Determination of oil–water partition coefficients of polar compounds: silicone membrane equilibrator vs. SPME passive sampler

Experimental determination of oil-water partition coefficients often poses difficulties associated with emulsion formation. The aim of this work was to find an appropriate technique for determination of oil–water partition coefficients of polar, nonvolatile compounds. Two different methods were tested. The first method used a “silicone membrane equilibrator.” For the second method, solid-phase microextraction (SPME) fibers with a polyacrylate (PA) coating were used as a passive sampler. With both methods, oil–water partition coefficients for 14 compounds with polar functional groups were determined at 37 °C with good repeatability (standard deviation 0.11 log units or lower). The partition coefficients determined with the silicone membrane equilibrator method ranged from 0.50 to 3.49 log units. The oil–water partition coefficients obtained with the PA-SPME passive sampling approach were significantly higher than those obtained with the silicone membrane equilibrator method for nine of 14 compounds. The differences were up to 0.39 log units (i.e., a factor of 2.5). Additional experiments suggested that this difference occurred because the sorption properties of the PA fibers used were influenced by the surrounding phase, e.g., through swelling of the polymer phase. Therefore, the SPME passive sampling method using PA fibers seems to be less reliable, whereas the silicone membrane equilibrator method was found to be a convenient technique for the determination of oil–water partitioning.     

A Novel Synthesis of 1-Isochromanols via Hetero Diels-Alder Reaction of Carbonyl Compounds with 1-Trimethylsilyloxy-benzocyclobutene as a Precursor of α-Oxy-o-Quinodimethane Under Mild Condition

Reaction of 1-trimethylsilyloxybenzocyclobutene(1) with carbonyl compounds catalyzed by tris(dimethylamino)sulfur (trimethylsilyl)difluoride (TASF) at room temperature gave 1-isochromanol derivatives as corresponding hetero Diels-Alder adducts in good yields.     

Preparation of nanoscale cellulose materials with different morphologies by mechanical treatments and their characterization

Rod-like cellulose nanowhiskers and spherical cellulose nanoparticles were prepared from wood-pulp-derived cellulose powder by mechanical refining processes such as high-pressure homogenization (HPH) and ball-milling (BM). The nanowhiskers obtained by the HPH method were found to be 200–500 nm long and 11–16 nm wide. The diameters of the nanoparticles were in the range 40–200 nm, depending on the BM time, and were reduced to 25–50 nm after extra HPH. By adjusting the BM time, cellulose nanoparticles having different polymorphs with similar morphologies were prepared. The X-ray diffraction patterns revealed the recrystallization of cellulose I (1 h of BM time) or cellulose II (4–8 h of BM time) in ball-milled nanoparticles after water washing and solvent exchange treatments. The nanowhisker widths derived from the specific surface areas (SSA) by adsorption methods such as Congo red dye, nitrogen, and water vapor, sorptions were in agreement with those obtained from transmission electron microscopy and atomic force microscopy images. Similar SSA values were obtained for micro- and nano-scale cellulose materials using water vapor adsorption methods, and the SSAs of nanoparticles obtained by different adsorption methods are also discussed.     

Super strong nuclear force caused by migrating K? mesons - Revival of the Heitler-London-Heisenberg scheme in kaonic nuclear clusters

We have studied the structure of K⁻pp comprehensively by solving this threebody system in a variational method, starting from the Ansatz that the Λ(1405) resonance (≡Λ^*) is a K⁻p bound state. The structure of K⁻pp reveals a molecular feature, namely, the K⁻ in Λ^* as an “atomic center” plays a key role in producing strong covalent bonding with the other proton. We point out that strongly bound $\bar{K}$ nuclear systems are formed by “super strong” nuclear force due to migrating real bosonic particles $\bar{K}$ a la Heitler-London-Heisenberg, whereas the normal nuclear force is caused by mediating virtual mesons. We have shown that the elementary process, p + p → K⁺ + Λ^* + p, which occurs in a short impact parameter and with a large momentum transfer, leads to unusually large self-trapping of Λ^* by the involved proton, since the Λ^*-p system exists as a compact doorway state propagating to K⁻pp.     

Enhanced CO2 adsorptivity of SWCNT by polycyclic aromatic hydrocarbon intercalation

We tuned the electronic properties of single wall carbon nanotube (SWCNT) with intercalation of naphthalene derivatives (NDs) having different electron donor or acceptor property in the SWCNT bundles. Characterization of the adsorbed SWCNT with Raman spectroscopy and electrical conductivity measurement clearly indicate the charge transfer interaction of ND molecules with SWCNT. Also X-ray diffraction supports the intercalation of ND molecules in the interstitial spaces and groove sites of SWCNT bundle. Intercalation of ND molecules enhances remarkably the CO₂ adsorptivity, which can be ascribed to the key importance of the interaction of the quadrupole moment of CO₂ with the local electrical field on the SWCNT induced by the charge transfer interaction.     

一种经氟化和热处理在双壁碳纳米管上生成缺陷的方法(英文)

Nanoscale defects in the outer tube to preserve the electrical and optical features of the inner tube can be engineered to exploit the intrinsic properties of double walled carbon nanotubes (DWCNTs) for various promising applications. We demonstrated a selective way to make defects in the outer tube by the fluorination of DWCNTs followed by the thermal detachment of the F atoms at 1000 °C in argon. Fluorinated DWCNTs with different amounts of F atoms were prepared by reacting with fluorine gas at 25, 200, and 400 °C that gave the stoichiometry of CF0.20, CF0.30, and CF0.43, respectively. At the three different temperatures used, we observed preservation of the coaxial morphology in the fluorinated DWCNTs. For the DWCNTs fluorinated at 25 and 200 °C, the strong radial breathing modes (RBMs) of the inner tube and weakened RBMs of the outer tube indicated selective fluorine attachment onto the outer tube. However, the disappearance of the RBMs in the Raman spectrum of the DWCNTs fluorinated at 400 °C showed the introduction of F atoms onto both inner and outer tubes. There was no significant change in the morphology and optical properties when the DWCNTs fluorinated at 25 and 200 °C were thermally treated at 1000 °C in argon. However, in the case of the DWCNTs fluorinated at 400 °C, the recovery of strong RBMs from the inner tube and weakened RBMs from the outer tube indicated the selective introduction of substantial defects on the outer tube while preserving the original tubular shape. The thermal detachment of F atoms from fluorinated DWCNTs is an efficient way to make highly defective outer tubes for preserving the electrical conduction and optical activity of the inner tubes.     

Structural Insights into Rice Straw Pretreated by Hot-Compressed Water in Relation to Enzymatic Hydrolysis

Pretreatment-induced structural alteration is critical in influencing the rate and extent of enzymatic saccharification of lignocellulosic biomass. The present work has investigated structural features of rice straw pretreated by hot-compressed water (HCW) from 140 to 240 °C for 10 or 30 min and enzymatic hydrolysis profiles of pretreated rice straw. Compositional profiles of pretreated rice straw were examined to offer the basis for structural changes. The wide-angle X-ray diffraction analysis revealed possible modification in crystalline microstructure of cellulose and the severity-dependent variation of crystallinity. The specific surface area (SSA) of pretreated samples was able to achieve more than 10-fold of that of the raw material and was in linear relationship with the removal of acetyl groups and xylan. The glucose yield by enzymatic hydrolysis of pretreated materials correlated linearly with the SSA increase and the dissolution of acetyl and xylan. A quantitatively intrinsic relationship was suggested to exist between enzymatic hydrolysis and the extraction of hemicellulose components in hydrothermally treated rice straw, and SSA was considered one important structural parameter signaling the efficiency of enzymatic digestibility in HCW-treated materials in which hemicellulose removal and lignin redistribution happened.     

Synthesis and radical polymerization of styrene‐based monomer having a five‐membered cyclic carbonate structure

A styrene‐based monomer having a five‐membered cyclic carbonate structure, 4‐vinylbenzyl 2,5‐dioxoran‐3‐ylmethyl ether (VBCE), was prepared by lithium bromide‐catalyzed addition of carbon dioxide to 4‐vinylbenxyl glycidyl ether (VBGE). Radical polymerization of the obtained VBCE was carried out using 2,2′‐azobisisobutyronitrile as an initiator. PolyVBCE with number‐averaged molecular weight higher than 13,800 was obtained by a solution polymerization in N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, and methyl ethyl ketone. The glass transition temperature and 5 wt % decomposition temperature of the polyVBCE were determined to be 52 and 305 °C by differential scanning calorimetry and thermal gravimetry analysis, respectively. It was confirmed that a polymer consisting of the same VBCE repeating unit can be also obtained via chemical modification of polyVBGE, that is, a lithium‐bromide‐catalyzed addition of carbon dioxide to a polyVBGE prepared from a radical polymerization of VBGE. Further copolymerization of VBCE with styrene gave the corresponding copolymer in a high yield. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A Hardy’s Uncertainty Principle Lemma in Weak Commutation Relations of Heisenberg-Lie Algebra

In this article we consider linear operators satisfying a generalized commutation relation of a type of the Heisenberg-Lie algebra. It is proven that a generalized inequality of the Hardy’s uncertainty principle lemma follows. Its applications to time operators and abstract Dirac operators are also investigated.     

Supramolecular polymer gels from polystyrene bearing cyclic amidine Group and acrylic acid/n‐butyl acrylate copolymers

We have prepared supramolecular polymer gels by mixing solutions of a polystyrene bearing cyclic amidine pendant groups (Poly‐A) and copolymers of acrylic acid and n‐butyl acrylate (Poly‐C), followed by evaporation. FT‐IR analysis indicated that the gels were formed through three‐dimensional network of the amidinium‐carboxylate salt bridge. DSC study showed that the Poly‐A and the Poly‐C were miscible when the salt bridge content was high. On the other hand, the mixtures with small salt bridge content showed phase separation. Dynamic shear measurements showed that the gel prepared from Poly‐A and Poly‐C with acrylic acid unit content of 15% had G' higher than G″ over a temperature range of ?22 °C to 32 °C, in which the G' value reached almost 1 MPa. The gel had a crossover point of G' and G″ at 32 °C, very close to room temperature, which suggested facile processability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 765–770