纳米SiO2-Al2O3/聚酰亚胺杂化薄膜的制备及表征

用溶胶-凝胶法制得二氧化硅(SiO2)及三氧化二铝(Al2O3)溶胶,将其掺入到聚酰胺酸基体中,得到SiO2-Al2O3/聚酰亚胺杂化薄膜,并对其结构性能进行了研究.结果表明,薄膜材料中SiO2和Al2O3粒子分散均匀,与有机相存在键合;材料热分解温度有所提高.     

溶胶-凝胶法制备无机纳米/聚酰亚胺杂化膜及其表征

采用溶胶-凝胶法制备了SiO2及A12O3溶胶,并将其掺入到聚酰胺酸基体中,得到无机纳米SiO2-Al2O3/聚酰亚胺杂化膜,并对其结构性能进行了研究.实验表明,薄膜材料中无机纳米SiO2和Al2O3粒子分散均匀,与有机相存在键合;材料热分解温度有所提高.     

Effect of amino-modified silica nanoparticles on the corrosion protection properties of epoxy resin-silica hybrid materials

In this paper, a series of organic-inorganic hybrid materials consisting of epoxy resin frameworks and dispersed nanoparticles of amino-modified silica (AMS) were successfully prepared. First of all, the AMS nanoparticles were synthesized by carrying out the conventional acid-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) in the presence of (3-aminopropyl)-trimethoxysilane (APTES) molecules. The as-prepared AMS nanoparticles were then characterized by FTIR, 13C-NMR and 29Si-NMR spectroscopy. Subsequently, a series of hybrid materials were prepared by performing in-situ thermal ring-opening polymerization reactions of epoxy resin in the presence of as-prepared AMS nanoparticles and raw silica (RS) particles. The as-prepared epoxy-silica hybrid materials with AMS nanoparticles were found to show better dispersion capability than that of RS particles existed in hybrid materials based on the morphological observation of transmission electron microscopy (TEM). The hybrid materials containing AMS nanoparticles in the form of coating on cold-rolled steel (CRS) were found to be much superior in corrosion protection over those of hybrid materials with RS particles when tested by a series of electrochemical measurements of potentiodynamic and impedance spectroscopy in 5 wt% aqueous NaCI electrolyte. The increase of corrosion protection effect of hybrid coatings may have probably resulted from the enhancement of the adhesion strength of the hybrid coatings on CRS coupons, which may be attributed to the formation of Fe-O-Si covalent bond at the interface of coating/CRS system based on the FTIR-RAS (reflection absorption spectroscopy) studies. The better dispersion capability of AMS nanoparticles in hybrid materials were found to lead more effectively enhanced molecular barrier property, mechanical strength, surface hydrophobicity and optical clarity as compared to that of RS particles, in the form of coating and membrane, based on the measurements of molecular permeability analysis, dynamic mechanical analysis, contact angle measurements and ultraviolet-visible transmission spectra, respectively.     

Polyimide/silica/titania nanohybrids via a novel non-hydrolytic sol–gel route

Polyimide/silica/titania hybrid films were prepared via a non-hydrolytic sol–gel route. Silicic acid and titanium tetrachloride were used as the precursors of silica and titania, respectively. The absorption band of Si–O–Ti bonds in FTIR spectra of the hybrid films revealed the formation of the hybrid inorganic network between SiO₂ and TiO₂. Scanning electron microscopy results indicated that the nanometer-scaled inorganic domains were homogeneously dispersed in polyimide matrix due to the introduction of silica-stabilized TiO₂ and the interactions between organic and inorganic phases. The studies on the optical properties of the hybrid films indicated the red-shift of the absorption band increased with increasing TiO₂ content, while all the hybrid films maintained their transparencies. The surface resistances of the hybrid samples decreased with increasing TiO₂ content. The thermal decomposition temperature of the ternary hybrid films decreased slightly with increasing TiO₂ content. This kind of hybrid materials may have potential application in the preparation of opto-electronic devices.     

Structure of polyphenylsilsesquioxane particles prepared by two-step acid-base catalyzed sol-gel process and formation of hollow particles

Spherical polyphenylsilsesquioxane (PhSiO(3/2)) particles, one of the inorganic-organic hybrid materials, were synthesized by a two-step acid-base catalyzed sol-gel process, and hollow particles were successfully prepared by washing the as-prepared particles with organic solvents. It was found that the inside and outside parts of the as-prepared particles were composed of PhSi03/2 species with relatively low and high molecular weight, respectively, i.e., the PhSiO(3/2) particles had a kind of "core-shell" structure. Because the core portion in the as-prepared particles was soluble in ethanol and tetrahydrofuran, hollow particles were obtained through washing the as-prepared PhSiO(3/2) particles with ethanol or tetrahydrofuran. Furthermore, the molecular weight of the as-prepared particles was varied by the concentration of phenyltriethoxysilane used as a starting alkoxide. As a result of the variation of the molecular weight, the hollow PhSiO(3/2) particles with different stabilities against organic solvents were formed.     

Fabrication of TiO2 nanoparticles loaded on coal fly ash composite with enhanced photocatalytic activity

By immobilized on the coal fly ashes, the TiO2 nanoparticles photocatalysts were obviously improved in removing organic compounds of the contaminated water. These composite catalysts were fabricated by three different methods involving hydrothermal method, physical blending and sol-gel method. The resulting materials have been characterized by XRD, SEM and FTIR. The photocatalytic activity of these as-prepared samples was assessed by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature under UV-light irradiation. The experimental results indicated that TiO2 nanoparticles were tightly dispersed on the surface of spherical coal fly ash particles, where the adsorption ability of the catalysts is effectively promoted. It was found that the catalysts prepared by hydrothermal method exhibited the highest photocatalytic activity than that prepared by physical blending or sol-gel method which mainly resulted from the synergistic effect of TiO2 nanopartcles and coal fly ashes.     

无机组分对聚酰亚胺杂化薄膜电性能的影响

初步探讨了聚酰亚胺薄膜在电场作用下的电学行为,采用溶胶-凝胶工艺制备了聚酰亚胺/二氧化硅纳米杂化薄膜,并对薄膜进行浸水24 h处理,利用原子力显微镜对制备的薄膜进行表面形貌表征,讨论了无机组分SiO2和水对薄膜电性能的影响.结果表明:无机组分的引入及两相间的界面形态将对杂化薄膜的电学性能产生重大的影响;偶联剂的引入使得两相间产生紧密的微相结合,并对电性能产生一定的影响.     

无机掺杂改性聚酰亚胺薄膜的制备及表征

采用聚酰亚胺为树脂基体,甲基三乙氧基硅烷、异丙醇铝和钛酸四丁酯为无机前驱体,在N,N-二甲基乙酰胺溶液中进行溶胶-凝胶反应,制备聚酰亚胺／SiO2／Al2O3和聚酰亚胺／SiO2／TiO2两种无机掺杂聚酰亚胺薄膜,采用红外光谱仪、热重分析仪、扫描电镜等测试方法对薄膜的化学结构和表面形貌及其热稳定性进行了表征分析．结果表明：在一定的无机组分含量范围内,无机相均匀的分散在有机基体中,但两种杂化薄膜的分散形态及粒径尺寸不同,热性能均较未掺杂的聚酰亚胺薄膜有所提高。     

Synthesis and optical properties of photosensitive polyimide/silica hybrid thin films

In this study, the photopatternable fluorinated polyimide/silica hybrid materials were synthesized by 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA), oxydianiline (ODA), aminopropyltriethoxysilane (APrTEOS), and 12 nm colloidal silica with a coupling agent. The monodispersed colloidal silica was used to form a silica domain instead of alkoxysilanes in the conventional process. The coupling agents used were 3-methacryloxypropyl trimethoxysilane (MPTMS) or (4-vinylphenethyl)trimethoxysilane (VPTMS). The coupling agent and the silica domain were designed to reduce the volume shrinkage and enhance the thermal properties, respectively. The retention of 2-methyl acrylic acid 2-dimethylamino-ethyl ester (MDAE) in the prepared hybrid films was supported by X-ray photoelectron spectroscopy (XPS) and thickness variation during the curing process. The particle size of silica in the hybrid materials based on SEM analysis was in the range of 10–25 nm. The prepared hybrid materials also exhibited a reduced refractive index after increasing the silica content. The SEM diagram suggested the prepared photosensitive hybrid materials could obtain lithographical patterns with a good resolution. These results indicate that the newly prepared photosensitive polyimide/silica hybrid materials may have potential applications for optical devices.     

Poly(vinyl alcohol)/silica hybrid nanocomposites by sol-gel technique: Synthesis and properties

Poly(vinyl alcohol)/silica organic inorganic hybrid composites were prepared by using sol-gel technique. Tetraethoxysilane was used as the precursor for silica. The reaction was carried out in an aqueous medium having a pH of 1.5 with concentrated hydrochloric acid, used as the catalyst. All the composites were optically clear. Interaction at organic-inorganic interfaces due to hydrogen bonds was speculated from infrared spectroscopic analysis of the hybrid composites. Transmission electron microscopic studies revealed the existence of silica nanoparticles, uniformly dispersed in the organic matrix, which were found to grow in size with increase in tetraethoxysilane loading in the composites. Uniform dispersion of silica particles within the hybrid nanocomposites was also supported from the energy dispersive X-ray mapping of silicon. Dynamic mechanical properties exhibited substantial mechanical reinforcements due to the dispersion of nanosilica particles in the matrix. The results were further supported by significant improvements in the Young's modulus and the tensile strengths of the samples. All the hybrid composites demonstrated excellent water resistance.     

Preparation and properties of the polyimide/multi-walled carbon nanotubes (MWNTs) nanocomposites

The polyimide/multi-walled carbon nanotubes (MWNTs) nanocomposite films were prepared by mixing of poly(amic acid) (PAA) solution and MWNTs/DMAc suspension follow by mixture casting, evaporation and thermal imidization. To increase the chemical compatibility between polyimide matrix and MWNTs, MWNTs were modified with mixed strong acid. The results show that the dispersion of the MWNTs is improved greatly in the polyimide matrix after acid modification. The modified MWNTs are dispersed homogeneously in the polyimide matrix while the structure of the polyimide and MWNTs structures is stable in the preparation process. With the incorporation of MWNTs, the mechanical properties of the resultant nanocomposite films were greatly improved due to the strong interfacial interaction between the modified MWNTs and the polyimide matrix. The thermal stability of the nanocomposites was lower a little than pure polyimide because of the drop of thermostability of MWNTs through acid-treatment. The electrical conductivity and the dielectric constant of the nanocomposites were also having sharp increase, which is favorable for practical use in anti-static materials and embedded capacitors.     

高模量、低热膨胀系数聚酰亚胺杂化薄膜的制备

通过在聚酰胺酸中加入正硅酸乙酯(TEOS)和硅烷偶联剂(KH550),制备了不同SiO2含量的PI/SiO2杂化薄膜.采用FTIR、TMA、SEM以及TGA分析了PI/SiO2杂化薄膜的性能和结构.结果表明,TEOS经水解缩合与聚酰亚胺(PI)形成了有机-无机杂化网络结构,SiO2均匀分散在聚酰亚胺基体中;SiO2和偶联剂的引入提高了杂化薄膜的热稳定性;随着SiO2含量的增加,PI/SiO2杂化薄膜的拉伸强度降低,但当SiO2含量达到20%时,弹性模量增大到3.4GPa.     

耐高温有机/无机杂化聚酰亚胺基体树脂

热固性聚酰亚胺树脂基复合材料已在航空航天领域得到了广泛的应用,然而随着航空航天技术的发展,传统有机聚酰亚胺基体树脂的耐温等级逐渐不足以达到飞行器的设计和应用需求,发展新型耐高温有机/无机杂化聚酰亚胺树脂成为国内外研究重点。本文总结了近年来国内外有机/无机杂化聚酰亚胺基体树脂的发展现状,重点从合成方法、结构设计与性能调控、固化过程和高温降解行为等方面对含笼状倍半硅氧烷聚酰亚胺、含碳硼烷聚酰亚胺和含硅氧烷聚酰亚胺的特点和耐热机制进行了介绍,并对有机/无机杂化聚酰亚胺树脂未来发展面临的挑战与机遇进行了讨论分析。     

B_4C_P/PI聚酰亚胺复合薄膜耐高温及热中子辐照屏蔽性能研究

以耐高温型聚酰亚胺为基体,微米碳化硼(B_4C)为热中子吸收剂,采用粉体表面改性及超声湿混-热亚胺化成膜工艺成功制备了一系列B_4CP/PI聚酰亚胺复合薄膜,重点探讨了不同B_4C含量条件下复合薄膜的耐热性能和力学性能以及不同B_4C含量、不同复合薄膜厚度条件下复合材料的热中子屏蔽性能。研究表明:采用上述工艺,B_4C功能粒子在聚酰亚胺基体中可均匀分散;B_4CP/PI复合薄膜的耐热性随B_4C含量的增加显著提高,力学性能则呈相反趋势;所制备的B_4CP/PI复合薄膜表现出优异的热中子屏蔽性能,中子透射率I/I0随复合薄膜厚度增加及B_4C含量增加呈指数变化规律。据此,可通过材料结构设计,满足不同领域对该类耐高温中子防护材料的应用需求。     

In situ thermal preparation of polyimide nanocomposite films containing functionalized graphene sheets

Graphene oxides (GO) were exfoliated in N,N-dimethylformamide by simple sonication treatment of the as-prepared high quality graphite oxides. By high-speed mixing of the pristine poly(amic acid) (PAA) solution with graphene oxide suspension, PAA solutions containing uniformly dispersed GO can be obtained. Polyimide (PI) nanocomposite films with different loadings of functionalized graphene sheets (FGS) can be prepared by in situ partial reduction and imidization of the as-prepared GO/PAA composites. Transmission electron microscopy observations showed that the FGS were well exfoliated and uniformly dispersed in the PI matrix. It is interesting to find that the FGS were highly aligned along the surface direction for the nanocomposite film with 2 wt % FGS. Tensile tests indicated that the mechanical properties of polyimide were significantly enhanced by the incorporation of FGS, due to the fine dispersion of high specific surface area of functionalized graphene nanosheets and the good adhesion and interlocking between the FGS and the matrix.     

聚酰亚胺/TiO2 复合膜的制备、表征和气体渗透性测定

以硅藻土-莫来石陶瓷膜管为支撑体，以TiO2为过渡层，通过溶胶-凝胶法制备了负载型聚酰亚胺／TiO2复合膜．采用FTIR、NMR、TG／DTA、TEM、BET和气体渗透法对复合膜进行了表征和测试．结果表明：TiO2相通过与聚酰亚胺链上羧酸基支链发生键连形成有机无机组分交错分布的网状结构；复合膜具有良好的热稳定性和有机无机兼容性；相对于聚酰亚胺膜，复合膜对H2、CO2、N2和H2O具有较高的分离性；TiO2含量为15wt％的复合膜对H2／N2、C02／N2和H20／N2的分离因子分别为64．2、42．5和80．8．     

Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis,characterization and morphology properties

Polyimide–silica nanocomposites are attractive hybrid architectures that possess excellent mechanical, thermal and chemical properties. But, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems. In this investigation, a reactive organoclay was prepared via ion exchange reaction between protonated form of difunctional l-isoleucine amino acid as a swelling agent and Cloisite Na⁺ montmorillonite. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acid functional groups were available for further interaction with polymer chains. Then organo-soluble polyimide (PI) have been successfully synthesized from the reaction of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride in N,N-dimethylacetamide. Finally, PI/organoclay nanocomposite films enclosing 1%, 3%, 5%, 7% and 10% of synthesized organoclay were successfully prepared by an in situ polymerization reaction through thermal imidization. The synthesized hybrid materials were subsequently characterized by Fourier transform infrared spectroscopy, X-ray diffraction, electron microscopy, and thermogravimetric analysis techniques. The PI/organoclay nanocomposite films have good optical transparencies and the mechanical properties were substantially improved by the incorporation of the reactive organoclay.     

Synthesis and properties of a novel isomeric polyimide/SiO2 hybrid material

A novel isomeric polyimide/SiO₂ hybrid material was successfully prepared through sol–gel technique, and its structure, thermal properties and nano-indenter properties were investigated. First, 3-[(4-phenylethynyl)phthalimide]propyl triethoxysilane (PEIPTES) was successfully synthesized, its structure was characterized by elemental analysis, FT-IR and ¹³C NMR. The researches on solubility and thermal properties of PEIPTES show that it can be used for modifying nano-SiO₂ precursor. Nano-SiO₂ precursor was synthesized by tetraethoxysilane (TEOS) through sol–gel technique. Then the PEIPTES solution and the nano-SiO₂ precursor were mixed for 6 h to let the PEIPTES molecules react with the nano-SiO₂ precursor, and modified nano-SiO₂ precursor was obtained. The modified reaction was confirmed by the analyses of FT-IR. At last, isomeric polyimide/SiO₂ hybrid material was produced by using isomeric polyimide resin solution and the modified nano-SiO₂ precursor after heat treatment process. The structure analysis by SEM indicated that SiO₂ particles dispersed in isomeric polyimide matrix homogeneously with nanoscale. Thermogravimetric analyzer, dynamic mechanical thermal analyzer and nano-indenter XP was employed to detect the properties of the materials, the results demonstrated that isomeric polyimide/SiO₂ hybrid material has much better thermal properties and nano-indenter properties than those of isomeric polyimide. It is confirmed that PEIPTES acts as a bridge between the SiO₂ particles and the isomeric polyimide matrix in the hybrid material, because the ethoxyl of PEIPTES could participate in the hydrolyzation and condensation to form chemical bond with SiO₂ particles and its phenylethynyl group could take part in the cross-curing reaction of isomeric polyimide.     

PMMA／TiO2-SiO2高分子杂化材料的制备与表征

用溶胶凝胶法和共混法相结合的方法制备了PMMA/TiO2-SiO2高分子杂化材料。并用傅里叶红外光谱(FT-IR)、原子力显微镜(AFM)和透射电镜(TEM)等测试方法对所得复合微粒进行了表征。结果表明,TiO2-SiO2复合粒子呈核-壳结构,具有Ti-O-Si网络;该核壳结构可均匀地分散在聚甲基丙烯酸甲酯中,形成PMMA/TiO2-SiO2高分子杂化材料。与纯的聚合物材料相比,PMMA/TiO2-SiO2高分子杂化材料有较好的热稳定性、优良的紫外屏蔽和可见光透过特性。     

Fabrication of silica/PDMS hybrid nanoparticles by a novel solvent adjustment route

The silica/polydimethylsilane (PDMS) hybrid nanoparticles were successfully synthesized by a novel solvent adjustment route. The as-prepared hybrid nanoparticles were characterized by transmission electron microscopy, UV-vis spectra, and IR spectra. The possible mechanism for the formation of silica/PDMS nanoparticles was discussed. The adjustment of solvents is a very important factor since it could tune the surface ligands and improve the coordination ability. On the other hand, it could also tune the interaction between precursors, intermediate or the target hybrid materials and guarantee the monodispersion of prepared nanoparticles. With the merits of PDMS and silica, the as-prepared SiO2-PDMS hybrid nanoparticles have a good application in hard coating material.