环氧化橡胶及其合金的研究与应用

综述了国内外环氧化橡胶及其合金的研究现状和应用趋势,重点介绍了环氧化天然橡胶、环氧化聚丁二烯、环氧化苯乙烯-丁二烯-苯乙烯三嵌段共聚物及其合金的优点,以及影响其物理机械性能的因素和环氧化橡胶的发展方向。     

Fabrication of MCM-41 mesoporous silica through the self-assembly supermolecule of β-CD and CTAB

Using the self-assembly β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTAB) as structure-directing agents, high-quality ordered MCM-41 silicas have been prepared. Small-angle X-ray diffraction (SXRD), N₂ adsorption-desorption and scanning electron microscope (SEM) techniques were used to characterize the calcined samples. Results showed that the pore structure of the resulting mesoporous silica belonged to the two-dimensional hexagonal structure (space group p6mm). The high-quality hexagonal structure was formed as n?1 (n denotes molar ratio of β-CD to CTAB). N₂ adsorption-desorption curves revealed type IV isotherms, H4 hysteresis loops, for all samples, and H1 hysteresis loops for samples at n=0, 0.1, 1 and 2, respectively. The pore size and the pore wall thickness of the samples increased with the increase in n values, respectively.     

Synthesis of N,N-dimethylaminoethyl methacrylate copolymers with N-vinyl caprolactam and their complexing and flocculating behavior

Thermosensitive copolymers of N-vinyl carprolactam with N,N-dimethylaminoethyl methacrylate have been synthesized via free-radical polymerization, and reactivity ratios in dioxane have been estimated as 2.44 and 0.07, respectively. It has been shown that temperatures of phase separation for 1% aqueous solutions of homopolymers are close and remain virtually unchanged with the copolymer composition. The efficiency of flocculating behavior of copolymers with respect to a polystyrene latex has been estimated from the initial rate of flocculation as a function of the polyelectrolyte concentration in an acidic medium.     

Vergleichende untersuchungen zur titrimetrischen,photometrischen und ionen-chromatographischen hydrogencarbonat-bestimmung in trink-und mineralwässern: A comparison of titrimetric,spectrophotometric and ion-chromatographic methods for the determination of hydrogencarbonate in drinking and mineral waters

A photometric method for hydrogencarbonate determination in various natural waters is presented, based on measurements with methyl red. Accuracy of the results is demonstrated by comparison with titrimetric and ion-chromatographic methods. The photometric method is suitable for contents in the range of 1–2000 mg l^?1. The linear range of the continous flow method varies form 6–60 mg l^?1 to 12–90 mg l^?1 depending on conditions.     

Dysfunction of Shh signaling activates autophagy to inhibit trophoblast motility in recurrent miscarriage

In early pregnancy, the placenta anchors the conceptus and supports embryonic development and survival. This study aimed to investigate the underlying functions of Shh signaling in recurrent miscarriage (RM), a serious disorder of pregnancy. In the present study, Shh and Gli2 were mainly observed in cytotrophoblasts (CTBs), Ptch was mainly observed in syncytiotrophoblasts (STBs), and Smo and Gli3 were expressed in both CTBs and STBs. Shh signaling was significantly impaired in human placenta tissue from recurrent miscarriage patients compared to that of gestational age-matched normal controls. VEGF-A and CD31 protein levels were also significantly decreased in recurrent miscarriage patients. Furthermore, inhibition of Shh signaling impaired the motility of JAR cells by regulating the expression of Gli2 and Gli3. Intriguingly, inhibition of Shh signaling also triggered autophagy and autolysosome accumulation. Additionally, knockdown of BECN1 reversed Gant61-induced motility inhibition. In conclusion, our results showed that dysfunction of Shh signaling activated autophagy to inhibit trophoblast motility, which suggests the Shh pathway and autophagy as potential targets for RM therapy.Subject terms: Embryology, Endocrine reproductive disorders, Autophagosomes     

Highly efficient electrocatalytic hydrogen evolution promoted by O–Mo–C interfaces of ultrafine β-Mo2C nanostructures

Optimizing interfacial contacts and thus electron transfer phenomena in heterogeneous electrocatalysts is an effective approach for enhancing electrocatalytic performance. Herein, we successfully synthesized ultrafine β-Mo₂C nanoparticles confined within hollow capsules of nitrogen-doped porous carbon (β-Mo₂C@NPCC) and found that the surface layer of molybdenum atoms was further oxidized to a single Mo–O surface layer, thus producing intimate O–Mo–C interfaces. An arsenal of complementary technologies, including XPS, atomic-resolution HAADF-STEM, and XAS analysis clearly reveals the existence of O–Mo–C interfaces for these surface-engineered ultrafine nanostructures. The β-Mo₂C@NPCC electrocatalyst exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in water. Theoretical studies indicate that the highly accessible ultrathin O–Mo–C interfaces serving as the active sites are crucial to the HER performance and underpinned the outstanding electrocatalytic performance of β-Mo₂C@NPCC. This proof-of-concept study opens a new avenue for the fabrication of highly efficient catalysts for HER and other applications, whilst further demonstrating the importance of exposed interfaces and interfacial contacts in efficient electrocatalysis.

Ultrafine β-Mo₂C nanostructures encapsulated in N-doped carbon capsules featuring O–Mo–C interfaces as the active sites for HER have been unveiled.     

Elucidation of stabilizing pickering emulsion with jackfruit filum pectin-soy protein nanoparticles obtained by photocatalysis

There is still the dearth of reports of jackfruit filum pectin-based nanoparticles as the Pickering emulsifiers with respect to the applications in foods, cosmetics and medicines. So we fabricated soy protein-jackfruit filum pectin nanoparticles (SPP) by photocatalysis as Pickering emulsifier. Jackfruit filum pectin exhibited lower yield (17.31%), degree of methoxylation (15.53%), but higher galacuronic acid content (74.22%). A strong linkage between pectin and soy protein was formed by photocatalysis. The conjugated polymer could self-assemble into compact near globular nanoparticle. The mean size of SPP was larger than that of soy protein nanoparticles but smaller than that of soy protein-pectin complex without photocatalysis. Besides, the zeta potential of SPP was ?33.8?mV, significantly lower than that of soy protein nanoparticles but higher than that of control sample, further confirming that SPP surfaces were completely covered with pectin molecules. Compared with control sample, the three-phase contact angle increased from 42.7 to 90.6°, indicated that SPP could be developed as effective Pickering emulsifiers. The emulsions stabilized by SPP exhibited high thermal stability and excellent salt tolerance as well as good freeze-thaw stability in comparison with emulsions covered with control sample. These findings would provide a potential way of producing effective Pickering emulsifier.GRAPHICAL ABSTRACT     

L-脯氨酸催化下甲基酮和1-芳基-2,2,2-三氟乙酮的不对称Aldol反应

Direct asymmetric aldol addition of methyl ketones to 2,2,2-trifluoro-1-phenylethanone and its ring-substituted derivatives was achieved using L-proline as a chiral promoter. Various optically active β-trifluoromethyl-β-hydroxy ketones were obtained in almost quantitative yields with moderate enantioselectivities up to 64 % ee.     

The first coordination polymers and hydrogen bonded networks containing octahedral Nb6 clusters and alkaline earth metal complexes

Three novel coordination polymers built of octahedral niobium cyanochloride clusters [Nb6Cl12(CN)6] and alkaline earth metal complexes have been prepared by reaction of aqueous solutions of (Me4N)4Nb6Cl18 and KCN with solutions of alkaline earth metal salts and 1,10-phenanthroline (phen) (1:2 molar ratio) in H2O/EtOH. The structures of [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] x (phen)(EtOH)1.6 (1), [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] x (phen)2 x 4H2O (2), and [Ba(phen)2(H2O)]2[Nb6Cl12(CN)6] (3) were determined by single-crystal X-ray diffraction. The three compounds were found to crystallize in the monoclinic system (space group Pn) with a = 11.5499(6) A, b = 17.5305(8) A, c = 21.784(1) A, beta = 100.877(1) degrees for 1; triclinic system (P1) with a = 12.609(4) A, b = 13.262(4) A, c = 16.645(5) A, alpha = 69.933(6) degrees, beta = 68.607(6) degrees, gamma = 63.522(5) degrees for 2; and a = 16.057(1) A, b = 16.063(1) A, c = 16.061(1) A, alpha = 86.830(1) degrees, beta = 64.380(1) degrees, gamma = 67.803(1) degrees for 3. Compounds 1 and 2 are built of cluster anions [Nb6Cl12(CN)6]4- trans-coordinated by two Ca2+ complexes via CN ligands to form neutral macromolecular units [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] in 1 and [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] in 2. Water of coordination and cyanide ligands form hydrogen bonded 3D and 2D frameworks for 1 and 2, respectively. The structure of 3 consists of [Nb6Cl12(CN)6]4- cluster anions and [Ba(phen)2(H2O)]2+ complexes linked through bridging cyanide ligands to form a neutral three-dimensional framework in which each barium complex is bound to three neighboring Nb6 clusters and each Nb6 cluster is linked to six Ba complexes.     

Real-time membrane fusion of giant polymer vesicles

Membrane fusion is very important for the formation of many complex organs in metazoans throughout evolution, such as muscles, bones, and placentae. Lipid vesicles (liposomes) are frequently used as model membranes to study the fusion process. This work demonstrates for the first time the real-time membrane fusion of giant polymer vesicles by directly displaying a series of high-resolution and real-time transformation images of individual vesicles. The fusion process includes the sequential steps of membrane contact, forming the center wall, symmetric expansion of fusion pore and complete fusion, undergoing the intermediates of "8" shape with a protruding rim at the contact site, peanut (pear) shape, and oblate sphere. The vesicle swells during fusion, and the fusing vesicle only deforms in the neck domain around the fusion pore in the lateral direction, which verifies the importance of the lateral tension on the fusion pore at the vesicle deformation level. The successful fusion of the synthetic and protein-free polymer vesicles reported here also supports that vesicle proximity combined with membrane perturbation suffices to induce membrane fusion, and that the protein is not necessary for the fusion process.