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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.

The main challenge to developing future display substrates is to synthesize flexible substrate materials that also have excellent optical and thermal properties, and low thermal expansion number. In this study, a novel trifluoromethylated asymmetric aromatic diamine, 4-[[4-(4-amino-2-trifluoromethylphenoxy)phenyl]sulfonyl-3-(trifluoromethyl)]benzenamine (AFPSFB), was synthesized through nucleophilic substitution. Conventional two-step polycondensation of AFPSFB with commercially available tetracarboxylic dianhydrides enabled the fabrication of fully or semi-aromatic polyimides (PIs). The resulting PIs were highly soluble in polar aprotic solvents with good optical and thermal properties. Next, polyhedral oligomeric silsesquioxane containing an amine group (NH2-POSS) was reacted with the resulting soluble PI. All the PI-POSS nanohybrids displayed excellent optical properties, including high transparency (>91% at 400 nm), low refractive index (

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.

A method to improve the optical properties of transparent poly(amide-imide) (PAI) by incorporating a new flexible diamine is demonstrated. The new diamine-incorporated PAI films show a lower glass transition temperature, yellow index, residual stress than neat PAIs irrespective of their structure. The DSC results show that the new diamine increases the flexibility of the polymer matrix indicating the poor packing of the matrix. However, the light transmittance reduces from 89.73 to 88.58%. This discrepancy can be clarified by measuring the residual stress of the PAI films. The results confirm that PAI has high elasticity and flexibility at low and high temperatures. Thus, flexible diamines can be added to PAI films for transparent materials owing to their good optical properties such as a transmittance of over 87%, yellow index lower than 2.8 and low residual stress

Due to rise in demand for mobile devices, development of complex stacked packaging technology such as multi-chip package, capable of both small size and high volume, are in high interest. As residual stress of individual chips increases, the degree of bending rises leading to more difficulty in package assembly process and decreased reliability of the final package product. To overcome this, deeper understanding of the thermal history and thermal behavior between the polymer film and substrates are needed. In this work, residual stress-temperature profiles of thermally stable polyimide/organically-modified layered silicate (PI/OLS) nanocomposite systems on Si wafer were investigated in situ during imidization and cooling process. This study provides systematic approach from the perspective of substrate design for multi-stacked semiconductor package.

When a large fuel cell power plant is connected to a district heating network, the cogeneration efficiency of the power plant is usually insufficient (60–79%). In this study, we focused on the latent heat of water generated from the fuel cell reaction H2 + O2 → H2O, which is an unutilized energy source. This technique is a potential solution for enhancing the total efficiency of the system. A new system linking a large-scale fuel cell power plant to a district heating system was developed. Its primary energy efficiency significantly increased (26.6%) owing to the maximum utilization of the latent heat from the water vapor condensation. This innovative system was installed in a 10.56 MW fuel-cell power plant, and operational data for the temperature and flow rate balance were obtained and analyzed. The results indicate that this system reduces investment costs by approximately 50% using cascade heat utilization technology for district heating systems, and consequently, the estimated payback period is less than 2 y.

Colorless polyimides (CPIs) with outstanding mechanical properties are used as essential materials in the production of future flexible display panels, foldable windows, and spacecraft cockpit materials. However, under repetitive stress and deformation, fatigue fractures caused by cracks and radio waves may act as critical determinants of the properties and duration of the material. To solve this problem, the present study developed a CPI capable of self-healing, wherein the transparency and any damage caused by external stress are rapidly and easily restored. Our synthesized CPI films showed ultra-transmittance (> 95%) and excellent self-healing efficiency (> 98%) with a simultaneously induced multi exchange network. Notably, the films exhibited excellent mechanical properties even after a bending fatigue test involving more than 10,000 cycles. This study therefore suggests a new type of CPI with a self-healing function and shows that the trade-off between the durability and functionality can be completely resolved.

Traditionally, electromagnetic interference (EMI) shielding material has been occupied by metallic materials due to its high electric conductivity and EMI shielding effect. However, with rising demands from technology development for light-weight, highly durable, and easily moldable materials, metallic materials are gradually being substituted by polymer composite materials. Still, there are limitations on polymer composite as EMI shields: High ratio of fillers in composite achieves excellent EMI shielding effect but it severely compromises its mechanical behaviors. In many studies, they have failed to fabricate the high-ratio filler films with good mechanical durability, but here the initially fragile high-ratio film has been transformed to a flexible film by a very simple method: Hot-pressing. This approach not only solved the problems mentioned above but further provided a possible breakthrough point for composite study by solving threshold of the maximum loading of the fillers in polymer matrix. The stiff composite of polyimide sponge with exceeding carbon black loading became a highly flexible EMI SE film with doubled tensile strength and enhanced EMI SE. As a result, a new way of fabricating flexible EMI shielding polymer composite is demonstrated with great potential applications in aerospace and wireless communications.

Direct spinning of carbon nanotube (CNT) fibers is a facile method to produce CNT fibers because of its high productivity and the simplicity of the spinning process from CNT aerogels. Directly spun CNT fibers, however, generally include amorphous carbon and weak shear interaction between tubes or bundles, thereby causing insufficient load transfer. Here, we report newly designed polyimide/reduced graphene oxide (PI/RGO)/CNT fiber composites in combination with polymer infiltration followed by photonic flash sintering on a time scale of 0.5 ms to overcome the critical drawbacks in directly spun CNT fibers. The mechanical performances of the CNT fibers were closely related to the junction strength in CNT bundles. In addition, PI can be interlocked with CNT bundles and effectively serve as a binder to link the GO and CNT fibers with strong interfacial interactions. The PI infiltrated CNT fibers showed the highest load transfer, resulting in a significantly enhanced increase of 83% in specific strength (1.1 N/tex) and a 477% increase in tensile strength (800 MPa) compared to pristine CNT fibers. Furthermore, the photonic sintered PI/RGO/CNT fibers improved electrical conductivity by over 244% (5.5 × 103 S cm−1) over pristine CNT fibers without deteriorating mechanical properties. The results demonstrate that the mechanical strength, modulus and electrical conductivity can be enhanced simultaneously by molecular-level coupling of polymer/graphene with CNT fibers via photonic flash sintering.

In this study, transparent thin films for coating material are synthesized by adding bulky CF3 and hydroxyl groups intro into poly(amide-imide)s. As expected, these poly(amide-imide)s show higher shear adhesion and higher glass transition temperatures than the neat poly(amide-imide) due to hydrogen bonding of the hydroxyl groups. In addition, the modification to the poly(amide-imide) structure leads to only slight decreases in transmittance and yellow index. Consequently, the successful synthesis of poly(amide-imide)s with wide applications as transparent coating materials due to their optical properties and high adhesion is demonstrated. Transparent flexible display and coating products can be manufactured with poly(amide-imide)s having high reliability and a low chance of cracking due to their favorable thermal properties.

We report a facile method to enhance mechanical properties of polymer nanocomposites using three-dimensional (3D) network structures of functionalized graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) in a polymer matrix. The GO and MWCNTs were functionalized using Fisher indole and diazonium-salt reactions to produce pyridine (Py) moiety on the GO and MWCNTs. The functionalized GO (Py-RGO) and MWCNT (Py-MWCNT) nanocomposites exhibited hydrogen-bond assisted 3D network structures in a polyimide (PI) matrix. By incorporating 1 wt% of carbon materials (0.9 wt% Py-RGO and 0.1 wt% Py-MWCNTs) in a PI, the tensile strength and modulus of the ternary nanocomposites reached 581 MPa and 31 GPa, respectively, which was an enhancement of 221% and 312% compared with pristine PI. The fracture energy of the PI/Py-RGO/Py-MWCNT nanocomposites improved 200% and approached 29.7 MJ m−3. The formation of the 3D network structure of the functionalized carbon nanomaterials is considered to significantly affect load transfer of nanofillers in the polymer matrix, and produce high performance polymer nanocomposites.

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.

The decomposition of formic acid (HCOOH) over ZrO2 catalysts synthesized by precipitation method was investigated and their catalytic activity based on unit mass of catalyst was compared by varying the calcination temperature in the 500–1000 °C range. The calcined ZrO2 samples were characterized using temperature-programed desorption (TPD) of iso-propanol (IPA), H2O, and HCOOH as well as X-ray diffraction (XRD), pyridine-adsorbed infrared spectroscopy (Py-IR) and N2 sorption. The catalytic activity as a function of the calcination temperature of ZrO2 showed a volcano-type curve with a maximum at 900 °C. The catalytic activity of ZrO2 in the decomposition of HCOOH well correlated with Bronsted acid site density, and it was influenced by the crystalline phase of ZrO2. Furthermore, the evolution of the Bronsted acid site density measured by Py-IR as a function of the calcination temperature was in good accordance with the desorption temperature determined by IPA- and HCOOH-TPD experiments. When H2O vapor was added, the conversion of HCOOH slightly decreased, while the CO selectivity remained almost constant. However, when CO was supplied, the conversion of HCOOH decreased continuously, and the selectivity to H2 gradually increased, indicating that the formation of zirconium suboxides with characteristics approaching those of metals was successful using CO as a reductant.

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.

New diamines for high-performance poly(ester imide)s (PEsIs) containing dimethyl groups at the ortho-position of amino groups and ester derivatives have been developed to improve optical transparency and glass transition temperature (Tg) while maintaining a low coefficient of thermal expansion (CTE). Four kinds of PEsIs derived from bis(4-amino-3,5-dimethylphenyl) terephthalate (BADMT) and aromatic dianhydrides such as 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4’-oxydiphthalic anhydride (ODPA), and 4,4'-(hexafluoroisopropylidene)diphthalic (6FDA) were synthesized via a two-step polycondensation. All PEsIs exhibited outstanding properties, such as light color, a good transmittance of >90% at 550 nm, high Tg above 289 °C and 5% weight loss temperature (483–511 °C), and low CTE (11–68 ppm/°C). The effect of the substituent on molecular packing and properties, including optical and thermomechanical properties for the resulting PEsIs were examined in detail. The temperature-dependent CTE of the PEsIs was determined using molecular dynamics (MD) simulation. The molecular orbital (MO) calculation models support the discussions on the electronic substituent effect of the PEsI main chains. Our molecular architecture and systematic property studies with MD and MO promote a better understanding of the polyimides.

A facile one-step method for synthesis of a porous monolithic polyimide aerogel was successfully developed. The specific thermal curing, slow desiccating process and swelling method were used in synthesizing monolithic polyimide aerogel without any additional chemical reaction to create a connected structure among the polyimide-based spherical aerogel microparticles. Using this method, the monolithic polyimide aerogel can be easily fabricated whilst using no additional chemicals for crosslinking. This type of polyimide aerogel was produced homogeneously by the polyimidization of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). The synthesized porous monolithic polyimide aerogel has many good properties which could be used in various industries, as it maintained a high thermal decomposition temperature (10% weight decomposition temperature: T d10% ) of approximately 577 °C and a glass transition temperature (T g ) of 432 °C, with bulk density of 490.7 kg/m 3 , porosity of approximately 45% and average pore size of 4 nm (by nitrogen adsorption test) of polymer and 157 nm (by mercury intrusion method) of space observed in FE-SEM image. Also, the monolithic polyimide aerogel had an excellent oil-adsorbing capacity of 150%, and the adsorbed oil could be separated easily using a simple drying process. The dried monolithic polyimide aerogel showed significant recoverability and reusability of adsorbed oil. In addition, the monolithic polyimide aerogel exhibited high mechanical resistance such that the structure can withstand a high pressure greater than 122.3 kPa, under which the monolithic polyimide aerogel (MPA) was compressed but did not break. This type of MPA shows excellent thermal, mechanical properties and great processability, and could be the new candidate for high performance materials in various industries, especially catalyst field.

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 .

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.

Simple self-healing behavior of polymers that respond to multiple physicochemical stimuli are highly desirable for industrial applications. In this study, under various external environmental stimulating factors, we focus on the self-healing kinetics of polymer bilayer films (PBFs) comprising a colorless polyimide (CPI) bottom-substrate layer and linseed oil loaded microcapsule (LOMC)-embedded polydimethylsiloxane (PDMS) upper-healing layer. The experimental results showed clear correlation between stimulating factors and the healing time. Although the crack-healing behavior of PBF with 5 wt% microcapsule under air atmosphere is fairly slow, it has an improved healing effect at the artificial crack interface heating to 70 °C; moreover, gradual healing is observed by moisture absorption in environments with relative humidity of 70%. Remarkably, we found that ultraviolet (UV)-light irradiation through the 5 wt% LOMC-filled PDMS layer triggers a noticeable kinematic advantage for the drying reaction that initiates interfacial self-healing. Short-time (20 min) UV-irradiated PBF 5 wt% exhibits a low water vapor permeability of 35.4 g m−2 day−1 and excellent healability with ~91% recovery by single capsule-type photochemical-induced self-healing. The proposed approach advances the extrinsic healing of colorless polymers in a kinetically effective way without compromising their chemical composition.

In recent times, with increase of requirements in function and appearance, it is important to improve the function of package components which are implemented in various electronic devices by developing reliable packaging technology such as wafer level chip scale packaging (WLCSP). For the package, insulation techniques are essential to reduce noise caused by high electrical current and overcome coefficient of thermal expansion (CTE) mismatch between interfaces of multi-layers. In this study, in order to investigate properties of polyimide based materials for WLCSP as dielectrics, a series of copolyimide/silica nanocomposite (CPS) films were prepared from sol-gel method and their residual stress behavior on Si wafer was evaluated in situ during thermal cure and cooling steps. This work provides a possible candidate for application in WLCSP industries by controlling desirable properties.

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).

Polyurethane acrylate/surface-modified colloidal calcium carbonate (PUA/SCaCO3) nanocomposite coatings were successfully prepared via a UV-curing technology. The structural and morphological features of the PUA/SCaCO3 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), and wide angle X-ray diffraction (XRD). The physical properties were strongly dependent upon chemical and morphological structures that originated from differences in SCaCO3 loading. A critical SCaCO3 concentration was observed for the evolution of both the structure and physical properties of the PUA/SCaCO3 nanocomposites as a function of SCaCO3 content. The thermal stability was measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively, and displayed some enhancement with the incorporation of SCaCO3 into PUA. Although the nanomechanical properties increased up to 3 wt% SCaCO3 content, they decreased due to lack of interfacial interaction with high SCaCO3 loading. Most importantly, the water uptake and water vapor transmission rate (WVTR) varied from 5.51 to 1.78 wt% and 28.9 to 19.9 g/m2 day, respectively, exhibiting significant enhancement in water resistance. The results clearly reveal that the performance of UV-curable PUA/SCaCO3 nanocomposites is strongly dependent on organically-modified colloidal SCaCO3 nanoparticles.

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.

A novel method for synthesizing a microsponge polyimide (PI) film with excellent thermal stability, chemical resistance, and heat insulation performance was developed. The synthesized microsponge PI film has open cells with sizes between 1 and 10 μm and a porosity of 76%. Furthermore, the film contains several layers overlapping in multiple grid structures, which complicates the heat transfer paths. Thus, the heat transfer coefficient of the microsponge PI film is 67% less than that of existing polyimide film (0.054 vs. 0.16 W/m·K). This reduced heat transfer coefficient results in excellent heat insulation performance of the microsponge PI film. The thermal decomposition (pyrolysis) of the microsponge PI starts at 498 °C and its glass transition temperature is 317 °C, which indicates excellent thermal stability. However, its Young's modulus, an indicator of mechanical strength, is nearly 74% less than that of conventional PI film (26 vs. 100.2 MPa).

A series of poly(urethane acrylate)/Cloisite 15A (PUA/C15A) nanocomposite films were successfully prepared via a UV-curing system, and their physical and barrier properties were investigated as a function of clay content. The physical properties were strongly dependent upon the chemical and morphological structures originating from differences in Cloisite 15A content. With high clay content, the PUA/C15A nanocomposite films displayed an intercalation/exfoliation combined structure. However, no strong interfacial interactions occurred between the PUA and clay, possibly leading to poor dispersion with relatively high clay content. The thermal stability displayed some enhancement with the introduction of clay into PUA, while the gas and moisture barrier properties showed significant enhancement. The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) decreased with increasing contents of Cloisite 15A, and varied within the range of 714.0–71.1 cm3/m2 day and 29.9–13.9 g/m2 day, respectively. Thus the enhanced gas and moisture barrier properties of PUA/C15A nanocomposite films make them promising candidates for food and pharmaceutical packaging applications. However, further studies will be performed to increase the compatibility and dispersion of clay particles in the PUA polymer matrix.

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%.

To increase the efficiency of a combined-cycle gas turbine (CCGT) power plant, an innovative system was built to recycle its internal unutilized energy and increase the heating output. CCGT circulation and absorption heat pump circulation were combined in the new system, and latent heat recovery from LNG combustion was realized with very slight power consumption. The innovative system was applied in a 200-MW power plant, and real operation data were obtained to design optimal temperature and flow rate balance. Finally, the effect of system transformation on the efficiency increase was analyzed. The proposed system enhanced the overall primary energy efficiency of cogeneration and thermal output by 2.6 and 7.4%, respectively.

Polybenzimidazole hybrid membranes (H1–H3) were prepared by incorporating different amounts (wt.%) of inorganic hetero poly acids (IHA-Si) into polybenzimidazole (PBI) matrix. Structural, morphological and thermal characteristics of all the hybrid membranes were studied by FT-IR, XRD, SEM and TGA and further investigated functional relationships between the materials structure and metal ion uptake using Hg(II), Pb(II), Y(III), and Cd(II). It was found that H3 was most selective toward Hg(II) as compared to H1 and H2 and further uptake capacity of H1–H3 was strongly dependent on mesoporous silica. The hybrid membranes with high mesoporous silica (H3) exhibited high thermal stability and high uptake capacity toward Hg(II) which was experimentally determined to be 2.48 mg g−1. Desorption study for the regeneration of adsorbent was also achieved using ethylenediaminetetraacetic acid solution. Ultimately, the proposed method provided reasonable results for the determination of Hg(II) in environmental water samples.

Surface-modified tetrapod zinc oxide whiskers (STZnO-W) were successfully synthesized via a thermal oxidation method and subsequent modification using a silane coupling agent and were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (WAXD) and scanning electron microscopy (SEM). Five different poly(urethane acrylate) (PUA)/STZnO-W composite films containing the as-synthesized STZnO-W were prepared via a UV curing method. The morphology, thermal stability, mechanical properties, barrier properties, and antibacterial properties of these films were investigated as a function of the STZnO-W content and were found to be strongly dependent upon the chemical and morphological structures. The thermal stability, barrier properties, and antibacterial properties of the composite films were enhanced as the STZnO-W content increased, which indicate that these materials are potentially suitable for many packaging applications. Barrier tests showed that the oxygen transmission rate (OTR) and water uptake decreased from 724.3 g/cc/day to 176.0 g/cc/day and 3.7–0.7 wt.%, respectively. Although the mechanical strength increased to 1 wt.% STZnO-W content, it decreased at relatively high STZnO-W loadings due to low interfacial interaction between polymer and filler and the resulting poor dispersion. Therefore, further studies are needed to maximize the performance of composite films by enhancing the compatibility of the polymer matrix and fillers.

A series of polyurethane acrylate (PUA)/ZnO nanocomposite films with different ZnO contents were prepared via a UV-curing system. To ensure good dispersion in the PUA matrix, ZnO nanoparticles were modified with a silane coupling agent and confirmed by FT-IR analysis. The morphological structures, thermal properties, mechanical properties and water transfer properties of the prepared films were investigated as a function of their ZnO concentration. WAXD and SEM analyses showed that the surface-modified ZnO nanoparticles were homogeneously dispersed in the PUA matrix and the molecular ordering increased with increasing ZnO content. Compared with neat PUA, the hardness and elastic modulus in films increased from 0.03 to 0.056 GPa and from 2.75 to 3.55 GPa, respectively. Additionally, the water uptake and WVTR in the PUA/ZnO nanocomposite films decreased as the ZnO content nanoparticles increased, which may come from enhanced molecular ordering and hydrophobicity in films. UV light below approximately 450 nm can be efficiently absorbed by incorporating ZnO nanoparticles into a PUA matrix, indicating that these composite films exhibit good weather ability and UV-shielding effects. The enhanced physical properties achieved by incorporating modified ZnO nanoparticles can be advantageous in various applications, whereas the thermal stability of the composite films should be increased.

Organic-inorganic nanohybrids, 3,4-dihydroxycinnamic acid/layered double hydroxide (CA/LDH), 4-hydroxy-3,5-dimethoxycinnamic acid/layered double hydroxide (SA/LDH), and 3-amino-5-triflouromethylbenzoic acid/layered double hydroxide (FBA/LDH) have been synthesized by co-precipitation reaction of organic ultraviolet (UV) ray absorbents such as 3,4-dihydroxycinnamic acid, 4-hydroxy-3,5-dimethoxycinnamic acid, 3-amino-5-triflouromethylbenzoic and Zn2Al layered double hydroxide (LDH). Detailed structural and absorption properties of the nanohybrids were studied by using X-ray diffraction (XRD), FT-IR and UV-Vis transmittance spectra which revealed that organic UV absorbents have been intercalated into the interlayer spaces of LDH and all nanohybrids showed excellent UV ray absorption. All the nanohybrids showed a lower catalytic activity as compared to the net organic UV ray absorbents by applying air oxidation to castor oil.

UV-cured poly(urethane acrylate- co -acrylic acid) (PU- co -AA) films with five different compositions were prepared by reacting isophorone diisocyanate (IPDI), polycaprolactone triol (PCLT), 2-hydroxyethyl acrylate (HEA), and different weight ratios of trimethylolpropane triacrylate (TMPTA) and acrylic acid (AA) as diluents. Their synthesis and physical properties including gel content, adhesion properties, morphological structure, thermal properties, and mechanical hardness were investigated as a function of the AA content. It was found that the physical properties of the PU- co -AA films are strongly dependent upon the AA content. Crosscut tests showed that PU- co -AA films with lower AA content showed 0% adhesion (0B), and the adhesion of films increased dramatically as the AA content increased to 40–50%. The pull-off measurements showed that the adhesion force of the PU- co -AA films to stainless steel substrates varied from 6 to 31 kg f /cm 2 and increased linearly with increasing AA content. PU- co -AA films with higher AA content can be good candidates for UV-curable coating of metal substrates such as stainless steel. However, the thermal stabilities and mechanical hardness decreased with increasing AA content, which results from the relatively linear and flexible structure of AA.

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.

In this study, a biomimetic template was prepared and applied for growing calcium carbonate (CaCO 3 ) nanorods whose shape and polymorphism were controlled. A biomimetic template was prepared by adsorbing catalytic dipeptides into the pores of an anodic aluminum oxide (AAO) membrane. Using this peptide-adsorbed template, mineralization and aggregation of CaCO 3 was carried out to form large nanorods in the pores. The nanorods were aragonite and had a structure similar to nanoneedle assembly. This aragonite nanorod formation was driven by both the AAO template and catalytic function of dipeptides. The AAO membrane pores promoted generation of aragonite polymorph and guided nanorod formation by guiding the nanorod growth. The catalytic dipeptides promoted the aggregation and further dehydration of calcium species to form large nanorods. Functions of the AAO template and catalytic dipeptides were verified through several control experiments. This biomimetic approach makes possible the production of functional inorganic materials with controlled shapes and crystalline structures.

In this study, Upilex-S [poly(biphenyl dianhydride- p -phenylene diamine)], one of polyimide films, was modified by coupling reactions with N,N-carbonyldiimidazole (CDI) to increase adhesion to copper for flexible copper clad laminate (FCCL). Imidazole groups show strong interaction with copper metal to make charge transfer complexes. Because polyimide film did not have active site with coupling agent, the film surfaces were modified by aqueous KOH solutions and reacted with dilute HCl solutions. Surface modified Upilex-S was analyzed by X-ray photoelectron spectroscopy (XPS) to examine the surface chemical composition and film morphology and investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Changes in the wettability were evaluated by measuring contact angle with the sessile drop method. After deposition of copper on surface modified Upilx-S, the adhesion strength of the copper/polyimide system was measured by a 90° peel test using the Instron tensile strength tester. The peel strength of the copper/polyimide system increased from 0.25 to 0.86 kg f /cm by surface modification. This result confirmed that the CDI coupling reaction is an effective treatment method for the improvement of the adhesion property between copper metal and polyimide film.

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.

A series of the semi-interpenetrating polymer network (semi-IPN) membranes based on sulfonated polyimide and poly(ethylene glycol) diacrylate were prepared and characterized comparing with pure sulfonated polyimide membrane and commercially available membrane, Nafion® 117. The proton conductivity increased with the increase of poly(ethylene glycol) diacrylate contents in spite of the decrease in ion exchange capacity which is a key factor to improve the proton conductivity. The water stability of semi-IPN membranes containing poly(ethylene glycol) diacrylate is higher than the pure sulfonated polyimide membrane. Morphological structure showed that amorphous nature of the films also increased with the poly(ethylene glycol) diacrylate contents, which could make a crosslink, so that the crystallinity of polyimide could disappear. Semi-IPN membranes based on sulfonated polyimide and poly(ethylene glycol) diacrylate, which show good conductivity comparable to Nafion® 117 in the range of 20–50% content of poly(ethylene glycol) diacrylate, could be promising proton conducting membranes in fuel cell application.

Rotationally fixed [3]ferrocenophane extends the variety of possible molecular geometries in its derivatives in comparison with unbridged ferrocenes. In this respect molecular geometry–liquid crystalline properties relationship studies in [3]ferrocenophane mesogens are of considerable interest. Different positional isomers of mono- and di-substituted [3]ferrocenophanes which are obtained by incorporating one or two promesogenic building blocks into the cyclopentadienyl rings are reported in this article. A series of mono-substituted [3]ferrocenophane-containing Schiff’s bases was synthesized by condensing isomeric p -aminophenyl [3]ferrocenophanes with appropriate aldehydes. Isomers of di-substituted [3]ferrocenophane amines gave rise to a series of azomethines with two promesogenic substituents in the cyclopentadienyl rings. Besides, a β-enaminoketone was prepared from 3-( p -aminophenyl)[3]ferrocenophane. Nematic and smectic mesophases were observed in the synthesized compounds under a polarizing optical microscope. The [3]ferrocenophane-containing β-enaminoketone showed complex mesomorphic behaviour connected with occurrence of the keto-enamine and imino-enol tautomeric equilibrium in this compound. On the base of computational models obtained by semi-empirical quantum chemistry calculations the molecular geometry–phase behaviour relationships were examined. It was demonstrated that mesomorphism of [3]ferocenophane azomethines depends on the spatial orientation of the substituents with respect to the propanediyl bridge in a case of mono-, and as well as to each other in a case of di-substituted derivatives.

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.

A fluorinated diamine, 1,3-bis(4-amino-2-trifluoromethylphenoxy)benzene (mBATB), was synthesized through nucleophilic substitution reaction of Resorcinol and 2-chloro-5-nitrobenzotrifluoride by catalytic reduction with H 2 gas and Pd/C. The synthesis and properties of a series of soluble fluorinated aromatic polyimides derived from mBATB and various dianhydrides via thermal and chemical imidization were described. Substituents of trifluoromethyl groups on the aromatic rings of metalinked ether aromatic diamine conferred enhanced solubility and transparency to the polyimide. The polyimides with various dianhydrides: 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) also exhibited exceptional thermal stability, comparatively low dielectric constants, and excellent optical properties. The outstanding features of the synthesized transparent polyimides are desirable candidate materials for advanced optoelectronics applications.

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.

This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated.

To investigate the difference of the trifluoromethyl (CF 3 ) group and ether group affecting the optical property of fluorinated polyimides (PIs), we prepared 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl ether ( 4 ) with three ether groups and 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane ( 5 ) with four CF 3 groups with 2-chloro-5-nitrobenzotrifluoride and 4,4′-dihydroxydiphenyl ether or 2,2-bis(4-hydroxyphenol)hexafluoropropane. Two series of organosoluble and light-colored PIs ( 4a – 4c , 5a – 5c ) were synthesized from 4 and 5 with various aromatic dianhydrides: 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) ( a ), 4,4-oxydiphthalic anhydride (ODPA) ( b ), and 4,4-hexafluoroisopropylidenediphthalic anhydride (6FDA) ( c ), prepared through a typical two-step polymerization method. These PIs were soluble in amide polar solvents and even in less polar solvents. The glass-transition temperatures ( T g ) of 4a – 5c were 221–249 °C and the 10% weight-loss temperatures were above 530 °C. Their films had cutoff wavelengths between 339 and 399 nm and yellowness index ranges from 1.95 to 42.60. The dielectric constants estimated from the average refractive indices are 2.59–2.93 (1 MHz). In a comparison of the PI series based on 4 , 5 , and 4,4′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl ( 6 ), we found that the CF 3 group and ether group on the diamine had almost same effect in lowering the color, but the ether group had better thermal stability. The color intensity of the three PI series was lowered in the following order: 6 > 4 > 5 . The PI 5c , synthesized from diamine 5 and dianhydride c , had six CF 3 groups in a repeated segment and ether group at the same time, so it exhibited the lightest color among the three series.

Directed methanol fuel cells (DMFCs) are fabricated on printed circuit board (PCB) substrates by means of a photolithography process. The effects of channel pattern, channel width and methanol flow rate on the performance of the fabricated DMFC are evaluated over a range of flow-channel widths from 200 to 400 μm and flow rates of methanol from 2 to 80 ml min−1. A micro-DMFC with a cross-stripe channel pattern gives superior performance compared with zig-zag and serpentine type of pattern. A single cell with a 200-μm wide channel delivers a maximum power density of 33 mW cm−2 when using 2 M methanol feed at 80 °C. An air-breathing multi-DMFC composed of eight single unit cells gave 180 mW cm−2 by using a methanol reservoir. It is considered that this may be the first reported attempt to develop a multi-DMFC with micro-channels fabricated on a PCB substrate.

A two-step fuel-rich/fuel-lean catalytic combustion seems to be one of the most effective methods to control simultaneously the NO generation and the hydrocarbon (HC) conversion from fuel-bound nitrogen. By controlling equivalent air ratio, space velocity, inlet temperature, and catalyst component, the HC and ammonia conversion efficiency higher than 95% could be achieved, with ammonia conversion to NO remaining below 5%. The experimental results would be applied to the combustion of land fill gas and to gasified refuse-derived fuels as a method of minimizing NO generation.