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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.

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

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, 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.

A transparent poly(amide-imide) (PAI) was synthesized with good thermal and optical properties and after that silica nano particles were introduced and removed for nano porous polymer matrix. The successful synthesis of PAI with nano scale porous structure was confirmed with FT-IR and FE-SEM measurement. The effects of free volume of polymer on thermal properties were measured with TGA and DSC. This physically modified polymer matrix showed increased thermal degradation and glass transition temperature over 250 °C. In the case of optical properties, UV-Vis and yellow index were measured and PAI with nano porous structure showed transparent colorless properties with light transmittance in the range of 80-40% and yellow index 2.1-1.1. The results also showed low dielectric constant in the range of 3.2-2.5 and contact angles that of 70-73°.

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.

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.

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.

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.

Light-colored polyimide hybrids with a quaternary alkylammonium modified montmorillonite, Cloisite® 20A (C20A) were successfully synthesized via a solution intercalation method. The structural and morphological features of the PI/C20A hybrids were characterized by Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), field emission scanning electron microscopy (FE-SEM), and spherical aberration correction scanning transmission electron microscope (STEM). The dimensional stabilities were strongly dependent upon the chemical and morphological structures which were influenced by the Cloisite® 20A loading content. A critical Cloisite® 20A concentration was obtained for the evolution of both the structural and physical properties of the PI/C20A hybrids. The dynamic stress behaviors were investigated in situ by using the wafer bending method during thermal imidization of the softbaked PI/C20A hybrid precursor and thermally cured hybrid films using a thin film stress analyzer. The PI/C20A hybrid films exhibited stability at 510 °C, high glass transition and relatively low coefficient of thermal expansion, and an improved solvent resistance capacity. Open image in new window

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.

The effects of norbornene (NE) crosslinking and diamine bridge linkages (ether, sulfone, and trifluoromethyl) on polyimide films were investigated. The purpose of this study was to study the behavior of the NE endcapped polyimide with different diamine bridge linkage structure at elevated temperatures on residual stress and modulus change. 5-Norbornene-2,3-dicarboxylic acid was introduced as the end-capping agent in order to increase the ratio of crosslinking in the structure through reverse Diels-Alder reaction. Wide angle X-ray diffraction (WAXD) was measured to study the relation of d-spacing and structure change of the bridge linkage of polymers through NE crosslinking. Coefficient of thermal expansion (CTE) and residual stress were measured to confirm the loaded stress between the substrate and polymer film through a thin film stress analyzer (TFSA). Storage (e′) and loss modulus (e″) were studied at elevated temperatures to study the relation of bridge linkage mobility of the polyimide at elevated temperature.

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).

Tetrapod zinc oxide whiskers (TZnO-Ws) were successfully prepared by a thermal oxidation method and confirmed using scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). A series of polyimide (PI)/TZnO-W composite films containing the as-prepared various TZnO-W contents were prepared and their physical properties were investigated to understand their potential use in flexible displays. The morphology, physical, and moisture barrier properties of the PI/TZnO-W composite films were interpreted as a function of the TZnO-W content. The PI/TZnO-W composite films exhibited an optical transparency greater than 80% at 550 nm (≤0.5 wt% TZnO-W content), a low coefficient of thermal expansion (CTE), and enhanced glass transition temperature. However, the thermal decomposition temperature decreased as the TZnO-W content increased. Although the mechanical strength increased up to 0.3 wt% TZnO-W content, it decreased due to poor interfacial interaction with high TZnO-W loading. The water vapor transmission rate (WVTR) and water uptake of the composite films, which were strongly dependent upon their morphological and chemical structure, varied from 508.3 to 325.2 g/m2/day and 3.7 to 1.3 wt%, respectively, greatly decreased as the TZnO-W content increased. The water resistance capacity of PI was greatly enhanced and moisture diffusion in the pure PI was retarded by incorporating the TZnO-W.

Polyimide is a major polymer material in the electronics industry, and we conducted a study to cure polyimide at low temperatures in order to improve its thermal and mechanical properties. In this study, polyimide/clay nanocomposites were prepared by the reaction of 4,4’-(hexafluoro isopropylidene) diphthalic anhydride (6FDA) and 4,4’-oxydianiline (ODA) with the addition of 1,4-dizabicyclo[2.2.2]octane (DABCO) as a low-temperature catalyst and nanoclay (Cloisite 20A). The synthesis of polyimide at low temperatures and the dispersion of a nanoclay in the polymer matrix was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Thermal stabilities of the nanocomposites were confirmed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties were measured by an universal testing machine. We demonstrated that when polyimide was cured at low temperatures and short curing times, it was possible to improve the thermal and mechanical properties via the addition of a catalyst and inorganic material. Polyimide with DABCO and 0.25 wt% nanoclay showed a 5 °C higher degradation temperature, 560.88 °C; a 6 °C higher glass transition temperature, 293.62 °C; and a 20 MPa greater tensile strength, 136.94 MPa. Therefore, the polyimide curing process was demonstrated to be successful at low temperatures.

A series of polyimide (PI) nanocomposite films with various surface-modified colloidal calcium carbonate (SCaCO3) contents were prepared and their physical properties were investigated to understand their possible use as polymer substrates. The morphology, thermal stability, residual stress behavior, moisture barrier and optical properties of nanocomposite films were investigated as a function of the SCaCO3 content and were found to be strongly dependent upon the chemical and morphological structures. With the addition of up to 0.5 wt% SCaCO3 in the PI matrix, resultant nanocomposite films exhibit not only enhanced thermal properties, but also minimized residual stress and excellent optical properties, simultaneously. With increasing SCaCO3 content, the water vapor transmission rate (WVTR) is greatly decreased from 630.76 to 484.22 g/m2/day. The residual stress was in the range of 26.0 to 12.1 MPa and is highly dependent on both temperature variation and SCaCO3 content. Although the residual stress becomes lower at 0.5 wt% SCaCO3 content, it increases at relatively high SCaCO3 loadings due to inadequate dispersion of the SCaCO3 and low interfacial interactions between the polymer and filler surfaces. Therefore, further studies are needed to maximize the performance of nanocomposite films by enhancing the compatibility of the polymer matrix and fillers.

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 the study described here, novel, polyimide (PI)-based spherical aerogelmicroparticles are fabricated. The aerogel microparticles proposed in this study have an advantage over film-shaped aerogels because the microparticles can be easily used for thermal insulation, drug release, and catalyst support. By using only a PI polymer as the raw material for the proposed PI aerogel microparticles, the problems associated with reinforcing conventional silica aerogels, such as inferior thermal resistance or incorporation with silica aerogel, are circumvented. The porosity of PI aerogel microparticles was determined to be 80% and specific surface area was determined as 103 m2 g−1. The pore sizes measured using mercury intrusion porosimetry are between 4 and 100 nm, with a representative pore size of 15 nm.

We investigated the decreased water diffusivity depending on the content and size of carbon black (CB) added to polyimide (PI) in order to synthesize composite films (PI-CB). CBs with different diameters were used: N110 (CB1, 11–19 nm), N326 (CB2, 26–30 nm) and N660 (CB3, 49–60 nm). The water diffusion coefficient of PI-CB decreased with increasing CB content from 2.67·10−9 for pure PI films to 0.22·10−9 cm2/s for PI-CB films containing 40 wt% CB1. Moreover, the decrease in water diffusivity with increasing CB content exhibited a linear relationship. The water diffusivity of PI-CB increased with the increasing size of CB at the same CB content. The water uptake of PI-CB had a linear relationship depending on the CB content, similar to water diffusivity; the water uptake of composite films decreased by 73% (from 3.67% to 0.98%) for PI-CB1 (40 wt%) films as compared to PI films. In addition, the water uptake varied not only with the CB content, but also by the size of the CB surface area. Open image in new window

Hollow polyimide (PI) microspheres are prepared through an electrospraying process, followed by surface imidization. The precipitation of droplets at the interface between two immiscible liquids provides a scaffold for the formation of a thin layer while an in situ imidization reaction prevents the irreversible deformation of the hollow shell. This strategy easily yields robust hollow structures of PI microspheres. The electrospray process permitts the sizes of the hollow PI microspheres to be controlled through adjustments to the flow rate and concentration of the poly(amic acid) (PAA) solution. The electrospraying approach described here may be the most facile means yet reported for obtaining size-controlled hollow PI particles without the need for additives or surfactants.

A series of ethyl-vinyl alcohol (EVOH) nanocomposite films with exfoliated graphite nanosheets (EGn) were prepared via a solution blending method and their physical and moisture barrier properties were investigated as a function of the EGn content. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EGn composition. The nanocomposite films showed no strong interactions between the polymer and EGn filler, and this resulted in poor dispersion in relatively high content EVOH/EGn nanocomposites. With increasing content of EGn particles, the water vapor transmission rate varied in the range of 1.29 to 3.14 cc/m2/day and the water uptake greatly decreased from 9.1 to 3.4 wt%. The water resistance capacity of EVOH was greatly enhanced and moisture diffusion in the pure EVOH film was retarded by introducing the EGn. However, thermal stabilities were not improved by incorporating EGn due to the poor interaction between EVOH polymer chains and the EGn surface. Open image in new window

Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 mu m and a nanometer sized thickness of 30-50 nm were successfully prepared by thermal treatment at 1050 degrees C and subsequent ultrasonication for application as a filler to improve the physical properties of eco-friendly poly(propylene carbonate) (PPC). A series of poly(propylenecarbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives

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.

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.

Tetrapod zinc oxide whiskers (TZnO-Ws) were successfully synthesized via a thermal oxidation method and confirmed using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. A series of poly(urethane acrylate) (PUA)/TZnO-W composite films with various TZnO-W contents were prepared via a UV curing method and their physical properties were investigated to understand their possible use as packaging materials. The morphological, thermal, mechanical, antibacterial and barrier properties of the PUA/TZnO-W composite films were interpreted as a function of TZnO-W content. The thermal stability, barrier properties and antibacterial properties of the composite films, which were strongly dependent upon their chemical and morphological structure, were enhanced as the TZnO-W content increased. The oxygen transmission rate and water vapor transmission rate decreased from 614 to 161 cm3 m−2 per day and 28.70 to 28.16 g m−2 per day, respectively. However, the mechanical strength of the films decreased due to the low interfacial interaction and poor dispersion with high TZnO-W loading. The enhanced barrier properties and good antibacterial properties of the PUA/TZnO-W composite films indicate that these materials are potentially suitable for many packaging applications. However, further studies are needed to increase the compatibility of polymer matrix and filler. © 2012 Society of Chemical Industry

The thermal cationic latent initiators, N-benzyl-3-methylimidazolium hexafluoroantimonate (BMH1) and N-butyl-3-methylimidazolium hexafluoroantimonate (BMH2) were synthesized and applied to the thermal cationic polymerization of diglycidyl ether of bisphenol A (DGEBA). The performance of BMH1 and BMH2 was examined by differential scanning calorimetry (DSC), which showed good thermal latent properties and excelled epoxy resin curing behavior. The morphology, thermal, mechanical, and water sorption properties of DGEBA resin cured by 1 wt% of BMH1 and BMH2 were measured by X-ray diffraction (XRD), scaming electron microscopy (SEM), thermogravimetric analysis (TGA), nanoindentation, and thin film diffusion analysis. The cured DGEBA/BMH1 system showed relatively higher thermal stability than the DGEBA/BMH2 system. The diffusion coefficient and water uptake were 14.2×10−9 cm2/s and 1.15 wt% for the DGEBA/BMH1 system and 11.5×10−9 cm2/s and 1.07 wt% for the DGEBA/BMH2 system, respectively. Therefore, DGEBA/BMH2 showed higher resistance to water sorption than DGEBA/BMH1. On the other hand, hardness and elastic modulus of DGEBA/BMH2 were higher than those of DGEBA/BMH1. This can be attributed to the difference in the end group of initiators as well as the degree of crosslinking in the cured resin network. Open image in new window

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.

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.

Page 1115, the Acknowledgments should be corrected as follows: This work was supported by the KIST Institutional Program (Project No. 2E26600-16-041) and National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2017R1D1A1B03033332).

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.

BACKROUND: Polyimide films coated on copper are a potential new substrate for fabricating printed circuit boards; however, adhesion between the copper and polyimide films is often poor. The relations between residual stress and adhesion strength according to the development of molecular orientation of polyimide films with different chemical backbone structure coated on copper were studied. RESULTS: The effect of chemical structures on properties including the residual stress and the adhesion strength were widely investigated for four different polyimides. Diamine 4,4′-oxydianiline (ODA) and dianhydrides 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′-oxydiphthalic anhydride (ODPA) and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) were used to synthesize polyimide. In an attempt to quantify the interaction of thermal mismatch with the polyimide films depending on various structures, residual stress experiments between polyimide film and CuSi wafer were carried out over a range of 25–400 °C using in situ thin film stress analysis. A universal test machine was used to conduct 180° peel test (ASTM D903-98) of polyimide film from cooper foil. The residual stress on CuSi (100) wafer decreased in the order 6FDA-ODA > BTDA-ODA > ODPA-ODA > PMDA-ODA, and the interfacial adhesion strength decreased in the order BTDA-ODA (5 N mm−2) > ODPA-ODA > PMDA-ODA > 6FDA-ODA. The results may suggest that the morphological structure, degree of crystallinity of chain orientation and packing significantly relate to the residual stress and adhesion strength in polyimide films. Wide-angle X-ray diffraction was used for characterizing the molecular order and orientation and X-ray photoelectron spectroscopy was used for the analysis of components on copper after polyimide films were detached to confirm the existence of copper oxide chemical bonding and to measure the binding energy of elements on the copper surface. CONCLUSION: In this research, it is demonstrated that BTDA-ODA polyimide has a low residual stress to copper, good adhesion property, good thermal property and low dielectric constant. Therefore, BTDA-ODA would be expected to be a promising candidate for a two-layer copper-clad laminate. Copyright © 2007 Society of Chemical Industry

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.

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.

In this work, we prepared epoxy/BMI composites by usingN,N′-bismaleimide-4,4′-diphenylmethane (BMI), epoxy resin (diglycidyl ether of bisphenol-A (DGEBA)), and 4,4’-diamino diphenyl methane (DDM). The thermal properties and water sorption behaviors of the epoxy and BMI composites were investigated. For the epoxy/ BMI composites, the glass transition and decomposition temperatures both increased with increasing BMI addition, which indicates the effect of BMI addition on improved thermal stability. The water sorption behaviors were gravimetrically measured as a function of humidity, temperature, and composition. The diffusion coefficient and water uptake decreased and the activation energy for water diffusion increased with increasing BMI content, indicating that the water sorption in epoxy resin, which causes reliability problems in electronic devices, can be diminished by BMI addition. The water sorption behaviors in the epoxy/BMI composites were interpreted in terms of their chemical and morphological structures.

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.

A series of six-membered sulfonated polyimides with aliphatic linkages (SPIAs) was successfully synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 4,4′-diaminobiphenyl 2,2′-disulfonic acid (BDSA) as the sulfonated diamine, and aliphatic diamines H2N(CH2)nNH2 where n = 6, 8, 10, 12. These SPIAs were evaluated for thermal stability, ion exchange capacity (IEC), water uptake, proton conductivity, and hydrolytic stability. Proton conductivity and hydrolytic stability of the SPIAs were compared with the fully aromatic polyimide (MDA-SPI) prepared from 4,4′-methylenedianiline (MDA), BDSA, and NTDA. All the SPIAs exhibited high thermal stability. As the chain length of the aliphatic diamine decreased, the IEC and water uptake of the SPIAs increased. The SPIAs showed higher proton conductivity than commercially available membranes such as Nafion 117 at high temperatures and higher proton conductivity than MDA-SPI at all temperatures. All SPIAs exhibited a hydrolytic stability more than twice as high as that of MDA-SPI. Copyright © 2006 Society of Chemical Industry

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.

New photochromic materials based on heteropolyoxometallates (HPOM) incorporated into a hybrid organic-inorganic binder were prepared and coated onto polycarbonate (PC) substrates. The hybrid binder was formed through the controlled hydrolysis and condensation of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA) by the sol–gel technique. The photochromic behavior of the materials was investigated by using ultraviolet-visible (UV-Vis) absorption spectroscopy and color index values. The results indicated that the films were reduced photochemically to yield a blue species under UV irradiation, with the film color changing to deep blue with increasing time, and HPOM and BPA content. The photosensitivity of several films with molybdenum HPOM showed faster coloration and much slower bleaching than the tungsten HPOM. A photochromic mechanism involving electron transfer between the GPTMS matrix with BPA, and PWO is proposed. After UV irradiation, the O–H and $O{=}W$ bonds decomposed gradually and W6 + was reduced gradually with increasing time. The photochromic coatings on PC substrate showed reversible transmittance change before and after UV irradiation, making then efficient light protectors under UV irradiation.

A series of sulfonated polyimides with increasing alkyl substituents in the o-position to diamine were synthesized from 4,4′-methylene dianiline, 4,4′-diamine-3,3′-dimethyl-diphenylmethane, and 4,4′-diamine-3,5,3′,5′-tetraethyl-diphenylmethane using 1,4,5,8-naphthalenetetracarboxylic dianhydride and perylenetetracarboxylic dianhydride by chemical imidization method. 4,4′-Diaminobiphenyl 2,2′-disulfonic acid was used as sulfonated diamine. The variation in the membrane properties with increase in substitution was analyzed. Solubility increased with substitution whereas the thermal stability decreased with increase in substitution. Ion exchange capacity and water uptake reduced with increase in substitution because of the low sulfonic acid content at a particular weight due to the increased molecular weight of the repeating unit. The conductivity of the substituted diamines was higher than the unsubstituted diamines at higher temperature regardless of low ion exchange capacity and water uptake. The increase in conductivity with increase in temperature was more rapid in polyimides than in Nafion®115. Hydrolytic stability of the polyimides with substitution is more than the unsubstituted diamines. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3621–3630, 2004

A series of poly(amide-imide)s were prepared using a new monomer, 1,3-bis(trimellitimido)-2,4,6-trimethyl benzene (BTB), with four different diamines: 1,4-phenylene diamine (PDA), 2,4-diamino mesitylene (DAM), 2,2'-dimethyl-4,4'-diamino biphenyl (DMDB), and 2,2'-bis(trifluoromethyl)-4,4'-diamino biphenyl (TFDB). They were prepared by the condensation method in N-methyl-2-pyrrolidinone (NMP) solvent using triphenyl phosphate and pyridine as condensing agents. The synthesized poly(amide-imide) were characterized by Fourier transform infrared and 1 H NMR techniques. Films were prepared and characterized using DSC, thermogravimetric analysis (TGA), a prism coupler, and a film dielectric property analyzer. DSC measurement showed that the glass-transition temperatures of the polymers were in the range of 259-327 °C. TGA analysis showed 5% weight loss, in the range of 472-514 °C. The refractive index varied from 1.6004 to 1.6586 in the following increasing order: BTB-TFBM < BTB-DAM < BTB-DMDB < BTB-PDA. For the poly(amide-imide) films, the birefringence varied in the range of 0.0319-0.0580, in the following increasing order: BTB-DAM < BTB-TFBM < BTB-DMDB < BTB-PDA. The capacitance method showed that the dielectric constant of poly(amide-imide) varied with the diamine structure; no difference was found by the optical method.

A series of low density polyethylene/paraffin wax (LDPE/PW) composite films were fabricated via a twin-screw extruder, and their morphologies, thermal properties, gas and vapor permeations, and surface properties were interpreted as functions of the PW contents. The PW was well dispersed into the LDPE matrix at low PW contents, whereas phase separation and an increase in surface roughness occurred with increasing PW content. The parameter results of surface properties such as contact angle, surface free energy, and solubility showed that the hydrophobicity of the LDPE/PW composite films also increased, and their phase changes and permeation properties were significantly dependent on the PW contents in the LDPE matrix. With increasing PW contents, both the oxygen transmittance rate (OTR) and water vapor transmittance rate (WVTR) of the LDPE/PW composite films decreased at a relatively low measuring temperature (23 °C), and increased at a relatively high temperature (48 °C). These results relate to the morphological structure (including tortuous paths and crystallinity) of the composite films via the incorporation of PW.