介孔二氧化硅-接枝胶原杂化材料的制备和表征(英)

利用接枝胶原与介孔二氧化硅制备一种新型生物无机杂化材料。用甲基丙烯酸甲酯为接枝剂对胶原进行共聚改性制得接枝胶原。以正硅酸乙酯为模板，十二烷基三甲基溴化铵为表面活性剂，用一个简单的热处理过程制得介孔二氧化硅。介孔二氧化硅-接枝胶原杂化材料通过超声分散接枝胶原与介孔二氧化硅的混合物制得，其三维结构用X射线衍射表征，晶格参数a，b和c分别为0.68，0.37和1.64 nm，为正交晶型。氮气吸附-解吸等温线显示杂化材料的比表面积可达273 m²·g^-1，孔体积为0.13 cm³·g^-1，平均孔径3.4 nm，分布窄。该杂化材料在8～14 μm波长的红外发射率可低至0.323，在光电子学器件和红外隐身领域具有潜在应用价值。     

十二烷基苯磺酸钠改性的尿素和甲醛聚合杂化法合成氧化硅微球

本文在存在十二烷基苯磺酸钠时利用正硅酸乙酯水解液中尿素和甲醛的结晶性聚合反应合成得到了氧化硅微球。首次考察了尿素和甲醛的物质的量比、尿素和甲醛的总用量、正硅酸乙酯(TEOS)用量、酸用量、以及十二烷基苯磺酸钠用量对所得氧化硅微球结构和形貌特征的影响。适当选择这些用量范围可以得到结构稳定、分散均匀的氧化硅微球。在微球生长中尿素和甲醛的量不足时,其突出的结晶性聚合与氧化硅杂化反应进程相互影响,导致了氧化硅微球核壳结构的形成。酸用量增加使氧化硅微球的孔径分布从复杂的双峰转变成均匀的单峰。表面活性剂的使用使氧化硅微球的孔分布从0～80 nm范围内的连续分布转化成单一分布。这些结果对正硅酸乙酯水解液直接合成氧化硅微球方法的推广和应用具有重要指导意义。     

多层核-壳结构P(AM-co-MAA)/W/UF复合微球制备研究

以反相悬浮聚合技术合成的丙烯酰胺(acrylamide,AM)和甲基丙烯酸(methacrylic acid,MAA)共聚高分子微凝胶P(AM-co-MAA)为模板,通过离心沉积法将微米级钨粉沉积于高分子微凝胶表面,得到具有核-壳结构的P(AM-co-MAA)/W复合微球材料;再以P(AM-co-MAA)/W复合微球为模板,通过控制甲醛和尿素的缩聚反应在模板与油/水相界面进行,制备得到了具有多层核-壳结构的高分子/钨/脲醛树脂[P(AM-co-MAA)/W/Urea-formaldehyde resin]复合微球材料.利用扫描电子显微镜(SEM)、红外(FT-IR)、X射线衍射(XRD)和热分析(TGA)等手段对复合微球进行了表征.实验结果表明,外壳层脲醛树脂的包覆量、复合微球的表面形貌可通过改变甲醛和尿素溶液的浓度、甲醛和尿素的物质的量之比等因素进行控制.复合微球的导电性测试结果表明,P(AM-co-MAA)/W复合微球表面壳层脲醛树脂包覆前后,其电导率由1.9×10-3降低为0.9×10-8S·m-1.该研究获得的三层核-壳复合微球材料其外层脲醛树脂的包覆较为完整、致密,其导电性接近于绝缘材料,为含钨复合微球作为电子元件的抗辐射涂层材料打下了基础.     

疏水介孔二氧化硅膜的制备与表征

用甲基三乙氧基硅烷(MTES)代替部分正硅酸乙酯(TEOS)作为前驱体，以聚乙烯醚-聚丙烯醚-聚乙烯醚三嵌段共聚物(P123)作有机模板剂，通过共水解缩聚反应制备了甲基修饰的介孔SiO₂膜。利用N₂吸附、FTIR、²⁹Si MAS NMR以及接触角测量仪对膜的孔结构和疏水性进行了表征。结果表明，修饰后的膜材料具有良好的介孔结构，最可几孔径为4.65 nm，孔体积为0.69 cm³·g^-1，比表面积为938.4 m²·g^-1；同时疏水性明显提高，当n_MTES/n_TEOS达到1.0时，其对水的接触角达到109°± 1.1°。气体渗透实验表明气体通过膜孔的扩散由努森机制所控制。     

碳酸镉@二氧化硅菱形体核壳结构以及二氧化硅菱形体空心结构微粒的制备

利用Stöber种子生长法, 第一次在尺寸为2 μm左右的碳酸镉菱形微粒表面直接包覆二氧化硅层, 得到碳酸镉@二氧化硅核壳结构的胶体粒子. 作为核壳结构的壳层部分, 二氧化硅层的厚度可以通过加入体系中的正硅酸乙酯的量来控制. 作为核层的碳酸镉胶体部分可以被盐酸刻蚀掉, 进而得到具有菱形体空心结构的二氧化硅微粒.     

立方介孔相含钕氧化硅的合成与表征

以十六烷基三甲基溴化铵为结构导向剂，通过水热法合成了具有立方结构的含钕Nd-MCM-48介孔分子筛材料。XRD和TEM测试表明当n_Nd/n_Si<0.05时可以获得典型的长程有序介孔立方结构相，随n_Nd/n_Si比的增加，晶胞参数的增大和红外吸收光谱(FT-IR)的变化为Nd进入介孔分子筛骨架中提供了有力证据。N₂吸附-脱附实验给出了其BET表面积为1 195 m²·g^-1，BJH平均孔径为3.6 nm。紫外-可见漫反射光谱(UV-Vis)证明钕氧形成一种八面体结构。X射线光电子能谱(XPS)进一步证明钕主要以三价形式存在于立方介孔分子筛骨架中。     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵（STAB）自组装体为模板和非离子型联二萘酚衍生物（S）作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明：反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变n_S：n_STAB比,从0.1：1到0.4：1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当n_S：n_STAB=0.5：1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

Au@SiO2核壳纳米粒子的制备及其表面增强拉曼光谱

采用柠檬酸钠还原氯金酸法制备金溶胶, 以正硅酸乙酯(TEOS)为硅源, 氨水作催化剂, 制备以金为核, 二氧化硅为壳的核壳纳米粒子. 金纳米粒子的粒径可以通过柠檬酸钠和氯金酸的比例控制, 通过调节TEOS的量和反应的时间可以控制二氧化硅壳层的厚度. 以苯硫酚为探针分子研究了核壳结构纳米粒子的表面增强拉曼散射(SERS)效应与二氧化硅壳层厚度之间的关系. 研究结果表明, 金内核电磁场增强效应随着二氧化硅壳层厚度的增加逐渐减弱, 且其衰减速度比具有相同尺度的双金属核壳结构纳米粒子的慢. 此外, 探针分子主要以物理作用吸附在二氧化硅的表面, 可通过洗涤方法将探针分子除去, 从而可使该复合结构基底用于循环SERS分析.     

石蜡基微胶囊相变材料研究进展北大核心CSCD

本文从微胶囊壁材出发,重点介绍了石蜡基/高分子、无机和高分子-无机杂化壳微胶囊的制备及应用,并总结了上述微胶囊的优势和不足。其中石蜡基/高分子壳微胶囊的壁材包括三聚氰胺-甲醛树脂、脲醛树脂、三聚氰胺-甲醛-尿素树脂、聚氨酯树脂、丙烯酸树脂等,石蜡基/无机壳微胶囊的壁材包括二氧化硅、二氧化钛、碳酸钙、氧化锌等,石蜡基/高分子-无机杂化壳的壁材包括三聚氰胺-甲醛树脂、三聚氰胺-甲醛-尿素树脂、丙烯酸树脂等与二氧化钛、二氧化硅等无机粒子复合。并对石蜡基微胶囊相变材料的未来发展方向和应用前景进行展望,以期为今后研究提供借鉴。     

松香基季铵盐为模板剂有序超微孔二氧化硅的合成

以松香基季铵盐(脱氢枞基三甲基溴化铵,标记为DTAB)为模板剂、正硅酸乙酯为硅源、氨水为碱性介质成功合成出具有纳米片状形貌的六方有序超微孔二氧化硅材料。采用X射线衍射、N₂吸附-脱附、透射电镜、扫描电镜等手段对样品进行表征,结果表明,体系中模板剂添加量、硅源添加量、碱性介质添加量、晶化温度、搅拌时间对前驱体的有序度有着较大的影响。当物质的量之比为n_Sio2:n_DTAB:n_NH3·H2O:n_H2O=1.0:0.1:11.3:924.0,晶化温度为373K,搅拌时间为24h,所得样品有序度最高。经煅烧后样品具有较大的比表面积(1024 m₂·g^-1)和孔容(0.56 cm³·g^-1),以及狭窄的孔径分布(集中于1.80 nm)。     

Pressure drop in CIM disk monolithic columns

Pressure drop analysis in commercial CIM disk monolithic columns is presented. Experimental measurements of pressure drop are compared to hydrodynamic models usually employed for prediction of pressure drop in packed beds, e.g. free surface model and capillary model applying hydraulic radius concept. However, the comparison between pressure drop in monolith and adequate packed bed give unexpected results. Pressure drop in a CIM disk monolithic column is approximately 50% lower than in an adequate packed bed of spheres having the same hydraulic radius as CIM disk monolith; meaning they both have the same porosity and the same specific surface area. This phenomenon seems to be a consequence of the monolithic porous structure which is quite different in terms of the pore size distribution and parallel pore nonuniformity compared to the one in conventional packed beds. The number of self-similar levels for the CIM monoliths was estimated to be between 1.03 and 2.75.     

Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques

Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO(2) frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO(2) monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1,400 degrees C resulted in the formation of a SiC-SiO(2) composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m(2) g(-1) and a pore volume of 0.8 ml g(-1).     

Post‐polymerization modification of a new reactive monolith for reversed phase and hydrophilic interaction capillary electrochromatography of neutral,polar, and biologically active compounds

A reactive monolith based on the polymerization of 3‐chloro‐2‐hydroxypropyl methacrylate, (HPMA‐Cl), with a crosslinking agent, ethylene glycol dimethacrylate (EDMA), was synthesized and post‐functionalized with a macromolecular ligand polyethyleneimine. Monolithic columns with controlled permeability and pore structure were prepared by free radical polymerization in the presence of a binary porogenic mixture of isopropanol and decanol. The presence of chloropropyl functionality in the pristine monolith allowed the synthesis of a post‐fuctionalized monolith carrying cationic groups that was used to control the magnitude of electroosmotic flow (EOF) in electrochromatographic separation. In the synthesis of pristine monoliths, the feed concentration of functional monomer (ie, HPMA‐Cl) was changed between 30 and 60 v/v % for obtaining cationic monoliths providing satisfactory electrochromatographic separation. The best electrochromatographic performance was obtained with the polyethyleneimine functionalized monolith prepared by using the pristine monolith obtained by 60% (v/v) monomer concentration. This monolith was used in reversed phase and hydrophilic interaction capillary electrochromatography modes for the separation of alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, and nucleosides, using mobile phases with low acetonitrile (ACN) contents ranging between 20% and 35% (v/v). This ACN range was remarkably lower than the content of ACN used on the hydrophilic polymethacrylate‐based monoliths reported previously (ie, >90%). The plate heights up to 5.3 μm were obtained for the separation of nucleosides with the environmental friendly mobile phases whose ACN contents were also remarkably lower than that of similar polymethacrylate‐based monoliths.     

Influence of the methacrylate monolith structure on genomic DNA mechanical degradation, enzymes activity and clogging

The chromatography of mechanically sensitive macromolecules still represents a challenge. While larger pores can reduce the mechanically induced cleavage of large macromolecules and column clogging, the column performance inevitably decreases. To investigate the effect of pore size on the mechanical degradation of DNA, column permeability and enzyme biological activity, methacrylate monoliths with different pore sizes were tested. Monolith with a 143 nm pore radius mechanically damaged the DNA and was clogged at flow rates above 0.5 ml min(-1) (26 cm h(-1)). For monoliths with a pore radius of 634 nm and 2900 nm, no mechanical degradation of DNA was observed up to 5 ml min(-1) (265 cm h(-1)) above which the HPLC itself became the main source of damage. A decrease of a permeability appeared at flow rate 1.8 ml min(-1) (95 cm h(-1)) and 2.3 ml min(-1) (122 cm h(-1)), respectively. The effect of the pore size on enzyme biological activity was tested with immobilized DNase and trypsin on all three monoliths. Although the highest amount of enzyme was immobilized on the monolith with the smallest pores, monolith with the pore radius 634 nm exhibited the highest DNase biological activity probably due to restricted access for DNA molecules into the small pores. Interestingly, specific biological activity was increasing with a pore size decrease. This was attributed to higher number of contacts between a substrate and immobilized ligand.     

General and simple approach for control cage and cylindrical mesopores, and thermal/hydrothermal stable frameworks

Highly ordered cage and cylindrical mesoporeous silica monoliths (HOM) with 2- and 3-dimensional (2D and 3D, respectively) structures, mesopore/micropore volumes, and thick-walled frameworks were successfully fabricated by instant direct templating of lyotropic phases of copolymer (EO(m)-PO(n)-EO(m)) surfactants. Large cage-like pores with uniform constriction sizes up to 10 nm and open cylindrical channel-like mesopores can be easily achieved by this simple and efficient synthesis design. Our results show that the cage-like pores could be fabricated at relatively lower copolymer concentrations used in the lyotropic phase domains at copolymer/TMOS ratios of 35 wt %. These ordered cage pore architectures underwent transition to open-cylindrical pores by increasing the copolymer concentration. High EO/PO block copolymers, in general, were crucially affected on the increase of the interior cavity sizes and on the stability of the cage mesopore characters. However, for F108 (EO(141)PO(44)EO(141)) systems, the fabrication of ordered and stable cage pore monoliths was achieved with significantly higher copolymer concentrations up to 90 wt %. Interestingly, the effective copolymer molecular nature was also observed in the ability to design various ordered mesophase geometries in large domain sizes. Our findings here show evidence that the synthetic strategy provides realistic control over a wide range of mesostructured phase geometries and their extended long-range ordering in the final replicas of the silica monolith frameworks. In addition, the HOM silica monoliths exhibited considerable structural stability against higher thermal temperature (up to 1000 degrees C) and longer hydrothermal treatment times under boiling water and steam. The remarkable structural findings of 3D frameworks, transparent monoliths, and micropores combined with large cage- and cylindrical-like mesopores are expected to find promising uses in materials chemistry.     

合成条件对硅胶整体柱中孔结构的影响

硅胶整体柱是目前备受关注的液相色谱固定相。本文考察了合成条件对硅胶整体柱中孔结构的影响,包括反应体系的pH值、聚乙二醇(PEG)含量及分子量。实验表明,反应体系的pH值能有效地调控硅胶整体柱的中孔孔径及孔结构,当pH值为2或5时,整体柱中孔孔径较小;而当pH值为3或9时,孔径较大,孔结构趋于圆筒状。整体柱的中孔平均孔径随着PEG含量和分子量的增加而增加,其孔径分布也逐渐变宽。     

Preparation and characterisation of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media

Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monolithic supports were prepared by radical polymerisation of the continuous phase of water in oil high internal phase emulsions. Morphology of monolithic materials was studied by scanning electron microscopy and mercury intrusion porosimetry. The ratio of phase volume and the degree of crosslinking influenced the void size and pore size distribution of resulting polymers. Void sizes between 1 and 10 microm were observed and average pore sizes around 100 nm. Polymers with 60, 75, 80 and 90% pore volume were prepared and even samples with highest pore volume showed good mechanical stability. They were modified to bear weak-anion exchange groups and tested on the separation of standard protein mixture containing myoglobin, conalbumine and trypsin inhibitor. Good separation was obtained in a very short time similar to the separation obtained by commercial methacrylate monoliths. However, higher dispersion was observed. Bovine serum albumin dynamic binding capacity for monolith with 90% porosity was close to 9 mg/ml.     

Nanoparticle-modified monolithic pipette tips for phosphopeptide enrichment

We have developed nanoparticle-modified monoliths in pipette tips for selective and efficient enrichment of phosphopeptides. The 5 μL monolithic beds were prepared by UV-initiated polymerization in 200 μL polypropylene pipette tips and either iron oxide or hydroxyapatite nanoparticles were used for monolith modification. Iron oxide nanoparticles were prepared by a co-precipitation method and stabilized by citrate ions. A stable coating of iron oxide nanoparticles on the pore surface of the monolith was obtained via multivalent electrostatic interactions of citrate ions on the surface of nanoparticles with a quaternary amine functionalized poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) monolith. Hydroxyapatite nanoparticles were incorporated into the poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) monolith by simply admixing them in the polymerization mixture followed by in situ polymerization. The nanoparticle-modified monoliths were compared with commercially available titanium dioxide pipette tips. Performance of the developed and commercially available sorbents was demonstrated with the efficient and selective enrichment of phosphopeptides from peptide mixtures of α-casein and β-casein digests followed by off-line MALDI/MS analysis.     

Synthesis of zirconia monoliths for chromatographic separations

The aim of this work is to join the advantages of two different kinds of stationary phases: monolithic columns and zirconia-based supports. On the one hand, silica monolithic columns allow a higher efficiency with a lower back-pressure than traditional packed columns. On the other hand, chromatographic stationary phases based on zirconia have a higher thermal and chemical stability and specific surface properties. Combining these advantages, a zirconia monolith with a macroporous framework could be a real improvement in separation sciences. Two main strategies can be used in order to obtain a zirconia surface on a monolithic skeleton: coating or direct synthesis. The coverage by a zirconia layer of the surface of a silica-based monolith can be performed using the chemical properties of the silanol surface groups. We realized this coverage using zirconium alkoxide and we further grafted n-dodecyl groups using phosphate derivatives. Any loss of efficiency was observed and fast separations have been achieved. The main advance reported in this paper is related to the preparation of zirconia monoliths by a sol-gel process starting from zirconium alkoxide. The synthesis parameters (hydrolysis ratio, porogen type, precursor concentration, drying step, etc.) were defined in order to produce a macroporous zirconia monoliths usable in separation techniques. We produced various homogeneous structures: zirconia rod 2 cm long with a diameter of 2.3 mm, and zirconia monolith inside fused silica capillaries with a 75 microm I.D. These monoliths have a skeleton size of 2 microm and have an average through pore size of 6 microm. Several separations have been reported.     

Comprehensive study of the macropore and mesopore size distributions in polymer monoliths using complementary physical characterization techniques and liquid chromatography

Poly(styrene‐co‐divinylbenzene) monolithic stationary phases with two different domain sizes were synthesized by a thermally initiated free‐radical copolymerization in capillary columns. The morphology was investigated at the meso‐ and macroscopic level using complementary physical characterization techniques aiming at better understanding the effect of column structure on separation performance. Varying the porogenic solvent ratio yielded materials with a mode pore size of 200 nm and 1.5 μm, respectively. Subsequently, nano‐liquid chromatography experiments were performed on 200 μm id × 200 mm columns using unretained markers, linking structure inhomogeneity to eddy dispersion. Although small‐domain‐size monoliths feature a relatively narrow macropore‐size distribution, their homogeneity is compromised by the presence of a small number of large macropores, which induces a significant eddy‐dispersion contribution to band broadening. The small‐domain size monolith also has a relatively steep mass‐transfer term, compared to a monolith containing larger globules and macropores. Structural inhomogeneity was also studied at the mesoscopic level using gas‐adsorption techniques combined with the non‐local‐density‐function‐theory. This model allows to accurately determine the mesopore properties in the dry state. The styrene‐based monolith with small domain size has a distinctive trimodal mesopore distribution with pores of 5, 15, and 25 nm, whereas the monolith with larger feature sizes only contains mesopores around 5 nm in size.