Highly functional biobased polyols and their use in melamine–formaldehyde coatings

Highly functional sucrose soyate polyol (SSP) resins were synthesized by ring-opening epoxidized sucrose soyate with methanol or ethanol and were subsequently crosslinked with a melamine–formaldehyde (MF) resin in the presence of an acid catalyst or blocked acid catalyst. The biobased polyols were characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, Brookfield viscosity, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The thermal properties of the biobased MF coatings were studied using differential scanning calorimetry and dynamic mechanical analysis. As controls, a soybean oil polyol (SBOP) with lower functionality and a commercial polyester polyol were studied for comparison. Overall, MF coatings formulated with SSPs showed superior properties to coatings formulated with SBOP and comparable properties to the commercial polyester which was attributed to the high hydroxyl functionality.     

A new photoresist based on hyperbranched poly(ary1ene ether phosphine oxide)

Summary Hydroxy-terminated hyperbranched poly(ary1ene ether phosphine oxide) (P2) was synthesized via nucleophilic aromatic substitution reaction of AB, monomer, bis(4-hydroxyphenyl)-4'-fluorophenylphosphine oxide with K₂CO₃ as a base in NMP. The obtained polymer was dissolved well in NMP and DMSO, and casting of the solution gave a transparent film. The study on dissolution behavior of the film containing 10 wt% of diphenyliodonium-9,l0-dimethoxyanthracene-2-sulfonate (DIAS) as a photoacid generator and 25 wt% of 4,4'-methylenebis-[2,6-bis(hydroxymethylphenyl) phenol] (MBHP) as a cross linker revealed that 0.5 wt% aqueous tetramthylammonium hydroxide (TMAH) solution was a suitable developer for this negative-type photoresist system. The photoresist system containing 10 wt% of DIAS and 25 wt% of MBHP showed the sensitivity of 9 mJ/cm² and the contrast of 1.6 when it was exposed to 365 nm light and postbaked at 12O°C, followed by developing with 0.5 wt% aqueous TMAH solution at room temperature. The heat-treated (300°C, 30 min) negative image did not show any distortion. Received: 7 October 2002/Revised version: 10 December 2002/ Accepted: 11 December 2002 Correspondence to Sang youl Kim     

In situ Raman spectroscopy analysis of local structure in dry gel for zeolite beta synthesis

To investigate faster crystallization of zeolite beta by the dry-gel conversion method, the local structure of the dry gel before synthesis was quantitatively evaluated using in situ Raman spectroscopy during the drying process. The dry gel prepared from Si and Al sources, and tetraethylammonium hydroxide solution was crystallized after several hours by the dry-gel conversion method. The conformational change of TEA⁺ cations was observed during the drying process by the deconvolution of the spectrum, and the conformational change was larger than that during the synthesis process. The rate of conformational change was increased with the drying temperature, and the apparent activation energy was estimated to be 68.2 kJ/mol. The generation and transformation of double three-membered silicate rings (D3Rs) and 4-2 type secondary building units (SBUs), which are essential for the crystallization of zeolite beta, were observed during the drying process. The transformation from D3R to 4-2 SBU in the dry gel during drying process could be confirmed quantitatively by the difference of the time variation for the amounts of these silicate building units estimated by in situ observation.     

Nanocomposite Derived from Core–Shell Nanoparticles via Creep Deformation of an Amorphous Silica Layer Below its Glass Transition Temperature

The microstructural design of ceramics is relevant to tune their properties. Nanostructuring can drastically modify ceramic properties because of enhanced interfacial effects, although the creation of such structures in ceramics is still challenging because of the interfacial reaction and grain growth at elevated temperatures during sintering. Here, we demonstrate densification of core – shell nanoparticles consisting of Fe₃O₄ (core particle, 20 nm diameter) and SiO₂ (shell layer, 2 nm thick) with over 90% of theoretical density below 500°C, which was achieved by facilitating plastic flow of amorphous SiO₂ under high pressure below its glass transition temperature. Thus, grain growth of the core nanoparticles was strongly suppressed, and the core nanoparticles remained separated by an amorphous layer in the final microstructure reflecting the original core–shell nanostructure. We also analyzed the densification behavior on the basis of a power law creep model, and estimated the pressures required to attain full density.     

Carbonation of low heat portland cement paste precured in water for different time

The carbonation technique was applied to accelerate the hydration of low heat portland cement （LHC）. Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that precuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the precuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope （SEM） observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry （MIP） results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.     

Transition of spherulite morphology in a crystalline/crystalline binary blend of biodegradable microbial polyesters

Crystalline/crystalline binary blend films of microbial polyesters composed of poly[(R)-3-hydroxybutyrate-co-(R)-3hydroxyhexanoate] (P(3HB-co-3HH)) and poly[(R)-3-hydroxybutyrate] (P(3HB)) that exhibit a morphological change are prepared by solvent casting. Differential scanning calorimetry measurements indicate that P(3HB-co-3HH) and P(3HB) are miscible for all blend ratios because a single glass transition temperature is observed. Polarization optical microscopy is used to investigate the transition of spherulite morphology and measure the radial growth rate of spherulites in the blend films. P(3HB-co-3HH) and P(3HB) contain positive spherulites, whereas in the binary blends, spherulite morphology changes from positive to negative. This change is related to the different growth rates of P(3HB-co-3HH) and P(3HB) lamellar crystals. Partial enzymatic degradation of the film surfaces reveals that the lamellar crystals of negative spherulites are oriented both perpendicular and parallel to the radial direction of spherulites. A new growth mechanism for spherulites in crystalline/crystalline blends is constructed from the results obtained for the blend films.     

Measurement and correlation of isobaric vapor-liquid equilibria for binary and ternary systems containing Methyl Tertiary Butyl Ether (MTBE), methanol and alkanes

Isobaric vapor-liquid equilibria (VLE) of four binary systems-methyl tertiary butyl ether (MTBE)+ methanol, MTBE+heptane, MTBE+octane and MTBE+i-octane-were measured at atmospheric pressure by using Othmer-type circulation method. The VLE of a ternary system, MTBE+methanol+heptane, were also measured at atmospheric pressure. These VLE data were predicted by ASOG and correlated by Wilson equation, and the prediction and correlation performances were discussed.     

Ceramization of Reflux-Treated Polymethylsilane Precursors to Silicon Carbide

The pyrolysis of polymethylsilane (PMS) in an argon gas environment with a flow rate of 1 L/min was investigated as a standard pyrolytic process, and the investigation showed SiSi network formation at 573 K. Subsequently, various condensed PMS resins were prepared by adjusting pre-heat-treatment or reflux conditions in the temperature range of 423–723 K. The effect of pre-heat treatment or refluxing on the ceramic yield at 1273 K was quantitatively evaluated. Structural evolution in the PMS resins prepared under various reflux conditions was investigated during pyrolysis up to 1873 K. The X-ray diffraction patterns of the pyrolysis products revealed crystallite growth of β-SiC and silicon at 1273–1473 K. ²⁹Si solid-state nuclear magnetic resonance with the single-pulse method was also conducted on the pyrolysis products at 1273 K.     

Synthesis of organosiloxane-based inorganic/organic hybrid membranes with chemically bound phosphonic acid for proton-conductors

Proton conductive inorganic-organic hybrid membranes were synthesized from 3-glycidoxypropyltrimethoxysilane (GPTMS) and phosphonoacetic acid (PA) with various ratios by a sol-gel process. Self-standing, homogeneous, highly transparent membranes were synthesized. TG-DTA analyses indicated that these membranes were thermally stable up to 200 °C. The results of FT-IR and ¹³C NMR revealed that phosphonic acid groups of PA were chemically bound to organosiloxane network as a result of reaction between PA and GPTMS. The leach out of phosphonic acid groups from GPTMS-PA to water was reduced compared with phosphoric acid groups from GPTMS-H₃PO_4. The proton conductivity of the hybrid membranes increased with phosphonic acid content. The conductivity of GPTMS/PA with a 1/1.05 ratio at 130 °C was 8.7 × 10⁻² S cm⁻¹ at 100% relative humidity (RH).     

Antitumor Effect of Regorafenib on MicroRNA Expression in Hepatocellular Carcinoma Cell Lines

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and is one of the leading causes of cancer-related deaths worldwide. Regorafenib, a multi-kinase inhibitor, is used as a second-line treatment for advanced HCC. Here, we aimed to investigate the mechanism of the antitumor effect of regorafenib on HCC and evaluate altered microRNA (miRNA) expression. Cell proliferation was examined in six HCC cell lines (HuH-7, HepG2, HLF, PLC/PRF/5, Hep3B, and Li-7) using the Cell Counting Kit-8 assay. Xenografted mouse models were used to assess the effects of regorafenib in vivo. Cell cycle analysis, western blotting analysis, and miRNA expression analysis were performed to identify the antitumor inhibitory potential of regorafenib on HCC cells. Regorafenib suppressed proliferation in HuH-7 cell and induced G0/G1 cell cycle arrest and cyclin D1 downregulation in regorafenib-sensitive cells. During miRNA analysis, miRNA molecules associated with the antitumor effect of regorafenib were found. Regorafenib suppresses cell proliferation and tumor growth in HCC by decreasing cyclin D1 via alterations in intracellular and exosomal miRNAs in HCC.