ABSTRACTS

The following is a list of the abstracts for papers which will be presented in THE FIFTH 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, Firefox ... etc.)

Application of Polyimide Microwires for Thermal Isolation of a Cryogenic Transistor Module

Cryogenic bolometer arrays having semiconductor sensors require transistor read-out electronics operated at temperatures well above that of the detectors. The detector array operates well below 1 Kelvin, however the transistors must be operated as high as 130 K in order to provide optimal noise performance. The transistors are kept in close physical proximity to the detector for optimal signal-to-noise performance. The excess heat from the transistor stage must be isolated to decrease the parasitic heat load on the detectors and preserve cryogens. Historically this isolation has been accomplished by suspending the transistors on a mechanical platform using a strong, low-thermal-conductance material such as Kevlar fibers, then stretching low conductance wires such as stainless steel, phosphor bronze, or manganin and soldering at both ends. Our approach to thermal isolation of the transistor platform is to integrate transistors with polyimide microwires. The transistors are fabricated using silicon-on-insulator wafers having a 6 micron thickness device layer. The bulk silicon handle layer is removed using deep reactive ion etching. The thinned transistors are suspended by polyimide supports containing aluminum traces. The methodology for producing the transistor modules with polyimide suspension will be presented.

1) University of Dayton Research Institute, University of Dayton, Dayton, OH 45469

2) Air Force Research Laboratory/MLBP, Wright-Patterson Air Force Base, OH 45433

High Performance SPBI/SPTES Composite Proton Exchange Membranes for H₂/O₂ Fuel Cell Applications

Fabrication of novel composite membranes comprising a fully sulfonatedpolyarylenethioether sulfone (SPTES) and sulfonated poly(p-phenylenebenzobisimidazole)(SPBI) and the evaluation of the membrane properties are described.The composite membrane was obtained via a solvent cast process in a mixture of DMAcand methanol as solvents. The composite membrane proton conductivity, as measured byfour probe impedance spectroscopy, was found to increase with increase in the SPTEScontent in the composite. The highest proton conductivity obtained was ~80mS/cm at65ºC and 85 % relative humidity for the SPTES/SPBI 70/30 composite membrane whichwas considerably less than the 300 mS/cm proton conductivity for the pure SPTESmembrane, but it was found that the swelling of the composite membranes was reduceddue to the reduced water uptake of the composite membrane relative to SPTES. Themorphology of the SPTES/SPBI composite membranes was also examined by acombination of techniques such as X-ray diffraction (WAXD), Scanning ElectronMicroscopy (SEM) and tapping mode Atomic Force Microscopy (AFM) to confirm thedispersion of SPBI and study the composite micro-structure. The MEA (MembraneElectrode Assembly) performance of the composite membranes was preliminary studiedfor H2/O2 fuel cells applications.

Some Aspects of Aging of High-Perfomance Fibers and Lifetime Prediction and Enhancement

In contrast to common clothing and home textiles, technical textiles as applied in fields as diverse as automotive industry, modern architecture and building construction, filtration, or general engineering, where textiles are used as machine elements, are subject to influences that have detrimental effects on usable lifetime. Depending on the field of application, the durability of the textile as a whole, but also of the main performance features of the textile are critical factors with regard to function and safety. Accordingly, high performance polymers such as para- and meta-aramides, polyimide (PI), poly(etheretherketone) (PEEK), but also fibers made of carbon and glass are often employed to meet the conditions of a specific application.

The aging of the fiber material may be caused by factors as diverse as mechanical stress - e.g. abrasion, high tensile forces -, climate, aggressive chemical environments, or high temperatures, to name a few. Given this background, the reliable prediction of the lifetime of these products, mainly based on appropriate aging simulation, is of increasing importance to manufacturers and users alike.

Some aspects of the design of accelerated aging simulations shall be discussed in this paper with a focus on high-performance fibers. A novel approach to lifecycle prediction based on a viscoelastic model and the potential of barrier coatings based on nanocomposites deposited by the sol-gel method to increase lifetime are presented.

Heterocyclic Aromatic Conjugated Polymers For Opto-Electronic Applications

Aromatic conjugated polymers have promising applications in the field of opt-electronics. The electronic properties and thermal stability of the polymers can also be varied by the incorporation of heterocyclic units to the polymer main chain. In addition, some heterocyclic moieties may act as ligands for a variety of metal ions. The resulting polymer complexes may also exhibit interesting optical and electronic properties. One example is poly(benzoxazole) incorporated with 2,2'-bipyridine moieties on the main chain. The metal free polymer exhibit an excellent thermal stability and the decomposition temperature was measured to be 650 °C. Ruthenium complexes can be formed by the coordination reaction on the main chain.

In other examples, ruthenium bis(terpyridine) complex containing polymers were synthesized by metal coordination or by palladium catalyzed C-C coupling reactions. The resulting polymers have modest charge carrier mobilities, and they are promising candidates for the photosensitizing materials in novel polymeric photovoltaic cells. The absorption spectra of the polymers can be varied by changing the heterocyclic moieties on the main chain. This allows us to broaden the absorption band of the polymer such that the entire solar energy spectrum can be utilized more efficiently.

Synthesis of Novel Semifluorinated Poly(ether Imide)s and Structure Property Relationship

(Abstract not yet available)

Developing a 300ºc Silicon Transistor Fabrication Process on Clear Plastic Substrates for Flexible Display Backplanes

The principal candidate substrates for flexible displays are clear plastic foils. Display backplanes require highly stable amorphous silicon thin-film transistors (a-Si:H TFTs). Since TFT stability is enhanced by increasing their processing temperature we have developed a 300^oC TFT fabrication process on clear plastic (CP). Substrates that are suitable for fabrication at this temperature require both a high glass transition temperature (Tg) and a low coefficient of thermal expansion (CTE). Our substrate has a CTE of < 10ppm/^oC and a Tg >300^oC. Prior to to deposition, the plastic needs to be prepared by preshrinking, and exposure to argon and hydrogen plasmas, which promote adhesion of subsequently deposited layers. This is followed by a silicon nitride (SiN_x) barrier layer deposition on both sides of the plastic. The coated plastic is now ready to be used as a substrate for TFT deposition.

The mismatch between the CTE of the inorganic device layers and of the plastic may result in a large thermal mismatch strain between the substrate and the deposited device layers. This can lead to a large total strain in the layered structure. Strain management is therefore essential to prevent device layer cracking, deformation of the substrate, and excessive changes in the substrate dimension which disturb the alignment between successive photomask layers. The choice of TFT geometry can also have on impact on the fabrication process. We have fabricated staggered gate back channel etched, back channel passivated and self-aligned back channel passivated a-Si:H TFTs on plastic at 300^oC In this paper we will provide an overview of our 300^oC fabrication process.)

ccy7@ccmail.ncku.edu.tw (Chuh-Yung Chen)

Characteristic of Polyimide-based Nanocomposites Containing Nano-scale Filler

Nanocompositions of two different system based on the polyimid , including LDHs/PI (Layered double hydroxides/polyimide) and mCNT/PI (modified multi-walled carbon nanotubes/polyimide ), were prepared by using our specific method. In LDHs/PI system, the amino benzoate, grafted on the surface of the Mg/Al nanolayers, as a connector improved the compatibility between the inorganic Mg/Al nanolayers and the organic polyimide molecules. The maximum tensile strength and elongation of the LDH-AB/PI nanocomposites were found with the LDH-AB content of 5 and 4 wt%, respectively.[1] In mCNT/PI system, the multi-walled carbon nanotubes (CNT) were modified by plasma treatment and maleic anhydride was grafted onto them. [2-3] After plasma modification, the mCNT showed good dispersal in the polyimide matrix and imparted excellent mechanical properties. The mechanical properties, and electrical property, were improved with increasing added mCNT content in the range 0.01 to 0.5 wt%. These results indicate that the nano-inorganic filler (LDHs and mCNT) incorporated into the polyimide matrix not only can have good dispersion, but also effectively reinforced the polyimide matrix.

Reference

[1] Hsueh H.-B., Chen C.-Y., Polymer 2003; 44: 1156.

[2] Tseng C.-H., Wang C.-C., Chen C.-Y., Chem. Mater. 2007; 19: 308.

[3] Tseng C.-H, Hsueh H.-B., Chen C.-Y., Comp. Sci. Technol 2007; 67:

New kind of Carbon-fiber-reinforced Phenylethynyl-terminated Polyimde Composites

Carbon-fiber-reinforced PETI-type polyimide composites were prepared based on new kind of polyimide matrix resin, which derived from dianhydride (s-BPDA), 2, 5-bis(4-aminophenoxy)-biphenyl(p-TPEQ) and 4-phenylethynylphthalic anhydride (PEPA). The candidate material exhibited a combination of properties required for RTM with melt viscosities of 93-300Paíñs at 300oC and good stability (>2h) at 280oC. With the advantages of this novel matrix resin, an optimized molding cycle was designed for fabricating carbon fiber/PI composites. The thermal and physical properties of the composites were measured by dynamic mechanical thermal analysis, thermogravimetric analysis, thermomechanical analysis, and composition tests. The mechanical properties were tested at both room temperature and 177 íC. The flexural properties were determined by 3-point-bending at room temperature. Thermal aging involved exposing samples to temperature 177íC over 500 hours. The mechanical properties were measured after isothermal aging for 200, 400, 600, 800 and 1000 hours. The tensile failure surfaces of the aged composites were also detected with scanning electron microscopy. From these studies, it was concluded that the composites exhibited not only remarkable environmental stability, but also excellent processability, as well as toughness improvement and thermooxidative stability.

1) Nanostructured and Biological Materials Branch, AFRL, Bldg 654, 2941 Hobson Way, Wright-Patterson Air Force Base, OH 45433

2) Non-Metallic Materials Division, University of Dayton Research Institute, 300 College Park Drive, Dayton OH 45469

Rigid-rod Polybenzimidazoles (PBIs): A Review of Their Synthesis, Properties, Processing and Applications

Polybenzimidazole (PBI) represents a unique class of polymers with exceptional thermo-mechanical properties suitable for a variety of applications ranging from flame-resistant fabrics to aerospace materials. While the applications of the commercial PBI Celazole^® as an amorphous, high temperature, high performance engineering thermoplastic are well-documented, this review seeks to emphasize the properties and potential applications of rigid-rod polybenzobisimidazoles. The review would primarily describe various rigid-rod PBI-based molecular motifs for proven as well as potential enhancement in the axial compressive properties of polymeric fibers. In somewhat minor detail, derivatized rigid-rod PBIs with pendant sulfonic acid and alkylsulfonate functionalities will also be described from the viewpoint of potential utilization in such areas as polyelectrolytes for fuel cells and battery applications as well as a rod-like reinforcement in molecular composites.

1) Delft University of Technology, Faculty of Aerospace Engineering, 20

Kluyverweg 1, 2629 HS, Delft, THE NETHERLANDS

2) NASA Langley Research Center, AMPB, Hampton, VA 23681-0001, USA.

Novel All-Aromatic Liquid Crystal Polyesters and Polyetherimides for Aerospace Applications

In order to meet the requirements for new structural aerospace resins, we are currently exploring new families of wholly aromatic thermotropic liquid crystalline thermosetting polymers (LCTs) and all aromatic melt processable liquid crystalline polyetherimides. Liquid crystalline polymers offer excellent thermal and mechanical properties; outstanding barrier characteristics and they are easy to process into high-modulus fibers, films and molded articles. We have synthesized reactive ester- and imide-based LC oligomers, based on affordable monomers such as Terephthalic acid (TA) and Hydroquinone (HQ), with Mn 3D 1000, 5000, and 9000 g/mol. All oligomers could be melt-processed and cured at 370 0C without the evolution of volatiles. The fully cured polymers show high glass-transition temperatures (164E28093275 0C), and exhibit high storage moduli at elevated temperatures (>2 GPa at 200 0C). Some oligomers exhibit low melt viscosities (10-100 Poise at 100 rad/s), and are therefore easy to process in complex articles such as fiber-reinforced composites. Our fully cured polymers show low CTEs and excellent adhesive properties, i.e. lap shear values of 22 MPa (Ti, 6Al-4V) could easily be obtained. Carbon fiber composites made with these resins showed typical moduli around 74 GPa and a flextural strength of 652 MPa.

Synthesis and Characterization of Multifluorinated Aromatic Polyimides for Photonic Applications

Fluorinated polyimides (FPIs) have attracted much attention in the last decades owing to their excellent combination of thermal, mechanical, dielectric and chemical properties, which make them good candidates for microelectronics applications. FPIs usually exhibit outstanding optical transparency and low optical loss in the range of the optical telecommunication wavelengths, which expand their applications to optical telecommunication field as optical waveguide circuits, thermo-optic switches, optical filters, and linear polarizers. In this research, the novel multifluorinated aromatic polyimides were investigated, aiming at development the polymeric optical waveguide materials. A novel fluorinated aromatic diamine, 1,1-bis(4-amino-3,5-dimethylphenyl)-1-(3',4',5'-trifluorophenyl)-2,2,2-trifluoroethane (6FMA), which containing multifluorinated phenyl group and trifluoromethyl substituent in the structure, was synthesized. A series of multifluorinated polyimides derived from the novel aromatic diamine 6FMA and various aromatic dianhydrides, such as 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonete tracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), were prepared by a high-temperature, one-step polycondensation procedure. The solubility, thermal and mechanical properties, electrical and dielectric properties, especially, the optical properties of the multifluorinated polyimides were investigated.

Metal-containing Polyimides for Contamination Sensing and Prevention in Space Applications

Contamination can have a very adverse affect on space systems. The ability of a spacegrade material to both sense and absorb molecular contamination is of great use. We have developed a series of polyimide materials that both sense and absorb moisture, a contaminant detrimental to optical space systems. The materials were prepared by introducing specific metals in to polyimide, with the hope of retaining the original properties of both the metal and the polymer. The metal both acts as contaminant absorber and visible sensor. The amount of absorption was found to be tailorable and the material could easily be regenerated again after absorption. Characterization of the materials and absorption/desorption data will be presented.

1) Institute of Chemical Sciences, 106 Walikhanov Str., Almaty, 050010, KAZAKHSTAN

2) Moscow Ped. State Univ., RUSSIA

3) P.Sezanne Univ. Marseille, FRANCE

4) Univ. Lille-1, FRANCE

5) Univ. Montpellier-2, FRANCE

New Combined Plasma-Wet Method of Metal Impregnation into Polyimide Films

Metallized polymer materials are attracting progressively growing attention of researchers due to microelectronics and aerospace needs. Over past decade polyimides (PIs) offer promise for metallization owing to their high thermal stability and low thermal expansion. However, a problem of metal adhesion into the polyimide surfaces has being kept in a case of homogeneous metal nano-distribution with minimal PI surface trauma.

Using a combined method of plasma PI surface pretreatment and chemical deposition of metals into the pretreated surfaces could be minimized both trauma effects on the surfaces and uniform metal distribution in PI. A polyimide was synthesized in two-step polycondensation in N-methyl-2-pyrrolidone between a dianhydride of tricyclodecentetracarbon acid and oxydianiline with final casting of polyimide solution. An initial PI film was treated by cold remote N₂-O₂ plasma within exposure time 0.5-10 min in order to functionalize the PI surfaces with opening of the imide cycles. Plasma glow discharge is 2450 MHz for pressures ranging from 10 to 1000 Pa it is possible to obtain a post-dischage with large volume extension at ambient temperature.

Metallized PI surfaces showed grain-type nanodistribution of silver crystallines due to their growing around a center of reducing metal initiation. A size distribution of metal grains is within 10-100 nm tightly packed together accordingly to SEM data, however at undersurface layer the grains are surrounded with polyimide matrix around. Scanning of an atomic force microscopy (AFM) showed the same nanosize range of silver grains those distributed into the PI surfaces in precise uniform order without obvious AFM visible surfacial traumas.

Polymer Thin Films Sputtered with Polyimide Targets

Polymer thin films were sputtered with thermally stable polymer targets onto a copper and glass slide substrate with a conventional RF sputtering apparatus. Polymer structures and adhesion and tribological properties of these polymer thin films were evaluated. Polymer thin films were sputtered onto copper substrate with two polyimide (Kapton-VTM and Upilex-STM) targets [1]. Argon, nitrogen and carbon tetrafluoride were introduced into the sputtering chamber for the sputtering gases. Friction coefficient and wear durability of the thin film sputtered with the nitrogen gas (N2 sputtered thin film) were higher than those of the thin film sputtered with argon gas (Ar sputtered thin film). The pull strength between the N2 sputtered thin film and copper substrate was higher than that between the Ar sputtered thin film and copper substrate [2]. Friction coefficient of the thin film sputtered with Ar and CF4 mixture (polyfluorocarbon thin film) was lower than that of the Ar sputtered thin film. The pull strength between the polyfluorocarbon thin film and copper substrate was lower than that between polyimide thin film sputtered with Ar gas and copper substrate. The pull strength of the polyfluorocarbon thin film to the copper substrate improved due to introduction of the N2 sputtered thin film between the polyfluorocarbon thin film and copper substrate [3].

Reference

[1] S.Iwamori, A.Uemura and Y.Yamada, J.Adhes.Sci.Technol., 18,

1771(2004)

[2] S.Iwamori and A.Uemura, J. Adhes. Soc. Jpn., 42, 89(2006)

[3] S.Iwamori and A.Uemura, Materials Science and Technology, 42,

278(2005)

Adhesion of Poly(tetrafluoroethylene) (PTFE) and Poly(vinyl Alcohol) (PVA) Composite Thin Films on the Nickel-Titanium Substrates

Poly(tetrafluoroethylene) (PTFE) and poly(vinyl alcohol) (PVA) and their composite thin films coated onto the nickel-titanium substrate by a spin coating were characterized. Relationship between the sintering temperature and mechanical properties, such as adhesion strength and shearing force, was evaluated. The adhesion strength of the PTFE-PVA composite and PVA thin films decreased with increase of the sintering temperature. Although shearing force of the PTFE thin film increased with increase of the sintering temperature, those of the PTFE-PVA composite and PVA thin films decreased. The adhesion strength between these PTFE thin films and nickel-titanium substrate were improved due to introduction of PVA interfacial layer [1]. In addition, friction coefficients of the spin coated thin films decreased with increase of the PTFE concentration [1].

Reference

[1] S.Iwamori and M.Mizoguchi, Materials Science and Technology, 43,

99(2006)

e-mail iwamoto@pe.titech.ac.jp

Organic Field Effect Transistor as a Maxwell Effect Element Using Polyimide and Polyvinylidene Poly(Vinylidene Fluoride) Films

Pentacene filed effect transistors (OFETs) using Poly(vinylidene fluoride), i.e., P(VDF-TeFE) and polyimide (PI) films as a gate insulator is analyzed as a Maxwell-Wagner (MW) effect element. The analysis reveals that the FET characteristics are ruled by carrier injection from the Source and Drain electrodes, where ferrodielectric behavior of P(VDF-TeFE) and insulating property of PI play an important role. The current peaks observed in the Ids-Vds characteristics were analyzed with taking into account the motion of accumulated charges at the pentacene/ P(VDF-TeFE) (or PI) interface and the dielectric polarization phenomena of PI and P(VDF-TeFE). Finally, the dielectric and insulating properties of spin-coated PI and P(VDF-TeFE) are discussed based on the analysis and experiments above.

Laboratoire de Chimie Physique Macromoléculaire, UMR CNRS-INPL 7568, Nancy Université, ENSIC, 1 rue Grandville, BP 20451, 54 001 NANCY cedex, FRANCE

Anne.Jonquieres@ensic.inpl-nancy.fr

New Ion-containing Polyimides for the Purification of One of the Most Promising Bio-fuels by a Membrane Separation Process

Two international patents [1,2] and also recent results [3] have shown that polymeric membranes containing cationic groups are highly efficient for the removal of protic species (e.g. alcohols) from organic mixtures, with an important potential application for the purification of ethyl-tert-butyl ether (ETBE). By appropriate fiscal privileges for the past ten years, the European Union has been strongly inciting the large production of this alkyl ether from agricultural ethanol. Thanks to its specific advantages and its much better biodegradability than methyl-tert-butyl ether (MTBE), ETBE is currently considered as one of the most promising bio-fuels [4,5]. Nevertheless, its industrial synthesis process leads to an azeotropic mixture containing 20 wt % of ethanol which has to be removed for ETBE purification. If the former copolymers were well performing for this separation, the rather poor control of their chemical structure did not allow any detailed analysis about the influence of the cationic sites on their permeability. Taking advantage of our former experience on polyimide block copolymers for this separation [6], we recently developed the synthesis and characterization of 3 families of new ion-containing polyimide copolymers, with a control of the number of their cationic ammonium groups, the length of their alkyl side chain and the type of their counter-ions [7,8]. On the basis of sorption and permeability results obtained for the purification of ETBE, the membrane features are discussed in terms of structure-property relationships. In particular, it is shown how simply changing the chemical structure of the cationic groups enables to increase sharply permeability with a very low impact on selectivity, therefore overcoming the usual trade-off permeability/selectivity.

References

[1] H. Steinhauser, H. Brüschke, European Patent 0674940 B1 (1995).

[2] H. Steinhauser, H. Brüschke, US Patent 5,700,374 (1997).

[3] S. Touchal, D. Roizard, L. Perrin, Journal of Applied Polymer Science, Vol. 99 (2006) 3622.

[4] H. Noureddini, Book of Abstracts, 219^th ACS National Meeting, San Francisco, CA, March 26-30, 2000.

[5] R. Koenen, W. Puettmann, Grundwasser, Vol. 10 (2005) 227.

[6] A. Jonquieres, R. Clément, P. Lochon, Progress in Polymer Science, Vol. 27 (2002) 1803. (review)

[7] M. Awkal, A. Jonquières, G. Creffier, R. Clément, P. Lochon, Macromolecules, Vol. 37 (2004), 684.

[8] M. Awkal, A. Jonquières, R. Clément, P. Lochon, Polymer, Vol. 47 (2006), 5724.

The Effect of Nanoclays on the Properties and Morphology of Injection Molded Polypropylene/ Polyamide 66 Nanocomoposites

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 PA66 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 nanoclays were added to 70/30 PP/PA 66 blends into an internal mixer. The resulting nanoblends will be characterised in terms of rheological, thermal, morphological and mechanical properties. The rheological results revealed a drastic reduction in MFI with a levelling off at 5 wt.% for the nanoblends containing treated clay. The impact properties of PP/PA66 modified nanoblends were improved significantly in the presence of treated nanoclay. SEM results revealed the formation of nanoblends as the nanoclay was intercalated and exfoliated.

Belarussian State Technological University, Department of Polymers,

Minsk-220050,Sverdlova Str.,13a.,BELARUS

Polyimide Blends

Blends of polyimides of any structural differences and with other polymers have received attention of many investigators due to the possibility to improve such properties as easy processability, with better thermomechanical properties and thermo-oxidative stability. They can be used in aerospace, military, nuclear plant, chemical process equipment, thermoplastic composites, films, fibres, as gas separation membrane materials, etc. Many works have been done on the structure-property relationships of polyimides by systematically changing the diamine or dianhydride moieties. It is of interest, however, to study blends of aromatic and cycloaliphatic polyimides. Cycloaliphatic and aromatic polyimides were obtained from dianhydride 1,2,3,4-cyclohexan tetracarbonic acid, pyromellitic dianhydride and 4,4`-diaminodiphenylether, 4,4`-diaminodiphenylmethan by polycondensation in N-methylpyrrolidone at room temperature followed by thermal cyclization in film form. Prepolymerfilms of poliamic acids blends were obtained by casting the prepolymer blends solutions onto glass plates followed by gradual heating to remove the solvent. It has been shown that by using pyridine and various tertiary amines as catalysts of thermal cyclization of cycloaliphatic and aromatic polyimides the rates of the imidization process can be increased. IR-spectroscopy was used to identify polymer products of the reaction. The number of amic acid units in the polymers was estimated from the amid range from 1530 to 1550 cm-1, the imide ring accumulation was determined from the band in the range of 720 to 760 cm -1. For polyamic acid -1380 and 1810 cm-1 absorption bands were used to calculate the imide and isoimide ring content, respectively. The optical densities of the bands, used for calculations were compared to the density of the band at 1015 cm-1(vibrations of aromatic ring) as the internal standard.

According to the date from thermogravimetric analysis, IR-spectroscopy the cyclization process of aromatic-cycloaliphatic polyamic acids blends is completed at the 300 oC. In this case polyimide blends with better processability than that of pure polypyromellitimides can be obtained.

1) Department of Chemical Engineering, National Yunlin University of Science & Technology, Yunlin 640, TAIWAN

2) Department of Chemical Engineering, National Chung Hsing University, Taichung 402, TAIWAN

Thermally Stable NLO Poly(amide-imide)s via Acylurea Intermediates

A series of thermally stable side-chain second-order nonlinear optical (NLO) poly(amide-imide)s have been developed via acylurea intermediates. Three difunctional azo chromophores were respectively reacted with excessive amount of 4, 4'-methylene-diphenylisocyanate to form an NLO-active poly(carbodiimide) (poly-CDI), and subsequently trimellitic anhydride was added to obtain an intermediate, poly(N-acylurea). The poly(N-acylurea) exhibits excellent organosolubility, which enables the fabrication of high quality optical thin films. Moreover, its moderate T_g characteristic allows the NLO-active polymer to exhibit high poling efficiency. After in-situ poling/curing process, N-acylurea moieties were converted to amide-imide structures, and the T_gs of the polymers were elevated significantly up to 70 ^oC higher than that of the poly-CDI sample. Linear and nonlinear optical properties were also investigated.

Polyimide Foam Nanocomposites from Powder Precursors

Polyimide foam nanocomposites have been developed through an in situ polymerization process followed by solid state powder foaming. The dispersion of the acid functionalized carbon nanotubes in the reaction media is achieved by means of surfactants, mechanical mixing and sonication. In order to enhance the dispersion, the acid - base reaction of the acid functionalities of the CNTs and the basic amine groups of the diamine monomer is favored. The CNT dispersion is used as the reaction media for the polymerization of the diamine and diester monomers. Polyamic acid with embedded CNTs is processed to solid powder to produce foam after a thermal treatment named solid state powder foaming. In an effort to determine the optimal processing conditions and the phenomena that take place in the material during its processing and lifetime, several experimental techniques have been used (TGA, DSC, AFM, SEM). An analysis of the effect of the CNTs over the polyimide matrix has been done to fully understand the nature, properties and behavior of this type of material.

Polyimides for Potential Space Applications

1,4-bis(4-aminophenoxy)-2-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl) phenylene (3) was synthesized by the nucleophilic aromatic substitution of 2-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl)-1,4-dihydroxy phenylene (1) with 4-fluoronitrobenzene, followed by catalytic hydrogenation. Light color, flexible and creasable polyimides with high molecular weight, high glass transition, high thermal stability, improved organo-solubility, and good oxygen plasma resistance were synthesized from the condensation of (3) with various aromatic dianhydrides in DMAc, followed by thermal imidization. The number-average molecular weights of polyimides are in the range of 7.0-8.3 x104 g/mol, and the weight-average molecular weights are in the range of 12.5-16.5 x104 g/mol. The Tgs of these polyimides range from 230 oC to 304 oC by DSC and from 228 to 305 oC by DMA. These polyimides are tough and flexible with tensile strength at around 100 MPa. The degradation temperatures (Td 5%) and char yields at 800 oC in nitrogen range from 544 to 597 oC and 59-65 wt %, respectively. Polyimides 5c and 5e, derived from OPDA and 6FDA respectively, with the cutoff wavelength of 347 and 342 &micro;m, respectively, show very light color. These polyimides also exhibit good oxygen plasma resistance, demostrating the potential space applications.

Rigid Rod Polyimide Polyelectrolytes: Comonomer Generated Free Volume

Linear rigid rod molecules can have very different organization when compared to normal flexible polymer molecules. One of the most important is they form nematic structures with all the molecules parallel. Therefore, if several units which are much bulkier than the rest of the units are incorporated into the backbone, their larger cross-section will tend to keep the molecules apart over their whole length. This generates channels between the polymer chains that can act as host to small molecules - in other words, free volume. Our research concentrated on polymers made using 1, 4, 5, 8-naphthalene tetra carboxy dianhydride reacted with benzidine 2, 2Æ-disulfonic acid. The acid groups kept the final polymers soluble and easy to handle. The comonomers that generated bulk were of two types, angled and linear. The two angled comonomers were di(4-aminophenyl) ether (ODA, oxy dianiline), and 9, 9-di (4-aminophenyl) fluorene (FDA, fluorenyl dianiline). These formed polymer segments that were at an angle to the nematic orientation and forced chains apart. Triphenylenediamines with three or four aromatic substituents on the central ring were synthesized and used as linear co-monomers. Random copolymers were made containing 2.5 to 10 mole % ofco-monomer.

Since these polymers were intended for use as polyelectrolyte membranes in fuel cells, the major focus was on water absorption and retention. Direct water absorption was studied by measuring water uptake at a given relative humidity and as a function of drying procedure. After three days at 90C under vacuum, homopolymer retained one water per acid group while the copolymers kept two waters. TGA studies showed that copolymers retained four water molecules per acid after drying at 25C; the temperature of the maximum rate of water loss correlated with the free volume.

Flat plate X-ray photos (under vacuum) of drawn fibers showed that the chain to chain distance increased as the comonomer bulk increased. Sharp reflections due to chain structure were identical for the homopolymer and all the copolymers. Volume increase based on x-ray measurements agreed with water retention after room temperature drying.

Ionic conductivity of cast, acidified films correlated with water retention. Increasing the free volume resulted in higher conductivity at low relative humidities.

Temperature-Responsive Polyimides from Diels-Alder Reactions

Telechilic polyimides possessing maleimide (PI-MI) and furan (PI-F) chain ends are prepared from conventional polyimide synthesis route and chain-end functionalization. PI-MI and Pi-F are used as precursors in preparation of high-molecular weight polyimides (PI-MIF) through the Diels-Alder reaction between maleimide and furan groups. The molecular weights of the resulted polyimides increased with increasing reaction time. The prepared polyimides possess maleimide-furan adduct linkages, which can thermally broken down to PI-M and PI-F through the retro-Diels-Alder reaction. The kinetics of the Retro-DA reaction was studied. Moreover, the solubility difference between PI-MIF and PI-MI/PI-F leads the polyimides to be potentially applied as temperature-responsive materials.

A Novel Photodefinable Poly(benzoxazole) Using A Negative-working Chemical Amplification System

Poly(benzoxazole) (PBO) is one of the thermal-stable polymers, which is widely used in silicon technology process integration such as insulating, buffer coating, interlayer dielectrics, and so on. Nowadays TMAH (tetramethylammonium hydroxide) processable photodefinable materials are preferred in this field in order to reduce process cost and to address environmental issues. For these aqueous developable materials, the photodecomposition of naphthoquinonediazide (NQD) into indene carboxylic acid is widely employed as a photochemical system [1]. Several types of photodefinable PBOs other than the NQD type are also proposed to date, however, many of them have not confirmed their practicality such as a thick film (more than 5 µm) fabrication, compatibility with a 300-mm wafer process and so on [2]. Our proposed negative working photodefinable PBO employs a chemical amplification system based on acid catalyzed cross-linkings. On the basis of dissolution behavior, we employed a methylol type cross-linker for this material. The proposed material gave excellent photolithographic properties and appropriate film properties to be used practically. Especially the sensitivity was less than 100 mJ/cm² for a 10-µm thick film, which is better than that of conventional NQD systems. In addition, the results of feasible studies on a 300-mm wafer process will be discussed.

References

[1] R. Rubner, Adv. Mater., 2, 452 (1990).

[2] (a) S. L-C. Hsu and W-C. Chen, Polymer, 43, 6743 (2002). (b) K. Ebara, Y. Shibasaki, and M. Ueda, J. Photopolym. Sci. Technol., 16, 287 (2003). (c) K. Fukukawa, Y. Shibasaki, and M. Ueda, Macromolecules, 37, 8256 (2004). (d) K. Fukukawa and M. Ueda, Macromolecules, 39, 2100 (2006). (e) C. S. Hong, M. Jikei, and M. Kakimoto, Polym. J., 35, 586 (2003). (f) K. Fukukawa, Y. Shibasaki, and M. Ueda, Polym. J., 37, 74 (2005).

Thermochemical Behavior of Organosilicon Films Elaborated by a Cold Plasma Polymerization Process

Plasma polymerization processes allow to deposit polymer films on any substrate. While organic compounds with polymerizable structure are needed for conventional type of polymerization, any organic compound can be used in the frame of assisted plasma processes. In this work, organosilicon thin films are obtained by a cold remote nitrogen plasma polymerization of 1,1,3,3-tetramethyldisiloxane monomer (pre-mixed or not with oxygen).Two applications are presented. In the first one, such a film is used to improve flame retardant properties of polyamide-6 and polyamide-6 clay nanocomposite substrates. Fire retardancy performances are evaluated using cone calorimeter measurements and limiting oxygen index tests. Deposited polymer films were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and by Scanning Electron Microscopy. In the frame of the second application, these films are used to promote bonding of a silica supported catalyst (Co/SiO2)on AlSl316L steel substrate used for Fisher-Tropsch synthesis in a micro-chamber reactor. To reach this aim, the deposited thin polymer film is firstly in-situ treated by the remote afterglow of an Oxygen containing plasma. Then, it is ex-situ thermally treated under air atmosphere in order to obtain a silicon oxide bonding layer. The influence of the deposition and post-treatments were investigated by FTIR, Raman spectroscopy and X-ray Photoelectron Spectroscopy.

1) Hitachi Chemical DuPont MicroSystems Ltd.13-1 Higashi-cho 4-chome, Hitachi-shi, Ibaraki 317-8555 JAPAN

2) Hitachi Chemical Co., Ltd., 13-1 Higashi-cho 4-chome, Hitachi-shi, Ibaraki 317-8555 JAPAN

*e-mail: m-ooe@hkg-net.co.jp

Low Temperature Curable, Positive-tone, Photo-definable, Poly (benzoxazole)

Due to their excellent thermal, mechanical and electrical properties, polyimides have been widely used as stress buffer coatings to improve the reliability of semiconductor devices. In recent years, there has been a trend away from non-photo-definable polyimides towards photo-definable polyimides (PSPI) with the reason being the ability of the PSPI to simplify the stress buffer layer fabrication process so resulting in process cost reduction. Furthermore, aqueous developable positive-tone PSPIs are now becoming main stream technology due to demands such as higher resolution, further reduction in process cost and the need for more environmentally friendly chemicals. These systems typically utilize polybenzoxazole (PBO) technology that has a thermal resistance equivalent to polyimides but which require cure temperatures >300ºC to achieve optimum end-use properties. However, in order to reduce damage and improve yields on certain devices such as the next generation memory devices, a low temperature cure less than 250ºC is now becoming an important requirement. To meet these demands, a low temperature curable (< 250ºC) positive-tone aqueous developable PBO has been developed by adopting an effective cure promoter without sacrificing any process (140 mJ/cm² exposure energy at 5um cured film thickness) or end-use properties (70% elongation).

Vallabh Vidhyanagar - 388120, Gujarat - INDIA

E-mail: hsp13152@rediffmail.com

Novel Polyimide System Based on Nitro Displacement/Diels-Alder Reaction - III

Poly(ether-imide)s were prepared by two simultaneous reactions i.e. Diels Alder reaction and nitro-displacement reaction. Thus 3-Nitrophthalic anhydride was reacted with furfuryl amine and the resultant amic acid was then reacted with six bismaleimides (2a-f) and disodium salt of 1,5-dihydroxy naphthalene. The obtained polymers (i.e. polyetheramic acids) were treated with acetic anhydride to form cyclic imide, as well as aromatization of Diels-Alder (DA) adduct. So called poly(ether-imide)s (PEIs) were characterized by IR spectral studies and theromgravimetry. The 'insitu' polymerization on glass fibers was also carried out and the laminates were characterized by physical, mechanical and chemical properties.

Chemical Modification of Polyimides with Alkylphenolformaldehyde and Epoxy-resins

The abstract is devoted to the chemical modification of poly-4,4'-diphenyloxidepyromellitimide with widely available modifiers - alkylphenolformaldehyde and epoxy-resins. We have found that the using of polyamidoacid compositions contained either alkylphenolformaldehyde or epoxy-resin allows to obtain films and fibre materials. We have studied stress-strained properties, thermal stability, energetic parameters and structural characteristics of mechanical destruction of modified polypyromellitimide fibres. The research demonstrates sufficient improvement of stress-strained properties and thermal stability of polypyromellitimide fibres contained such modifiers as alkylphenolformaldehyde or epoxy-resins. Epoxy-resins proved to be more effective as modifiers of polyimide films and fibre materials. It can be explained by the difference in the mechanisms of netting polymer structure formation and the quality of the sewing process itself. Alkylphenolformaldehyde contains only -OH groups, while sewing process in compositions with epoxy-resins can be performed by both -OH groups and epoxy cycles. On the basis of comparison of stress-strained properties and thermal stability of polypyromellitimide fibres containing different modifiers it can be concluded that the variety and quantity of functional groups is considered to be the main factor causing the increase of this essential operational properties.

Multiple Relaxatation Processes in Swift Heavy Ion Irradiated Kapton-H Polyimide

Swift heavy ion irradiation effects in kapton-H polyimide have been investigated using thermally stimulated depolarization current (TSDC) technique. The kapton-H samples were irradiated with 100MeV ¹⁶O, 100MeV ³⁰Si, 100MeV ⁵⁸Ni and 50MeV ⁷Li ion using PELLETRON facility at Nuclear Science Center, New Delhi. Samples were also irradiated with 11.6 MeV/n ²³⁸U ions at GSI, Amsterdam Germany. The range of fluence varies from 10⁴ to10¹² ions/cm². The two major relaxatation processes in kapton-H polyimide, viz. b-relaxatation associated with dipolar nature of the carbonyl groups and a-relaxatation associated with the space charge relaxatation process, are both affected due to ion irradiation. The TSDC spectra obtained for various poling temperatures (80⁰-250⁰C) and poling fields (40-600kV/cm) of irradiated samples reveal on one hand the significant loss in the b-relaxatation due to demerization of carbonyl groups and on the other hand there is an enhancement in the a-relaxatation owing to the formation of new energy trap centers. Though the general behaviour of the TSDC spectra is not much affected by the nature of ion, the fluence and the energy of the ion play a significant role in modifying these relaxatation processes. Some new radiation induced relaxatation process due to enhancement of water absorptivity (g-relaxatation) and unsaturated bond formation (d-relaxatation) have been recognized. The distribution in the relaxatation time for the TSDC spectra has been estimated using cole-cole distribution function. The cole-cole distribution curves show the formation of new sub-polar groups with different characteristic time. The different relaxatation parameters viz. activation energy, relaxatation time have also been calculated.

E-mail - msrde2000@yahoo.com

Synthesis and Properties of Novel Bismaleimides, Polyaspartimides and Organosoluble Polyimides

Aromatic polyimides have been widely used in microelectronics, aerospace and other engineering industries. However, many commercially available polyimides have restricted applications due to their insolubility, intractability and processing requirements, therefore many efforts have been made on synthesizing soluble, tractable polyimides without appreciable sacrifice in their desired properties. One of the successful approaches has been to introduce pendant phenyl and alkyl groups into the polymer. Bismaleimides are another approach to improve processability. Hence, in the present study, new diamine monomers were synthesized by treating a substituted aldehyde with 2,6 dimethyl aniline in the presence of dry hydrochloric acid to yield the diamine bis (4-amino 3,5-dimethyl phenyl) X' phenyl methane (where X' = Cl,Br,F,-OCH₂C₆H₅,-OCH₃) and bis (4-amino-3,5-dimethyl phenyl) anthramethane. A series of organo soluble polyimides were prepared from the diamine with various aromatic tetra carboxylic acid dianhydrides via one step and two step method. All the polyimides were soluble in aprotic solvents such as NMP, DMF, DMAc, and DMSO. The polyimides show excellent thermal stability and good mechanical properties. The glass transition temperature of the various polyimides range from 210-325 ⁰C and the temperatures at which 10 % weight loss occurs are in the range 460-496 ⁰C. All polyimides formed tough transparent films with tensile strength 79 - 118 MPa, % Elongation 8 - 12 % and modulus 1.5 -2.3 GPa. These polyimide films have low dielectric constant (3.29 - 3.80 at 1 KHz and 3.14 - 3.76 at 10 KHz) and low moisture uptake 0.52 -1.10 %. Bismaleimides were also synthesized from the prepared diamines and maleic anhydride via bismaleamic acid as an intermediate followed by cyclodehydration. The structure was confirmed by FTIR, ¹H-NMR and Elemental analysis. Further, a series of polyaspartimides were synthesized by addition reaction of bismaleimides (BMDA) with various diamines. The polymers were characterized by IR and Elemental analysis. Tg of polyaspartimides are in the range of 125-278⁰C and T_10% weight loss are in the range of 398-476⁰C.

E-mail - msrde2000@yahoo.com

Structure Property Relationship of Processable Heat Resistant Poly (Amide-imide-imides) for High Temperature Applications

Polyimides and polyamide-imides are of high interest for many engineering applications due to their excellent thermal and mechanical properties. The aerospace, automobile, and microelectronics industries have developed many important applications. However, the processing of these thermoplastic polymers has been greatly hindered because they lack softening or melting behaviour at usual processing temperatures, and they tend to degrade before or at the softening temperature. Various attempts have been made to bring down the Tg or melting temperature of aromatic polyamides to make them processable, either by introducing kinked and flexible bridging units. Unfortunately, the loss of thermal stability and significant decrease in mechanical properties on heating are usually a consequence of the reduced chain stiffness. In the present study a series of novel aromatic diamines bis (4-amino-3, 5-dimethyl phenyl) (X) phenyl methane (X®3-chloro, 3-bromo, 4-methoxy) from corresponding aldehydes and 2, 6 dimethyl aniline; bis (4-amino-3, 5-dimethyl phenyl) cyclohexane from cyclohexanone and 2,6 dimethyl aniline; bis (4-amino-3,5-dimethyl phenyl) cycloheptanone from cycloheptanone and 2,6 dimethyl aniline; bis (p-amino phenoxy)-methyl phenyl silane from p- aminophenol and dichloro methyl phenyl silane were prepared. Tetrimide dicarboxylic acids were prepared by reacting the prepared diamines with PMDA/BPDA and p-aminobenzoic acid. The polymers were prepared by treating the tetrimide diacid with different aromatic diamines. The structures of the monomers and polymers were identified by Elemental analysis, FTIR, ¹H-NMR and ¹³C-NMR. The polymers show excellent solubility. The polymers are amorphous and have high optical transparency. They also show good thermal stability and their Tg is found to be in the range 268-372⁰C.They had 10% weight losses at temperatures beyond 530⁰C and left more than 50% char yield even at 800⁰C in nitrogen atmosphere. The thin films cast from DMAc exhibit tensile strengths of 96-101 MPa, elongation at break of 9-14% and initial moduli of 1.9-2.3 GPa. The properties of the different polymers were compared and discussed and correlated to their structures.

1) Department of Chemistry, Anna University, Chennai - 600025, INDIA

2) Division of Rubber and Plastics Technology, Madras Institute of Technology,Chrompet,Chennai-600044, INDIA

E-mail - msrde2000@yahoo.com

Structural Characterization and Mechanical and Thermal Properties of New Cyanate/ Epoxy and Cyanate/BMI Blends and Composites

The application of cyanate esters as an aerospace material (as advanced composites matrices) is a more recent development and this places them in direct competition for the market share of epoxy and bismaleimide (BMI) resins. However, being at an earlier stage of development than of these more established products, they are currently more expensive, and recent commercial developments have involved the preparation of binary (Cy/BMI, Cy/epoxy) or ternary (Cy/BMI/epoxy) blends. It is now generally accepted that cyanates and BMIs do not co-react directly; instead they form interpenetrating networks. There are also reports on the chemical reaction between cyanate and epoxy resin making them highly compatible. Hence, different diols were prepared by the condensation of 2,6-dimethyl phenol/1-naphthol with different aldehydes, dichlorodiphenylsilane with 1, 4-dihydroxy anthraquinone and vanillin with different diamines. All the diols prepared and 1,4-dihydroxy anthraquinone were converted to dicyanate. The synthesized diols and dicyanates were characterized by elemental analysis, FT-IR, ¹H-NMR and ¹³C-NMR spectra. The cure behaviour of all the dicyanate monomers and their blends with epoxy/BMI was studied using DSC. The monomers were then cured into thermoset polymers after heating at 180ºC for 1 hr and 220ºC for 1 hr. FT-IR, solid state NMR, TGA and DSC were used to characterize the polymers. All the polymers exhibit a common maximum decomposition temperature of 420 ± 5ºC, which is characteristic of the cyanurate ring. However, the percentage char yield is found to depend on the chemical structure. The T_g of the polycyanates depends on the structure of the monomer. The dicyanates were blended with commercial epoxy/DDM system. The Schiff base functionalized cyanate ester was blended with BMI at various proportions. The blends were characterized by FT-IR,. Composite laminates were fabricated from E-glass fiber plain-woven fabric and epoxy resin or cyanate/epoxy or BMI blend. The mechanical properties like tensile, flexural, impact strength and fracture toughness of the blends and composites were studied as per ASTM standards. The blends and composites were evaluated by SEM analysis and DMA.

1) Department of Chemistry, Anna University, Chennai - 600025, INDIA

2) Division of Rubber and Plastics Technology, Madras Institute of Technology,Chrompet,Chennai-600044, INDIA

E-mail - msrde2000@yahoo.com

Structural Characterization and Mechanical and Thermal Properties of New Cyanate/ Epoxy and Cyanate/BMI Blends and Composites

The application of cyanate esters as an aerospace material (as advanced composites matrices) is a more recent development and this places them in direct competition for the market share of epoxy and bismaleimide (BMI) resins. However, being at an earlier stage of development than of these more established products, they are currently more expensive, and recent commercial developments have involved the preparation of binary (Cy/BMI, Cy/epoxy) or ternary (Cy/BMI/epoxy) blends. It is now generally accepted that cyanates and BMIs do not co-react directly; instead they form interpenetrating networks. There are also reports on the chemical reaction between cyanate and epoxy resin making them highly compatible. Hence, different diols were prepared by the condensation of 2,6-dimethyl phenol/1-naphthol with different aldehydes, dichlorodiphenylsilane with 1, 4-dihydroxy anthraquinone and vanillin with different diamines. All the diols prepared and 1,4-dihydroxy anthraquinone were converted to dicyanate. The synthesized diols and dicyanates were characterized by elemental analysis, FT-IR, ¹H-NMR and ¹³C-NMR spectra. The cure behaviour of all the dicyanate monomers and their blends with epoxy/BMI was studied using DSC. The monomers were then cured into thermoset polymers after heating at 180ºC for 1 hr and 220ºC for 1 hr. FT-IR, solid state NMR, TGA and DSC were used to characterize the polymers. All the polymers exhibit a common maximum decomposition temperature of 420 ± 5ºC, which is characteristic of the cyanurate ring. However, the percentage char yield is found to depend on the chemical structure. The T_g of the polycyanates depends on the structure of the monomer. The dicyanates were blended with commercial epoxy/DDM system. The Schiff base functionalized cyanate ester was blended with BMI at various proportions. The blends were characterized by FT-IR,. Composite laminates were fabricated from E-glass fiber plain-woven fabric and epoxy resin or cyanate/epoxy or BMI blend. The mechanical properties like tensile, flexural, impact strength and fracture toughness of the blends and composites were studied as per ASTM standards. The blends and composites were evaluated by SEM analysis and DMA.

E-mail - msrde2000@yahoo.com

Phthalocyanine Terminated Polyimides for High Temperature Composites Applications

A series of novel imide-containing phthalonitrile polymers with flexible aryl ether units have been synthesized and characterized. Bisphenol monomers bis (4-hydroxy-3, 5-dimethyl) phenyl methane, bis (4-hydroxy-3, 5-dimethyl)-2-methoxy phenyl methane and bis (4-hydroxy-3, 5-dimethyl)-2, 4-methoxy phenyl methane were synthesized by a multi step synthesis involving a condensation reaction between benzaldehyde, anizaldehyde and 2, 4-dimethoxy benzaldehyde with 2, 6-dimethyl phenol respectively. The bisphenols obtained were reacted with 4-nitrophthalonitrile to form aryl ether linkage containing bisphthalonitriles. The bisphthalonitriles were hydrolyzed to tetra carboxylic acid, which were subsequently converted into corresponding dianhydrides. The obtained dianhydrides were end capped with synthesized 4-(3-aminophenoxy) phthalonitrile by thermal imidization formed imide-containing phthalonitrile monomers. The synthesized monomers were cured with three (two commercial and one synthesized) different aromatic bulky diamines.The structure and properties of all compounds synthesized were confirmed by using elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, DSC and TGA . The results show that all the compounds were synthesized in quantitative yields and exhibited good thermal properties. The cure temperatures were in the range of 245-294°C, the temperature of initial and 10% weight loss from TGA were in the range of 400-420 and 440-472 °C in N_2, char yield at 800 °C of 40-51%.

1) EPG Engineered nanoProducts Germany, Inc., Zweibr C3 BCcken, GERMANY

2) Akdeniz University, Antalya, TURKEY

High Abrasion Resistant Low Surface Free Energy Amide-Imide Coatings

Amide-Imide coatings in the form of inorganic-organic composites have been prepared from various amino precursor groupings linked to alkoxy silanes, such as aminopropyl triethoxysilane together with appropriate anhydrides or dianhydrides. The formation of imides only takes place at temperatures above 140C. The inorganic backbone was formed by hydrolysis and condensation of the alkoxy silanes during a reflux process. The inorganic cross-linking reaction (Si-O-Si formation) was controlled during the synthesis through limited hydrolysis, and the system could be kept at low viscosity in order to carry out coating processes. For obtaining specific properties, such as high abrasion resistant and low surface free energy (easy to clean and anti-adhesive properties), additives have been used. For the low free energy, oligomeric perflourinated hydrocarbons have been added, some of them having functional groupings, such as double bonds to be additionally cross-linked. The hydrocarbons could be dispersed homogeneously in the reaction mixture. Since the addition of nanoparticles did not improve the abrasion resistance, abrasive additives such as silicon carbide, aluminum oxide and quartz powders in the micrometer range has been added between five and 15 wt.-%. Coatings of 10 to 20x10^-6 m in thickness on stainless steel and aluminum have been prepared and cured and temperatures up to 250 C. Depending on the type of additives, the coatings are more or less translucent. The abrasion resistance was tested with a Taber Abrader device, using 1000 cycles at a load of 500 g. The best coatings showed a surprisingly low weight loss of around 1 g, which is close to ceramic glazings. The contact angles against water were up 110C, against octanol about 60C and are unchanged after the abrasion test. The combination of high temperature stability, very high abrasion resistance and easy to clean/anti-adhesive properties makes these coatings useful for many industrial applications.

Synthesis and Characterization of Polyimide Epoxy Hybrid Films

The present work reports the synthesis and characterization of some new polyimide epoxy hybrid films in view of their flexible nature and reduced brittleness as compared to epoxy diamine network and aromatic polyimide epoxy hybrid films. This was achieved by synthesizing aromatic diamines linked through aliphatic spacers and hence polyimides were derived from them. First of all epoxy diamine network was established using these synthesized diamines and a commercial epoxy. Then polyimide was dispersed into the network in different weight ratios for the formation of hybrid films. The synthesized diamines were characterized by IR, NMR spectra and elemental analysis. The formation of epoxy diamine network, polyimides and the hybrid films thereof was studied via FT-IR. Samples for thermal analysis have been sent and the results are awaited. The thermal and mechanical properties of the films (polymers) can be studied using techniques such as DSC, TGA and tensile testing machines.

Semi-Fluorinated Polymers Derived from Aromatic Trifluorovinyl Ethers

(Abstract not yet available)

tagawa@mech.kobe-u.ac.jp , yokota@mech.kobe-u.ac.jp

Fluorination of PMDA-ODA Polyimide using Hyperthermal Atomic Fluorine Beams

Surface fluorination of PMDA-ODA polyimide was performed by a hyperthermal electrically neutral broad atomic fluorine beam, which is created by a laser detonation atomic beam source. The fundamental properties of hyperthermal atomic fluorine beam-exposed polyimide surface are reported based on the analytical results by X-ray photoelectron spectroscopy and contact angle measurements. It was observed that CF, CF₂ or CF₃ moieties were formed at the atomic fluorine-exposed polyimide surfaces depending on the atomic fluorine fluences. Accompanying the atomic oxygen beam, which is used in the companion paper, advancing contact angles of water can be controlled from 60 to 120 degrees by varying the atomic fluorine (or oxygen) fluences. Surface roughness analyzed by atomic force microscopy slightly increased with atomic fluorine exposures due probably to the formation of volatile products such as CF₄. It was also identified that the hydrophobic properties of the modified polyimide surface was stable in an ambient air condition at least a couple of months. From a series of experiment, it has been demonstrated that the hyperthermal atomic beam can provide a stable fluorination of polyimide surfaces.

Amy L. Brunsvold ³, Brian J. Petteys⁴, Andrew J. Guenthner⁴,

Gregory R. Yandek¹, Joseph M. Mabry¹

1) AFRL/PRSM, Materials Applications Branch, Air Force Research Laboratory, 10 E. Saturn Blvd, Bldg. 8451, Edwards AFB, CA 93524, USA, sandra.tomczak@edwards.af.mil

2) ERC Incorporated, Materials Applications Branch, Air Force Research Lab,

10 East Saturn Blvd, Bldg 8451, Edwards AFB, CA 93524, USA

3) Department of Chemistry and Biochemistry, Montana State University, 108 Gaines Hall, Bozeman, MT 59717, USA

4) Research & Engineering Sciences Department, Chemistry Division, NAVAIR-US NAVY, China Lake, California 93555-6100.

Space-Survivability of Main-Chain and Side-Chain POSS-Kapton^® Polyimides

Kapton® polyimde (PI) is an extensively used space material in solar arrays, spacecraft thermal blankets, and space inflatable structures. Upon exposure to atomic oxygen (AO) in low Earth orbit (LEO), Kapton® is severely degraded. An effective approach to prevent this erosion is chemically bonding polyhedral oligomeric silsesquioxane (POSS) into the polyimide matrix by copolymerization of POSS-diamine with the polyimide monomers. POSS is a silicon and oxygen cage-like structure surrounded by organic groups which can be polymerizable. The copolymerization of POSS provides Si and O in the polyimide matrix on the nano-level. After exposure to a fluence of 8.5 x 1020 O atoms cm-2 from a hyperthermal AO beam, erosion yields of 3.5 and 7 wt % Si₈O₁₁ main chain (MC) POSS-PI samples were 3.7 and 0.98 percent, respectively, of the erosion yield for Kapton H®. X-ray photoelectron spectroscopy surface studies on POSS-Kapton® polyimides exposed to AO in ground-based facilities and in low Earth orbit (LEO) on an approximately 4 year flight on the Materials International Space Station Experiment (MISSE), show that a silica surface layer forms on POSS-Kapton® polyimide films during the exposures. Comparison of MC-POSS-Kapton® PIs and a recently synthesized side-chain (SC) POSS-Kapton® PI showed these polymers have similar AO resistance, and have similar physical properties to Kapton H®. A comparison of physical properties, AO-resistance, transmission electron microscopic images, and scanning electron microscopic images of various POSS-Kapton® polyimides will be presented.

Soluble Polyimides Based on Aromatic Diamines Bearing Long-Chain Alkyl Groups

Although polyimides have been widely used for microelectronics, the one of disadvantages of these polymers is that these are insoluble in common solvents. The author has systematically investigated the synthesis and characterization of soluble polyimides based on alicyclic tetracarboxilic dianhydrides, aromatic diamines bearing long chain alkyl groups, and aromatic diamines containing dendric moieties. In this paper, the effects for the enhancement of solubility based on aromatic diamines such as alkyloxydiaminobenzene (AODB-10~14, number; carbon numbers of alkyl chain), alkyldiaminobenzophenone (ADBP-9~14), diaminobenzoic acid alkylester (DBAE-8-14), and alkyldiaminobenzamide (ADBA-9~14) were discussed in detail and the conclusions were as follows; (1) the effect of functional diamines were increased as AODB > ADBP > ADBA > ADBE, (2) long chain alkyl groups bearing twelve carbon atoms are the most effective, (3) long chain alkyl groups bearing even numbers of carbon atoms are more effective, (4) branched alkyl chains are more effective. The polyimides having dendric side chains were also investigated. For example, the terphenylene diamine monomer having a first generation of monodendron, 3,4,5-tris(n-dodecyloxy)benzoate and the monomer having a second generation monodendron, 3,4,5-tris[-3’,4’,5’-tri(n-dodecyloxy) benzyloxy] benzoate were successfully synthesized and the corresponding soluble polyimides were obtained by polycondensation with tetracarboxilic dianhydride monomers such as benzophenone tertracarboxilic dianhydride (BTDA). The properties of obtained polyimides such as thermal stability and solubility were examined and the application for alignment films for LCDs was investigated, and it was found that these polyimides having dendric side chains were applicable for the vertical aligned nematic liquid crystal

Department of Chemistry, Alan G.Macdiarmid Institute, Jilin University, Changchun, P. R. China, 130012.

New Kind of Carbon-Fiber-Reinforced Phenylethynyl-Terminated Polyimde Composites

Carbon-fiber-reinforced PETI-type polyimide composites were prepared based on new kind of polyimide matrix resin, which derived from dianhydride (s-BPDA), 2, 5-bis(4-aminophenoxy)-biphenyl(p-TPEQ) and 4-phenylethynylphthalic anhydride (PEPA). The candidate material exhibited a combination of properties required for RTM with melt viscosities of 93-300Pas at 300^oC and good stability (>2h) at 280^oC. With the advantages of this novel matrix resin, an optimized molding cycle was designed for fabricating carbon fiber/PI composites. The thermal and physical properties of the composites were measured by dynamic mechanical thermal analysis, thermogravimetric analysis, thermomechanical analysis, and composition tests. The mechanical properties were tested at both room temperature and 177 °C. The flexural properties were determined by 3-point-bending at room temperature. Thermal aging involved exposing samples to temperature 177°C over 500 hours. The mechanical properties were measured after isothermal aging for 200, 400, 600, 800 and 1000 hours. The tensile failure surfaces of the aged composites were also detected with scanning electron microscopy. From these studies, it was concluded that the composites exhibited not only remarkable environmental stability, but also excellent processability, as well as toughness improvement and thermooxidative stability.

Vladislav Borovik ³, Oleg Shkurko³, Dmitry Mognonov ^1,2

1) Buryat State University , Smolina st., 24a, Ulan-Ude , RUSSIA

2) Baikal Institute of Nature Management SB RAS, Sakhyanovoy st., 6, Ulan-Ude, RUSSIA

3) Novosibirsk Institute of Organic Chemistry SB RAS, Acad. Lavrentjev Ave., 9, Novosibirsk, RUSSIA

Novel Pyrimidine Containing Polyimide and Films for Fuel Cells

The novel pyrimidine-thienyl containing diamine, 6-thienyl-2,4-bis-(p-aminophenyl)pyrimidine, and pyrimidine containing bisitaconimide, 2-phenyl-4,6-bis-(-itaconimidophenyl)-pyrimidine, were prepared. The novel pyrimidine-thyenyl containing oligoaminobisitaconimide was prepared by polyaddition of pyrimidine-thienyl containing diamine to the pyrimidine containing bisitaconimide:

The reaction was carried out in N-methylpyrrolidone-2 at 115-120°C, with catalyst C₆H₅COOH and C₆H₅COOLi. The resulting compound was characterized by conventional measurements. The composite films based on pyrimidine containing oligoaminobisitaconimide and aromatic polybenzimidazole were prepared. Doping of composite films was carried out by immersing in ₃₄ solutions. Specific conductivity of film (90% polybenzimidazole + 10% oligoaminobisitaconimide) increases from 0.024´10^-3 S/ up to 29.5010^-3 S/ with increase of temperature up to 400 K. This film possesses good mechanical properties after doping. Therefore these composites can be used for proton conducting membranes for fuel cells.

2350 E. El Segundo Blvd., M2-248, El Segundo, CA 90245

Zeolite Modified Polyimides as Absorption Materials for Molecular Contamination

Polyimide is a unique spacecraft material because of its incredible strength and astounding heat and chemical resistance. Modifying polyimide with chemical specificity while retaining its material properties is important to develop multi-function materials to solve challenging contamination, thermal regulation, and space environment problems. A particular contaminant of interest is water. Moisture contamination leads to deterioration of absorbance and transmittance properties of optical surfaces. Zeolites have been widely known to absorb water and other molecular contaminants, with enhanced absorption properties when synthesized on the nanoscale level. Nanozeolite particles were superficially modified to promote uniform inclusion into the polyimide matrix. In this presentation, the water absorption properties of this new multi-functional polymide material will be compared to the unmodified parent polyimide.

1) NASA, Kennedy Space Center, FL 32899

2) NASA, Langley Research Center, VA 23681

Polyimide Foam Composites for Enhanced Thermal and Acoustical Insulation

NASA has had a growing need for high-performance polymer foams for cryogenic insulation, fireproofing, energy absorption and other applications. Commercially available foams, however, do not meet all of the requirements for surviving extreme environments. Most low-density foams crack at cryogenic temperatures, and the foams that can withstand extreme temperatures do not have the required structural integrity or thermal performance. Chemists and Engineers at NASA's Kennedy Space Center and Langley Research Center have collaborated in the development of a polyimide foam composite based on TEEK polyimide technology with enhanced thermal performance and sound attenuation properties. The foam composites can be fabricated to target densities; high density foam composites for structural applications and low density foam composites where more flexibility might be advantageous. Heat transfer reduction is driven primarily by inorganic aerogel filler, with aerogel blankets composites having the most significant reduction in heat transfer, improved acoustic insulation and vibration attenuation. The TEEK composites are fire resistant and have good weathering resistant properties. The composite technology also lends itself to other foam systems. These materials may prove useful in process piping, tanks for transporting and storing hot or cold fluids, ship and boat building and especially aerospace applications.

1) National Institute of Aerospace, Hampton, VA 23666

2) Advanced Materials and Processing Branch, NASA Langley Research Center, Hampton, VA 23681

Polymer Nanocomposites for Aerospace Applications

Breakthrough materials for use in the next generation of air and spacecraft will almost certainly need to meet several criteria before serious consideration will be given to their use; among these are light weight, excellent mechanical properties, and multifunctional behavior. High performance polymer nanocomposites are one class of materials with the potential to meet these criteria. Our focus has been on developing nanocomposites composed of high aspect ratio carbon nanofillers (single, double, and multiwall carbon nanotubes and expanded graphene oxide platelets) dispersed in high performance polymer matrices (polyimide derivatives). A common problem encountered in producing these nanocomposite materials is the poor dispersability of the filler particles in the matrix. This is usually addressed by modifying the filler to improve its compatibility with the matrix. Following this approach with the graphitic fillers mentioned above, however, would have a deleterious effect on the very properties, electrical and mechanical, that make them attractive for this application. Instead, we have focused on how the polymer comprising the matrix can be redesigned to improve the quality of dispersion. We take a multidisciplinary approach to this work by combining molecular modeling, lab scale processing, and state of the art characterization. This contribution will highlight recent work which has improved our understanding of what makes a particular polymer a good (or bad) matrix material for graphitic nanofillers and present results demonstrating the excellent electrical and mechanical properties that can be achieved with high quality nanocomposites.

Preparation of Highly Reflective And Conductive PI/Ag Composite Films by Ion-exchange and Self-Metallization Techniques

A direct ion-exchange self-metallization technique is used to prepare the surface silver metallized polyimide. The method involves performing an ion exchange reaction of damp-dry poly(amic acid) films in silver aqueous solution to form silver(1)-containing precursor films. Thermal treatment under tension converts the poly(amic acid) into polyimide and simultaneously reduces the silver(1) to silver(0), yielding silver layers with excellent reflectivity and conductivity on both film sides. This work focuses on the influence of polyimide structure, the sorts of silver salt, ion exchange time and the curing condition on the morphology and properties of films. Three polyimide matrices derived from BTDA/ODA, OPDA/ODA and PMDA/ODA respectively and two silver salts including AgN03 and AgF are taken into consideration. XRD, TEM, SEM, XPS, AFM and so on are used to characterize the structure and morphology of polyimide/Ag composite films. The results show that the BTDA/ODA based polyimide and AgF are more efficient to obtain highly reflective and conductive films than the others.

Email: Shiyang@iccas.ac.cn

Aromatic Polyimide Resins for High Density Packaging Substrates

Molecular weight-controlled aromatic polyimide resins for fabrication of high density IC packaging substrates have been developed. The aromatic polyimide resins showed good laminate processability, which could easily dissolve in organic solvent to give low viscosity resin for impregnation of E-glass fiber cloths. After completely removal of the organic volatile, the polyimide/glass fiber (PI/GF) cloth prepreg could be plied up and then thermally cured at 280 ^oC to give the PI/GF laminate suitable as packaging substrate core. Experimental results indicated that the polyimide laminates have the desirable characteristics for packaging substrate core, including 1) excellent thermal stability with initial thermal decomposition temperature of >500 ^oC, CTE (in-plane) of 18-20 ppm/^oC and glass transition temperature of >240 ^oC; 2) good mechanical properties with flexural strength of >430 Ma and flexural modulus of 20 GPa, tensile strength of > 230 MPa and impact toughness of 84 KJ/mm²; 3) great electrical insulating and dielectric properties with volume resistance of >10¹⁶/cm, dielectric constant of 4.1 and dissipation factor of 0.005 etc.; and 4) high peel strength of copper foil to laminate in Cu-claded laminate( >1.0 N/mm).

1) Department of Mechanical Engineering, Faculty of Engineering, Kobe University, 1-1 Rokko-dai, Nada, Kobe 657-8501 JAPAN

2) Japan Aerospace Exploration Agency

3) Kyushu Institute of Technology

Durability of a Silicon-Containing Polyimide in a Simulated Low Earth Orbit Space Environment

Erosion properties of a silicon-containing polyimide in a simulated low Earth orbit (LEO) space environment have been studied. Hyperthermal atomic oxygen beam, which is formed by a laser-detonation beam source, was used to simulate atomic oxygen environment in LEO. In contrast, a 172 nm excimer light is utilized for the simulation of vacuum ultraviolet (VUV) environment. Mass of the silicon-containing polyimide film formed on a gold electrode of quartz crystal microbalance was measured during the exposures. X-ray photoelectron spectroscopy revealed that the thin silicon dioxide film was formed on the polyimide surface by the reaction with atomic oxygen. The silicon dioxide film prevents the further direct reaction of impinging atomic oxygen with carbon atoms in the polyimide structure. As a result, erosion rate (or mass loss) of a silicon-containing polyimide gradually decreases with increasing atomic oxygen fluence and it reaches one tenth of the conventional PMDA-ODA polyimide. The erosion rate by 172 nm VUV in O₂ atmosphere (1 atm.) is greater than the PMDA-ODA polyimide, however, it is still quite small for a polymer used for aerospace applications. A series of experimental results suggested that the silicon-containing polyimide has a high durability against both atomic oxygen and VUV environments which simulate LEO environments.

Preparation of Ultra-low Dielectric Constant Polyimide Foam via Phase Inversion Process

(Abstract not yet available)