Thermal molecular motion at surface of atactic polypropylene films

Surface molecular motion in atactic polypropylene (aPP) films was studied by scanning force microscopy. Glass transition temperature at the surface, T_g^s, was determined to be 251±1 K on the basis of temperature dependence of lateral force, whereas its bulk glass transition temperature, T_g^b, by dynamic viscoelastic and differential scanning calorimetric measurements was 262 K. In general, polyolefin is easily oxidized, and thus, many kinds of additives are mixed in it for practical use. Hence, effects of oxidation and additives on surface properties of the aPP surface were examined as well. To achieve oxidation, the aPP films were annealed at 428 K for 100 min under the ambient atmosphere. After this treatment, T_g^s decreased by approximately 15 K in comparison with the intact film due to degradation of surface chains. On the contrary, in the case of the aPP containing 10 wt% antioxidant, T_g^s was almost the same as that of the intact film before and even after the oxidation treatment.     

Fabrication of Ceramic–Polymer Photonic Crystals by Stereolithography and Their Microwave Properties

Three-dimensional photonic crystals with periodic variations in the dielectric constant were fabricated using a stereolithographic rapid prototyping method. The structures were composed of millimeter-scale ordered epoxy lattices in which ceramic particles with high dielectric constants (such as silica and titania) were dispersed. These crystals were designed to reflect microwaves via the formation of photonic band gaps in a gigahertz range. The attenuation of transmission amplitude through the photonic crystals, which was measured as a function of frequency using a network analyzer, clearly showed the formation of band gaps in the microwave range.     

Anionic polymerization of vinylsilanes

Summary The anionic polymerization of dimethylphenylvinylsilane with sec-butyllithium/N,N,N,N-tetramethylethylenediamine (TMEDA) was investigated. The polymerization proceeded up to 100% yield and afforded the polymer having isomerized-structure units. The polymerization was accompanied by chain transfer reaction to the monomer and the polymerization rate in the presence of TMEDA was much lower than in the absence of TMEDA.     

Diffusion of p-aminoazobenzene in SBS block copolymer

The temperature dependence of p-aminoazobenzene diffusion in a styrene–butadiene–styrene (SBS) triblock copolymer film, prepared from a toluene or ethyl acetate solution, was investigated in the temperature region from 40° to 110°C by using a sublimative desorption method. Parallel studies on the mechanical relaxations of this copolymer were carried out in the same temperature range to be compared with the diffusion data. The penetrant-diffusion characteristics were interpreted in terms of Fujita's free-volume theory with due consideration of the different SBS domain morphology. The value of B_d, defined as the diffusional volume ratio of a penetrant molecule to a segment, was then estimated as 0.45–0.55 above the T_g of the polystyrene phase or 0.7 below that temperature. Interestingly, sigmoidal desorption appeared in the range under the T_g of the polystyrene phase for film cast from ethyl acetate; the anomalous behavior was considered to reflect the slow relaxation process of the copolymer chain ascribable to the predominant exposure of the polystyrene phase on the film surface.     

Stegobiol,a new sex pheromone component of drugstore beetle (Stegobium paniceum L.)

New sex pheromone component of femaleStegobium paniceum L. was isolated and identified as 2,3-dihydro-2,3,5-trimethyI-6-(1-methyl-2-hydroxybutyl)-4H-pyran-4-one, stegobiol, by spectral data and chemical conversion from stegobinone. Relative configuration at C-2, C-3, and C-1 was determined as 2S,3R,1S by the conversion from (2S,3R,1R)-stegobinone. This new sex pheromone elicits the pheromonal response from the species.     

Hydrogenation of Yūbari coal coated with ZnCl2-MCln (CuCl,CrCl3 and MoCl5) catalyst melts

Hydrogenation of Yūbari coal coated with 5 wt% of ZnCl₂-MCl_n (CuCl, CrCl₃ and MoCl₅) was carried out at 400 °C for 3 h with an initial hydrogen pressure of 9.8 MPa. The binary melt catalysts showed relatively higher activity in increasing the yield of hexane-solubles than did ZnCl₂ alone. The ZnCl₂-MoCl₅ catalyst melt was best in view of its highest conversion (90.9 wt%), the highest yield of hexane-soluble material (50.5 wt%) and the smallest hydrogen consumption. In terms of yield of monoaromatics of the hexane-soluble material relative to polar materials, ZnCl₂-CrCl₃ catalyst was superior to ZnCl₂-MoCl₅ although its hydrogen consumption was high. The roles of CuCl, CrCl₃ and MoCl₅ in association with ZnCl₂ in coal-hydrogenation are discussed.     

Cloning of the pepX gene of Lactobacillus helveticus IF03809 encoding salt-tolerant X-prolyl dipeptidyl aminopeptidase and characterization of the enzyme

X-prolyl dipeptidyl aminopeptidase (X-PDAP) from Lactobacillus helveticus IF03809 expressed nearly full activity under high salt conditions, such as 2 M NaCl. We cloned and sequenced the pepX gene for X-PDAP. The calculated M, of deduced X-PDAP (803 amino acids) was 90,847 and the protein was distantly related (35 to 44% identity) to known X-PDAPs of Lactobacillus sp. including L. helveticus CNRZ32 (40% identity). Native and recombinant X-PDAP were purified to homogeneity from both L. helveticus IF03809 and Escherichia coli DH5alpha harboring the pepX gene on a plasmid, respectively. The native enzyme appeared to be a dimer of 220 kDa, as estimated by gel filtration column chromatography. It hydrolyzed an X-prolyl-linkage, but not prolyl- or X-prolyl-X-peptide bonds, and tolerated up to 2 M NaCl as well as some other chlorides of monovalent cations. Determination of the flanking sequences revealed two divergent genes. The upstream region of the pepX gene encodes oppA gene for a putative oligopeptide permease, while the downstream region encodes tnp gene specifying a possible transposase of the IS3 family. The oppA gene shares a 176 bp-promoter region with pepX in the intergenic region, implying a relationship between this oligopeptide transport system and X-PDAP.     

Residual stress versus microstructural effects on the strength and toughness of phase-separated PbO–B2O3–Al2O3 glasses

A few authors have reasonably proposed that liquid–liquid phase-separated (LLPS) glasses could show improved fracture strength, S_f, and toughness, K_Ic, as the second phase could provide a barrier to crack propagation via deflection, bowing, trapping, or bridging. Due to the associated tensile or compressive residual stresses, the second phase could also act as a toughening or a weakening mechanism. In this work, we investigated five glasses of the PbO–B₂O₃–Al₂O₃ system spanning across the miscibility gap: Four of them undergo LLPS—three are binodal (two B₂O₃-rich and one PbO-rich) and one is spinodal—and one does not show LLPS (composition outside the miscibility gap). Their compositions were designed in such a way that the amorphous particles are under compressive residual stresses in some and under tensile residual stresses in others. The following mechanical properties were determined: the Vickers hardness, ball on three balls (B3B) strength, and toughness, K_Ic-SEVNB (single-edge V-notch beam [SEVNB]). The microstructures and compositions were analyzed using scanning electron microscopy with energy-dispersive X-ray spectrometry. The spinodal glass showed, by far, the best mechanical properties. Its K_Ic-SEVNB = 1.6 ± 0.1 MPa m^1/2, which embodies an increase of almost 50% over the B₂O₃-rich binodal composition, and 90% considering the PbO-rich binodal composition. Moreover, its fracture strength, S_f = 166 ± 7 MPa, is one of the highest ones ever reported for an LLPS glass. Fracture analyses evidenced that the spinodal composition exhibited the lowest net stress at the fracture point. Moreover, calculations indicate that the internal residual stress level is the lowest in the spinodal glass. The overall results indicate that the microstructural effect of the spinodal glass is the most significant factor for its superior mechanical properties. This work corroborates the idea that LLPS provides a feasible and stimulating solution to improve the mechanical properties of glasses.     

Effects of Grafting Maleic Anhydride onto Poly-ɛ-caprolactone on Facilitative Enzymatic Hydrolysis

Plastic waste is a global issue because it causes overflowing landfills and pollution, leading to environmental concerns. To address this crisis, materials that can be decomposed in the natural environment are introduced to replace conventional plastics. Poly-ɛ-caprolactone (PCL) is a commonly used plastic that can degrade in natural environments. However, owing to its hydrophobicity, its natural decomposition rate is low. In this study, PCL is modified with maleic anhydride (MA) (PCL-g-MA) to increase hydrophilicity and amorphous region for faster decomposition. To assess the hydrolysis in seawater, lipase hydrolysis is performed to compare the decomposition of PCL-g-MA and PCL. Consequently, in a Pseudomonas lipase-containing PBS solution, it takes 72 and 120 h for complete hydrolyze of PCL-g-MA and PCL, respectively. MA grafted onto PCL increases the amorphous region, where lipase can easily diffuse into PCL-g-MA. Morphological (FESEM and POM images), thermal (TGA and DSC), and structural (FTIR, XRD, and XPS) analyzes support the hydrolysis reaction. The mechanisms proposed in this study confirm that lipase hydrolysis starts in the amorphous regions and then transfers to the crystal regions. This hydrolysis progress is expected to facilitate the creation of eco-friendly low-cost PCL-g-MA composites with high-rate hydrolysis, such as bio-plastics and bio-fibers.