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Highly conductive and stable anion exchange membranes (AEMs) are important components of high-performance anion exchange membrane fuel cells (AEMFCs). Here, we report the use of crosslinked poly(arylene ether sulfone) (PAES) AEMs containing quaternary ammonium (QA) and triazolium cations. The crosslinked PAES-triazole-hydroxide membrane (cPAES-TA-OH) had a higher ion exchange capacity (IEC) than that of the non-crosslinked membrane (PAES-TA-OH) owing to the presence of triazolium cations. The IEC values of cPAES-TA-OH and PAES-TA-OH were 1.75 and 1.31 meq/g, respectively. The IEC value affects the water uptake and swelling ratio of a membrane. The water uptake and swelling ratio of cPAES-TA-OH were higher than those of PAES-TA-OH at 30 °C and 80 °C. In addition, hydroxide conductivity and membrane stability were enhanced by crosslinking; the hydroxide conductivity of cPAES-TA-OH was 92.1 mS/cm at 80 °C under 95% RH (in contrast to 86.2 mS/cm for PAES-TA-OH), and its conductivity retention was 67% after treating with 1M NaOH at 80 °C for 24 h (in contrast to 51% for PAES-TA-OH).

Herein, we report significantly enhanced mechanical properties and thermal conductivity of polyimide (PI) by incorporating a small amount (0.01 wt %) of individualized boron-doped high-quality graphene as a filler. The boron-doped expandable graphite (B-EG) was synthesized by mixing boric acid (H3BO4) with expandable graphite (EG) and thermally treating the mixture at 2450 °C for 30 min using a graphite furnace in an argon atmosphere. The boron-doped graphene (B-g) was prepared by the solution-phase exfoliation of B-EG with an ultrasonication process, which is a method to obtain individualized graphene as well as few-layer graphene. The PI nanocomposites were prepared using the obtained graphene. The PI nanocomposites synthesized with high-quality B-graphene (B-g) showed enhanced mechanical properties and thermal conductivity compared to those of pure PI due to the doping effects and strong interfacial interactions between graphene and the PI matrix.

Self-healing polyurethane with disulfide bonds was synthesized using polycarbonate diol as a soft segment, and methylene diphenyl diisocyanate and 2-hydroxyethyl disulfide as a hard segment. Well-developed phase separation as the hard segments increased was confirmed by Fourier transform infrared spectra. The X-ray diffraction data showed that the crystallinity of the polycarbonate with a semicrystalline structure decreased as the HS increased, which affected the thermal, mechanical, and thermomechanical properties of the PU block copolymer. As the hard segments increased, the yield point on the strain-stress curve disappeared, and the mechanical properties (elongation at break and breaking stress) and the shape recovery rate of SHPU improved. The increase in the physical crosslinking between the hard segments contributed to improving shape recovery and mechanical properties. In particular, self-healing polyurethane with 30, and 35 wt% hard segments showed excellent self-healing ability at 80 C, while the self-healing ability for self-healing polyurethane with 40 wt% hard segments was decreased. The increase of the hard segment restricted the movement of the soft segment, thus the self-healing ability of SHPU with 40 wt% HS was decreased. It could be concluded that self-healing polyurethane synthesized using semicrystalline PC diol has a significant effect on shape recovery and self-healing efficiency due to the crosslinks between the hard segments.

A rod-rod diblock copolymer (diBCP), poly(3-hexylthiophene)-block-poly(furfuryl isocyanate) (P3HT-b-PFIC), was synthesized through the anionic polymerization with an oxyanionic macroinitiator of P3HT. The properties of the diBCP (molecular weight, dispersity, composition, thermal stability, UV-visible absorption, and thin film morphology) were determined by various analytical methods. P3HT-b-PFIC was blended with C60 in a toluene solution to prepare a thin film of binary electron donor/acceptor system. Such blending enabled partial conjugation of the two components by the Diels-Alder reaction between furan and C60 at 60 °C for 3 h; the mixture was then spin-cast as a thin film, and annealed at 250 °C for 24 h. Tapping-mode atomic force microscopy (AFM) revealed that P3HT and C60 domains had nanoscale interfaces without a large phase segregation. This result indicated that the microphase separation of C60-functionalized P3HT-b-PFIC preserved even at high temperature provided free C60 molecules with channels to diffuse on the sides of P3HT domain, thus preventing the macroscopic crystallization of free C60 through the interfacial stabilization.

Soft contact lenses made with poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels modified with various comonomers such as N-vinyl pyrrolidone, methacrylic acid, glycidyl methacrylate, and glycerol monomethacrylate were prepared to investigate the effect of adding the comonomer on the water content, surface wettability, and tensile modulus. These polymers were synthesized by the free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) with the comonomers in the presence of divinyl benzene used as the crosslinker and azobisisobutyronitrile as the initiator. The chemical structure and transmittance of the hydrogels were analyzed by FTIR and UV/Vis spectrophotometers. The surface wettability and tensile modulus were also studied by measuring the contact angle and tensile modulus with a universal testing machine (UTM). Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). As the concentration of crosslinker in the hydrogels increases, the tensile strength also increases, whereas the internal water content and contact angle decrease. The effect of the comonomer composition of the hydrogels was also investigated to optimize the various properties of these comonomers for soft contact lenses.

In this work, we synthesized a Co-based catalyst supported on modified SBA-15 to obtain the uniform particle size of active metal and selective products with certain carbon number distribution. For the comparison, modified SBA-15 was prepared with the different molar ratios of Si/Al = 5, 7 and 10 and compared with the SBA-15 support. Catalysts were prepared by the impregnation method and prepared catalysts were characterized by various analytical techniques such as N2 physisorption, XRD, SAXS, TPR, NH3-TPD, FT-IR, and TEM. It was found that, by adding the aluminum to SBA-15, the catalyst acid site was increased and it produced a relatively middle range of hydrocarbons. It was also found that the interaction between cobalt metal and the support was increased, affecting the catalyst activity for Fischer–Tropsch synthesis.

Atom transfer radical polymerization (ATRP) technique was applied successfully for the synthesis of poly(n-butyl methacrylate-b-styrene-b-n-butyl methacrylate) (PBMA-b-PS-b-PBMA), (BAB) and poly(methyl methacrylate-b-n-butyl methacrylate-b-styrene-b-n-butyl methacrylate-b-methyl methacrylate) (PMMA-b-PBMAb- PS-b-PBMA-b-PMMA), (CBABC) linear tri- and pentablock copolymers, respectively, in solution for the first time. Difunctional polystyrene macroinitiator that contains a bromide end-group was prepared by ATRP of styrene with dimethyl-2,6-dibromoheptanedioate (DMDBHD). The formation of block copolymers was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) spectroscopy, and differential scanning calorimetry (DSC). Good agreement was observed between the theoretical and experimental molecular weights. The molecular weight distribution (MWD) was narrow and did not change much with the progress of the reaction. A linear increase in the number average molecular weight (M n ) with conversion was observed indicating that the polymerizations followed a ‘living’/controlled process. Both BAB and CBABC block copolymers showed core-shell type flower-like micellar structures when toluene is used as a selective solvent for A block (polystyrene).

Nanocomposite films with palladium nanoparticles were prepared in a block copolymer with different morphologies. Poly(2-vinylpyridine) (P2VP) and polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymers were synthesized by living anionic polymerization using a vacuum apparatus system. To fabricate the nanocomposites, palladium nanoparticles with P2VP chains on their surfaces, which were prepared by alcohol reduction (Pd-P2VP) were introduced to the block copolymers. These palladium nanoparticles (4 nm) were embedded selectively in the P2VP domain of PS-b-P2VP. Various nanocomposites with different morphologies were obtained as the volume ratio of the block copolymer and the amount of Pd-P2VP nanoparticles. The block copolymers, nanoparticles and nanocomposites were analyzed by size exclusion chromatography (SEC), 1H nuclear magnetic resonance spectroscopy (1H NMR), UV/Vis spectroscopy (UV/Vis), and energy filtering-transmission electron microscopy (EF-TEM). Open image in new window

In order to introduce an isocyanate (NCO) functional group into low density polyethylene (LDPE), grafting of 2-hydroxyethyl methacrylate (HEMA) combined with isophorone diisocyanate (IPDI) on to LDPE was carried out in solution using a radical initiator. The spectra of infrared (i.r.) and proton nuclear magnetic resonance for HEMA combined with IPDI showed that the hydroxyl group of HEMA and the NCO group of IPDI were reacted to form urethane, and the secondary NCO group preferentially reacted over the primary NCO group. From the i.r. spectra of the grafted LDPE, it was found that NCO groups were introduced into LDPE. Thermal stability of the grafted LDPE was investigated by differential scanning calorimeter analysis, and rheological values were observed to evaluate processability.

Tantalum oxide film formation by plasma-enhanced chemical vapour deposition (PECVD) using TaCl5 as a source material was examined. The effects of deposition temperature on the formation, structure and electric properties of the Ta2O5 film were investigated for Al/Ta2O5/ p-Si (MTS) capacitors. The deposition rate and refractive index increased with increasing deposition temperature. It was found that the structure of Ta2O5 deposited by PECVD was amorphous as-deposited. However, crystalline δ-Ta2O5 of hexagonal structure was formed by a 700 °C, 1 h heat treatment in argon. Capacitance and relative dielectric constant of the PECVD Ta2O5 were found to be 2.54 fF μm−2 and 23.5, respectively. The PECVD films obtained in this study have higher dielectric constants and remarkably better general film characteristics than those obtained by other deposition methods.

Tantalum oxide film formation by plasma-enhanced chemical vapour deposition (PECVD) using TaCl5 as a source material was examined. The effects of deposition temperature on the formation, structure and electric properties of the Ta2O5 film were investigated for Al/Ta2O5/ p-Si (MTS) capacitors. The deposition rate and refractive index increased with increasing deposition temperature. It was found that the structure of Ta2O5 deposited by PECVD was amorphous as-deposited. However, crystalline δ-Ta2O5 of hexagonal structure was formed by a 700 °C, 1 h heat treatment in argon. Capacitance and relative dielectric constant of the PECVD Ta2O5 were found to be 2.54 fF μm−2 and 23.5, respectively. The PECVD films obtained in this study have higher dielectric constants and remarkably better general film characteristics than those obtained by other deposition methods.

We synthesized novel cross-linkable fluorinated copoly(arylene ether sulfide)s for optical waveguide applications, which have high thermal stability, high optical transparency in the infrared communication region, and much smaller birefringence than other thermally stable fluorinated polyimides. The refractive index of the material can be easily controlled from 1.515 to 1.587 by changing the copolymer composition in the materials. The birefringence of the cured polymers were 0.0031∼0.0039 at the wavelength of 1.55 μm. This is much lower than those of fluorinated polyimides for optical waveguides. The refractive index of fluorinated poly(arylene ether sulfide) (FPAESI) after being stored at 100 °C for 1000 hr remains almost constant demonstrating the thermal stability. The propagation loss of the channel waveguides fabricated using reactive ion etching was less than 0.4 dB/cm at the wavelength of 1.55 μm.

The photophysical formation of surface relief grating (SRG) was compared between isocyanate-based polymeric and non-polymeric thin films of low molecular weight organics containing azobenzene group. The non-polymeric film forms faster and more efficient surface grating formation than the polymeric film when exposed to an interference pattern of polarized Ar+ laser beams at 488 nm. However, the polymeric materials exhibited higher stability of SRG and orientation of azobenzenes than non-polymeric ones. The relation between the rate of photoinduced surface modulation and orientation of azobenzenes is discussed.

We report for the first time the conformational and structural details of peptide-mimic poly(n-hexyl isocyanate) (PHIC). PHIC is a representative poly(n-alkyl isocyanate)s, which have received significant attention because of their unique stiff chain characteristics and potential applications in various fields. A well-ordered hexagonal close packing structure of PHIC with 83 helical conformation was clearly observed in the nanoscale thin films that were selectively annealed with carbon disulfide (CS2). A well-ordered multi-bilayer structure of the polymer with β-sheet conformation was also clearly formed in the films that were selectively annealed with toluene. In addition, a fully reversible transformation between these two self-assembled structures was demonstrated by consecutive annealings with CS2 and toluene. A family of peptide-mimic polymers — polyisocyanates with linear alkyl side groups — are known to have a stiff helical backbone. These structural features have garnered attention for the development of chiral recognition, optical switches, liquid crystals or degradable materials. Yet the exact conformation the chains adopt, and how they pack in the solid state, remains unclear. Through detailed characterization, Moonhor Ree, Jae-Suk Lee and co-workers in Korea have now confirmed that, in a thin film, the polymer ‘poly(n-hexyl isocyanate)’ forms one of two different, well-ordered structures. The two morphologies were obtained, and reversibly converted into each other, by annealing under different solvent vapours. In the presence of carbon disulfide, helical chains self-assembled into a hexagonal close packing structure, whereas the use of toluene yielded a multi-bilayer lamellar structure consisting of polymer chains in β-sheet conformation. This intriguing transformation arises from the solvent molecules' different affinities with the backbone and side groups of the polymer chain. Peptide-mimic poly(n-hexyl isocyanate) (PHIC) with stiff chain characteristics demonstrated to selectively form a well-ordered hexagonal close packing structure with 83 helical conformation in the nansocale thin films annealed with carbon disulfide. Moreover, this polymer showed to selectively form a well-ordered multi-bilayer structure with β-sheet conformation in the thin films annealed with toluene. These two self-assembled structures were reversibly transformed by consecutive annealing with carbon disulfide and toluene. These chain conformations and self-assembled structures were confirmed by synchrotron grazing incidence X-ray scattering analysis.

Thermal stability, microstructure and electrical property of molybdenum nitride film were studied for application of ULSI's DRAM capacitor electrode and copper diffusion barrier. Phase transformation from Mo to γ-Mo 2 N was observed at 20% N2/(Ar+N 2 ) flow ratio and γ-Mo 2 N and Δ-MoN phases coexisted at 50% N 2 flow ratio. γ-Mo 2 N film was found to crystallize at 400°C. Amorphous γ-Mo 2 N deposited at 300 °C remained stable upon 750 °C heat treatment. Breakdown strengths of Y -Mo 2 N/Ta 2 O&/Si MOS capacitor before and after 850 °C annealing were 2.4 MV/cm and 1.85 MV/cm at 1×10 -6 A/cm 2 , respectively. After 850 °C annealing, dielectric constant of Ta 2 Os film decreased to 19.