聚酰亚胺无机纳米杂化材料

聚酰亚胺(PI)作为一种功能材料，具有良好的介电性、优良力学性能，已被广泛应用于航空航天及微电子领域，但其明显的吸水性和热膨胀性限制了其在高温和精密状态下的应用。无机纳米材料具有很低的热膨胀系数和较低的吸水性，非常适合于对PI的改性。本文阐述了PI纳米杂化材料的制备方法。概要介绍了PI纳米杂化材料的类型、特点、性能及应用领域，并对这类材料的发展前景进行了综述。     

One-step fabrication of ultralow dielectric polyimide films consisting of size-controlled mesoporous nanoparticles

Dielectric materials with ultralow dielectric constants (<2.0) are desiderated in the integrated circuits (ICs). In this work, we fabricated polyimide (PI) films consisting of mesoporous nanoparticles (MPNPs-PF) through a one-step solvent evaporation induced self-assembly method. Poly(amic acid) was selected as the polymer matrix; and the commercial triblock copolymer F127 was adopted as the mesoporous template as well as the nanoparticle morphology controller, respectively. After imidization and template removal, the dense films consisting of closed-packed PI nanoparticles with an average diameter less than 50 nm were obtained. Since the nanoparticles were fully composed of worm-like mesopores, the dielectric constant (k value) of the resultant porous PI films can reach as low as 1.92. When the reactive end-capper of maleic anhydride (MA) was blended into poly(amic acid), k value decreased even lower to 1.86. Meanwhile, the modulus of the resultant porous PI films was higher than 1 GPa.     

Structural and dielectric properties of POSS reinforced polyimide nanocomposites

In this study, a series of [3-(2-aminoethyl)amino]propyl-heptaisobutyl substituted polyhedral oligomeric silsesquioxane (AHIP) containing polyimide (PI) nanocomposites were successfully prepared. Structural, thermal and electrical properties of the polyimide nanocomposites were studied. The properties of AHIP containing polyimides were compared with those of the neat polyimide films. The surface morphology of the prepared AHIP containing polyimides were determined by using Scanning Electron Microscopy (SEM). The hydrophilic/hydrophobic nature of AHIP/polyimide composites were analyzed by measuring their water contact angles. It was found that the addition of AHIP into the polyimide slightly increased the contact angle values. The incorporation of 5% AHIP to the PI matrix decreased the dielectric constant value of pure PI from 8.6 to 11.7, respectively. Furthermore he dielectric permittivity was changed from 8.6 (neat polyimide) to 5.5 (PI3).     

New poly(ether-imide)/MWCNT nanocomposite

New polyimide (PI) nanocomposites containing two different amounts of MWCNT (PI/MWCNT) were prepared via in situ polymerization technique. Transmission electron microscopy showed that MWCNT was exfoliated in the polymer matrix, resulting in well-dispersed morphologies at 1 and 3 mass% MWCNT contents. The effects of multiwalled carbon nanotubes (MWCNT) on the thermal and flammability properties of new PI derived from 1,3-bis[4,4′-aminophenoxy]propane and biphenyl dianhydride were investigated by thermogravimetric analysis (TG) in nitrogen and air atmosphere, differential scanning calorimetry, and microscale combustion calorimeter (MCC). The PI/MWCNT nanocomposites were electrically conductive with maximum conductivity obtained at 3 mass% MWCNT, which is favorable for many potential applications. TG results showed that the addition of MWCNT resulted in a substantial increase of the thermal stability and char yields of the nanocomposites compared to those of the neat PI. Flame retardancy of the nanocomposites was significantly improved in the presence of MWCNT.     

一种半晶性联苯酯侧基聚酰亚胺

聚酰亚胺作为一种高强度、高模量、耐热性材料正越来越广泛地得到应用．但是，因其刚性或半刚性的分子链，以及分子之间强烈的相互作用，使其熔融温度很高(很多高于其分解温度)，并且不溶解于大多数有机溶剂，这为成型加工带来困难．在聚酰亚胺大分子主链上引入侧链或侧基，     

Simultaneous Preparation of PI/POSS Semi‐IPN Nanocomposites

Summary: This investigation presents a simultaneous and convenient approach to produce a high‐performance polyimide with a low dielectric constant by introducing the octa‐acrylated polyhedral oligomeric silsesquioxane (methacrylated‐POSS) into a polyimide matrix to form polyimide semi‐interpenetrating polymer network (semi‐IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) results indicate that the self‐curing of methacrylated‐POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi‐IPN structure of polyimide/POSS‐PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50–60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly cross‐linked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer‐scale porous structure of POSS.

FT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS.     

Synthesis,morphology, and properties of hydroxyl terminated‐POSS/polyimide low‐k nanocomposite films

Polyhedral oligomeric silsequioxane (POSS), having eight hydroxyl groups for the preparation of nanocomposites with polyimide (PI) was synthesized by the direct hydrosilylation of allyl alcohol with octasilsesquioxane (Q₈M₈^H) with platinum divinyltetramethyl disiloxane Pt(dvs) as a catalyst. The structure of allyl alcohol terminated‐POSS (POSS‐OH) was confirmed by FTIR, NMR, and XRD. A high performance, low‐k PI nanocomposite from pyromellitic dianhydride (PMDA)‐4,4'‐oxydianiline (ODA) polyamic acid cured with POSS‐OH was also successfully synthesized. The incorporation of POSS‐OH into PI matrix reduced dielectric constant of PI without loosing mechanical properties. Furthermore, the effects of POSS‐OH on the morphology and properties of the PI/POSS‐OH nanocomposites were investigated using UV–vis, FTIR, XRD, SEM, AFM, transmission electron microscope (TEM), TGA, and contact angle. The homogeneous dispersion of POSS particles was confirmed by SEM, AFM, and TEM. The nanoindentation showed that the modulus increased upon increasing the concentration of POSS‐OH in PI, whereas the hardness did not increase very much with respect to loading of POSS, due to soft‐interphase around POSS molecules in the resulting nanocomposites. Overall results demonstrated the nanometer‐level integration of the polymer and POSS‐OH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5887–5896, 2008     

Spectral characterization of apatite formation on poly(2-hydroxyethylmethacrylate)-TiO2 nanocomposite film prepared by sol-gel process

Poly(2-hydroxyethylmethacrylate) films incorporated with titanium dioxide nanoparticles were successfully synthesized by an in situ sol-gel process. The in vitro bioactive properties of the films were assessed after immersion in simulated body fluid for up to 21 days through biomimetic method. Hydroxyapatite formation was observed on the surfaces of nanocomposites. This indicates that prepared composites are bioactive. Fourier transforms infrared spectroscopy, X-ray diffraction patterns, X-ray photoelectron spectroscopy and scanning electron microscope images confirm the hydroxyapatite formation on nanocomposite. The present study provides an analytical method for the assessment of titanium dioxide nanoparticles filled poly(2-hydroxyethylmethacrylate) polymer nanocomposites for biomedical applications.     

通过掺杂柔性二胺单体增强聚酰亚胺性能:分子动力学模拟

聚酰亚胺(PI)被视为一类以其卓越性能而闻名的高性能聚合物材料。传统聚酰亚胺的一个关键问题是其熔体的加工性能较差。在本研究中,设计了一种新的聚酰亚胺单体Am-Di,其特点是由氮原子连接的苯环组成的柔性结构。通过详尽的研究,我们对Am-Di掺杂到聚酰亚胺中对其玻璃化转变温度、均方位移、力学性能和相对介电常数等性质的影响进行了深入探讨。结果表明,在聚酰亚胺体系中,掺杂新型二胺可以加速聚酰亚胺分子链的运动,从而降低聚酰亚胺体系的玻璃化转变温度。在Am-Di掺杂量为20%的情况下,PI-20%表现出最高的弹性模量(4.505Gpa),比纯PI高1.2倍。此外,随着掺杂比例的增加,聚酰亚胺的相对介电常数降低。这些发现表明,Am-Di的掺杂对聚酰亚胺材料的性能具有积极影响,特别是在增强机械性能和调控电气性能方面,为进一步改进聚酰亚胺材料的设计和应用提供了有价值的见解。     

Preparation of Meldrum's acid-functionalized polyimides exhibiting organo-soluble,reactive, self-crosslinkable,and colorless features

Functional polyimides (PIs) having some desired properties, for example, organo-solubility, chemical reactivity, crosslinkable feature, and high transparency in visible region, are attractive for specific applications. This work reports an effort to integrate the above-mentioned properties in one polyimide through introduction of Meldrum's acid (MA) moieties to polyimide chains with using a MA-containing diamine (MADA) as a monomer. The polyimide prepared with MADA and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (PI[MADA-6FDA]) has a number-averaged molecular weight of 56,800 g mol⁻¹, shows good solubility in tetrahydrofuran and aprotic high polar solvents, and exhibits post-reactivity/crosslinkability through MA-mediated ketene chemistry. Crosslinked PI(MADA-6FDA) film shows a glass transition temperature of 289°C, a dielectric constant of about 2.78, and high flexibility bearing a near-180° bending. The MA-mediated ketene chemistry contributes to in situ building up covalent linkages between PI chains and silica nanoparticles (SNPs) in preparation of PI/SNPs nanocomposite films (NCF). Formation of the PI/SNPs NCFs enhances the thermal and mechanical properties, reduces the dielectric constants, and increases the transparency. The properties of the MA-functionalized PI are attractive for further studies on their applications.     

Dual capacitor technique for measurement of through‐plane modulus of thin polymer films

Polymer thin films are widely used as coatings and interlevel dielectrics in microelectronic applications. In thin‐film structures, stresses are generated due to interaction with adjacent layers and film shrinkage due to solvent evaporation or curing. This causes polymer chain orientation resulting in anisotropic (direction dependent) film properties. The dual capacitor technique has been developed to measure in situ, the through‐plane (z) stress‐strain behavior of thin polymer films. A parallel plate capacitor device and an interdigitated electrode structure were used as sensors to detect changes in dielectric permittivity and thickness of thin polymer films under compression. The analytical and finite element models used to interpret the capacitance measurements have been presented. The Clausius–Mossotti equation was used to determine the volume change in the film from the permittivity measurements. Results have been reported for 10–14 μm thick, Cyclotene 4026‐46 benzocyclobutene films and 10–12 μm thick films of polyimide PI‐2611. The Cyclotene 4026‐46 films were found to be mechanically isotropic, whereas the PI‐2611 films were highly anisotropic. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1634–1644, 2000     

Octahedral oligomeric silsesquioxane (OAPS and OG) - Polyimide hybrid nanocomposite films: Thermo-mechanical,dielectric and morphology properties

Abstract

The nano-sized SQS based polyimides have been successfully synthesized with different oxide groups such as phosphineoxide, sulfone and siloxane as in the backbone of polymer. The SQS-Polyimide nanocomposites prepared through the condensation process using amine and epoxy functionalized SQS as precursor. The presence of SQS in the resulting polyimide nanocomposites was confirmed by FTIR and XRD analyses. The presence of SQS and greatly enhances the char yield to an extent of 16% when compared to that of neat polyimide. The incorporation of SQS into polyimide lowered the value of dielectric constant from 3.31 to 2.09 at 1?MHz and the value of thermal expansion coefficient from 56.6 to 42.7?ppm/K. The composites sample prepared using 20?wt% SQS possess the lowest value of dielectric constant and CTE value. The hydrophobic nature of SQS contributes to lower the water uptake of composites from a value of 2.76 (neat polyimide) to 2.42 for POS-PI containing 20?wt% SQS. Further, the SQS polyimide composite systems possess the enhanced values of thermal stability and glass transition temperatures according their percentage weight. Data obtained from different studies, it is suggested that these hybrid composites can be used as an effective insulation materials for high performance microelectronics applications.     

Poly(ether‐imide) and related sepiolite nanocomposites: investigation of physical,thermal, and mechanical properties

Novel poly(ether‐imide) and sepiolite nanocomposites were synthesized based on a unique diamine monomer with the aim of improving physical and mechanical properties of final polyimide films. The diamine was polycondensed with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride to produce related poly(ether amic acid) prepolymer. Pure poly(ether‐imide) and nanocomposite films were prepared via thermal imidization process of poly(ether amic acid). Coexistence of ether, pyridine, and phenylene functional groups in the diamine chemical structure resulted in flexible polyimide films with significant thermal, physical, and mechanical properties. Thermal stability, glass‐transition temperature, dimensional stability, and tensile properties of polymer and nanocomposites were studied and compared. Morphology of nanocomposites was also investigated using scanning and transmission electron microscopic methods to study the distribution and dispersion behavior of sepiolite nanofibers in the polyimide matrix. By introduction of sepiolite nanoparticles, overall improvement of properties was observed in respect to pure polyimides. Copyright © 2015 John Wiley & Sons, Ltd.     

Comparative study of particle size analysis of hydroxyapatite-based nanomaterials

The purpose of this work was to compare hydroxyapatite (HAP) and composites of HAP, HAP with chitosan (CS), and HAP with poly(vinyl pyrrolidone) (PVP), in terms of their particle size and morphology, using different methods, such as Coulter counter analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Although many researchers have studied HAP and CS/HAP and PVP/HAP composites extensively, there is no evidence of a comparative study of their particle sizes. For this reason, different complementary methods have been used so as to provide a more complete image of final product properties — particle size — from the perspective of possible applications. The syntheses of HAP and HAP with polymer nanoparticles were carried out employing a precipitation method. Variation in particle size with synthesis time and influence of the reactants’ concentration on the materials’ preparation were systematically explored. Crystallite size calculated from XRD data revealed nanosized particles of HAP, CS/HAP, and PVP/HAP materials in the range of 2.5–9.2 nm. Coulter counter analysis revealed mean particle sizes of one thousand orders of magnitude larger, confirming that this technique measures agglomerates, not individual particles. In addition, the particles’ morphology and an assessment of their binding mode were completed by TEM measurements.     

(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.     

Magneto-responsive nanocomposites: Preparation and integration of magnetic nanoparticles into films,capsules, and gels

This review reports on the latest developments in the field of magnetic nanocomposites, with a special focus on the potentials introduced by the incorporation of magnetic nanoparticles into polymer and supramolecular matrices. The general notions and the state of the art of nanocomposite materials are summarized and the results reported in the literature over the last decade on magnetically responsive films, capsules and gels are reviewed. The most promising concepts that have inspired the design of magneto-responsive nanocomposites are illustrated through remarkable examples where the integration of magnetic nanoparticles into organic architectures has successfully taken to the development of responsive multifunctional materials.     

Nanoparticle Dispersion and Glass Transition Behavior of Polyimide-grafted Silica Nanocomposites

How to control the spatial distribution of nanoparticles to meet different performance requirements is a constant challenge in the field of polymer nanocomposites.Current studies have been focused on the flexible polymer chain systems.In this study,the rigid polyimide(PI) chain grafted silica particles with different grafting chain lengths and grafting densities were prepared by "grafting to" method,and the influence of polymerization degree of grafted chains(N),matrix chains(P),and grafting density(a) on the spatial distribution of nanoparticles in the PI matrix was explored.The glass transition temperature(Tg) of PI composites was systematically investigated as well.The results show that silica particles are well dispersed in polyamic acid composite systems,while aggregation and small clusters appear in PI nanocomposites after thermal imidization.Besides,the particle size has no impact on the spatial distribution of nanoparticles.When σ·N0.5<<(N/P)2,the grafted and matrix chains interpenetrate,and the frictional resistance of the segment increases,resulting in restricted relaxation kinetics and Tg increase of the PI composite system.In addition,smaller particle size and longer grafted chains are beneficial to improving Tg of composites These results are all propitious to complete the microstructure control theory of nanocomposites and make a theoretical foundation for the high performance and multi-function of PI nanocomposites.     

Hydrolytic Stability of Films of Aromatic Polyimides and Composites on Their Basis,Filled with Carbon Nanocones

Variation of the mechanical and thermal characteristics of poly(4,4′-oxydiphenylenepyromellitimide) and poly{1,3-bis(3′,4-dicarboxyphenoxy)benzene [4,4′-bis)4′-N-phenoxydiphenylsulfone]imide} films and nanocomposites based on these polyimides and filled by carbon nanocones/disks in the course of hydrolysis in an alkaline solutions was studied. The goal of the study was to obtain systematic information about the influence exerted by carbon nanoparticles introduced into polyimide films with varied chemical structure on the stability of the resulting film materials against a prolonged action of active hydrolyzing media. It was shown that the hydrolytic stability of the materials under study is largely determined by the molecular packing density. Introduction of nanoparticles into the polymers under study may result in that the concentration in the material of the excess free volume localized at polymer–filler interfaces increases. This, in turn, causes a decrease in the hydrolytic stability of the nanocomposite film as compared with unfilled films of the matrix polyimide. The opportunity was considered of raising the hydrolytic stability of the polyimide and nanocomposite material by making higher the average packing density.     

Carbon nanocones/discs – a new type of filler to improve the thermal and mechanical properties of polymer films

The mechanical characteristics and thermal properties of composite films based on the thermally stable aromatic polyimide (PI) (PMDA‐ODA) and carbon nanocones/discs (CNC) were studied. The introduction of CNC to PMDA‐ODA leads to the substantial increase of film stiffness. The Young's modulus values of the composite films are somewhat higher than those of the previously characterized composite films of this PI filled with nanoclay, carbon nanofibers, and asbestos‐like hydrosilicate nanotubes. The introduction of CNC into PMDA‐ODA (concentrations of CNC were up to 15 vol%) does not cause any marked aggregation of nanoparticles. The presence of CNC in the PI matrix does not affect the glass transition temperature of the polymer but hinders chain mobility at temperatures above T_g. This behavior makes it possible to increase the working temperature range of the composite films containing more than 5 vol% of CNCs, up to the temperature of thermal decomposition. The introduction of CNC into PMDA‐ODA leads to dramatic (～12 orders of magnitude) increase of active electrical conductivity of the material. Copyright © 2011 John Wiley & Sons, Ltd.     

High modulus polyimide/polyimide molecular composite films that utilize acetylene unit as a crosslink site

Polyimide/polyimide molecular composite (MC) films comprised of a rigid polyimide derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) and a flexible polyimide derived from BPDA and bis (3,3'-diaminodiphenyl) acetylene (intA) and/or oxydianiline (ODA) were prepared by blending the polyamic acid solutions in 7 : 3 weight ratio, and then imidizing the blend films. Acetylene content in the flexible polyimide backbone was controlled by the ratio of intA and ODA. Cold-drawing of the blend polyamic acid films, followed by imidization, gives high modulus polyimide/polyimide MC films. The modulus of the MC films increased almost linearly with the draw ratio, reaching 25.5 GPa for the 40% drawn film. Acetylene groups in the flexible polyimide can be thermally cured to crosslink. The onset of exotherm appeared at 340°C on DSC, reaching maximum at 398°C. After the thermal crosslinking, the MC films maintained the high modulus, though elongation became small. Taking advantage of the crosslinkable acetylene units, two MC films were laminated and processed at 400°C for 20 min under 100 kg/cm² to give a good-quality laminate film. The interface of the two films was strongly bonded through the crosslinking of acetylene groups. Laminate films maintained the high modulus afforded by the cold-drawing. © 1994 John Wiley & Sons, Inc.