分子内杂化纳米结构体多面体低聚倍半硅氧烷研究进展

多面体低聚倍半硅氧烷(POSS)是基于化学键合作用形成的分子内杂化体系,其改性后的材料是一类具有广泛潜在应用价值的新型有机-无机杂化材料。文中介绍了多面体低聚倍半硅氧烷单体的结构、性能、单体及其衍生物的合成,以及其改性聚合物材料在航空、航天、卫生、电子等高科技领域内的应用前景。针对国内的研究现状,指出低聚倍半硅氧烷-聚合物杂化体系研究所存在的问题。     

原子转移自由基聚合制备PMMA/POSS杂化材料

以八(γ-氯丙基)倍半硅氧烷(OCP-POSS)为引发剂,通过原子转移自由基聚合(ATRP)制备了PMMA/OCP-POSS有机/无机杂化材料.采用GPC、DSC和TGA对杂化材料的结构与性能进行了表征.结果表明,在DMF、异丙醇、甲苯等3种不同溶剂中均可合成分子量分布较窄的PMMA杂化材料.以DMF为溶剂,所得PMMA/OCP-POSS杂化材料的分子量分布系数可达到1.18.与分子量相当的线形PMMA相比,含OCP-POSS的PMMA杂化材料具有更高的玻璃化转变温度和热稳定性.     

由二氧化硅低温合成可聚合倍半硅氧烷的研究

以无定形二氧化硅(SiO2)为基本原料,经过系列反应成功合成了带有甲基丙烯酸酯基团的笼形倍半硅氧烷。采用红外光谱、差示扫描量热等分析方法对各步反应产物进行了表征。结果表明,所合成的倍半硅氧烷带有可聚合的不饱和基团且具有笼形核/壳结构。可聚合的笼形倍半硅氧烷为具有特殊杂化结构聚合物的合成和应用奠定了基础。     

笼型倍半硅氧烷-聚乳酸星型聚合物的制备及表征

以缩水甘油、氨丙基三乙氧基硅烷为原料合成了多羟基笼状倍半硅氧烷(POSS-AH),并在微波辐射条件下以POSS-AH上的羟基引发左旋丙交酯(L-LA)开环聚合,在无机POSS核表面引入有机左旋聚乳酸(PLLA)链段。利用正交试验确定最佳反应条件为微波反应功率45w,反应时间45min,反应温度120℃,催化剂含量1.5wt%。在该反应条件下,通过控制POSS-AH与丙交酯的投料比可以控制接枝聚乳酸链段的长度,采用核磁氢谱对接枝前后笼状倍半硅氧烷的组成进行了表征。在此基础上通过偏光显微镜对POSS-PLLA的结晶形态进行观察,结果表明该杂化材料与PLLA共混后,在140℃等温结晶能够形成环带球晶。     

笼型倍半硅氧烷的合成与应用

笼型倍半硅氧烷(POSS)是一种新型有机硅杂化材料,在耐高温材料、阻燃材料以及高分子增强材料方面具有广阔的发展前景.主要介绍了苯基、氨基、环氧基和甲基等4种官能团取代笼型倍半硅氧烷的合成方法及影响因素、性能和应用前景.     

笼型倍半硅氧烷(POSS)合成的研究进展

笼型倍半硅氧烷(POSS)是一类引人注目的新型纳米材料。POSS独特的有机无机杂化结构赋予其许多优异的性能,如高的耐热性、力学性能、良好的介电性能及光学性能等,展示出广泛的应用前景。文中首先介绍了POSS的结构和性能特点,然后详细综述了笼型倍半硅氧烷(POSS)合成方面的研究进展,将笼型倍半硅氧烷的合成方法分成三官能团硅烷的水解缩聚反应法、顶端-带帽法、硅氢化反应法、侧基转化法和POSS的结构重排法等5种合成方法。     

聚乳酸-聚乙二醇-聚乳酸/二氧化钛杂化材料的制备及表征

以辛酸亚锡为催化剂,合成了聚乳酸-聚乙二醇-聚乳酸(PLA-PEG-PLA)共聚物;基于溶胶凝胶(sol-gel)工艺,将PLA-PEG-PLA与TiO2溶胶杂化反应,制备了PLA-PEG-PLA/TiO2杂化材料。采用红外光谱(FT-IR)、光电子能谱(XPS)、差示扫描量热(DSC)和X射线衍射(XRD)方法对杂化材料进行表征和分析。FT-IR和XPS分析结果显示,TiO2溶胶与PLA-PEG-PLA间发生了杂化反应,形成了Ti-O-C键。DSC分析结果显示,随TiO2%(质量分数,下同)含量的增加,杂化材料的耐热性能提高。XRD证实了杂化材料为无定型结构,有利于降解。     

笼型倍半硅氧烷纳米杂化材料的研究进展

介绍了笼型倍半硅氧烷(POSS)作为一种新型的有机一无机杂化材料,在近10年的研究中引起了极大关注.阐述了POSS单体的结构特点及官能化POSS的合成,并指出了POSS聚合物在催化剂、发光材料、介电材料等领域内的应用前景.     

新型功能性倍半硅氧烷的合成与表征

以三氯丙基三甲氧基硅烷、苯基三甲氧基硅烷为原料,在一定条件下合成了笼形八聚(三氯丙基)倍半硅氧烷和双层倍半硅氧烷。进一步与叠氮钠、冠醚等通过取代反应、点击反应等方法来合成多种功能性的倍半硅氧烷,它们在复合材料等领域将有很好的应用前景。利用1-核磁共振光谱、13-核磁共振光谱、29-Si核磁共振光谱、基质辅助激光解吸电离飞行时间质谱等手段,对它们的结构分别进行了表征。     

γ-(甲基丙烯酰氧)丙基倍半硅氧烷膜性能研究

为了研究γ-(甲基丙烯酰氧)丙基倍半硅氧烷膜(m-M-S)的性能,采用溶胶-凝胶法制备了TEOS改性的倍半硅氧烷膜材料(m-MST),利用扫描探针电镜、扫描电镜、差示扫描量热法、热重分析等技术对m-MST成膜材料的性能进行了表征.研究结果表明,此膜为有机-无机杂化纳米结构薄膜材料,波长345～2500nm范围内膜层的透光率为98%～99%;TEOS含量在20%时,薄膜体系的机械性能和耐腐蚀性性能最佳.     

Comparison of the protonic acidity of HY,LZY-82, HSAPO-37, and HEMT: Effect of the structure and of the nature of T atoms

Four different zeolites built from sodalite cages and hexagonal prisms are compared using infrared spectroscopy with regards to their hydroxyl properties and to their interaction with benzene. Among the three materials that have the faujasite structure (HY, LZY-82. and HSAPO-37), HSAPO-37 is the most stable with regards to hydroxyls and texture. The presence of P also facilitates the generation of very strong acid sites for pretreatments above around 1000 K. The different arrangement of building units in HEMT involves a mean stronger acidity than in zeolites with the faujasite structure. The overall order of thermal stability (hydroxyls and texture) is HY < HEMT < LZY-82 < HSAPO-37. The interaction of benzene with the hydroxyls of the two infrared bands (HF and LF) is total in HSAPO-37. Because of lack of space, not enough benzene can enter the cages of HY to titrate all the protons and a part of the LF band is unaffected. There is space enough in HEMT; nevertheless, a fraction of the LF hydroxyls is trapped in the sodalite cage and is not attracted in the large cages. The integrated intensity l of the CH out of plane vibration of benzene adsorbed is similar for all the materials.     

有机/无机杂化室温固化热控涂层的制备

以正硅酸乙酯(TEOS)与硅氧烷共水解缩聚反应制备得到粘结剂,然后与作为固化催化剂的3-氨基丙基三乙氧基硅烷(APTES)和作为光学颜料的ZnO粉末混合,制备了一系列有机-无机杂化热控涂层(TCCS)。所制备的热控涂层可以在室温下自然固化, 且具有较低的太阳吸收比α_S和较高的发射率ε_H。红外光谱(FT-IR)和凝胶色谱(GPC)分析结果表明,所制备的混合粘结剂含有大量的活性羟基,聚合度适中。热重分析(TGA)表明,所制备的热控涂层在200℃以下具有良好的热稳定性。通过增加涂层厚度可以降低α_S/ε_H值,通过提高TEOS含量,可以降低涂层在红外波段的光学吸收。这为获得具有低α_S/ε_H值的室温固化TCCS提供了有效途径。     

Microcapsules for cell entrapment by template polymerization of a synthetic hydrogel coating around calcium alginate gel: preliminary development

Stable, water-soluble copolymers of glycidyl methacrylate with n-vinyl pyrrolidinone (I) were prepared by free-radical polymerization. Water-soluble copolymers of 2-hydroxyethyl methacrylate with methacrylic acid (II) were examined as co-reactants with (I) to form hydrogel matrices. Upon mixing of (I) and (II) in solution, a covalently crosslinked hydrogel was formed, presumably by etherification of epoxy functionality on (I) with hydroxyls on (II). Synthetic hydrogel-coated gel beads were prepared from an aqueous mixture of sodium alginate and (II) by treatment with solution containing (I) and calcium ion. An elastic, defect free and indefinitely stable covalently crosslinked hydrogel coating was formed around the calcium alginate by surface reaction of (I) and (II). Encapsulated guinea-pig red blood cells suffered minimal lysis over a 4 day period due to isolation and protection from the reacting species by the interior alginate gel matrix.     

Mechanochemical synthesis of dispersed layer composites on the basis of talc and a series of biological active species

Interaction of mineral talc as an inert carrier with bioactive species (salicylic acid, glycerol, olive oil) in a mechanochemical process was studied by FTIR spectroscopy. Reaction of the talc silicate hydroxyls with carboxyl or alcohol moieties was observed for all the species studied. Dispersed layered composites, built from the silicate (talc) matrix, to which a bioactive component is bound, are formed in this interaction on the time scale of 1–5 min. The formation of new materials viz. layered dispersed mechano-composites proceeds due to etherification or esterification of the active sites on the silicate surface with acids or alcohols.     

Preparation and characterization of EP/SiO<Subscript>2</Subscript> hybrid materials containing PEG flexible chain

EP/SiO₂ hybrid materials, which contained flexible chain, were prepared by epoxy resin (EP) and polyethylene glycol (PEG)-grafted polysilicic acid (PSA), which was obtained by endcapping polyethylene glycol-1000 with toluene 2,4-diisocyanate (TDI), followed by a reaction with polysilicic acid. The formation of hybrid materials was confirmed by a wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) analysis. Results showed that the EP/SiO₂ hybrid particles were nanosized and the average size was about 20–50 nm. The mechanical properties, dynamic mechanical properties, and thermal properties were evaluated and compared with the corresponding matrix. The improvement in impact properties in hybrid materials was explained in terms of the impact fracture surface analysis by scanning electron microscope (SEM).     

熔融法制备高岭石/2-吡啶甲酸插层复合物

以高岭石/二甲亚砜(DMSO)作为前驱体,采用熔融插层法在130℃温度下制备了高岭石/2-吡啶甲酸插层复合物,采用X射线衍射和Fourier变换红外光谱进行了表征.结果表明:高岭石/2-吡啶甲酸插层复合物中,高岭石的层间距由0.72nm扩张到1.409nm,插层率达到84％;在此基础上,分析了2-吡啶甲酸的插层机理,即2-吡啶甲酸分子中羰基与高峰石的内表面羟基形成了氢键,2-吡啶甲酸分子可能以单分子层近似垂直排列与高岭石层间.     

Poly(methyl methacrylate)–titania hybrid materials by sol–gel processing

Sol–gel derived poly(methyl methacrylate)–titania hybrid materials were synthesized by using acrylic acid or allyl acetylacetone (3-allyl-2,4-pentanedione) as coupling agent. Titanium butoxide modified with acrylic acid (or titanium isopropoxide modified with allyl acetylacetone) was hydrolysed to produce a titania network, and then poly(methyl methacrylate) (PMMA) chains, formed in situ through a radical polymerization, were chemically bonded to the forming titania network to synthesize a hybrid material. Transparent hybrid materials with different contents of titania were achieved. With increase of the titania content, the colours of the products changed from yellow to dark red. The synthesis process was investigated step by step by using Fourier transform–infrared spectroscopy, and the experimental results demonstrated that acrylate or acetylacetonato groups bound to titanium remain in the final hybrid materials. The thermal stability of the hybrid materials was considerably improved relative to pure PMMA. Field emission scanning electron microscopy analyses showed the hybrid materials are porous and pore diameters vary from 10–100 nm. The hybrid materials using allyl acetylacetone as coupling agent exhibited a thermochromic effect that neither pure PMMA nor titania exhibit. This revised version was published online in November 2006 with corrections to the Cover Date.     

Silica coating of vapor grown carbon fibers

Silica coatings have been applied to vapor grown carbon fibers (VGCFs) by a liquid phase deposition process. Unlike the coating of single walled carbon nanotubes, the addition of a surfactant to “solubilize” the VGCFs results in an extremely non-uniform coating consisting of spherical silica aggregated around the tubes. As was observed for fullerenes, hydroxylation of the surface of the VGCF appears to be key to the formation of a uniform silica coating. Irrespective of the type of VGCF, heating a suspension of VGCFs in nitric acid to dryness (Type II) gave us the best results in terms of silica growth around the VGCF and there is a correlation between the percent of hydroxyls present on the VGCF surface and on the type of growth that occurs on the VGCF. Nitric acid treatment of VGCFs for 1 day in solution were precipitated with acetone (Type III treatment), and then coated with silica. This acid treatment made the coated fibers highly soluble in EtOH.     

水杨酸铽/聚乙烯醇杂化光功能材料的制备和性能

采用溶胶/凝胶方法制备了一系列含有铽-水杨酸配合物的聚乙烯醇高分子杂化光功能材料,考察了偶联剂的引入对杂化材料的形貌和光学性能的影响。利用红外光谱表征材料的结构,扫描电镜和荧光光谱表征材料的性能。结果表明,随着偶联剂的引入,可以有效避免相分离现象和荧光淬灭,显著提高了杂化材料的光学性能。