Biodegradable polyester/modified mesoporous silica composites for effective bone repair with self‐reinforced properties

A series novel composites based on poly(_L‐lactide) (PLLA) oligomer modified mesoporous silica (MCM41) homogeneous dispersed into poly(_L‐lactide‐co‐trimethylene carbonate‐co‐glycolide) (PLTG) terpolymer has been successfully prepared. The structure of PLTG terpolymer was characterized by ¹H NMR. The structure and properties of modified and unmodified MCM41 were attested by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), X‐ray diffraction (XRD), N₂ adsorption–desorption, scanning electron microscope (SEM), and transmission electron microscope (TEM), which demonstrated that the MCM41 was successfully grafted by the PLLA oligomer. The effect of different concentration of modified MCM41 in PLTG matrix on thermal properties, mechanical properties, and hydrophilicity was investigated by TGA, differential scanning calorimetry (DSC), mechanical testing, contact angle measurement, and SEM. The results of mechanical tests showed that 5 wt% of modified MCM41 nanoparticles gave rise to optimal reinforcing effect. The tensile strength, Young's modulus, and elongation at break of the PLTG/PLLA‐MCM41 (5%) composites were 33.2 Mpa, 1.58 Gpa, and 268.7%, respectively, which were all higher than the PLTG/MCM41 (5%) composites and pristine PLTG matrix, which were due to good interfacial adhesion between the PLTG matrix and MCM41 nanoparticles. TGA and DSC have shown that 5% modified MCM41 in the PLTG increased the temperature of composite degradation and T_g. Water contact angle measurement showed the hydrophilicity of the composites increases with the increase of modified MCM41 content. The live/dead assay showed that the modified MCM41 existing on the PLTG matrix presents very excellent cytocompatibility. Therefore, the novel composite material represents promising way for bone tissue engineering application.     

Immobilization of cerium (IV) and erbium (III) in mesoporous MCM‐41: Two novel and highly active heterogeneous catalysts for the synthesis of 5‐substituted tetrazoles,and chemo‐ and homoselective oxidation of sulfides

Two well‐ordered 2D ‐ hexagonal cerium (IV) and erbium (III) embedded functionalized mesoporous MCM ‐ 41(MCM‐41@Serine/Ce and MCM ‐ 41@Serine/Er) have been developed via functionalization of mesoporous MCM ‐ 41. The surface modification method has been used in the preparation of serine‐grafted MCM ‐ 41 and led to the development of MCM‐41@Serine. The reaction of MCM‐41@Serine with Ce (NH₄)₂(NO₃)₆·2H₂O or ErCl₃·6H₂O in ethanol under reflux led to the organization of MCM‐41@Serine/Ce and MCM‐41@Serine/Er catalysts. The structures of these catalysts were determined using scanning electron microscopy, mapping, energy‐dispersive X‐ray spectroscopy, Fourier transform‐infrared, thermogravimetric analysis, X‐ray diffraction, inductively coupled plasma, and Brunauer–Emmett–Teller analysis. These MCM‐41@Serine/Ce and MCM‐41@Serine/Er catalysts show outstanding catalytic performance in sulfides oxidation and synthesis of 5‐substituted tetrazoles. These catalysts can be recycled for seven repeated reaction runs without showing a considerable decrease in catalytic performance.     

Novel Preparation of Polyethylene from Nano‐extrusion Polymerization Inside the Nanochannels of MCM‐41/MgCl2/TiCl4 Catalysts

The MCM‐41 and SiO₂ supported TiCl₄ and TiCl₄/MgCl₂ catalysts with different molar ratios of Mg/Ti were synthesized and used for ethylene polymerization under atmospheric pressure. The nanochannels of MCM‐41 serve as nanoscale polymerization reactor and the polyethylene nanofibers were extruded during the reaction. The nanofibers were observed in SEM micrographs of resulting polyethylene. The effect of MgCl₂ on catalytic activity and thermal properties of resulting polyethylene is investigated too. In the presence of MgCl₂, the catalytic activity increased and more crystalline polyethylene with higher melting points were formed. However, no fibers could be observed in the polyethylene prepared by SiO₂ supported catalysts.     

Synthesis and Luminescence of Eu‐N2,N6‐Bis(2‐hydroxyethyl)pyridine‐2,6‐dicarboxamide Complexes Containing Mesoporous Material

Ligand N²,N⁶‐bis(2‐hydroxyethyl)pyridine‐2,6‐dicarboxamide (L=BHPC) was synthesized and used to construct lanthanide‐based mesoporous material Eu‐L‐MCM‐41. In the structure of resulting Eu‐L‐MCM‐41, Eu³⁺ was chelated by BHPC, and the Eu‐L complexes were anchored into the forming MCM‐41 host by the reaction between the hydroxyl group and active Si‐OH. The mesoporous material Eu‐L‐MCM‐41 was characterized by UV, IR, small‐angle X‐ray diffraction (SAXRD) patterns, nitrogen adsorption/desorption isotherms, TGA and fluorescence spectra. The results indicate that ligand and Eu³⁺ have been introduced into the MCM‐41 host, and Eu‐L‐MCM‐41 exhibits characteristic luminescence of Eu³⁺.     

Synthesis,Characterization and Catalysis of Ce‐MCM‐41

The cerium‐containing MCM‐41 (Ce‐MCM‐41) has been synthesized by direct hydrothermal method. The low‐angle XRD patterns revealed the typical five major peaks of MCM‐41 type hexagonal structures. The interplanar spacing d₁₀₀ = 38.4 Å was obtained that can be indexed on a hexagonal unit cell parameter with a_o = 44.3 Å which was larger than that of pure siliceous MCM‐41 (Si‐MCM‐41). Transmission electron micrograph shows the regular hexagonal array of uniform channel characteristics of MCM‐41. The BET surface area of Ce‐MCM‐41 was 840 m²/g, which is much reduced as compared to that of Si‐MCM‐41, with the pore size of 26.9 Å and mesopore volume of 0.78 cm³/g were measured by nitrogen adsorption‐desorption isotherm at 77 K. Along with the results, the synthesized Ce‐MCM‐41 exhibited a well‐ordered MCM‐41‐type mesoporous structure with the incorporation of cerium. Using Ce‐MCM‐41 as a support, the Rh (0.5 wt%) catalyst exhibited very high activity for the NO/CO reactions.     

Synthesis and characterization of indium and thallium immobilized on isonicotinamide‐functionalized mesoporous MCM‐41: Two novel and highly active heterogeneous catalysts for selective oxidation of sulfides and thiols to their corresponding sulfoxides and disulfides

Two highly ordered isonicotinamide (INA)‐functionalized mesoporous MCM‐41 materials supporting indium and thallium (MCM‐41‐INA‐In and MCM‐41‐INA‐Tl) have been developed using a covalent grafting method. A surface functionalization method has been applied to prepare Cl‐modified mesoporous MCM‐41 material. Condensation of this Cl‐functionalized MCM‐41 with INA leads to the formation of MCM‐41‐INA. The reaction of MCM‐41‐INA with In(NO₃)₃ or Tl(NO₃)₃ leads to the formation of MCM‐41‐INA‐In and MCM‐41‐INA‐Tl catalysts. The resulting materials were characterized using various techniques. These MCM‐41‐INA‐In and MCM‐41‐INA‐Tl catalysts show excellent catalytic performance in the selective oxidation of sulfides and thiols to their corresponding sulfoxides and disulfides. Finally, it is found that the anchored indium and thallium do not leach out from the surface of the mesoporous catalysts during reaction and the catalysts can be reused for seven repeat reaction runs without considerable loss of catalytic performance.     

A Direct and Rapid Route to Synthesize Pd/Si‐MCM‐41 at Room Temperature

The pure silica mesoporous molecular sieve MCM‐41 was synthesized under hydrothermal conditions. Pd/Si‐MCM‐41 was prepared by the incipient wetness impregnation of pure silica MCM‐41 with mixed solution of PdCl₂, ethanol and CH₂Cl₂. The samples were characterized by x‐ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms at 77 K. The XRD and TEM results reveal that Pd is actually anchored inside the pores of Si‐MCM‐41 and the Si‐MCM‐41 structure is clearly maintained after impregnation.     

Cationic polymerization of cyclohexyl vinyl ether within MCM‐41 channels

Cationic polymerization of cyclohexyl vinyl ether (CHVE) within mesoporous, siliceous molecular sieves (MCM‐41) yields novel MCM‐41‐polyCHVE host‐guest hybrid materials. Initiation within the channel can be achieved by triphenylmethylium or bis(4‐methoxyphenyl)methylium silanolate ion pairs, as well as by mobile acidic silanols to a certain extent. Generation of the carbenium ions on MCM‐41 is investigated by a special UV/VIS technique. The structure of poly(vinyl ether) generated within the channels of MCM‐41 depends on the mechanism of initiation as shown by means of solid state ¹³C{¹H} and ²⁹Si{¹H} CP MAS NMR spectroscopy.     

Liquid Phase Hydrogenation of t,t,c‐1,5,9‐Cyclododecatriene over Ni/MCM‐41 and Ni/SiO2 Catalysts

Ni‐loaded pure siliceous and aluminosilicate MCM‐41 (Ni/MCM‐41) and nickel‐loaded silica (15Ni/SiO₂) were synthesized via wet impregnation and were characterized by various techniques. The H₂ consumption in the TPR analysis was found to be proportional to the Ni amount in the calcined samples. After reduction the average Ni particle sizes of 15Ni/MCM‐41 and 15Ni/SiO₂ were 9–12 and 16 nm, respectively, by means of XRD and TEM measurements. All catalysts owned weak and intermediate Lewis acid sites that increased slightly with increasing the Ni amount and the Al content. In the liquid phase hydrogenation of t,t,c‐1,5,9‐cyclododecatriene over Ni/MCM‐41, the catalytic activity was parallel to the Ni content and enhanced slightly with the acid amount of the catalysts. Consequently, it was proposed that the Ni metallic sites contributed the major effect to the catalytic activity while the Lewis acid sites promoted a small but significant influence on the catalytic performance. It is noteworthy that all 15Ni/MCM‐41 catalysts exhibited remarkably higher activity than that of the conventional 15Ni/SiO₂ catalyst.     

Syndiotactic polypropene with MCM‐41 supported metallocene [Me2C(Cp)(Flu)]ZrCl2

Mesoporous aluminosilicates – type MCM‐41 – were used as carriers for syndiospecific propene polymerisation using [Me₂C(Cp)(Flu)]ZrCl₂/MAO as catalyst. Alumina‐free mesoporous MCM‐41 reveals a far greater polymerisation activity than the analogous carrier containing alumina. The use of MCM‐41 as carrier material at low propene concentration and high polymerisation temperature produces syndiotactic polypropene (sPP) with higher syndiotacticity and higher melting points than achieved when using a homogenous system or a supported system based on spherical SiO₂.     

MCM‐41‐Supported Bidentate Phosphine Rhodium Complex: An Efficient and Recyclable Heterogeneous Catalyst for the Hydrosilylation of Olefins

MCM‐41‐supported bidentate phosphine rhodium complex (MCM‐41‐2P‐RhCl₃) was conveniently synthesized from commercially available and cheapγ‐aminopropyltriethoxysilane via immobilization on MCM‐41, followed by reacting with diphenylphosphinomethanol and rhodium chloride. It was found that the title complex is a highly efficient catalyst for the hydrosilylation of olefins with triethoxysilane and can be recovered and recycled by a simple filtration of the reaction solution and used for at least 10 consecutive trials without any decreases in activity.     

Synthesis of Aromatic Ketones from Aromatic Compounds Using Vanadium‐Containing Mesoporous Silicates

Aromatic ketones were synthesized from aromatic compounds via liquid‐phase oxidation at 60 °C and 1 atm over vanadium‐containing MCM‐41 catalysts using a batch reactor. The catalysts were prepared by direct hydrothermal (4V‐MCM‐41) and wet impregnation (9V/MCM‐41) methods. Their physico‐chemical properties were determined with various characterization techniques. For the oxidations of all substrates in this work, 4 V‐MCM‐41 exhibits superior catalytic performance than 9 V/MCM‐41 due to its larger values of unit cell parameter, BET surface area, and vanadium dispersion as well as stronger oxidation ability of vanadium‐oxygen species. Apparently, the single site, isolated vanadium centers in 4V‐MCM‐41 possess much higher activity (based on the turnover number) than those containing more vanadium atoms in 9V/MCM‐41. In addition, the substrate activities decrease in the order of diphenylmethane > fluorene > 9,10‐dihydroanthracene > ethylbenzene ≥ 4‐nitroethylbenzene, which are attributed to their distinct molecular structures.     

Efficient Liquid‐Phase Oxidation of Diphenylmethane to Benzophenone over Vanadium‐Containing MCM‐41 Catalysts

The liquid‐phase oxidation of diphenylmethane with tert‐butylhydroperoxide has been studied using vanadium‐containing MCM‐41 materials, which were prepared by direct hydrothermal (V‐MCM‐41) and wet impregnation (V/MCM‐41) methods. These catalysts were characterized in detail by ICP‐AES, N₂‐sorption, XRD, FT‐IR, ²⁹Si and ⁵¹V NMR, TPD of ammonia, TPR of hydrogen, and chemisorption of oxygen. Both series of catalyst show good catalytic results, which are attributed to their highly ordered mesoporous structure, large BET surface area as well as the presence of easily accessible vanadium‐oxygen species as active centers in the catalyst. Further, V‐MCM‐41 exhibit superior catalytic activity (based on turnover number) than V/MCM‐41 mainly due to well‐dispersed tetrahedral vanadium‐oxygen species with higher oxidation ability. The effect of reaction parameters, i.e., temperature, time, solvent, etc. were investigated. Catalyst recycling test reveals good stability with only slight extent of leaching during the reaction.     

Photocatalytic Degradation of Imidacloprid by Phosphotungstic Acid Supported on a Mesoporous Sieve MCM‐41

Solid catalysts consisting of polyoxometalates (POM) namely phosphotungstic acid H₃PW₁₂O₄₀ (HPW) supported on a mesoporous sieve MCM‐41 have been prepared and characterized by FT‐IR, X‐ray diffraction, nitrogen adsorption and high resolution transmission electron microscope (HRTEM). The HPW/MCM‐41 with different HPW loadings from 10 to 60 wt% possess large specific surface area and rather uniform mesopores. Keggin structure of HPW retains on the prepared composite catalysts. The photocatalytic performance of HPW/MCM‐41 was examined by degradation of a durable pesticide imidacloprid. It is found that the prepared photocatalysts exhibit high activity under irradiation of 365 nm monochromatic light. For 50 mL of imidacloprid (10 mg/L), conversion of imidacloprid using 20 mg of HPW/MCM‐41 with 50 wt% loading level and calcined at 300°C reaches 58.0% after 5 h irradiation.     

Photovoltaic activity of Ti/MCM‐41

Ti/MCM‐41 is a well‐known heterogeneous catalyst for alkene epoxidation with organic peroxides. This titanosilicate contains isolated titanium atoms forming part of a framework of mesoporous silica whose structure is formed by parallel hexagonal channels 3.2 nm in diameter. The surface area and porosity of Ti/MCM‐41 are about 880 m² g^?1 and 0.70 cm³ g^?1, respectively. These values are among the highest for any material. Herein, we show that Ti/MCM‐41 exhibits photovoltaic activity. Dye‐sensitized solar cells using mesoporous Ti/MCM‐41 (2.8–5.7 % Ti content) as active layer, black dye N3 as photosensitizer and I₃^?/I^? in methoxyacetonitrile as electrolyte exhibit a V_OC, J_SC and FF of 0.44 V, 0.045 mA cm^?2 and 0.33, respectively. These values compare well against 0.75 V, 4.1 mA cm^?2 and 0.64, respectively, measured for analogous solar cells using conventional P‐25 TiO₂. However, the specific current density (J_SC/Ti atom) for the Ti/MCM‐41 is very similar to that of P25 TiO₂.     

Influence of Pore Structure on Catalytic Properties of Mesoporous Silica-supported Co-B Amorphous Alloys in Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Co‐B amorphous alloy catalysts supported on three kinds of mesoporous silica (common SiO₂, MCM‐41 and SBA‐15) have been systematically studied focusing on the effect of pore structure on the catalytic properties in liquid‐phase hydrogenation of cinnamaldehyde to cinnamyl alcohol (CMO). Structural characterization of a series of different catalysts was performed by means of N₂ adsorption, X‐ray diffraction, transmission electron microscopy, hydrogen chemisorption, and X‐ray photoelectron spectroscopy. Various characterizations revealed that the pore structure of supports profoundly influenced the particle size, location and dispersion degree of Co‐B amorphous alloys. Co‐B/SBA‐15 was found more active and selective to CMO than either Co‐B/SiO₂ or Co‐B/MCM‐41. The superior catalytic activity could be attributed to the higher active surface area, because most of Co‐B nanoparticles in Co‐B/SBA‐15 were located in the ordered pore channels of SBA‐15 rather than on the external surface as found in Co‐B/SiO₂ and Co‐B/MCM‐41. Meanwhile, the geometrical confinement effect of the ordered mesoporous structure of SBA‐15 was considered to be responsible for the enhanced selectivity to CMO on Co‐B/SBA‐15, inhibiting the further hydrogenation of CMO to hydrocinnamyl alcohol.     

Synthesis and Characterization of Mesoporous Titanosilicate as an Adsorbent for Toxic Metal Ions

Hexagonal mesoporous titanosilicates (Ti‐MCM‐41) have been prepared using cetyltrimethylammonium bromide (CTAB) as the structure directing agent under the mild alkaline conditions. Powder X‐ray diffraction, nitrogen gas sorption, FTIR spectroscopy and thermogravimetry analysis of samples have confirmed that well ordered MCM‐41 type mesoporous materials were prepared. The potential of removing toxic metal ions from waste waters using mesoporous titanosilicates was evaluated. Separation of Co^II‐U^VI, Cs^I‐U^VI and Sm^III‐U^VI has been developed on columns of this adsorbent.     

Effect of Sodium Alginate on the Properties of Thermosensitive Hydrogels

Sodium alginate (SA ) was combined with poly(N ‐isopropylacrylamide) (PNIPAAm ) to prepare thermosensitive hydrogels through semi‐interpenetrating polymer network (semi‐IPN ) and fully interpenetrating polymer network (full‐IPN ). The thermosensitive, swelling, mechanical, and thermal properties of pure PNIPAAm , SA /PNIPAAm semi‐IPN , and Ca‐alginate/PNIPAAm full‐IPN hydrogels were investigated. The formation of semi‐IPN and full‐IPN significantly improved the hydrogels’ swelling capability and mechanical properties without altering their thermosensitivity. 5‐Fluorouracil (5‐Fu) was selected as a model drug to study the release behaviors of the hydrogels. It was found that in vitro controlled drug release from semi‐IPN hydrogels showed an initial release burst, followed by a slower and sustained release, before reaching equilibrium. Full‐IPN hydrogels showed slow and sustained release during the whole process. Temperature and pH were found to affect the rate of drug release. Ca‐alginate/PNIPAAm full‐IPN hydrogels have potential application as drug delivery matrices in controlled drug release.     

Asymmetric Transfer Hydrogenation Catalyzed by Mesoporous MCM‐41‐Supported Chiral Ru‐Complex

Chiral N‐sulfonyldiamine was successfully anchored on mesoporous MCM‐41 silica. The MCM‐41‐supported chiral N‐sulfonyldiamine was used as an efficient heterogeneous chiral ligand in the asymmetric transfer hydrogenation of ketones. This heterogeneous system offered satisfactory enantioselectivities up to 94 % with excellent conversions.     

Novel synthesis of nano‐calcium carbonate (CaCO3)/polystyrene (PS) core–shell nanoparticles by atomized microemulsion technique and its effect on properties of polypropylene (PP) composites

Calcium carbonate (CaCO₃)/polystyrene (PS) nanoparticles (<100 nm) with core–shell structure were synthesized by atomized microemulsion technique. The polymer chains were anchored onto the surface of nano‐CaCO₃ through triethoxyvinyl silane (TEVS) as a coupling agent. Ammonium persulfate (APS), sodium dodecyl sulfate (SDS) and n‐pentanol were used as initiator, surfactant, and cosurfactant, respectively. Polymerization mechanism of core–shell latex particles was discussed. Encapsulation of nano‐CaCO₃ by PS was confirmed by using transmission electron microscope (TEM). Grafting percentage of core–shell particles was investigated by Thermogravimetric Analyzer (TGA). Nano‐CaCO₃/PS core–shell particles were characterized by Fourier transform infrared (FTIR) spectrophotometer and differential scanning calorimeter (DSC). The results of FTIR revealed existence of a strong interaction at the interface of nano‐CaCO₃ particle and PS, which implies that the polymer chains were successfully grafted onto the surface of nano‐CaCO₃ particle through the link of the coupling agent. In addition, TGA and DSC results indicated an enhancement of thermal stability of core–shell materials compared with the pure nano‐PS. Nano‐CaCO₃/PS particles were blended with polypropylene (PP) matrix on Brabender Plastograph by melt process with different wt% of loading (i.e. 0.1–1 wt%). The interfacial adhesion between nano‐CaCO₃ particles and PP matrix was significantly improved when the nano‐CaCO3 particles were grafted with PS, which led to increased thermal, rheological, and mechanical properties of (nano‐CaCO₃/PS)/PP composites. Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed a perfect dispersion of the nano‐CaCO₃ particles in PP matrix. Copyright © 2011 John Wiley & Sons, Ltd.