The following is a list of the abstracts for papers which will be presented in THE FOURTH INTERNATIONAL SYMPOSIUM ON POLYIMIDES AND OTHER HIGH TEMPERATURE POLYMERS: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS. The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
Department of Chemistry, College of Sciences, Shiraz University, Shiraz, 71454, IRAN
Synthesis and Properties of New Aromatic Polyimides Based on
2,2'-dibromo-4,4,5,5'-benzophenone Tetracarboxylic Dianhydride
New polyimides with enhanced thermal stability and high solubility were synthesized in common organic solvents from a new dianhydride, 2,2'-dibromo-4,4',5,5'-benzophenone tetracarboxylic dianhydride (DBBTDA). DBBTDA was used as monomer to synthesize polyimides by using various
aromatic diamines. The incorporation of 2,2'-disubstituted moieties into rigid-rod polyimides forces benzophenone rings into a highly non-coplanar conformation.The polymers were characterized by IR and NMR pectroscopy and elemental analysis. These polyimides had good inherent viscosities in N-methyl-2-pyrrolidinone (NMP) and also high solubility and excellent thermo-oxidative stability, with 5 % weight loss in the range 433 to 597 C.
Concepts of Textile Composites for Short- and Longterm Application under High Temperatures
An increasing demand for textile composites capable to withstand high temperature conditions not accessible to conventional products can be observed in modern machinery and transport systems. Reasons for this development have to be seen in increased processing speeds e.g. of continuous presses, which necessitate higher process temperatures of more than 200 °C, but also the wish to be able to transport very hot goods, which may cool down on the belt, without any effect on the textile.
The first case demands composites which are permanently temperature stable in all components, i.e. fabric(s) and coating(s) or alternatively carry permanently stable insulating layers on top of a (conventional) construction. The transport of very hot goods, which may cool down on the belt, demands composites which carry a short-term stable and insulating layer on top of a (conventional) construction.
The aim of the presented studies was to develop concepts of high temperature stable composites on the basis of conventional and low cost support fabrics, i.e. made of PET. A broad spectrum of different textile fabrics were characterized with regard to their potential to act as insulating layers by time-dependent measurements of the temperatures on ‚hot' and ‚cold' side of the fabrics. The samples were of varying textile construction and made of varying organic and inorganic fibers.
With constant surface temperatures of roughly 200 °C the heat up rate and the maximum ‚cold' side temperature were measured over long periods of time. Up to now, experimental results are in favor of fabrics made of inorganic fibers or combinations with high-performance polymers such as PEEK, respectively. A model for the physical description of the results with regard to thermal and textile parameters of the sample is being developed at present. Short-term stress with a dynamic temperature function was simulated by applying hot metal blocks on top of the sample. In these experiments the surface temperatures exceed 350 °C for a short time. Up to now, the available results indicate that ceramic layers (non-wovens) offer high insulating factors and no damage at the same time. Examples of composites to these concepts were manufactured in laboratory scale and were able to withstand the extreme thermal conditions.
Temperature Stability of Metal Films on Polyimide: Analysis by High Resolution RBS
Thin films of gold and chromium in the thickness range 5 to 50 nm were deposited on polyimide foils by evaporation at room temperature and subsequently heated up to 450° C. The thickness and structure of the metal films were analyzed during heating in situ by high-resolution Rutherford backscattering spectroscopy (HRBS). All metal films are very rough which is already known from literature. Au films thinner than 6 nm are thermally unstable: they decompose upon annealing. Thicker Au films are thermally stable. All Au films get increasingly covered by polyimide at higher temperatures which apparently diffuses to the sample surface along pores and grain boundaries. A buffer layer of chromium seems to inhibit this outdiffusion of polyimide, but the layers still remain rough.
The picture changes when a cold polyimide substrate is used. Au films deposited at -68° C are homogeneous in thickness, tight with respect to polyimide outdiffusion, and thermally stable.
Compatibilizing Effect of Maleated Polypropylene on the Properties and Morphology of Injection Molded Polypropylene/ Polyamide6,6 Nanoclay Nanoblends
Polymer blends based on Polyolefins and polyamides constitute materials of a great interest owing to their large range of properties and practical applications. However, due to the poor compatibility of the components, most of these systems are generally characterized by high interfacial tension, low degree of dispersion and poor mechanical properties.
It is generally accepted that PP and PA6,6 are not compatible and that blending of these materials results in poor properties. This compatibility can be improved by the addition of a Compatibilizer.
In this study, PP is first functionalized with Maleic Anhydride (MAH) in the presence of an optimized amount of Dicumyl Peroxide (DCP). The reaction was carried out in the molten state using an internal mixer.
Once the compatibilizer (PP-g-MAH) was prepared, it was mixed with PP in a single screw extruder. Various amounts (0-8 wt %) of treated and untreated nano-clay were added to 70/30 PP/PA 6,6 blends into an internal mixer. The resulting nanoblends will be characterised in terms of rheological, thermal, morphological and mechanical properties.
Thuy D. Dang2
1. University of Dayton Research Institute, 300 College Park Drive Dayton OH 45469
2. AFRL/MLBP, Materials Directorate, 2941 Hobson Way, Bldg. 654, Wright-Patterson Air Force Base, OH 45433
3. AFRL/PRPS, Propulsion Directorate, 1950 5th street, Bldg.18, Wright-Patterson Air Force Base, OH 45433
Highly Sulfonated Polyarylenethioethersulfones As PEMs For Fuel cells: Synthesis, Characterization and Performance
Highly sulfonated polyarylenethioethersulfones (SPTES) in a wide range of compositions and with bulky organic endgroups, were synthesized from 3,3'-disulfonated-4,4'-difluorodiphenylsulfone (or the corresponding dichloro monomer) , 4,4'-difluorodiphenylsulfone and 4,4'-thiobisbenzenethiol via a base-catalyzed nucleophilic displacement reaction in polar aprotic solvents. All the polymers were of high molecular weight as evidenced by solution viscosity and GPC measurements and could be solvent cast into tough, ductile, free-standing films for the measurement of proton conductivity.. The proton conductivities of the PEMs, evaluated by a standard four-electrode measurement setup, ranged from 100 mS/cm to 300 mS/cm for the composition ranging from SPTES-50 to SPTES-100. The highest measured proton conductivity was at least three times higher than that of Nafion-117 membrane under comparable conditions (65C, 85 % relative humidity). The proton conductivities of the SPTES homo- and copolymers correlated very well with their ion exchange capacity (IEC) and water uptake. A preliminary comparison of the performances of Membrane Electrode Assemblies (MEAs) fabricated from SPTES-50 and Nafion-117, at 80C and 55 % relative humidity, demonstrated that a peak power density twice that of Nafion-117 was obtained for the SPTES copolymer membrane (0.34 W/cm2 @ 0.6 amp/cm2 for the SPTES membrane and 0.17 W/cm2 @ 0.4 amp/cm2 for Nafion-117).
1) Sordal Inc. (Holland, Michigan USA)
2) Russian Academy of Sciences, Institute of Macromolecular Compounds
Very Low Density Polyimide Foam Incorporating Nanostructure Technologies
Under a grant from the US Civil Research & Development Foundation (Washington, DC) Sordal Incorporated and the Russian Academy of Sciences, a.k.a. RAS, (St. Petersburg, Russia) are developing new approaches to synthesize classical monomers and nano-technologies into polyimide foams.
Since the discovery of carbon nanotubes (CNT) by Iijima¹, intense interest has been generated in utilizing their remarkable mechanical properties for structural and materials applications. With a tensile strength fifty times that of stainless steel (100 GPa vs. 2 GPa) and with a thermal conductivity five times that of copper, CNTs are obvious choices for creating a new class of composite materials. Sordal-RAS propose the incorporation of CNT into polymeric materials to improve the mechanical properties of polymer composites significantly; thereby expanding their use in structural applications usually afforded only to more robust materials. It has been shown that nanotubes will increase the conductivity of the polyimides to a surface resistivity of 106 to 1010 /square at relatively low loading levels (~0.02% w/w). With the incorporation of only small amounts of CNT, the desired level of electrical conductivity can be achieved without drastically effecting optical transparency, solar absorptivity, k-value or flexibility.
There are a number of methods to disperse CNTs into polymer systems such as the use of surfactants, noncovalent functionalization, and chemical functionalization. Although these techniques are effective at dispersing CNTs to some extent, they have certain limitations and can result in changing physical properties. To this end, Sordal-RAS researchers will chemically modify carbon nanotubes by attaching them to 3, 4-ODA (the diamine monomer of polyimide foam). This will allow the CNTs to be incorporated into the base formulation in a controlled manner.
¹ Dr. Sumio Iijima, Japan, discovered carbon nanotubes in 1991.
1) Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoy pr.V.O. 31, 199004 St.-Petersburg, Russia;
E-mail: xelmic@ imc.macro.ru
2) Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic,V.Holesovickach 41, 18209 Prague 8, Czech Republic;
3) Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, Bolshoy pr.V.O. 61, 199178 St.-Petersburg, Russia;
Polyimide's Binders for Carbon-carbon Composites with Turbostratic Structure
Polyimide binders ITA and ITA-PM (Fig.1) were synthersized at the Institute of Macromolecular Compounds RAS by transacylation of diacetylic derivatives of aromatic diamines by bis-phthalic anhydrides of tetracarboxylic acids. These polyimides with addition of pitch were used as precursor for carbon-carbon (C/C) composites. Structure, mechanical and tribological properties of these carbon plastics and C/C composites were investigated. It was shown that after graphitization at 2200oC/1h the turbostratic structure appeared in C/C composite based on ITA-PM. The low weight loss during carbonization makes it possible to obtain C/C composites based on ITA-PM matrix with addition of 40% pitch. Carbon yield of this type of composites was about 84%, whereas for composites based on ITA, carbon yield was about 70%. It results in improvement of tribological properties and increasing of crack resistance of composites. Such kind of materials is of potential interest for high temperature applications and biomedical purposes.
FIG.1 Chemical structure of ITA-PM
Block Copolyimides soluble in Organic Solvents - Preparation, Catalysis and Properties
(Abstract not yet available)
Different Behaviors in Preparation Processes Between Soluble Block Copolyimides Containing PMDA and Other Tetracarboxylic Dianhydrides
(Abstract not yet available)
Industrial application of Screen Printing Block Copolyimides Ink, Screen Printing Block Copolyimides Photo-imageable Polyimide Ink and Aqueous Electrodeposition Polyimide Solutions
In recent years, digital devices have rapidly become smaller and more sophisticated. This trend is expected to continue to accelerate in future, so that the printed wiring boards that are mounted with electronic components are required to have higher density and more layers. Flexible printed circuitry was originally designed as a replacement for traditional cabling in point-to-point interconnects. It offers the advantages of increased reliability, greater impedance control, weight and space savings, and a reduction in mechanical connectors. Flexible circuit is an array of conductors bonded to a thin dielectric polyimide film. In all applications using flexible circuits, the circuit is designed and engineered specifically for the intended application, thus minimizing Efficiency in both cost and performance. In response to these requirements, PI R&D has developed a screen printing polyimide ink, a screen printing photo-imageable polyimide ink and an aqueous electrodeposition polyimide solution used for coverlay coating of printed circuit board with all-layer flexible wiring essential for lighter weight, reduced volume, durability and environmental resistance. Photo-imageable polyimide ink for coverlay and build-up applications will combine the strengths of polyimide with the resolution needed for today's higher density circuits into next generation FPC features: "Thin & Light weight" "Good flexibility" "Connecting reliability" "Design freedom" with this kind of special structure. Our developed polyimide products also offer low cure temperature, resulting in significant process simplification and manufacturing cost reduction of flexible print circuit board industry.
Recently Developed Applications of Polyimides: Photoelectro Devices, electro Deposition, Superconducting Tunnel Junction Devices and Polyimide Film dispersed Carbon Nanotubes
(Abstract not yet available)
Synthesis of Novel Polypyromellitimides and Their Liquid Crystal Aligning Properties
In our laboratory a continued endeavor has been devoted to develop new polypyromellitimides with flexible side chains at 3,6-positions of the pyromellitic ring. The synthesis of a series of new polypyromellitimides has been successful by appropriately implementing nucleophilic substitution reactions and Suzuki coupling reaction, even though the reactions are basically difficult because the number of hydrogen atoms to substitute is only two in a pyromellitic dianhydride ring. All the new polypyromellitimides exhibited remarkably enhanced pretilt angles when 4-cyano-4'-n-pentylbiphenyl molecules are aligned on their rubbed surfaces.
A Novel Approach for Synthesizing Pyridine Containing Poly(imide-siloxane) Copolymers and Their Characterizations
A series pyridine containing poly(imide-siloxane) copolymers were synthesized from 2,6-diaminopyridine (DAP), ,'-aminopropylpoly(dimethylsiloxane) (PDMS), 1,3-bis(4-aminophenoxy)benzene (APB), and 4,4'-oxydiphthalic dianhydride (ODPA). According to our previous study, the pyridine improves the adhesion between polyimide films and copper significantly and the molar fraction of DAP in diamine was fixed at 1/7. In this series, the content of PDMS varied from 0 to 15wt% in diamine with multiple segment lengths. Because the reactivities of DAP and PDMS were not as good as APB, a new synthesizing approach was developed in this study. The content of DAP and PDMS in poly(imide-siloxane)s using this novel synthesizing approach was much higher than it obtained by conventional synthesizing method. The structure of copolymers was verified by Fourier Transform Infrared (FT-IR) and Nuclear Magnetic Resonance (NMR). Their thermal degradation temperatures with respect to 5% weight loss all exceeded 500oC. The adding of DAP would raise the glass transition temperature (Tg) of copolymers because of the rigidity of pyridine, however, the flexible PDMS segment would lead the Tg of poly(imide-siloxane) to a lower value. The Tg of copolymers increased with increasing the content and segment length of PDMS due to the increased rigid imide ring. Because the PDMS segment is unpolar, the incorporation of PDMS lowered the dielectric constant of copolymers. The surface resistivity of films declined as PDMS segment increased due to the unpolar PDMS segment segregated to the surface of films. The poly(imide-siloxane) copolymers adhered to copper foil at 350oC under 50Kgf/cm2 for 1min. The adhesion reached 1.5Kgf/cm as the PDMS content was 15wt% in diamine.
Formation of Carbon-Polyimide Hybrid Materials for High Performance Separations
Formation of new, higher performance, gas separation membranes will likely require the use of materials other than solution-processable polymers. Carbon molecular sieves (CMS), produced from the high-temperature pyrolysis of high-performance polyimides, have separation potential that exceeds that of polymers. These properties result from a nano-scale pore size distribution which is sensitive to several key processing parameters; therefore, CMS materials can be tailored for use in a variety of separations. Unfortunately, CMS materials lack the physical resilience necessary for large scale membrane application. A hybrid system containing submicron sieves dispersed in a properly selected polyimide matrix could provide a membrane with significantly improved separation ability (from the sieves) while maintaining the needed mechanical properties (of the polymer). This paper will discuss two topics: 1) controlled production of CMS membranes for a variety of gas separations and 2) formation of advanced gas separation membranes based on hybrid materials that exceed the performance capabilities currently available in polymeric membranes. Altering the surface of the CMS particles to control the interfacial region between CMS and polymer appears to be the most important factor in the successful implementation of this technology. Systematic analysis of the impact of various processing parameters will be considered.
1) Leibniz-Institute for New Materials, Im Stadtwald, Geb. 43 A, 66123
2) Akdeniz Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü, 07058 ANTALYA
Polyimide Nanocomposites Coating Materials with Special Functions
A new type of polyimide has been synthesized, having a high abrasion resistance as well as a low surface free energy. The abrasion resistance was obtained by fillers combining nano and sub-µm ceramic particles and the imide structure by reacting amino grouping containing aromatic monomers with anhydrides and subsequent temperature treatment. The low surface free energy (hydrophobic and oleophobic properties at the same time) was obtained by copolymerizing hydroxyl group containing fluoro oligomers during the overall reaction. Coatings prepared from these systems show contact angles of 110 to 120° against water and 60 to 70° against hexadecane. It is remarkable that the contact angles change only slightly even after 1000 cycles taber abrader test.
High Thermostable Polyethersulfimides Prepared by Polycondensation of Diethersulfimides with (1,3-dimethyl- 4,6)- and 1,4- Dichloromethylbenzenes
(Abstract not yet available)
Synthesis of Chlorinated Tri- and Tetracyclic Polyimide Ethers with Given Spatial Structure
(Abstract not yet available)
Development of Ultra High Temperature Polymers
(Abstract not yet available)
Covalent Molecular Assembly: Pathway to Robust Structures
A wide range of new materials for many applications can be formed by controlling the composition and order of constituents at the molecular level. For organic/polymeric systems thus engineered, ensuring chemical, thermal and mechanical robustness is a major challenge. Consequently, polyimides and imide-containing moieties are therefore attractive as matrices for functional materials.
We are investigating the construction of functional nanostructures in organic/polymeric matrices with clearly demonstrated chemical, thermal and mechanical stability. Surface functionalisation, layer-by-layer assembly in various media (including supercritical), incorporation of functional moieties including nanoparticles, dendrimeric and electro/opto-active components, molecular orientation and interfacial reactions are areas of interest.
We have demonstrated the robustness of ultrathin film structures containing polyimides and oligoimides formed by layer-by-layer (LbL) molecular assembly with inter-layer covalent links. Functionality has been bestowed to such structures in the form of electro-activity (with polythiophene as a constituent), nano-porosity (with dendrimeric components) and by embedding nanoparticles in molecularly assembled polymeric matrices. Covalent bonding between the layers provides strength while utilization of a supercritical medium for processing results in the deployment of a solvent-free environment and avoids problems related to residual solvent, thereby improving film quality when compared to conventional films.
1) Institute of Electrical Engineering of Technical University of Szczecin Sikorskiego 37, Szczecin 70-313, Poland
2) Vavilov State Optical Institute, St. Petersburg, 199034, Russia
Dielectrical Spectroscopy of Polyimide Films Doped by Fullerene
The results of investigation of dielectric characteristics of aromatic polyimides doped by fullerene are discussed. The tests were carried out for five types of polyimide foil samples, differing in either their chemical structure or the amounts of doped fullerene (0,1-2,0%).The measurements of frequency correlations between the dielectric loss factor and relative dielectric permitivity were taken for the temperature range from 160K up to 380K and the frequency range 100Hz up to 1MHz.The analysis of resulting data was performed using Novocontrol software. The frequence correlation of complex dielectric permitivity were approximated according to the Havriliak-Negami formula. The essential differences in relaxation were observed for the low frequency range and high temperature range. The influence of temperature and contens of fullerene on the time constants of relaxation and charge relaxation are discussed.
1) Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoy pr. 31, 199004 St.- Petersburg, RUSSIA
2) Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, ISRAEL
Liquid Crystalline Textures and Crystallization Morphology in Aromatic Bisimides and Their Blends with Semicrystalline Polyimide
This study introduces a novel crystallization behavior of low molecular weight bisimides (BIs), based on 4,4`-bis-(4`-aminoxy)biphenyl diamine and 1,3-bis(3`,4-dicarboxyphenoxy)benzene dianhydride and their blends with the semicrystalline polyimide (PI) of the related chemical structure. The supermolecular structure, morphology and phase transitions were examined by WAXD, SEM, DSC and hot stage polarized light microscopy. It was shown that in the process of thermal or chemical imidization, some BIs crystallize with the formation of various crystalline modifications while only one semicrystalline structure can form in the pure PI. During cooling from their isotropic melts, BIs and their blends with PI underwent a monotropic liquid crystalline (LC) transition to form a nematic-like phase or smectic-like phase followed by a transition to a more ordered crystalline structure at room temperature. Different LC textures can be formed in BIs, depending on the cooling rate. A pronounced acceleration of crystallization was observed within a wide temperature range whenever this was preceded by LC phase formation. Changes in the LC textures and in the morphology of the PI with the addition of BIs were observed
1) Department of Polymers, Institute of Chemical Technology,
166 28 Prague 6, CZECH REPUBLIC
2) Department of Physical Chemistry, Institute of Chemical Technology, 166 28 Prague 6, CZECH REPUBLIC
Transport Properties of Gases, Organic and Water Vapors Through Membranes Based on Polyimides
Separation processes employing polymeric membranes belong to a newer type of mass-separation techniques which have been applied in various technological processes. One of the most important research aim in this field is the preparation of the membrane-formable polymeric materials with an overall stability having a sufficient flux (permeability) and separation factor (selectivity). Some general aspects controlling the membrane transport properties will be presented. In our work the dense, flat membranes based on (modified) polyimides (copolymers, hybrids, crosslinked with elastomers, hyperbranched, enabling chemical bonds with (micro)porous fillers) were prepared. Their preparation and structure-property relationships, especially the transport characteristics of gases (namely nitrogen, oxygen, carbon dioxide), organic vapors (toluene, methanol, hexane) and water vapors, will be discussed.
This work was supported by the research programme MSM 6046137302 and by the Grant Agency of the Czech Republic through the grant No. 104/03/0680.
Water Sorption in Polysulfones: Water Solubility and Diffusivity
Taking into account their obvious practical and thoretical interest, structure-hydrophilicity relationships in polymers are studied but not yet elucidated. Our attention is focused on the structural serie of polysulfones (PSU,PPSU,PES) for which sorption isotherms have been recorded at temperatures from 50°C to 70°C using a Dynamic Vapor Sorption (DVS) apparatus. These isotherms are linear in the full activity range without any positive curvature showing cluster formation as it can be observed for some polymers. This means that the Henry law is applicable and the concepts of solubility S and heat of dissolution take sense. In fact Hs is an increasing function of the concentration of hydrophilic groups (sulfones). A possible explanation of this surprising dependence is that hydrophilic sites are composed of two close polar groups. A very simplified model based on these observations is proposed. Diffusion obeys Fick's law. In this structural serie of polysulfones diffusivity is a decreasing function of the water equilibrium concentration: the higher is the hydrophilicity, the slower is the diffusion. These results indicate clearly that the water/polymer interactions play a role in the diffusion. Moreover the diffusivity obeys Arrhenius law. The diffusion energy activation is put in relation with the heat of dissolution.
1) Department of Chemistry, College of William and Mary, Williamsburg, VA 23187
2) Advanced Materials and Processing Branch, Langley Research Center, NASA, Hampton, VA 23681
Single-stage Near-surface Silver Metallization of Fluorinated Polyimides Yielding Reflective Nanoparticulate Hybrid Membranes at Low Metal Concentrations
The synthesis of highly reflective flexible nanoparticulate polyimide films by a single-stage matrix mediated metallization process involving the (hexafluoroacetylacetonato)silver(I) complex dissolved in solutions of the poly(amic acid)s and polyimides which are formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropanedianhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy]hexafluoropropane (4-BDAF) as well as the poly(amic acids) of traditional non-fluorinated polyimide such as BTDA/ODA is described. Thermal treatment of cast silver(I)-poly(amic acid) films leads to cycloimidization of the amic acid with concomitant Ag(I) reduction and nano-aggregation into a monolayer of closely packed ca.60 nm spherical Ag particles very near (within nanometers of) the surface. The bulk also contains nanometer-sized Ag particles which are much smaller than those near the surface. Specularly reflective films for Ag concentrations at the low concentration of 2 wt% are realized, but the films are not electrically conductive. A 2% Ag 6FDA/4-BDAF film gives specular reflectivites from 70-80% relative to vapor deposited Ag. TEM and SEM measurements have been used to characterize the Ag particles. The formation and position of the near-surface silver layer will be analyzed in terms of the theory of Vincett and Kovacs. Several additional polyimides with 2% silver will also be discussed. Additional polyimide films with 2% silver will be discussed.
Synthesis, Properties And Application of Cycloaliphatic Polyimides
Film-forming cycloaliphatic polyimides have substantial advantages in comparison with aromatic analogues and are very prospective materials for the production of new devices and instruments of micro- and optoelectronics.
On the ground of systematic investigations of the reactivity of the row of dianhydrides of cycloaliphatic tetracarboxylic acids with aromatic diamines of different chemical structure there was developed a one-stage high-temperature synthesis of polyimides on the base of cyclopentane - and cyclohexanetetracarboxylic acids and the row of aromatic diamines in the medium of polar aprotonic solvents at the temperature of 180-190°C. There was studied an influence of monomers, catalysts, temperature concentrations on these polyimides properties. An optimal conditions where found for the synthesis of soluble polyimides and for the obtaining film materials from them.
The mechanical, thermal and electrical properties of film materials obtained were investigated and the possibilities and effectiveness of their usage in the technology of integral circuit, semi-conducting devices and optoelectronic devices production, which have higher reliability. were shown.
I) Institute of Electrical Engineering of Technical University of Szczecin,
Sikorskiego 37, 70-310 Szczecin, POLAND
2) Centre of Polymer Chemistry, Polish Academy of Sciences, M. Curie Sklodowska 34, 41-819 Zabrze, POLAND
Novel Optical Transparence Copolyimide Films
Introduction of aliphatic monomers in polyimides, for example aliphatic diamines as comonomers seems reasonable to reduce the chain-chain interaction because the aliphatic diamines are more flexible and may disrupt the interactions between aromatic moiety effectively. On the one hand using aliphatic monomers causes enhancement of the transparency, decrease the dielectric constant and improvement of solubility. The use of the alicyclic monomers may be a good compromise between processability and thermal properties of polyimides. Soluble and almost entirely colorless copolyimides (CPI) synthesized from cyclic dianhydride: cyclopentanetetracarboxylic dianhydride and aromatic diamine with methyl groups and a few aliphatic diamines are presented in this paper.
A series of aliphatic-aromatic CPI have been synthesised by high temperature copolycondensation of the aliphatic diamines H2N(CH2)n NH2, where n= 4,6,7,9,10,12, 4,4'-methylenebis(2,6-dimethylaniline) and cyclopentantetracarboxylic dianhydride. Most CPI films exhibit cutoffs at wavelengths shorter than 340 nm and are entirely transparent and colorless. Transparency in the visible region was evaluated by averaging the transmittances in the range from 400 to 780 nm in the UV-VIS spectrum.
1. University of Dayton Research Institute, 300 College Park Drive, Dayton OH 45469
2. Electrical Technology Branch, Propulsion Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433
3. Polymer Branch, Materials Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433
High Temperature Polymer Dielectrics For Capacitive Energy Storage Applications
The profound challenges of high voltage, pulse-power applications make it an imperative to design novel polymer dielectric materials for developing high- energy density capacitor systems. Since the energy density has a square dependence on the dielectric breakdown voltage (BDV) but varies only linearly with the dielectric constant, enhancement in the dielectric breakdown strength is considered critical to the performance of an electrostatic capacitor. Based on CVD diamond film paradigm as an outstanding high temperature capacitor with energy storage capability of 10 J/cc, we developed a rationale for the design, synthesis and dielectric evaluation of cardo-type polyesters (PEs) incorporating cycloaliphatic/ diamondoid structural units in the backbone. The glass transition temperatures ranged from 330C- > 400C for the polyesters incorporating trans-1,4-cyclohexyl, 1,3-adamantyl and 4,9-diamantyl moieties. Tough, flexible and transparent thin films were solvent cast from these high molecular weight polymers. The metallized polyester thin film containing 4,9-diamantyl unit was found to have the highest average breakdown voltage (5.43 MV/cm), corresponding to a calculated material energy density of 3.8 J/cc. As demonstrated earlier within a series of polyaryleneethertriphenylphosphine oxide dielectrics containing cycloaliphatic/diamond-like sub-units, findings in this study indicate the potential for enhanced energy storage capability in polymer dielectrics incorporating even higher order diamondoids.
Synthesis and Characterization of Novel Fluorinated Polyimides
Fluorinated aromatic polyimides have been proven to show improved solubility, outstanding optical transparence, reduced dielectric constant and dissipation factor, as well as low moisture absorption1. Two series of novel fluorinated aromatic polyimides were synthesized derived from 4,4'-[2,2,2-trifluoro-1-(4-trifluoromethylphenyl)ethylidene] diphthalic anhydride (HFDA) and 4,4'-[2,2,2-Trifluoro-1-(3',5'-bis(trifluoromethyl) phenyl)ethylidene]diphthalic anhydride (9FDA), which were prepared by coupling of trifluoromethyl-substituted 2,2,2-trifluoroacetophenones with o-xylene catalyzed by trifluoromethanesulfonic acid, followed by oxidation of KMnO4 and dehydration2 (Scheme 1). The fluorinated aromatic polyimides obtained (Scheme 2) exhibited great solubility in common solvents and low dielectric constant and low moisture uptakes.
Scheme 1 Scheme 2
(1). B.Y. Myung, etc., Polymer, 2004, 45, 3185.
(2). S. Y. Yang, etc., J. Polym. Sci.; Part A: Polym. Chem. Ed 2004, 42, 4143.
Organo-Soluble Polyimide/Clay Nanoaomposite Materials and Their Application as Advanced Corrosion Protection Coatings
A series of organo-soluble polymer-clay nanocomposite (PCN) materials that consist of organo-soluble polyimide (SPI) and and layered montmorillonite (MMT) clay are successfully prepared by the solution dispersion technique. The as-synthesized PCN materials are characterized by infrared spectroscopy, wide-angle powder X-ray diffraction, transmission electron microscopy and scanning electron microscopy.
Polyimide-clay nanocomposite materials, incorporating with low clay loading on cold-rolled steel (CRS) are found much superior in anticorrosion efficiency over those of bulk SPI on the basis of electrochemical measurements of corrosion potential, polarization resistance and corrosion current in 5 wt% aqueous NaCl electrolyte. Effects of the material composition on the O2?H2O molecular permeability, optical clarity and thermal stability of SPI along with PCN materials, in the form of both membrane and fine powder, are also studied and compared to insoluble polyimide system prepared from the thermal imidization by molecular permeability analysis, UV-vis transmission spectra, differertial scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively.
New Results for Polyimide-Inorganic Nanocomposites.
(Abstract not yet available)
Study on Imidizing Poly(ester-amine salt) Precursors to Polyimides
Poly (ester-amine salt) (PEAS) is a kind salt-like precursor that can be converted into polyimide. To reveal the imidization process, 3,3',4,4'- benzophenonetetracarboxylic dianhydride (BTDA)/4,4'-oxydianilne (ODA) based PEAS precursor was synthesized and its thermal imidization was investigated. Through the imidization degree examination and characteristic absorption inferred from FT-IR, the effects of heating temperature and time were examined, and the intermediate in imidization process was discussed. Together with the model compounds reactions, it was found that the imide structures could be formed from PEAS via two ways. The first one was amic acid intermediate process occurring at lower temperature. In this process, the amic acid structure formed through ammonolysis of ester units, and then converted into imide units. The second was anhydride intermediate process at higher temperature, in which the consequent reactions were consisted of salt structure dissociating to ester-acid and amine, eliminating ester-acid to anhydride, and condensing anhydride and amine into form imide.