.8 to 25.8 cN·dtex-1, the thickness of the grafted layer on the fiber surface was above 30-40 nm after the graft modification with 5 wt % glycidyl POSS, and the interfacial shear strength (IFSS) increased by 62.55% to 26.22 MPa. Thus, the modified glycidyl AFs can be used for the reinforcement of composite materials.

G-POSS connected double network starch gels for protein release

Starch is one of the most frequently preferred natural polymers in hydrogel synthesis. Herein, we combined two strategies of associating brittle and ductile networks in a structure and incorporating inorganic particles into the polymeric gel to design mechanically enhanced nanocomposite double network (DN) starch gels. For the first time in the literature, nanocomposite starch gels (s-NC) were designed by cross-linking starch chains with 8-armed glycidyl-polyhedral oligomeric silsesquioxane (g-POSS) units. Fourier Transform Infrared Spectroscopy and Energy Dispersive X-Ray Spectroscopy analyses have proven that g-POSS is included in the gel structure and is homogeneously distributed throughout the network. More stable d-NC-DMA and d-NC-VP gels were obtained by incorporating N,N-dimethylacrylamide (DMA), or 1-vinyl-2-pyrrolidinone (VP) units, respectively, into g-POSS-linked starch gels, and the reaction kinetics were followed in situ. In SEM images, it was observed that d-NC-DMA had smaller pores and thicker pore walls compared to s-NC and d-NC-VP starch gels, and its mechanical strength was shown to be much superior by rheological tests, compression, and tensile analyses. In addition to increasing the mechanical strength of the gels, the potential of starch in protein release applications using amylase sensitivity has been demonstrated in vitro experiments using the model protein BSA.

Solvation structure reorganization and interface regulation of poly (glycidyl POSS)-based electrolyte for quasi-solid-state lithium-ion batteries

The interfacial stability and some unexpected side reactions in quasi-solid-state lithium-ion batteries (LIBs) impede the practical application of the in-situ crosslinked polymer electrolytes. Herein, a novel in-situ crosslinked polymer electrolyte with eight-armed crosslinked supramolecular structure is constructed via cationic ring-opening polymerization of glycidyl polyhedral oligomeric silsesquioxane (POSS). The strong electrostatic and hydrogen bonding interactions of the POSS blocks with anions reorganize the solvation structure, and the overall oxidation resistance of anions can be also effectively enhanced benefiting from the relatively electron-withdrawing effect of the POSS blocks. Simultaneously, a hierarchical cathode-electrolyte interphase with flexibility and oxidation resistance is constructed involving the boron difluoride radical-catalyzed cleavage of Si-O-Si linkages in POSS frameworks. The poly (glycidyl POSS)-based electrolyte enables the Li||NCM83 cell to possess a high capacity retention of 79.1 % after 500 cycles. Moreover, the SiOx||NCM83 battery shows a capacity retention of 87.6 % after 200 cycles. These insights gained form this work opens up an avenue for the development and practical application of quasi-solid-state LIBs.

Multifunctional Properties of Polyhedral Oligomeric Silsesquioxanes (POSS)-Based Epoxy Nanocomposites.

In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to formulate multifunctional structural nanocomposites tailored for aeronautic and aerospace applications. This work aims to demonstrate how the skillful combination of desired properties, such as good electrical, flame-retardant, mechanical, and thermal properties, is obtainable thanks to the advantages connected with nanoscale incorporations of nanosized CNTs with POSS. The special hydrogen bonding-based intermolecular interactions between the nanofillers have proved to be strategic in imparting multifunctionality to the nanohybrids. All multifunctional formulations are characterized by a Tg centered at values close to 260 °C, fully satisfying structural requirements. Infrared spectroscopy and thermal analysis confirm the presence of a cross-linked structure characterized by a high curing degree of up to 94% and high thermal stability. Tunneling atomic force microscopy (TUNA) allows to detect the map of the electrical pathways at the nanoscale of the multifunctional samples, highlighting a good dispersion of the carbon nanotubes within the epoxy resin. The combined action of POSS with CNTs has allowed to obtain the highest values of self-healing efficiency if compared to those measured for samples containing only POSS in the absence of CNTs.

R-Curve Behavior of Polyhedral Oligomeric Silsesquioxane (POSS)–Epoxy Nanocomposites

Polyhedral oligomeric silsesquioxane (POSS) is a suitable nanoscale reinforcement for thermosetting polymers, such as epoxy resin systems in order to modify its mechanical, thermal and chemical properties. The inclusion of POSS in the epoxy resin at higher loading (greater than 1 wt.%); however, it introduces the ductility during the fracture behavior of these nanocomposites. Consequently, the J-integral is used to quantify the fracture behavior of these materials and characterize the crack growth resistance curve against stable crack growth. A range of nanocomposites is prepared by adding 0.5, 1, 3, 5, and 8 wt.% of glycidyl POSS into DGEBF epoxy resin cured with an amine-based curing agent. From fracture toughness experiments, the load-displacement result confirms that when the POSS reinforcement is greater than 1 wt.%, the fracture behavior of the nanocomposite changes from brittle to ductile. For both brittle and ductile nanocomposites, the addition of POSS molecules improves the crack initiation toughness. The development of POSS–POSS compliant domains, reported previously, is responsible for this change in the failure behavior. The fractured images of POSS–epoxy nanocomposites, obtained by using scanning electron microscopy, show that the increase in fracture resistance at higher values of POSS loading occurs due to the extensive shear yielding. Meanwhile, the increased fracture toughness at lower values of POSS loading occurs due to crack pinning and crack deflection.

Reactive compatibilization of PLA/PBS bio‐blends via a new generation of hybrid nanoparticles

AbstractPoly(butylene succinate) (PBS) is a worthy biodegradable thermoplastic polyester for blending along with other biopolymers, especially with poly (lactic acid) (PLA), to overcome its inadequacies in mechanical and thermal characteristics. Since binary blends of PLA and PBS showed that they are incompatible, compatibilization is required. In this work, multi‐epoxide polyhedral oligomeric silsesquioxane (Glycidyl POSS) was added to PLA and PBS using the melt blending method to make them compatible. The blends were prepared at different weight ratios having different amounts of compatibilizer. SEM analysis showed that the Glycidyl POSS impacted the interfacial adhesion and other properties of PLA and PBS blends. Noticeable improvements in mechanical properties were revealed by tensile and impact test results. Tensile strength and Young's modulus were improved when epoxy‐POSS was added up to 1 and 3 wt% into ternary blends, but further increasing POSS concentrations resulted in lower values. FTIR analysis showed a strong interaction between the epoxide group of POSS and the end groups of PBS or PLA. The thermal properties of samples were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The shifts in glass transition temperatures of the PLA phase towards lower values appeared in DSC, confirming the enhanced compatibility of PLA and PBS. Also, the reinforcing ability of the POSS inorganic core structure impacted the thermal stability of the blends.

The Effect of Various Polyhedral Oligomeric Silsesquioxanes on Viscoelastic, Thermal Properties and Crystallization of Poly(ε-caprolactone) Nanocomposites

Polyhedral oligomeric silsesquioxane POSS nanoparticles can be applied as reinforcing additives modifying various properties of biodegradable polymers. The effects of aminopropylisobutyl POSS (amine-POSS), trisilanolisooctyl-POSS (HO-POSS) and glycidyl-POSS (Gly-POSS) on the viscoelastic, thermal properties and crystallization of biodegradable poly(ε-caprolactone) PCL were studied. The analysis of the viscoelastic properties at ambient temperature indicated that aminopropylisobutyl POSS (amine-POSS) and glycidyl-POSS (Gly-POSS) enhanced the dynamic mechanical properties of PCL. The increase in the storage shear modulus G' and loss modulus G″ was observed. The plasticizing effect of trisilanolisooctyl POSS (HO-POSS) due to the presence of long isoctyl groups was confirmed. As a result, the crystallization of PCL was facilitated and the degree of crystallinity of χc increased up to 50.9%. The damping properties and the values of tan δ for PCL/HO-POSS composition increased from 0.052 to 0.069. The TGA results point out the worsening of the PCL thermal stability, with lower values of T0.5%, T1% and T3%. Both HO-POSS and Gly-POSS facilitated the relaxation of molten PCL. The presence of Gly-POSS influenced the changes that occurred in the viscoelastic properties of the molten PCL due to the thermo-mechanical degradation of the material; a positive impact was observed.

Effect of POSS on the Dielectric Properties of Thermally Aged Epoxy Resin Insulating Materials

Polyhedral oligomeric silsesquioxane (POSS) can significantly improve the short-term insulation ability of epoxy materials under high electric field, which makes epoxy/POSS composites show a wide application prospect in high-voltage power equipment. The changes in performance due to aging is the concern of the long-term application of epoxy materials in power equipment. Therefore, the influence of Glycidyl POSS on the insulation performance of epoxy materials in the aging process needs to be investigated. In this article, different mass fractions of epoxy/POSS composites were prepared and the effect of POSS on the dielectric loss of epoxy materials after thermal aging was investigated. The results show that the addition of a small amount of POSS can effectively inhibit the low-frequency dielectric loss of epoxy insulating materials during thermal aging. Combined with the dc volume resistivity test of epoxy composites and the quantum chemical calculation results of POSS molecules, a possible mechanism of POSS inhibiting the dielectric loss of epoxy resin during thermal aging was proposed. The present work provides a reference for further development of POSS in the field of electrical insulation and the application of POSS modified composites in power equipment such as low-frequency transmission and dc transmission equipment.

Electrical Investigation by Tunneling Atomic Force Microscopy of Carbon Fiber‐Reinforced Panels Manufactured by Modified Resin Film Infusion

AbstractThe purpose of this work is the detection of the electrical current map by tunneling atomic force microscopy (TUNA) of carbon fiber‐reinforced panels (CFRPs). The impregnation of the CFRPs is carried out through a multifunctional epoxy formulation containing glycidyl polyhedral oligomeric silsesquioxane (GPOSS), for improving flame resistance, and multiwall carbon nanotubes (CNT) to contrast the electrical insulating properties of the epoxy resin. The multifunctional panels are manufactured by an appropriately modified resin film infusion (RFI) process. The effects of the different ply numbers (seven, 14, and 24) on the TUNA electrical performance are assessed. In particular, TUNA technique, which is able to detect ultralow currents ranging from 80 fA to 120 pA, allows to identify the conductive paths due to CNTs. The CNTs result firmly anchored to the carbon fibers of the fabric layers. The adopted manufacturing process allows the transit of the nanofilled resin avoiding filtration effects. TUNA's current images highlight the presence, in the interlayer space of carbon fibers, of conductive three‐dimensional networks of CNTs through the plies. This occurrence ensures good electrical properties of the multifunctional panels, which results suitable for advanced structural applications.

Bionanocomposites from spent hen proteins reinforced with polyhedral oligomeric silsesquioxane (POSS)/cellulose nanocrystals (CNCs)

The utilization of bio-renewable and environmentally sustainable materials has been growing tremendously. Spent hen is a major poultry industry by-product; in this study, we aimed to develop spent hen proteins (SHP) based films for food packaging applications. The spent hen proteins were modified with cellulose nanocrystal (CNCs) and glycidyl polyhedral oligomeric silsesquioxanes (POSS) individually and transformed into bionanocomposite films using compression molding. All protein derived bionanocomposite films were characterized by dynamic mechanical analysis (DMA), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). The incorporation of CNCs and POSS as a reinforcing agents into the protein's polymer matrix showed a substantial increase in the mechanical strength, water barrier and thermal properties. The mechanical strength of neat protein films increased from 2.65 ± 0.50 to 6.47 ± 0.50 MPa and 8.48 ± 0.98 MPa with POSS (3%) and CNCs (5%), respectively. The strong interactions of nanoparticles with proteins were observed which improved the physical and thermal properties of the spent hen proteins derived films. Thus, POSS or CNCs modified spent hen protein films being renewable and environmentally benign, have great potential to be used as a food packaging material to replace petroleum based polymers.

High-Performance Properties of an Aerospace Epoxy Resin Loaded with Carbon Nanofibers and Glycidyl Polyhedral Oligomeric Silsesquioxane

This paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional requirements. In particular, this paper explores the advantages deriving from the combined use of GPOSS and CNFs (short carbon nanofibers) to obtain multifunctional resins. The multifunctional material was prepared by incorporating in the epoxy matrix heat-treated carbon nanofibers (CNFs) at the percentage of 0.5 wt% and GPOSS compound at 5 wt% in order to increase the mechanical performance, electrical conductivity, thermal stability and flame resistance property of the resulting nanocomposite. Dynamic mechanical analysis (DMA) shows that the values of the Storage Modulus (S.M.) of the resin alone and the resin containing solubilized GPOSS nanocages are almost similar in a wide range of temperatures (from 30 °C to 165 °C). The presence of CNFs, in the percentage of 0.5 wt%, determines an enhancement in the S.M. of 700 MPa from −30 °C to 180 °C with respect to the resin matrix and the resin/GPOSS systems. Hence, a value higher than 2700 MPa is detected from 30 °C to 110 °C. Furthermore, the electrical conductivity of the sample containing both GPOSS and CNFs reaches the value of 1.35 × 10−1 S/m, which is a very satisfying value to contrast the electrical insulating property of the epoxy systems. For the first time, TUNA tests have been performed on the formulation where the advantages of GPOSS and CNFs are combined. TUNA investigation highlights an electrically conductive network well distributed in the sample. The ignition time of the multifunctional nanocomposite is higher than that of the sample containing GPOSS alone of about 35%.

Homogeneous sub-nanophase network tailoring of dual organosilica membrane for enhancing CO2 gas separation

Dual organosilica membranes were synthesized to investigate the effects of differing molar ratios of bis (triethoxysilyl) ethane (BTESE)/glycidyl Polyhedral oligomeric silsesquioxane (glycidyl POSS) on the membrane performance. The reaction mechanism behind CO2 capture using the organosilica membranes under ambient conditions was also investigated. A facile in-situ framework synthesis approach was introduced for the copolymerization reaction of dual organosilica. BTESE has a smaller molecular size than that of glycidyl POSS, and the Si–C–C–Si linkage is the main structure contributing to its high CO2 affinity. Additionally, the dimensional and mechanical stability were maintained at high doping levels owing to the inclusion of glycidyl POSS. Consequently, the free volume of the resulting hybrid networks increased owing to the cage structure and high cross-link density, which was attributed to the coexistence of epoxy ring-opening polymerization and condensation polymerization. The characterization and permeation tests revealed that the 1B0.5P gel with the best copolymerization effect exhibits a high CO2 permeance of 5.74 × 10−8 mol m−2 s−1 Pa−1 at 25 °C and ideal selectivity values of 11.61, 37.55 and 63.67 for CO2/H2, CO2/CH4 and CO2/N2, respectively. Moreover, a new analytical technique was proposed to investigate the surface microstructure of organosilica membranes for the first time using optical microscopy.

High performance flame-retardant organic-inorganic hybrid epoxy composites with POSS and DOPO-based co-curing agent.

Polyhedral oligomeric silsesquioxane (POSS) and a highly effective 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based flame retardant co-curing agent (D-bp) were chemically introduced into the 4,4′-diaminodiphenyl methane (DDM)/diglycidyl ether of bisphenol A (DGEBA) epoxy system to create organic–inorganic hybrid epoxy composites with simultaneously improved flame retardancy and mechanical properties. The results revealed that POSS/D-bp/DGEBA hybrid composites exhibited excellent comprehensive performance, in which the V-0 criterion of the UL-94 test was passed and the peak of heat release rate (P-HRR) was significantly decreased from 939 to 371 kW m−2 when the phosphorus content was only 0.25 wt%. The glass transition temperature (Tg) increased by 16.2 °C and obvious improvement in the mechanical properties was also evidenced.

Engineering the Surface Pattern of Microparticles: From Raspberry-like to Golf Ball-like.

Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.

Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

Reactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

Epoxy-polyhedral oligomeric silsesquioxanes (POSS) nanocomposite vitrimers with high strength, toughness, and efficient relaxation

Although considerable progress has been made in developing vitrimers, on-going challenges for vitrimers for high-performance applications include the improvement in mechanical properties and identification of more efficient exchange reactions. By incorporation of glycidyl polyhedral oligomeric silsesquioxane (POSS) as a nanoscale filler in epoxy, we produced epoxy-POSS nanocomposite vitrimers that show high strength, toughness, thermal stability, and efficient relaxation. With 10 wt% POSS, the ultimate tensile strength and strain at break of the epoxy-POSS nanocomposite vitrimers increased by ~64% and ~76%, respectively, while at 160 °C the stress relaxation time increased by ~260% in comparison to that of pure epoxy vitrimer. The epoxy-POSS nanocomposite vitrimers show high malleability due to the efficient transesterification reaction and re-processability with little degradation of their initial mechanical properties, suggesting opportunities for sustainable plastics.

Improving adhesion between polyester cord and rubber by using glycidyl‐POSS

AbstractPoly(ethylene terephthalate) (PET) cords are usually coated with epoxy and/or isocyanate solutions (like methylene diphenyl diisocyanate [MDI]) before resorcinol‐formaldehyde‐latex (RFL) to increase the adhesion efficiency of RFL. In this article, the addition of glycidyl polyhedral oligomeric silsesquioxane (GPOSS) as an adhesion promoter to PET cord was investigated for reinforcing PET cord/rubber interfacial adhesion. Therefore, GPOSS treated PET cords (GPOSS + MDI + RFL) were prepared in different process conditions like different GPOSS ratios and oven curing times and then vulcanized with rubber. RFL, GPOSS + RFL, MDI + RFL, and commercial epoxies treated PET cord samples were also prepared for comparison with GPOSS+MDI + RFL treated PET cord. The thermal, mechanical, and morphological properties of the treated PET yarn and their composites with rubber were investigated. It was seen that in the GPOSS coated PET yarns increased the stiffness and no change was observed in the tensile strength of the PET yarns. It was determined that the utilization of GPOSS in the PET cord improved the adhesion of the cord to rubber when compared with other treated PET cords via H‐adhesion and strip peel adhesion tests. Especially, since adhesion values give better results than commercially used epoxies, GPOSS as an adhesion promoter can be recommended in the rubber industry.

Improvement in separation performance of PEI-based nanofiltration membranes by using L-cysteine functionalized POSS-TiO2 composite nanoparticles for removal of heavy metal ion

L-cysteine as an amino acid was used for the modification of glycidyl POSS in the synthesis of L-cysteine functionalized POSS, including carboxyl, hydroxyl, and diamine groups. Then, the synthesized nanoparticles were applied to fabrication of L-cysteine POSS-TiO2 composite nanoparticles. NF membranes were prepared from the incorporation of different concentrations of the synthesized composite nanoparticles into the polyether-imide (PEI) as the membrane matrix. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM). Moreover, the separation performance of the NF membranes was examined by pure water flux (PWF) and the separation of Na2SO4, Pb(NO3)2, Cr(NO3)2 and Cu(NO3)2 aqueous solutions. The results showed the increase of pure water flux due to present hydrophilic groups on the membrane surface. The highest pure water flux obtained was 22.03 L/m2h in 1 wt% of nanoparticles. Furthermore, the rejection of Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 improved to 78%, 64%, 67% and 66% that increased 11%, 33%, and 22%, and 39% compared with the pristine PEI membrane, respectively. Finally, the best FRR% (81%) was obtained for 0.1 wt% of the composite nanoparticles (M3).

In situ synthesis of star copolymers consisting of a polyhedral oligomeric silsesquioxane core and poly(2,5‐benzimidazole) arms for high‐temperature proton exchange membrane fuel cells

Star copolymers with good film-forming and mechanical properties were in situ synthesized for fabricating proton exchange membranes. The monomers of 3,4-diaminobenzoic acid were first grafted onto glycidyl-polyhedral oligomeric silsesquioxane (G-POSS) cores and then propagated to the poly(2,5-benzimidazole) (ABPBI) chains. The introduction of the star copolymer improves the movement of the ABPBI polymer chains, resulting in a lower internal viscosity and larger free volume that favor increased membrane flatness and absorbilities of water and phosphoric acid molecules, respectively. It was found that the star copolymers with 1.0 wt% of incorporated POSS (ABPBI-1.0POSS) had the best balance of the acid retentivity and film-forming property as well as mechanical properties that are desirable for proton exchange membranes without PA loss operating at high temperatures. The enhanced cell performance characteristics obtained using the ABPBI-1.0POSS-based membranes indicate that star copolymers are promising materials for use in high-temperature proton exchange membrane fuel cells.