Fabrication of highly refractive BaTiO3 nanocomposite films using heat resistant polymer as matrix

Highly refractive, heat-resistant BaTiO₃ nanocomposite films were fabricated via in situ polymerization to homogeneously disperse barium titanate (BT) nanoparticles into polyimide (PI) matrix. BT nanoparticles surface-modified with O-phosphorylethanol phthalimide (PPHI) were employed to the in situ polymerization in which condensation reactions of a diphthalic anhydride and a diamine were conducted to form the prepolymer of poly(amic acid) (PAA) that was thermally imidized in the following step. The nanoparticles surface-modified were added to PAA solution at different times in the polymerization to examine the effect of PAA molecular weight on the refractive index (RI) of the nanocomposite films, which indicated that relatively low molecular weights (<10,000) of PAA formed at the point of nanoparticle addition was appropriate for enhancement of nanocomposite RI. An additional treatment of chemical imidization using acetic acid anhydride and pyridine, which was followed by the thermal imidization, was performed to examine the effect of polyimide structure on RI of nanocomposite films. The RI of nanocomposite films with excellent thermal stability could be successfully enhanced to n = 1.88 by the chemical imidization.     

Preparation of Shell-Core Cu(2)O-Cu Nanocomposite Particles and Cu Nanoparticles in a New Microemulsion System

Shell–core Cu₂O–Cu nanocomposite particles and metal Cu nanoparticles are synthesized in a new microemulsion system which consists of saturated Cu²⁺ salt aqueous solution dispersed in isopropanol and stabilized by polyvinylalcohol (PVA). The size of the composite particles and the thickness of the Cu₂O shell layer can be controlled by the volume ratio of isopropanol to H₂O (the ratio is defined as R). When R ≥ 1000, it is available to obtain metal Cu nanoparticles.     

Preparation of nonwoven polyimide/silica hybrid nanofiberous fabrics by combining electrospinning and controlled in situ sol-gel techniques

A controlled in situ sol-gel synthesis combined with the electrospinning technique and postspun imidization was applied in the fabrication of polyimide/silica hybrid nonwoven nanofiberous fabrics with excellent thermal and mechanical performance. The nanofiberous fabrics were prepared by electrospinning of the solution of tetraethoxysilane (TEOS) and polyamic acid (PAA). The different silica contents in the fabrics were achieved by varying the amount of TEOS while fitting the solid content of PAA. The final polyimide/silica fabrics was obtained after imidization of PAA and gelation of silica phase simultaneously accomplished through a step-wise heating process. Some specific IR techniques and other characterizations indicated the successful incorporation of the silicon dioxide (SiO₂) into the PI matrix and the relatively even distribution of the SiO₂ in the fabrics. An increase of 133 °C in the decomposition temperature and 4-fold enhancement of the ultimate tensile strength were achieved for the hybrids with a 6.58 wt.% of SiO₂ content, compared to the pure PI fabric. The excellent performance could be attributed to the good compatibility between the polyimide and silica, and good adhesion among the fibers, which resulted from the controlled TEOS hydrolysis and the simultaneous imidization and gelation process.     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

Preparation of Poly(amic acid) and Polyimide via Microwave-Assisted Polycondensation of Aromatic Dianhydrides and Diamines

Summary: A copolycondesation-type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4′-oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier-transform infrared (FT-IR) spectroscopy, Proton nuclear magnetic resonance (¹H NMR) spectrometry, viscosity, X-ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT-IR spectra of the polymer revealed characteristic peaks for PI around 1778^– and 1723 cm^–1. TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N₂ was 587 °C.     

Study of the formation of polyimide from complexes of benzophenonetetracarboxylic acid diester with different diamines. 3. Dielectric study of thermal imidization

Dielectric loss peaks caused by thermal imidization were observed for the three complexes of benzophenonetetracarboxylic acid dimethyl ester (BZPE) with different diamines. The mechanism of the formation of imide rings from complexes with hydrogen bonds and with separated charges was specified. The specific features of thermal imidization of the BZPE·diaminopyridine dimeric complex were confirmed and it was shown that heat treatment of the complex of BZPE with hexamethylenediamine yields a softening polyimide and thermal imidization takes place at lower temperatures.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 534–539, March, 1990.     

Synthesis and crystal structure of a new copper (II) complex,designed to produce efficient successor of Cu2O,toward synergy of adsorption and photodegradation of MB

A new copper (II) coordination complex formulated as [Cu (dipic)(phen)(2-MePy)]. 2H₂O ( 1 ) where phen = 1, 10-phenanthroline, dipic²⁻ = pyridine-2,6-dicarboxylato and 2-MePy = 2-methyl pyrrole was synthesized through a simple and environment-friendly reaction under ultrasound irradiation. Also, complex 1 was synthesized by hydrothermal process at 120 °C for 3 days. The corresponding structure of complex 1 was characterized by elemental analysis, atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP), conductivity measurement, Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV–Vis), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and fluorescence. The crystal structure of the hydrothermally synthesized complex was characterized by single crystal X-ray diffraction (SC-XRD(, which revealed a triclinic structure. In the remainder of this study, the Cu₂O nanoparticles have been prepared via thermal decomposition of hydrothermal and ultrasound complexes and characterized by ICP, FT-IR, powder X-ray diffraction (XRD), SEM and N₂ adsorption/desorption. Adsorption and visible-light-driven photocatalytic capabilities of two synthetic Cu₂O were investigated in the removal of MB from water. The result showed that the synthesized catalysts have good catalytic activity and the photocatalytic degradation is more effective in dye removal of MB compared with the adsorption.     

Simple and easy recycling of poly(amic acid) gels through microwave irradiation

Poly(amic acid)s (PAAs), which are precursors of polyimides, often undergo gel formation during their synthesis or storage, and these insoluble gels have been discarded. In this work, we discovered that the gels could be converted to homogeneous PAA solutions by fast and simple microwave (MW) irradiation. The PAA gels were placed inside a domestic MW oven, and MW irradiation was carried out with 240 W for 2 min. The recycled PAA solutions afforded polyimide films, coatings, and powders. The polyimides prepared from the recycled PAA solutions exhibited higher glass transition temperatures (T_gs), decomposition temperatures, and char yields than comparison polyimides obtained from ordinary PAA solutions. Flexible free‐standing polyimide films were obtained by drop‐casting of the MW‐treated solutions and subsequent thermal imidization. Mechanical properties and dielectric constants were measured for the polyimide films and coatings, respectively. This new method has significant advantages for the environment, economy, and industry. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 981–987     

耐超高温双酮酐型聚酰亚胺的合成及性能

以4,4'-对苯二甲酰二邻苯二甲酸酐(TDPA)为芳二酐单体,对苯二胺(PPD)为芳二胺单体,经低温溶液缩聚制得成膜性能优良的高相对分子质量聚酰胺酸(PAA),再经过热亚胺化制备双酮酐型聚酰亚胺(PI)薄膜。 采用傅里叶变换红外光谱仪(FT-IR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)、动态热机械分析仪(DMA)、热重分析仪(TGA)、紫外-可见分光光度计(UV-Vis)及力学性能等技术手段表征了聚酰亚胺膜的结构和性能,考察了不同亚胺化温度对合成的双酮酐型聚酰亚胺膜性能的影响。 结果表明,经程序升温至320 ℃能使PAA热亚胺化基本趋于完成。 PI薄膜为部分有序聚集态结构,玻璃化转变温度(T_g)为298 ℃,具有优异的热性能,热失重温度(T_5%)为523 ℃。 拉伸强度达到130 MPa,弹性模量为5.77 GPa。 PI薄膜紫外光透过截止波长为375 nm,在可见光区具有良好的透光性能及耐溶剂性能。     

The synthesis of Cu/plate-like ZnO nanostructures and their self-assembly mechanism

A composite Cu/ZnO nanostructure with Cu nanoparticles supported on ZnO hexagonal nanoplates has been successfully fabricated by a heating approach, using their metal oleate salts as the precursors without any additives. Combined Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and other examination technologies, the structural properties and formation mechanism of as-synthesized Cu/ZnO nanocomposites are studied in detail. The results reveal that the nanostructures are plate-like with uniform shape and size, and Cu nanoparticles exhibit specific (111) plane matching with the (002) facet of ZnO, indicating a surface-induced interaction mechanism. Further characterization demonstrates that copper nanoparticles can be generated by a decomposition/self-reduction route of copper salts, and the oleate ions act as dual roles in the process: reducing and protecting agents. The difference of decomposition temperature between metal oleates also plays important roles in the formation of Cu/ZnO nanostructure. In addition, the catalytic performance of these nanocomposites is evaluated and it can be found that compared with Cu/rod-like ZnO, as-synthesized samples are highly selective for methanol.     

Controlled formation of optically reflective and electrically conductive silvered surfaces on polyimide film via a direct ion-exchange self-metallization technique using silver ammonia complex cation as the precursor

Double-surface-silvered polyimide films have been successfully fabricated using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxidianile- (BTDA/ODA-) based poly(amic acid) (PAA) as the polyimide precursor via a direct ion-exchange self-metallization technique. The process has been clarified to involve the loading of silver(I) into PAA via ion exchange, the thermally induced reduction of silver(I) to silver(0) and the concomitant imidization of PAA to polyimide upon thermal treatment, the subsequent silver-catalyzed and oxygen-assisted decomposition of the polyimide overlayer, and the self-accelerated aggregation of silver clusters on the film surface to produce well-defined surface silver layers. By employing [Ag(NH3)2]+ solution with a concentration of only 0.01 M and an ion-exchange time of no more than 10 min, the controlled formation of highly reflective and conductive silver surfaces upon thermal treatment at 300 degrees C for less than 4.5 h indicates that the present work provides an efficient route and an effacious silver species for polyimide surface metallization. Although the alkaline characteristics of [Ag(NH3)2]+ have a strong hydrolysis effect on the polyimide precursor chains, the final metallized films retain the key mechanical and thermal properties of the pure polyimide. Films were characterized by ATR-FTIR, XPS, ICP-AES, SEM, TEM, DSC, TGA, reflectivity, conductivity, and mechanical measurements.     

Nanostructured polyamic acid membranes as novel electrode materials

This paper describes a new approach for the preparation of polyamic acid (PAA) composites containing Ag and Au nanoparticles. The composite film of PAA and metal particles were obtained upon electrodeposition of a PAA solution containing gold or silver salts with subsequent thermal treatment, while imidization to polyimide is prevented. The structural characterization of the films is provided by 1H NMR and Fourier transform infrared spectroscopy (FTIR), while the presence of metallic nanoparticles within the polymeric matrix was confirmed by scanning electron microscopy (SEM), cyclic voltammetry (CV), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This approach utilizes the unique reactivity of PAA by preventing the cyclization of the reactive soluble intermediate into polyimides at low temperature to design polymer-assisted nanostructured materials. The ability to prevent the cyclization process should enable the design of a new class of electrode materials by use of thermal reduction and/or electrodeposition.     

Cu2O/g-C3N4催化合成吲哚-2-羧酸酯

我们通过原位还原的方法将吸附在g-C3N4表面上Cu2+还原,制备出Cu2O/g-C3N4复合材料,并利用XRD、SEM、FT-IR、XPS等分析手段表征Cu2O/g-C3N4.表征结果显示:Cu元素主要以Cu2O的形式吸附在g-C3N4载体上.另外,还考察了Cu2O/g-C3 N4在“一锅法”合成吲哚-2-甲酸乙酯的反应中的催化性能.结果表明:即使在较低的催化担载量和温和的反应条件下,Cu2O/g-C3 N4仍能表现出良好的催化性能并获得44.1％的收率.     

(Co)polyimides from commonly used monomers, and their nanocomposites

Synthesis of (co)polyimides from aromatic dianhydrides (pyromellitic dianhydride (PMDA), symmetric 3,3′,4,4′-biphenyltetracarboxylic dianhydride (sBPDA)) and diamines (4,4′-oxydianiline (ODA), p-phenylenediamine (PDA)) commonly used for the production of commercial polyimides, as well as the preparation of their nanocomposites with SiO₂ nanoparticles were performed with the aim to find ways to control technical performance of polyimides. The (co)polyimide films prepared under mild thermal imidization conditions were analyzed by FTIR, WAXD, DSC and TG, and characterized by transition temperatures and the temperatures of 5% and 10% mass loss, as well as tensile parameters.Films of PMDA/sBPDA–ODA copolyimides at the ambient temperature had a 20% higher ultimate strength and exhibited a higher tensile modulus than the reference polyimide (PMDA–ODA). However, lowering the transition temperature of the polyimide by partial substitution of an sBPDA monomeric unit for PMDA resulted in lowering the modulus at higher temperatures. The best performance was exhibited by semi-crystalline films of sBPDA–ODA/PDA copolyimide, which had a 35% higher ultimate strength and a 64% higher elongation at break at the ambient temperature than the reference polyimide (sBPDA–PDA), and also retained the strength and exhibited a 200% higher elongation at a temperature of 200 °C.Unexpectedly, the elongation at break of PMDA–ODA based (co)polyimide nanocomposites with hydrophobic SiO₂ nanoparticles was greater than that of the baseline (co)polyimides. It was neither the case with PMDA–ODA nanocomposites with hydrophilic SiO₂ nanoparticles, nor with sBPDA–PDA (co)polyimide based nanocomposites with hydrophobic SiO₂ nanoparticles.     

Synthesis, crystal structure and thermal decomposition of a new copper propionate [Cu(CH3CH2COO)2]·2H2O

A new copper propionate complex was synthesised and characterized for application as precursor for CuO based oxide thin films deposition. The FT-IR and X-ray diffraction analyses have revealed the formation of a cooper propionate complex [Cu(CH₃CH₂COO)₂]·2H₂O. The crystal and molecular structure of a new copper propionate complex was determined by XRD on the copper propionate single crystal. The copper propionate complex has a binuclear structure, connected by bridging bidentate carboxylates groups and a Cu?Cu bond of 2.6 Å. The thermal decomposition of copper propionate has been investigated by thermal analysis using thermogravimetric (TG) and differential thermal analysis (DTA), differential thermal analysis coupled with quadrupole mass spectrometry-QMS, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) techniques. TG and XRD data indicate the reduction of Cu(II)-Cu(I,0) during the decomposition of copper propionate.     

Probing the Nature of Zinc in Copper-Zinc-Zirconium Catalysts by Operando Spectroscopies for CO2 Hydrogenation to Methanol

Active Zn species in Cu-based methanol synthesis catalysts have not been clearly identified yet due to their complex nature and dynamic structural changes during reactions. Herein, atomically dispersed Zn on ZrO₂ support is established in Cu-based catalysts by separating Zn and Zr components from Cu (Cu−ZnZr) via the double-nozzle flame spray pyrolysis (DFSP) method. It exhibits superiority in methanol selectivity and yield compared to those with Cu−ZnO interface and isolated ZnO nanoparticles. Operando X-ray absorption spectroscopy (XAS) reveals that the atomically dispersed Zn species are induced during the reaction due to the strengthened Zn−Zr interaction. They can suppress formate decomposition to CO and decrease the H₂ dissociation energy, shifting the reaction to methanol production. This work enlightens the rational design of unique Zn species by regulating coordination environments and offers a new perspective for exploring complex interactions in multi-component catalysts.     

The thermal dehydration and decomposition of Ba[Cu(C2O4)2(H2O)]·5H2O

The thermal behaviour of Ba[Cu(C₂O₄)₂(H₂O)]·5H₂O in N₂ and in O₂ has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The enthalpy for the dehydration was found to be 311±30 kJ mol^–1 (or 52±5 kJ (mol of H₂O)^–1). The overall enthalpy change for the decomposition of Ba[Cu(C₂O₄)₂] in N₂ was estimated from the combined area of the peaks of the DSC curve as –347 kJ mol^–1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly deceleratory and the -time curves could be described by the three dimensional diffusion (D3) model. The values of the activation energy and the pre-exponential factor for the dehydration were 125±4 kJ mol^–1 and (1.38±0.08)×10¹⁵ min^–1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.The values ofE _a andA were 206±23 kJ mol^–1 and (2.2±0.5)×10¹⁹ min^–1, respectively, for the fast process, and 259±37 kJ mol^–1 and (6.3±1.8)×10²³ min^–1, respectively, for the slow process.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Structure and infrared emissivity of silicon-containing polyimide/BaTiO3 nanocomposite films

Silicon-containing polyimide/BaTiO₃ nanocomposite films were prepared by the direct mixing of silicon-containing polyamic acid and BaTiO₃ nanoparticles under ultrasonic wave irradiation, followed with thermal imidization. Structure and thermal properties were measured with FTIR, XPS, SEM, DSC and TGA. The results showed that the compatibility of BaTiO₃ and a polyimide might be improved by the introduction of dimethylsilylene groups into the backbone of a polyimide; and BaTiO₃ nanoparticles in the nanocomposites tended to form clusters. The clusters coalesced into a more uniform structure at a higher BaTiO₃ filling than at a lower one.The interfacial interaction between BaTiO₃ and the silicon-containing polyimide resulted in the increase of the glass transition and the thermal decomposition temperature. It was found that the nanocomposites exhibited lower infrared emissivity value than the pure polyimide and the magnitude of infrared emissivity value was related to the content of BaTiO₃ in the nanocomposites.     

In situ sol–gel fabrication of new poly(amide–ether–imide)/titania (TiO<Subscript>2</Subscript>) nanocomposite thin films containing <Emphasis Type="SmallCaps">l</Emphasis>-leucine moieties

In this study, the synthesis, morphology, and thermal properties of amino acid containing polyimide/titania nanohybrid films are investigated. At first, a chiral diamine containing l-leucine moieties in the structure (synthesized previously) was polymerized with 4,4′-oxydiphthalic anhydride in extremely dry conditions. Resulted poly(amic acid) (PAA) was mixed with a moisture-sensitive titania precursor (tetraethyl orthotitanate [Ti(OEt)₄]) and casted to a dust-free glass plate. The water derived from thermal imidization of PAA hydrolyzed Ti(OEt)₄ to titania nanoparticles with almost spherical shapes. The thermogravimetric analysis of various nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. The transmission electron microscopy of nanohybrid films with 3%, 5%, and 10% w/w of titania contents confirms well dispersion of nanoparticles in the polymer ground. The X-ray diffraction spectra showed that the titania contents have amorphous structure.     

Solvent-Free Synthesis of ZnO Nanoparticles by a Simple Thermal Decomposition Method

This paper reports on a novel processing route for producing ZnO nanoparticles by solid-state thermal decomposition of zinc(II) acetate nanostructures obtained by the sublimation of zinc(II) acetate powder. The sublimation process of the Zn(OAc)₂ powder was carried out in the temperature 150 °C for 2 h. In addition, nanoparticles of ZnO were obtained by solid-state thermal decomposition of the synthesized Zn(OAc)₂ nanostructures. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy. The sublimation process of the Zn(OAc)₂ powder was carried out within the range of 150–180 °C. The XRD studies indicated the production of pure hexagonal ZnO nanoparticles after thermal decomposition.