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Molten carbonate fuel cells (MCFCs) are environmentally friendly, large-capacity power generation devices operated at approximately 650°C. If MCFCs are to be commercialized by improving their competitiveness, their cell life should be increased by operating them at lower temperatures. However, a decrease in the operating temperature causes a reduction in the cell performance because of the reduction in the electrochemical reaction rate. The cell performance can be improved by introducing a coating on the cathode of the cell. A coating with a high surface area expands the triple phase boundaries (TPBs) where the gas and electrolyte meet on the electrode surface. And the expansion of TPBs enhances the oxygen reduction reaction of the cathode. Therefore, the cell performance can be improved by increasing the reaction area, which can be achieved by coating nanosized LiCoO2 particles on the cathode. However, although a coating improves the cell performance, a thick coating makes gas difficult to diffuse into the pore of the coating and thus reduces the cell performance. In addition, LiCoO2-coated cathode cell exhibits stable cell performance because the coating layer maintains a uniform thickness under MCFC operating conditions. Therefore, the performance and stability of MCFCs can be improved by applying a LiCoO2 coating with an appropriate thickness on the cathode.

We investigated the effects of hydrogen separation using high-temperature anhydrous proton-exchange membrane fuel-cell technology. Various acid-doped para-polybenzimidazole (p-PBI)-chain end-tethered amine-polyhedral oligomeric silsesquioxane (NH2-POSS) membranes were prepared via a unique sol–gel transition method termed as the poly(phosphoric acid) process. The resulting NH2-POSS-capped p-PBI membranes exhibited a higher phosphoric acid-doping level (128–223.5%) and proton conductivity (0.23–0.29 S cm−1 at 160 °C and 0% relative humidity) than the parent p-PBI membrane. The chemical chain end-termination of p-PBI with cage-like NH2-POSS significantly enhanced the electrochemical H2/CO2 and H2/CO separation at 160 °C. The hydrogen separation of the NH2-POSS-capped p-PBI system required a relatively small amount of energy, and the system exhibited a good dynamic response. The favorable interfacial interaction between the NH2-POSS and the p-PBI host, high thermomechanical stability, and good fuel-cell and hydrogen-separation performance at high temperatures up to 160 °C indicate the applicability of the NH2-POSS-capped p-PBI membranes to electrochemical power generation and hydrogen pumps for practical industrial applications in harsh and extreme environments.

Fuel cells are cleaner alternatives of sustainable green energy sources. Their proton exchange membranes continue to be a key component; however, there are several challenges associated with their ...

Here, highly stretchable and transparent UV curable poly(urethane-acry-late) elastomer has been synthesized by reacting urethane acrylate oligomer and two reactive diluents monomers. The synthesized elastomers can be stretched up to 600% and have high transparency of over 90% transmittance. The synthesized elastomers have been applied to several applications. Simple 3D model was printed with a 3D printer on the market. Stretchable ionic conductors were fabricated by a facile method of adding salt with ionic conductivity. Similarly, the resin with β-cyclodextrin, a cage-structured molecule, was cured and foam was generated simultaneously under the UV radiation. This research paves a new way for further development in applications of UV curable transparent elastomer and 3D printable elastomeric material.

Polyimides, a widely used engineering plastic, require use of large amounts of toxic and hazardous organic solvents which threaten our daily lives, calling for new and easy synthetic methods for sustainable environmentally friendly development. In this paper, highly soluble fluorinated polyimides based on 4,4′-(hexafluoroisopropylidene) diphthalic anhydride were synthesized via hydrothermal process without using any toxic organic solvents and the advantages of the newly demonstrated synthetic methods are shown by comparative analysis performed with the two conventional synthetic methods using organic solvent: thermal and chemical imidization. Lower temperature is required (~200 °C) compared to thermal imidization and functional groups for high fusibility formed more easily compared to chemical imidization. According to the comparative analysis, hydrothermally synthesized PIs showed excellent solubility and maintained high thermal stability (&gt, 500 °C) and glass transition temperature (&gt, 300 °C) compared to conventional PI. The hydrothermally synthesized polyimide is much more convenient to store and manage than other form of polyimide which is much more stable when it is exposed to humidity as it is a powder form. The hydrothermal synthetic method is verified to be a “Green” and facile method for sustainable PI synthesis.

An inexpensive and general-purpose carbon fiber was prepared using coal tar pitch. In contrast to the solvent extraction process employing expensive solvents, a low-cost centrifugal separation method facilitated the reduction of loss due to the pitch purification and an overall yield increase. The coal tar pitch purified by centrifugation and subsequently co-carbonized with pyrolysis fuel oil improved in spinnability. Moreover, the resulting spinnable pitch had a softening point of 250 °C. The obtained carbon fibers were heat-treated at 1000 °C for 5 min, resulting in a tensile strength of approximately 1000 MPa and an average diameter of 9 μm. In this study, we present an effective method for obtaining low-cost general-purpose isotropic carbon fibers.

Polymer composite membrane technology is promising for enhancing the performance of membrane electrode assemblies for high-temperature fuel cells. In this study, we developed a novel anhydrous proton-exchange polybenzimidazole (m-PBI) composite membrane using Al-substituted mesoporous silica (Al-MCM-41) as a proton-carrier support. The surface-substituted Al-MCM-41 formed effective proton-transport pathways via its periodic hexagonal channel and improved the proton conductivity. The proton conductivity of an m-PBI filled with 9 wt.% filler was 0.356 S cm-1 at 160 °C and 0% humidity, representing an increase of 342% compared to that of a pristine m-PBI. Further, the current density at 0.6 V and maximum power density of m-PBI composite membranes were increased to 0.393 A cm-2 and 0.516 W cm-2, respectively. The enhanced fuel-cell performance was attributed to the proton-transfer channels and H3PO4 reservoirs formed by the mesopores of the Al-MCM-41 shell. The results indicated that Al-MCM-41 is suitable with respect to the hybrid homologues for enhancing the proton transport of the m-PBI membrane.

Crosslinked metal oxide containing nanocomposite membranes, in which the filler also acts as crosslinker, were prepared by blending polybenzimidazole (PBI-OO) and phenylsulfonated TiO2 particles (s-TiO2). Thermal curing changes the ionically crosslinked system into a covalently crosslinked system. The synthesized s-TiO2 nanoparticles were analyzed by thermal gravimetric analysis and scanning electron microscopy. The covalently crosslinked nanocomposite membranes (c-sTiO2-PBI-OO) were doped with phosphoric acid (PA) for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. The membrane properties, such as PA uptake, dimensional change, gel content, proton conductivity, mechanical property, and single cell performance were evaluated and compared with the properties of acid-doped c-PBI-OO. PA doped 6-c-sTiO2-PBI-OO (6 wt% sTiO2) showed the highest uptake of 392 wt%, and a proton conductivity at 160 °C of 98 mS cm−1. In the fuel cell, a peak power density of 356 mW cm−2 was obtained, which is 76% higher than that of a c-PBI-OO based system (202 mW cm−2). To evaluate the stability of the membrane performance over time, the best performing membrane was tested for over 700 h.

Nanocomposite polymer electrolyte membranes comprising a crosslinked polymer blend of poly(vinyl alcohol)/poly(styrene sulfonic acid-co-maleic acid) (PVA/PSSA-co-MA) and fumed silica nanoparticles were prepared for direct methanol fuel cell (DMFC) applications. Silica nanoparticles could be incorporated well uniformly in the completely miscible system, which can form a three-dimensional network structure to achieve the enhancement of mechanical properties as well as the additional reduction of methanol permeability. The optimized proton conductivities and methanol permeability of the PVA/PSSA-co-MA membrane with silica nanoparticles of 10 wt.% were 0.0482 S cm-1 at room temperature and 5.78 × 10-7 cm2 s-1 at the methanol concentration of 40% (w/w), respectively.

The development of tannic‐acid‐based textile materials is a good candidate that enables both flame retardancy and antibacterial properties. When nanocarbon materials are used together, it is possible to not only realize complex functions but also increase physical properties, thereby expanding the potential range of application of the materials.

In this study, the improvement of synthesizing method of sponge-type polyimide (PI) membrane and its newly developed pore size control techniques are mainly described. The sponge-type polyimide membrane with large pore size (0.1–10 µm) and high permeability was successfully synthesized by using non-solvent phase separation method (NIPS) in continuous process and its full polyimidization is confirmed via Fourier-transform infrared technique. The theoretical approach in this research induced by Jurin's law which describes the height of a liquid within a thin capillary tube. In this theory, the pore size of membrane is highly influenced by the interactive tension between the polymer and solvents during synthesizing process of polymer membrane. There are two ways of controlling pore size established from Jurin's law. The validity of the application of Jurin's law was proven via comparison with theoretical and experimental data. Its inner structure of membrane and pore size are identified by field emission-scanning electron microscopy.

Molten-carbonate fuel cells (MCFCs) are high-temperature fuel cell systems that typically operate at approximately 650 °C. Due to their high operating temperature, the thermal degradation of MCFC components limits the lifetime of the MCFC. Therefore, lowering the operating temperature is an effective way to reduce thermal degradation. However, the electrochemical reaction on the cathode also becomes slower as the operational temperature decreases. To improve the performance and stability, atomic layer deposition (ALD) of ZrO2 on the cathode is proposed. ALD produces a uniform, thin coating with precise thickness control. Therefore, nano-coating can be performed via ALD without affecting the porous structure of the cathode. The uniform ZrO2 coating donates electrons to NiO due to the low electronegativity of Zr. The electron-rich environment of NiO improves the cell performance by providing electrons for the oxygen reduction reaction. Also, the single cell using ZrO2-coated cathode demonstrates improved stability compared to the uncoated cathode cell due to the inhibition of NiO sintering by the ZrO2 coating layer.

Supercritical methanol is a popular fluid as a supercritical medium for decrosslinking reaction of crosslinked polyethylene. However, due to its toxicity, a safe alternative medium is much to be desired. In this work, various sub- and supercritical fluids with different polarity characters were investigated to find a safe alternative medium for continuous decrosslinking of silane-crosslinked polyethylene (S-XLPE). Like methanol, all examined fluids, including ethanol, propanol, and water, exhibited first-order reaction kinetics regarding the gel content in the continuous decrosslinking process. The reaction rate constant values were observed as 2.806, 2.569, 2.383, and 2.130 min −1 in supercritical methanol, supercritical ethanol, supercritical 2-propanol, and subcritical water at 380 °C, respectively. As a non-toxic fluid with reaction kinetics very comparable to that of methanol, ethanol was found to be the best alternative medium for the continuous decrosslinking reaction of S-XLPE.

For the first time, a kinetic study on the supercritical decrosslinking reaction of silane-crosslinked polyethylene (S-XLPE) in a continuous process was conducted. The decrosslinking reaction in a continuous process was corresponding to the first-order reaction model in which the reaction rate was linearly proportional to the gel content. The residual gel content exponentially decreased with reaction time. Reaction constant was observed exponentially related to the reaction temperature. The continuous decrosslinking reaction revealed kinetic constants of 1.355 ± 0.103, 2.715 ± 0.177, and 4.348 ± 0.218 min −1 at 360, 380 and 390 °C, respectively and activation energy of 132.36 kJ mol −1 .

In this study, poly(amide-imide)s are synthesized for electronic materials by adding amide groups into polyimide. As it is expected, poly(amide-imide) shows an amorphous structure with a lower glass transition temperature and residual stress than the neat polyimide due to the high steric hindrance of the amide group. Also, the modification to the polyimide structure leads to higher transmittance and enhances colorless properties. Consequently, successful synthesis of poly(amide-imide)s is demonstrated which has wide applicability in the electronic industries due to their low glass transition temperature. It is expected that semiconductor and integrated circuit products can be manufactured utilizing poly(amide-imide)s with high reliability and a low chance of cracking due to their lower residual stress. Furthermore, it envisioned that the improved optical properties of poly(amide-imide) materials will allow for their applications in transparent displays and coating products.

Graphene nanoparticles coated with tannic acid were synthesized as non-halogen flame retardants; further, these nanoparticles were electrospun with polyurethane to produce multifunctional composite nanofibers. The composite nanofibers showed improved flame retardant, antimicrobial, and mechanical properties with increasing amounts of bio-based, non-halogen flame retardant. For instance, at 5 wt% of flame retardant, the peak heat release rate was reduced from 340.75 to 235.23 W/g along with 500% and 135% improvement in the antimicrobial activity and Young's modulus, respectively, compared to neat polyurethane fibers. These multifunctional composite nanofibers have potential applications in various fields, such as automobile, construction, and biomedical device.

Molten carbonate fuel cell (MCFC) is a high-temperature fuel cell for power plants. Since MCFC is operated at approximately 650 °C, the lifetime of the MCFC is limited by the thermal degradation of MCFC components. To reduce thermal degradation, the lower temperature for long-term operation is suggested. However, the electrochemical reaction on the cathode becomes slower at the lower operational temperature. To improve the performance for the long-term operation of MCFC, a ZrO2 coated cathode was fabricated by atomic layer deposition. The cell using the ZrO2 coated cathode showed a high voltage of 0.867 V at a temperature of 600 °C and a current density of 150 mA/cm2. The charge transfer resistance is also reduced dramatically at that same time. It can be confirmed that the high cell performance is presented when the electron-rich environment of NiO by ZrO2 coating improved the performance of the cell. Also, the cell using the ZrO2 coated cathode kept a stable performance over 2,000 h due to the prevention of NiO sintering by the uniform ZrO2 coating layer.

To cope with the demand for cleaner alternative energy, polymer electrolyte membrane fuel cells (PEMFCs) have received significant research attention owing to their high-power density, high fuel efficiency, and low polluting by-product. However, the water requirement of these cells has necessitated research on systems that do not require water and/or use other mediums with higher boiling points. In this work, a highly porous meta-polybenzimidazole (m-PBI) membrane was fabricated through the non-solvent induced phase inversion technique and thermal cross-linking for high-temperature PEMFC (HT-PEMFC) applications. Standard non-thermally treated porous membranes are susceptible to phosphoric acid (PA) even at low concentrations and are unsuitable as polymer electrolyte membranes (PEMs). With the porous structure of m-PBI membranes, higher PA uptake and minimal swelling, which is controlled via cross-linking, was achieved. In addition, the membranes exhibited partial asymmetrical morphology and are directly applicable to fuel cell systems without any further modifications. Membranes with insufficient cross-linking resulted in an unstable performance in HT-PEMFC environments. By optimizing thermal treatment, a high-performance membrane with limited swelling and improved proton conductivity was achieved. Finally, the m-PBI membrane exhibited enhanced acid retention, proton conductivity, and fuel cell performance.

We herein report an effective way to fabricate high-performance polybenzimidazole (PBI) nanocomposite membranes using sulfophenylated titanium oxide (s-TiO2) nanoparticles for application in high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The s-TiO2, multifunctional inorganic proton conductors that can improve proton conductivity and cell performance of PBI, was obtained through the surface modification. The PBI nanocomposite membranes were doped with phosphoric acid (PA) for performance evaluation. Properties such as PA doping level, proton conductivity, PA retention and cell performance were evaluated and compared to neat PBI. PA doped PBI-sTP2 (2 wt% TiO2) showed the highest doping of 12.1 and proton conductivity of 0.096 S/cm at 150 °C. In the cell test, peak power density of 621 mW/cm2 was obtained, roughly 30% better performance compared to neat PBI (471 mW/cm2).

To enhance the thermal stability and barrier properties of pure poly(vinyl alcohol) (PVA), five different cross-linked poly(vinyl alcohol)/boric acid (PVA/BA) hybrid films were prepared via a solution blending method, and their properties including barrier properties, thermal stability, transparency, and mechanical properties were investigated as a function of the BA content. The physical properties of the PVA/BA hybrid films were strongly dependent upon the chemical structure and morphology of the films originating from the amount of BA and change in degree of cross-linking. With increasing BA content, the size and amount of PVA crystallites decreased, whereas the cross-linking density increased, resulting in more compact packing of the molecules and lower free volume in the amorphous regions. The glass transition temperature and thermal stability were highly enhanced with increasing BA content. The oxygen transmission rate (OTR) of pure PVA decreased from 5.96 to 0.15 cc/m 2 day with increasing BA content and were greatly suppressed by 22.8% for 1% BA, 7.7% for 3% BA, and 2.5% for 3% BA, respectively, relative to pure PVA film. With increasing BA content, their water-resistant pressure and tensile strength increased with BA loading. All the hybrid films showed good transparency. These properties of the cross-linked PVA/BA hybrid films make them potential candidates for versatile applications as coatings, films, and packaging materials.

Cuprous oxide (Cu2O) has received much attention as a photocatalyst due to its direct band gap structure, small band gap energy, non-toxicity, and abundance. However, Cu2O usually suffers from poor stability because the oxidation state of copper is easily changed. In this work, Cu2O particles of three different shapes were prepared with distinct surface structures: cubes with (100) facets, octahedra with (111) facets, and rhombic dodecahedra with (110) facets. Their shape stability was estimated in deionized water with or without light irradiation. The Cu2O(100) facets were selectively deformed under dark conditions, as expected from density functional theory calculations. The rhombic dodecahedra showed the most violent degradation under light irradiation, with many large thorns appearing on the surface. When water splitting was attempted using the shaped Cu2O particles, the rhombic dodecahedra produced the most hydrogen, whereas the cubes produced none. Oxygen was not measured because the holes generated upon light absorption were used to oxidize the Cu2O surface to CuO. A conformal TiIrOx overlayer was successfully formed on the rhombic dodecahedral Cu2O particles, and the coated particles presented overall water splitting producing both hydrogen and oxygen. They also showed significantly improved stability over repeated water splitting reactions relative to bare Cu2O particles or TiOx-coated Cu2O particles.

Cross-linked polyimides (PIs) were synthesized by reacting 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFDB) with various ratios of the cross-linkable, end-capping agent cis-1,2,3,6-tetrahydrophthalic anhydride (CDBA) via ring-opening metathesis polymerization. Residual stress behaviors were investigated in-situ during thermal imidization of the cross-linked PI precursors using a thin film stress analyzer (TFSA) by wafer bending method. The thermal properties were investigated via differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA). The optical properties were measured by ultraviolet-visible spectrophotometer (UV-vis) and spectrophotometry. All properties were interpreted with respect to their morphology of cross-linked networks. With increasing the amounts of the end-capping agent, the residual stress decreased from 27.9 to -1.3 MPa, exhibited ultra-low stress and high thermal properties. The minimized residual stress and enhanced thermal properties of the cross-linked PI makes them potential candidates for versatile high-density multi-layer structure applications.

In this study, the swelling method for controlling the pore size of the polyimide aerogel is demonstrated. The swelling method allows the pore size to be increased by changing the spherulitic formation. This newly developed method is simple and hardly affects original polymer chain and thus can be applied to a variety of precursor polymers without hindering the synthesis process. Unlike other methods, no foreign additives such as additional chemicals or crosslinkers are required to enlarge the pores of the aerogel, which contributes to higher homogeneity of the material. In order to test its effectiveness in pore size control and observe its behavior with different polyimides, various monomers—pyromellitic dianhydride, 3,3′,4,4′-benzophenonete-trac-arboxylic dianhydride, and 4,4′-oxydiphthalic anhydride—were tested to verify the potential of the proposed method. Depending on different polymer backbone, each aerogel showed a similar slope but different increase rate of the pore size. The retained thermal and structural properties of the synthesized aerogels were confirmed by thermogravimetric analysis, differential scanning calorimetry, and Fourier-transform infrared spectroscopy. This newly proposed simple method showed its effectiveness in increasing the pore sizes, enlarging the mesopore size from 4 nm to 20 nm and total pore volume from 1.29 cm 3 / g to 2.06 cm 3 / g for swollen aerogel when pyromellitic dianhydride was used. Also, the surface area increased from 54 m 2 / g to 88 m 2 / g , and the porosity increased from 58% to 73%.

친환경 소재인 폴리프로필렌카보네이트(PPC)를 포장소재로서 응용하기 위하여 가로세로비가 큰 박리흑연 EFG (exfoliated graphite)를 이용하여 함량을 달리한 6종류의 PPC/EFG 나노복합필름을 제조하였다. 제조한 나노복합필름의 수분흡수 거동을 gravimetric method를 이용하여 측정하였으며, 나노복합필름의 수분에 대한 화학적 친화성(chemical affinity)과 모폴로지(morphology) 변화를 이용하여 해석하였다. 필름 내로의 수분확산 거동은 박막의 불균일성에도 불 구하고 Fickian diffusion model에 잘 부합하였으며, EFG의 함량이 증가할수록 수분 확산계수와 수분 흡수량은 12.5 × 10 -10 cm 2 sec -1 에서 7.2 × 10 -10 cm 2 sec -1 , 8.9 wt%에서 4.2 wt%로 각각 감소하였다. 이는 수분에 대한 PPC의 차단특성이 EFG의 도입에 따라 향상되는 것을 의미한다. 높은 가로세로비를 가진 EFG를 PPC에 도입함으로써 PPC/EFG 나노복합 필름의 수분에 대한 우수한 차단성 특성 발현은 패키징분야를 포함한 차단성이 요구되는 분야로의 친환경 PPC 응용 성이 클 것으로 기대된다. 한편, EFG의 도입효과를 극대화하기 위한 추가적인 EFG의 분산성 향상연구가 필요하다.

The current paper describes enhanced electrochemical capacitive performance of chemically grown Cobalt hydroxide (Co(OH)2) nanorods (NRs) decorated porous three dimensional graphitic carbon foam (Co(OH)2/3D GCF) as a supercapacitor electrode. Freestanding 3D porous GCF is prepared by carbonizing, high internal phase emulsion (HIPE) polymerized styrene and divinylbenzene. The PolyHIPE was sulfonated and carbonized at temperature up to 850 °C to obtain graphitic 3D carbon foam with high surface area (389 m2 g−1) having open voids (14 μm) interconnected by windows (4 μm) in monolithic form. Moreover, entangled Co(OH)2 NRs are anchored on 3D GCF electrodes by using a facile chemical bath deposition (CBD) method. The wide porous structure with high specific surface area (520 m2 g−1) access offered by the interconnected 3D GCF along with Co(OH)2 NRs morphology, displays ultrahigh specific capacitance, specific energy and power. The Co(OH)2/3D GCF electrode exhibits maximum specific capacitance about ~1235 F g−1 at ~1 A g−1 charge-discharge current density, in 1 M aqueous KOH solution. These results endorse potential applicability of Co(OH)2/3D GCF electrode in supercapacitors and signifies that, the porous GCF is a proficient 3D freestanding framework for loading pseudocapacitive nanostructured materials.

A novel hyper-branched polybenzimidazole (HB-PBI) has been synthesized and efficiently utilized as a conducting polymer for the fabrication of an efficient high temperature fuel cell. The developed fuel cell showed outstanding proton conductivity (0.168 Scm(-1) at 150 A degrees C) along with excellent single cell performance, displaying a maximum power density of 0.346 Wcm(-2). The HB-PBI has been synthesized by polymerization of bibenzimidazole diterephthalic acid (BBIDTA) and 3,3'-diaminobenzene in the presence of poly phosphoric acid while the BBIDTA was synthesized by treating trimellitic anhydride with 3,3'-diaminobenzene. Both HB-PBI and BBIDTA were structurally characterized by nuclear magnetic resonance (H-1 and C-13 NMR). HB-PBI showed high thermal stability and mechanical properties, findings that were corroborated by thermogravimetric analysis and use of a universal testing machine. Additionally, proton conduction and the thermal and mechanical properties of HB-PBI were compared with polybenzene imidazole (m-PBI), and found that HB-PBI has higher proton conducting, thermal and mechanical properties.

Organic-inorganic hybrid membranes (HM1-HM4) were synthesized by incorporating 3 wt% (HM1), 5 wt% (HM2), 10 wt% (HM3), and 20 wt% (HM4) of silica precursors into UV-curable polyurethane acrylate (PU) matrix using sol-gel technique. PU, which was prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI), was used as the starting organic polymer whereas tetraethoxysilane (TEOS) was used as a precursor for the development of the inorganic phase. The completion of the polymerization reaction of PU and the synthesis of hybrid membranes were confirmed by Fourier transform infrared spectroscopy (FTIR) whereas the morphology was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal, mechanical, and anti-water sorption properties of the hybrid membranes were examined by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nanoindentator and thin film diffusion analysis, which revealed that HM2 has the highest thermal, mechanical, and anti-water sorption properties. TGA demonstrated that the thermal decomposition temperature (T d10%) of HM2 increased significantly, being 30 °C higher than that of pure PU, whereas DSC indicated that the introduction of 5 wt% of TEOS increased the glass transition temperature from 93.8 to 103 °C. Accordingly, the mechanical and water sorption properties were also enhanced greatly as evidenced by nanoindentation analysis and anti-water sorption data, in which HM2 shows the highest elastic modulus (8.354 GPa), hardness (0.262 GPa), and lowest water sorption capacity. These thermal, mechanical, and anti-water sorption improvements are important for the practical process and applications of PU.

Organic-inorganic hybrids (H1-H5) based on environmentally friendly and biodegradable polymer, poly (propylene carbonate) (PPC) and tetraethoxysilane (TEOS) were synthesized using the sol-gel technique. The synthesized hybrids were characterized structurally and morphologically by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). H1-H5 were examined in term of detailed thermal, mechanical, and anti-water sorption properties using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) nanoindentation, and thin film diffusion analysis, which revealed that H4 has the highest thermal, mechanical, and anti-water sorption properties. H4 greatly increased the thermal decomposition temperature (T d10%) and glass transition temperature, which are 45 and 11 °C higher than that of pure PPC. Accordingly, H4 showed a high storage modulus (2.54 × 109 Pa), elastic modulus (2.601 ± 0.110 GPa), hardness (0.175 ± 0.013 GPa), and lowest water absorption. This improvement in the thermal, mechanical, and anti-water absorption properties of PPC shows that PPC can be used as a packaging and bio-material.

Nanohybrids based on UV-curable polyurethane acrylate (PU) and cloisite 20B (C-20B) have been synthesized by solution blending method using different loading levels of C-20B. The structures of PU/C-20B nanohybrids were confirmed by Fourier transform infrared spectroscopy (FTIR) while X-ray diffraction and transmission electron microscopy (TEM) showed the intercalation of PU into layer silicates. The thermal properties of PU and PU/C-20B nanohybrids were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). TGA tests revealed that the thermal decomposition temperature ( T d10% ) of the nanohybrid containing 5 wt% of C-20B increased significantly, being 61 °C higher than that of pure PU while DSC measurements indicated that the introduction of 5 wt% of clay increased the glass transition temperature from 89.7 to 101 °C. Accordingly, the mechanical and anti-water absorption properties proved also to be enhanced greatly as evidenced by nanoindentation anylsis and water absorptions data in which the nanohybrid containing 5 wt% of clay have highest elastic modulus (4.508 GPa), hardness (0.230 GPa) and lowest water absorption capacity. Thus the formations of nanohybrids manifests through the enhancement of thermal, mechanical and anti-water absorption properties as compared with neat PU due to the nanometer-sized dispersion of layered silicate in polymer matrix.

A simple method to synthesize silver or silver sulfide nanoparticle-decorated nanotubes without additional templating molecules or thermal treatment is reported in this study. Silver precursor ions were transferred to organic phase using phase-transfer agent from the aqueous precursor and organic solvent mixture, and then reduced to form nanoparticle-decorated nanotubes under the guidance of the self-assembled alkylthiol molecules at room temperature without additional templates. During the reduction of the precursor metal ions, the alkylthiol molecules formed cylindrical template as well as capped silver and silver sulfide nanoparticles, simultaneously. Through this multifunctional role of alkylthiol molecules, one-step preparation of nanoparticle-decorated nanotubes or nanorods was achieved. A series of control experiments were carried out in order to survey the effect of thiol amount on the nanotube formation. The concentration of alkylthiol was turned out to be a key factor determining the final morphology of the product. In addition, the nanotube formation is governed by the type of metal precursor ion used. These results will provide an advanced synthesis method on the alkylthiol-based nanotubes decorated with functional nanoparticles.

Catalyst coating in micro-channel reactor for steam reforming of methanol (SRM) is advantageous compared to micro-packed reactor as one part of fuel processor in the application of fuel cell for portable application. In the present study, the performance and pressure drop of catalyst coated and catalyst packed in micro-channel reactor with commercial catalyst in both cases were compared for steam reforming of methanol. The different sols (alumina, zirconia and mixed sol of alumina and zirconia) as a binder for the catalyst have been used to compare the stability and performance. Though the initial performance exhibited by using different sols was same at 290 °C, the performance decay of 20% was observed after 6 days of continuous operation in the case of using zirconia as binder. This may be due to relatively unstable catalyst coating and nonuniform dispersion of catalyst particles on the ZrO 2 binder. Among the different sols, mixed sol of alumina and zirconia comparatively showed better stability and performance. Though the pressure drop in packed catalyst in micro-channel reactor was higher compared to that in catalyst coated micro-channel reactor, the almost complete conversion of methanol in SRM reaction was achieved with packed catalyst in micro-channel reactor at lower temperature.

The in situ polymerization and crosslinking of sodium salt of sulfonated styrene in the pores of nafion 117 membrane has been studied for the evaluation of electrical performance of the resultant semi-IPN (semi-interpenetrating polymer network) membrane in direct methanol fuel cell (DMFC). The formation of semi-IPN is confirmed from the presence of aromatic characteristics peak in the FTIR spectra. Impedance results indicate that the semi-IPN sample with higher water uptake exhibits lower interfacial resistance compared to a sample with water uptake. This indicates that the semi-IPN formed in the pores of nafion 117 membrane has the ability to reduce methanol crossover by blocking the transportation. At higher temperatures (>110 °C) and lower current density ( −2 ), the electrical performance (power density) of a DMFC with a representative semi-IPN sample is observed to be higher than that with a nafion membrane.

Organic–inorganic composite membranes from partially aliphatic sulfonated polyimides and heteropolyacids (HPAs) were synthesized. A series of composite membranes with varying amounts of heteropolyacid were prepared by altering the weight ratio of polyimide and HPA. The partially aliphatic sulfonated polyimides are synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-diaminobiphenyl 2,2′-disulfonic acid as the sulfonated diamine, and decamethylenediamine as the aliphatic diamine. The incorporation of HPA is confirmed by FT-IR analyses. When appropriately embedded in a hydrophilic polymer matrix, the hydrated HPAs are expected to endow the composite membrane with their high proton conductivity, while retaining the desirable mechanical properties of the polymer film. These composite membranes were evaluated for thermal stability, ion exchange capacity, water uptake and proton conductivity. Also the extraction of HPA from the polyimide membranes and their stability in water were determined. Though water uptake and IEC decreased with increase in HPA content, the proton conductivity of the composite membranes increased with increase in HPA weight content. This study shows that partially aliphatic sulfonated polyimide composite membranes with HPA can be a viable substitute for Nafion ® for fuel cells which show good conductivity comparable to Nafion ® 117 at temperatures nearing 100 °C, keeping in mind that polyimides have good thermal stability and low cost.

Micro-channel reactor for steam reforming of methanol seems to be attractive for portable application as one part of fuel processor in fuel cell. In the present study, steam reforming of methanol was performed in one stainless steel micro-channel reactor coated with commercial catalyst. The different sols (alumina, zirconia and mixed sol of alumina and zirconia) as a binder for the catalyst were applied to compare the stability and performance. Among the different sols, mixed sol of alumina and zirconia comparatively produced better stability and performance.

Novel sulfonated co-polyimide and poly ethylene glycol diacrylate based semi-interpenetrating polymer network membranes have been prepared for the fuel cell applications. These membranes were characterized by determining, ion exchange capacity, water uptake and proton conductivity. The proton conductivity of the membranes was in the order of 10- 1Scm-1 at 90 {degree sign}C and generally increased with increasing poly ethylene glycol diacrylate content.

Sulfonic-functionalized heteropolyacid–SiO 2 nanoparticles were synthesized by grafting and oxidizing of a thiol-silane compound onto the heteropolyacid–SiO 2 nanoparticle surface. The surface functionalization was confirmed by solid-state NMR spectroscopy. The composite membrane containing the sulfonic-functionalized heteropolyacid–SiO 2 nanoparticles was prepared by blending with Nafion ® ionomer. TG–DTA analysis showed that the composite membrane was thermally stable up to 290 °C. The DMFC performance of the composite membrane increased the operating temperature from 80 to 200 °C. The function of the sulfonic-functionalized heteropolyacid–SiO 2 nanoparticles was to provide a proton carrier and act as a water reservoir in the composite membrane at elevated temperature. The power density was 33 mW cm −2 at 80 °C, 39 mW cm −2 at 160 °C and 44 mW cm −2 at 200 °C, respectively.

Heteropolyacid (H 3 PW 12 O 40 , HPA)/SiO 2 nanoparticles were synthesized by a microemulsion technique to prevent the dissolution of HPA in polar solvents including water. The particle size was controlled within the range from 100 to 500 nm. The solid-state NMR, FT-IR and the adsorption of trimethylphosphine were used to characterize the HPA/SiO 2 nanoparticles. The surface properties including the BET surface area, acidity and catalytic activity depended on the particle size of HPA/SiO 2 . The reduction of particle size of HPA/SiO 2 improves the surface area and the acidity of the nanoparticles. The interaction of HPA with silica surfaces was observed by solid state NMR. Selective ethanol oxidation was tested as probe reaction on HPA/SiO 2 . The catalytic activity of ethanol oxidation was enhanced with the reduction of the particle size of HPA/SiO 2 . The catalytic properties of HPA in the silica nano phase might be different from those in the bulk phase due to the physico-chemical differences of nano phase.

TiO2 supported on SiO2 surface is effective on the recovery of photocatalyst, morphological control, and coating on the substrate. Furthermore, it shows much higher photocatalytic activity than pure TiO2. The silica support is quite influential on the surface properties of TiO2 supported on SiO2. The enhanced photocatalytic activity of TiO2–SiO2 could be explained by the effects of surface area, adsorption, band-gap energy and local structure. However, it is difficult to say which one is the most important factor responsible for the photocatalytic property of TiO2–SiO2. For example, the reduction of particle size could effect on both of the surface area and band-gap energy. And, Ti–O–Si bonds could modify the band-gap energy and local structure. Therefore, the photocatalytic properties of TiO2–SiO2 should be expressed by sum of many factors such as surface area, adsorption, band-gap energy and local structure.

The effect of a crosslinkable imide moiety, bismaleimide (BMI), on the water sorption properties of poly(ether imide) (PEl) was gravimetrically measured and interpreted together with the chemical and morphological structures in composite films. The morphological structure of composite films was investigated by using a prism coupler and X-ray diffraction pattern. It indicated that the in-plane orientation and intermolecular packing order increased as the content of BMI in composite films increased. The water sorption behaviors showed dependence on the morphological change originating from the addition of BMI to PEI. The composite film with relatively high content of BMI exhibited a relatively high degree of in-plane orientation and a small mean intermolecular distance, which resulted in a decrease in the diffusion rate and water sorption and an increase in the activation energy in composite films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1692–1697, 2006

The laminated composite polymer electrolyte membrane is prepared as a sandwich structure, i.e., Nafion–Nafion/polyvinylene difluoride (PVdF)–Nafion. The conductivity of the laminated membrane is 1.1×10−2 S cm−1. The middle layer of PVdF/Nafion successfully blocks methanol cross-over. In tests in a direct methanol fuel cell (DMFC), all of the Nafion–Nafion/PVdF–Nafion membranes give higher power densities than with a Nafion membrane. The highest current density using a blend membrane with 20% PVdF at a constant cell voltage of 0.3 V is 217.64 mA cm−2 at 110 °C. It is noteworthy that the Nafion–Nafion/PVdF–Nafion laminated membrane sustains high performance at temperatures above 130 °C, whereas the performance of a Nafion membrane is drastically decreased.

We prepared poly(p-phenylene pyromellitimide) (PMDA–PDA), poly(p-phenylene 4,4′-hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10−10 to 11.3 × 10−10 cm2/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in-plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003

Isotactic polyacrylonitrile (PAN) has been prepared by using a zeolite as a host. After introduction of acrylonitrile monomers, they were subsequently polymerized with radical initiators in Na–Y and Na–β zeolite channels, followed by extraction with hydrofluoric acid. 13C-NMR results show that the isotacticity of extracted PAN is higher than that of bulk PAN prepared under the same reaction conditions and is also affected by the pore structure of host. Thermal and physical properties of extracted PAN were also investigated using GPC, DSC and XRD.

Polyimide films have been prepared from reaction of 1,4-phenylenediamine (PDA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), 4,4′-oxydiphthalic dianhydride (ODPA), diphenylsulfone tetracarboxylic dianhydride (DSDA) or (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). The water sorption behaviour of thin films of the polyimides was strongly dependent on the chemical structure of the internal linkage and the morphological structure of the films. The in-plane orientation and molecular chain order decreased with increasing bulkiness of the internal linkage, leading to relatively low diffusion coefficient in DSDA-PDA and 6FDA-PDA films. The water diffusion coefficient varied in the range of 1.7×10 −10 to 10.5×10 −10 cm 2 /s, and was in the increasing order: BPDA-PDA

This work demonstrates that extrusion process can be used as a continuous reactor for the recycling of crosslinked polyethylene (XLPE) via supercritical methanol decrosslinking reaction. The multistage single screw extruder (L/D = 36, D = 40 mm) with methanol injection pump was customized for the continuous supercritical decrosslinking reaction. Reaction temperature was ranged from 360°C to 390°C. The amount of methanol was varied from 0 to 7 mL/min. The extruder provided the crosslinked polymers with the supercritical conditions of methanol during continuous process. The gel content of XLPE decreased with the increase in the reaction temperature and methanol content. Although XLPE experienced supercritical methanol for less than 2 min retention time in the continuous supercritical extruder, it was completely decrosslinked above 390°C at the methanol feeding rate of 7 mL/min. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41442.

Heteropoly acid entraped in nano silica matrix was prepared by the microemulsions method. The primary particle size was less than 400nm and it decreased with the content of the heteropoly acid. When these silica particles were blended with sulfonated polyethersulfone, the HPA could be effectively immobilized in aqueous environment. The conductivity of this composite electrolyte was 1.4×10−3 S/cm with the 15% HPA.

Zeolite composite membranes were prepared for the separation of VOCs by the pressurized coating method. On the top of the composite membrane, TiO2, polyimide or polyethersulfone were coated by the same tech-100 nm-sized nique.ZSM-5 coated membranes show higher selectivity for n-hexane in n-hexane/benzene mixture than 500 nm sized ZSM-5 coated membrane. Composite membrane coated with 100 nm zeolite and polymer showed the highest selectivity (44) for n-hexane/benzene.

The effect of film thickness on the water-sorption behaviors of poly(3,4′-oxydiphenylene pyromellitimide) (PMDA-3,4′ODA) films was gravimetrically investigated and interpreted with a Fickian diffusion model in films. The diffusion coefficient increased with increasing film thickness, whereas the water uptake and the activation energy decreased. Overall, the water-sorption behaviors of PMDA-3,4′ODA films are strongly dependent on the changes in morphological structure, which originated from the variation in the film thickness. As the film thickness increased, the molecular in-plane orientation decreased, consequently leading to the increased diffusion coefficient and decreased activation energy. In contrast, the water uptake decreased with increasing film thickness because of the increase in the out-of-plane packing order. The diffusion coefficient and activation energy were strongly dependent on the in-plane orientation in the films. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 669–676, 2001

The water diffusion behaviors and activation energies of PDA- and ODA-based polyimide thin films were quite dependent on both the chemical structure and the morphological structure in the films. The water diffusion coefficients of polyimide thin films increased with increasing temperature. The activation energies varied in the range of 5.81 to 9.27 kcal/mol and were relatively higher for the PDA-based polyimide thin films than for the corresponding ODA-based polyimide thin films. For the PDA- and ODA-based polyimide films, the differences in the morphological structures and the chemical affinity to water molecules might be reflected directly on the water diffusion behaviors. The PDA-based polyimide films exhibited a relatively more ordered morphological structure (high crystallinity and good in-plane orientation) than that of the corresponding ODA-based polyimide thin films, which may serve as impenetrable obstacles for the water diffusion in the out-of-plane direction. Consequently, it may lead to a relatively slower water diffusion and high activation energy in the PDA-based polyimide thin films. Additionally, the PDA-based polyimide films with relatively lower chemical affinity showed relatively low diffusion coefficients and high activation energies. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 731–737, 2001