Molecular Structures and Mechanical Properties of Microbe Rapid Coagulation Natural Rubber

In this work,molecular structures,dynamic mechanical properties and glass transition temperatures of microbe coagulated natural rubber(NR) samples were analyzed by using pyrolysis gas chromatography-mass spectrometry(py-GC/MS),rubber process analyzer(RPA) and dynamic mechanical thermal analysis(DMA).And the cross-linked network structures and mechanical properties of the corresponding NR vulcanizates were further determined by using nuclear magnetic resonance(NMR) crosslink density spectrometer(XLDS-15) and universal testing machines.The results show that NR raw rubber produced by rapidly coagulated with microorganism exhibits a simple molecular structure composition and good dynamic mechanical properties,and the corresponding NR vulcanizates possess the aggregation structure of high cross-linked density,a high glass transition temperature of-61.5 ℃ and high mechanical properties(tensile strength reaches 25.2 MPa),as compared with that coagulated with acetic acid.     

Poly(1,8-octanediol citrate)/bioactive glass composite with improved mechanical performance and bioactivity for bone regeneration

Poly(1,8-octanediol-co-citrate)(POC) represents a new promising biocompatible and biodegradable polyester that has been extensively investigated for soft tissue engineering. However, the poor mechanical performance and poor bioactivity limit its application in bone regeneration. In this study, a series of POC/bioactive glasses(BG) composites were developed using 45 S5 Bioglass~ and a phytic acidderived bioactive glass(referred as PSC). The results indicated that calcium in BG could enhance the crosslinking of the POC/BG composites by forming calcium dicarboxylate bridges and thus improve their mechanical performances. When PSC were used, the composites exhibited significantly better mechanical properties compared to composites with 45 S5 Bioglass~. For example, by incorporating70 wt% PSC, the compressive strength of POC/PSC composites could be improved to approximately50 MPa and modulus 1.3±0.1 GPa. Furthermore, all these POC/PSC composites showed good in vitro bioactivity and cellular biocompatibility. Histology results in femoral condyle defects of Sprague-Dawley rats indicated that the POC/PSC samples integrated well with surrounding tissues and stimulated bone regeneration. The improved mechanical properties and bioactivity of POC/PSC composites make them promising for potential application in bone regeneration.     

Annealing induced microstructure and mechanical property changes of impact resistant polypropylene copolymer

The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer(IPC) were investigated. Different annealing temperatures ranging from 80 °C to 160 °C were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The crystalline structure changes in the IPC sample, including the i PP matrix and PE component, were investigated using wide angle X-ray diffraction(WAXD) and differential scanning calorimetry(DSC). Dynamic mechanical analysis(DMA) was used to analyze the relaxation extent of IPC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing temperature(140 °C), largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.     

Improved oxygen permeability and mechanical strength of silicone hydrogels with interpenetrating network structure

<正>The interpenetrating polymer network(IPN) silicone hydrogels with improved oxygen permeability and mechanical strength were prepared by UV-initiated polymerization of monomers including methacryloxypropyl tris(trimethylsiloxy)silane(TRIS),2-hydroxyethylmethacrylate(HEMA) and N-vinyl pyrrolidone(NVP) in the presence of free radical photoinitiator and cationic photoinitiator.The polymerization mechanism was investigated by the formation of gel network.The structure of IPN hydrogels was characterized by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC) and transmission electron microscopy(TEM).The results showed that the IPN hydrogels exhibited a heterogeneous morphology.The mechanical properties,surface wettability and oxygen permeability were examined by using a tensile tester,a contact angle goniometer and an oxygen transmission tester,respectively.The equilibrium water content of the hydrogels was measured by the gravimetric method.The results revealed that the IPN hydrogels possessed hydrophilic surface and high water content.They exhibited improved oxygen permeability and mechanical strength because of the incorporation of TRIS.     

Preparation and characterization of polystyrene-based monolith with ordered macroporous structure

In this paper,polystyrene-based monoliths with highly ordered macroporous structure were synthesized by using SiO₂ colloidal crystal as template.SEM observation shows that the macropores are highly ordered and are interconnected by small windows.The BET surface area of PS monolith is about 36.17 m²/g.The polymer monoliths can resist 5 MPa pressure,showing high mechanical and compressive strength.     

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied.One of the resins was a bifunctional epoxy resin based on diglycidyl ether ofbisphenol A and the other resin was a multifunctional epoxy novolac resin.Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples.The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin.The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples.The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples,probably due to enhanced cross-link density and molecular weight.Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples.The epoxy blends exhibited significantly higher fracture toughness (by 23％ at most) compared with the neat samples.The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.     

Preparation and characterization of crosslinked chitosan-based nanofibers

Crosslinked chitosan-based nanofibers were successfully prepared via electrospinning technique with heat mediated chemical crosslinking followed.The structure,morphology and mechanical property of nanofibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR),scanning electron microscopy(SEM),Instron machine,respec- tively.The results showed that,nanofibers exhibited a smooth surface and regular morphology,and tensile strength of nanofibers improved with increasing of triethylene glycol dimethacrylate(TEGDMA)content.     

PREPARATION AND CELL COMPATIBILITY OF FUNCTIONALIZED BIODEGRADABLE POLY(DL-LACTIDE-co-RS-β-MALIC ACID

In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the copolymers were measured.In copolymerization,the proportion of MA in the derived copolymers was lower than that in the feeding dose,a consequence of its lower reactivity. The molecular weight of the copolymers decreased with increasing MA content.The protective benzyl groups were completely removed in hydrogenolysis.The glass transition temperature(T_g)of the protected copolymers decreased with increasing MA content.The mechanical strength test showed that the tensile strength of PDLLMA decreased while elongation increased with MA content increasing,and the tensile strength increased and elongation decreased with increasing malic acid content in PDLLMAc for the formation of hydrogen bonding.The water uptake showed that more hydrophilic malic acid adsorbed more water in PDLLMAc.In order to test the reactivity of functional pendant groups,bioactive RGD peptide was immobilized on the functionalized polymer film surface and smooth muscle cells(SMCs)were cultured on it. The results showed that the functionalized copolymer was biocompatible and could be potentially applied in vascular tissue engineering.     

聚合物泡孔材料为模板的溶胶－凝胶法制备大孔结构二氧化钛陶瓷

Macroporous titania monoliths were prepared via sol-gel method using polymer foam as templates.The poly-mer foam polymerized via concentrated emulsion polymerization was immerged in a solution of titanium(IV)iso-propoxide in 2-propanol,which underwent a sol-gel process.The organic components were subsequently removedby calcination.The effects of various parameters,including the nature of the monomer,the volume fraction of dis-persed phase of the concentrated emulsion,and concentration of the sol-gel solution were investigated.The SEMmicrographs of the macroporous titania monoliths thus obtained showed that the porous structure of the final mate-rial was effectively controllable.     

VOx / Titanate复合材料纳米棒的水热合成及其电化学性能研究

Vanadium oxide/titanate composites nanorods (VO_x/ Titanate-CNRs) were synthesized in high yield by using titanate nanotubes as templates and V₂O₅·nH₂O sol as the precursors under hydrothermal conditions (200 ℃, 48 h). Samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive analysis by X-ray (EDAX). X-ray diffraction structure determination showed that this new phase had the composition of V₃O₇·H₂O and crystallized with orthorhombic symmetry. SEM and TEM tests showed that the samples were uniform straight rods with the diameter range from around 100 to 300 nm and the length over 10 μm. The chemical compositions of the samples were determined with EDXA. The electrochemical tests of samples (titanates nanotubes, V₂O₅ and VO_x/ Titanate-CNRs) prove that VO_x/ Titanate-CNRs exhibit a better electrochemical performance.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.