bluuebunny/crossref_metadata_2025 huggingface dataset:
Dewetting Properties of Polystyrene Homopolymer Thin Films on Grafted Polystyrene Brush Surfaces
Authors: Sharma S , Rafailovich M H , Sokolov J , Liu Y , Qu S , Schwarz S A , Eisenberg A
Published: August 2002

We have found that the critical molecular weight for auto dewetting of a homopolymer on a polymer brush of the same chemical composition is approximately NH = 0.5 NB, in good agreement with the mean field theory prediction. The measured velocity on the brush surface is at least an order of magnitude faster than that of the polystyrene (PS) on a homopolymer interface, with a greatly decreased dependence on the PS molecular weight. This suggests slippage as a possible mechanism for the dewetting dynamics.
New Soluble Polyimides Containing Hydroxylic Groups: I. Synthesis and characterization
Authors: Schab-Balcerzak Ewa , Sek Danuta
Published: August 2002

A series of aromatic polyimides from different diamidedianhydrides and 2,4-diaminophenol dihydrochloride was synthesized using a one-step high-temperature polycondensation. The structural characterization of the prepared polyimides was carried out by using Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The influence of the monomers’ structures on the polymers’ properties has been investigated.
One-Pot Synthesis of Copoly(Aliphatic–Aromatic)Oxadiazoles: How to Control the Formation of Random or Block Structures?
Authors: Briffaud T , Garapon J , Sillion B
Published: August 2002

The polyoxadiazole synthesis in P2O5/CH3SO3H solution has been improved by precipitation of the reaction mixture in cold NMP. The polyoxadiazole obtained by this process did not contain uncyclized hydrazide moieties and was more stable in strongly acidic media. This process has been used to prepare some copolyoxadiazoles with dodecanedioic and isophthalic diacids or dihydrazides. The microstructure of the copolymers (alternate versus block) depends on the nature of the isophthalic derivative. With isophthalic dihydrazide, which is soluble in the reaction mixture like the dodecanedioic derivative, an alternate structure is obtained. With isophthalic diacid, which exhibits low solubility, the dodecanedioic derivate first reacts giving an aliphatic oxadiazole sequence and finally a block copolymer is obtained. The microstructure was determined by proton NMR spectroscopy allowing us also to calculate the average sequence length. UV–vis spectra of the block copolymers show a bathochromic effect compared with the spectra of the alternate copolymers. The block copolymer obtained with 75% dodecanedioic and 25% isophthalic diacid shows three transitions at −10°C ( Tg1), 50°C ( Tm) and 220°C ( Tg2). Heated at 150°C, a moulded specimen has been stretched up to 100%, and cooled down at room temperature under stress. The temporary shape is stable at room temperature and the initial shape is restored by heating at 110°C. The mechanical stress stored in the temporary shape was about 1.6 MPa.
Constitutional Isomerism: Synthesis and Characterization of Ordered Polyamides from Isophthalic Acid and N-Phenylethylenediamine by Direct Polymerization
Authors: Li Li , Haba Osamu , Endo Takeshi , Ueda Mitsuru
Published: August 2002

An ordered (head-to-head (H–H) or tail-to-tail (T–T)) polyamide was prepared by direct polycondensation of a symmetric monomer, isophthalic acid (1) with N-phenylethylenediamine (2) as a non-symmetric monomer using the condensing agent diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate. The polycondensation was carried out by slow addition of (1) to (2), and gave polyamide (3d) with an inherent viscosity of 0.29 dl g−1. On the other hand, authentic H–H or T–T ordered polyamide (3a) and H–T ordered polyamide (3b) were obtained by a multi-step route. Random polyamide (3c) was synthesized by mixing isophthaloyl chloride and 2 all at once in N-methyl-2-pyrrolidinone. The microstructure of the polymers was investigated by 1H and 13C NMR spectroscopy. It was found that their spectra were different due to their different constitutions, while polymer 3d obtained by direct polycondensation had the expected H–H or T–T sequence. Furthermore, the model reactions were studied in detail to demonstrate the feasibility of selective amidation and polymer formation.
Synthesis and Characterization of Ordered Polyurethanes from Tolylene 2,4-Diisocyanate and Ethylene Glycol
Authors: Hikita Takami , Mochizuki Amane , Takeuchi Kazuhiko , Asai Michihiko , Ueda Mitsuru
Published: August 2002

An ordered polyurethane with a head-to-head or tail-to-tail (H–H or T–T) content of 90% was prepared by polyaddition reaction of a nonsymmetric monomer, tolylene 2,4-diisocyanate (1) with a symmetric monomer, ethylene glycol (2). The polymerization was conducted in toluene in the presence of dibutyltin dilaurate (DBTL) at 0°C by slow addition of a half amount of 2 to 1, followed by removing toluene and then adding the rest of 2 in DMF at once at room temperature in the presence of DBTL. Furthermore, the authentic ordered and random polymers were prepared to verify the structure of the ordered polymer and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced on their thermal properties.
Synthesis of All Aromatic Poly(Thioether-Ketone)s, Sulfur-Containing High Performance Polymers with High Solubility
Authors: Matsumura Sumiko , Kihara Nobuhiro , Takata Toshikazu
Published: August 2002

Novel aromatic poly(thioether-ketone)s (PTEKs) bearing the 2,6-dimethyl-1,5-naphthylene unit were synthesized by the polycondensation of aromatic dihaloketones and aromatic dithiols in the presence of K2CO3. High molecular weight ( Mn∼ 65 000, Mw∼ 350 000) PTEKs were obtained in quantitative yields. The molecular weight and yield of PTEK obtained from dichloroketone and dithiol were much higher than those of the corresponding poly(ether-ketone) obtained from dichloroketone and biphenol. The use of the fluoroketone as a monomer did not increase the Mn of PTEK. The effect of reaction conditions on the yield and the molecular weight of PTEKs was investigated. The phase-transfer-catalysed polycondensation and the polycondensation using masked dithiol and dichloroketone were also investigated. The PTEKs prepared have high solubility in ordinary organic solvents. Flexible, transparent, and strong cast films were prepared. The PTEKs had high glass transition temperatures (PTEK-1, 245°C and PTEK-2, 215°C) and 5% weight loss temperatures (PTEK-1, 435°C and PTEK-2, 436°C).
Study of Related Poly(1,3,4-Oxadiazole-Amide)s Containing Silicon or Hexafluoroisopropylidene Groups in the Main Chain
Authors: Iosip Mariana Dana , Bruma Maria , Robison Jenifer , Kaminorz Yvette , Schulz Burkhard
Published: August 2002

Two series of related poly(oxadiazole-amide)s have been synthesized by solution polycondensation reaction of aromatic diamines containing preformed 1,3,4-oxadiazole rings with diacid chlorides having silicon or hexafluoroisopropylidene groups. All these polymers were soluble in polar amidic solvents, such as N-methylpyrrolidinone and dimethylformamide and gave thin transparent free-standing films on casting their solutions. The polymers exhibited high thermal stability, with the initial decomposition temperature being above 400 °C. Most of these polymers did show a glass transition, being in the temperature range of 238–275 °C. Very thin coatings, in the range of tens of nanometres, which were deposited onto silicon wafers exhibited smooth and pinhole-free surfaces in atomic force microscopy investigations. The study of photoluminescence properties revealed that some of these compounds emit blue light, in the range of 440–475 nm. All these characteristics are discussed and compared with those of conventional aromatic poly(1,3,4-oxadiazole)s.
Preparation and Properties of Novel Aromatic Polyimides from 5,7-Diamino-1,1,4,6-Tetramethylindan and Aromatic Tetracarboxylic Dianhydrides
Authors: Tamai S , Kamada J , Goto K , Yamaguchi A
Published: August 2002

Novel aromatic polyimides containing indan structure units were prepared from 5,7-diamino-1,1,4,6-tetramethylindan and various aromatic tetracarboxylic dianhydrides. The glass transition temperatures ( Tg’s) of these polyimides were not observed by differential scanning calorimetry at a temperature lower than 500 °C and the 5% weight loss temperatures ( Td5’s) of them were above 422 and 474 °C in air and nitrogen, respectively. Polyimide prepared from 5,7-diamino-1,1,4,6-tetramethylindan and 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride was soluble in organic solvents such as tetrahydrofuran, cyclopentanone, chloroform, acetone, ethyl acetate, N-methyl-2-pyrrolidinone and cresol at 20 wt% concentration at ambient temperature. The other resulting polyimides obtained from this diamine possessing an indan structure were also soluble in several organic solvents. These results indicated that polymer properties such as thermal behaviour and solubilities were influenced by the indan structure unit in a repeating structure.
Space Environment Simulation for Radiation Tests of Materials: Third Version of an International Standard
Authors: Briskman Boris , Belyakov Alexander , Klinshpont Eduard , Stepanov Vladimir , Shavarin Yuli , Borson Eugene , Novikov Lev , Makletsov Andrey
Published: August 2002

In the framework of the International Organization for Standardization (ISO) activity of 1996 we started development of an international standard series for a space environment simulation of on-ground tests of materials. A draft of the first international standard ‘Space environment simulation for radiation tests of materials’ (first version) was presented at the 7th Int. Symp. on Materials in Space Environment by Briskman et al (1997). The second version of the standard was limited to nonmetallic materials and was presented at the 20th Space Simulation Conf. The Changing Testing Paradigm by Briskman et al (1998). The third version of the standard was discussed at the last ISO TC20/SC14 meeting (Torino, Italy, 1999); in essence it was completely revised.

A new standard orbit for the International Space Station is introduced in the recommended list of such orbits. The values of energy fluences for electrons and protons at all six orbits are calculated just as the absorbed doses on the 1 mg cm−2 depth in aluminum. Values of the depth distribution criterion of the absorbed dose for two exponents are also calculated for four standard orbits. Now the list of radiation includes the near ultraviolet region. The spectral solar irradiances for far and near ultraviolet radiation based on ASTM E 490 data are introduced into the document. Accordingly, the ‘Radiation sources for simulation’ issue is enlarged and the section ‘Terms and definitions’ is replaced with a new version, the list being enlarged from seven to 32 terms. For the section ‘Requirements for simulation of space radiation’ a fixed procedure is recommended for space environment simulation of the radiation tests. For the section ‘Simulation of radiation dose rate’ extra sections are introduced that correspond to induced factors limiting the conduct of radiation tests conduction: radiation heating, residual atmosphere impact, vacuum requirements and electrical charging. Special attention is focused on dose rate effects in nonmetallic material, irradiated in vacuum.
Radiation-Induced Conductivity of Poly(Ethylene Terephthalate): Theoretical Model and its Applications
Authors: Tyutnev Andrey P , Kundina Yuliya F , Saenko Vladimir S , Doronin Alexander N , Pozhidaev Evgenii D
Published: August 2002

A theoretical model describing radiation-induced conductivity in polymers generally and in poly(ethylene terephthalate) (PET) in particular and based on the multiple trapping formalism in terms of hopping conduction has been presented. The physical meanings of the main parameters used in the model are also briefly discussed. An express method to determine these parameters for PET has also been given. Experimental data relating to pulse and continuous irradiation are used to assess charging effects in thin (<10 μm) Mylar films under simulated substorm conditions at geosynchronous orbit. It has been shown that punchthrough discharges are likely to occur only in penumbra conditions at low temperatures (<−50 °C). We also discuss a tentative approach to the development of high-performance polymers as far as their photo- and radiation-induced conductivity is concerned.
The Effect of Structure on the Performance of Luminescent Polystyrene Composites
Authors: Borisenko A Yu
Published: August 2002

This paper is devoted to the investigation of the effect of structure and production method son the performance of luminescent polystyrene composites. It has been shown that the production conditions of luminescent polystyrene composites define the matrix molecular-mass distribution and their material structures. The selection of a technological regime of composite production allows one to increase the optical homogeneity of products and to provide high material strength.
Some Peculiarities in Laboratory Simulation of Polymer Film Degradation by Solar Vacuum Ultraviolet Radiation in a Space Environment
Authors: Skurat Vladimir E , Samsonov Pavel V
Published: August 2002

A theoretical analysis has been made on the reliability of the simulation of solar radiation effects on polymer films under conditions of the space environment by using various light sources under laboratory conditions. Two main factors are noted that can influence the possible differences in the results of natural and laboratory tests; namely, the differences between the spectral distributions of solar radiation and laboratory light sources and the differences in the intensity of the radiation used in tests. It is found that at least two radiation sources are needed for the simulation of the erosion and the deterioration of the mechanical properties of polymer films. The effect of intensity occurs for polymers that are destroyed by radiation (a typical example is Teflon) and this has as a basis in the limited rate of evaporation of fragments of polymer chains.
Nonlinear Phenomena in the Mass Loss of Polyimide Films under Hyperthermal Atomic Oxygen Beam Exposure
Authors: Kinoshita Hiroshi , Tagawa Masahito , Yokota Kumiko , Ohmae Nobuo
Published: August 2002

Erosion phenomenon of polyimide film under the hyperthermal atomic oxygen beam exposure, which is a simulated low Earth orbit space environment, has been investigated. The polyimide film was spin-coated on a sensor crystal of a quartz crystal microbalance, and the mass of the film was measured under the atomic oxygen beam exposure. The spin-coated polyimide film which was exposed to a 4.7 eV atomic oxygen beam showed a mass gain at the beginning of the reaction and then steady-state mass loss followed. The experimental results of the mass change was analysed by the computational model, and the results showed that the carbon abstraction rate at the oxygen-adsorbed sites was two orders higher than that at the unoxidized polyimide surface. The computational results suggested that a large fraction of the carbon abstraction reaction occurred in the oxygen-adsorbed site through a Langmuir–Hinshelwood reaction mechanism.
Preparation and Properties of Resacetophenone-Thiourea-Trioxane Polymers
Authors: Pancholi Hemendra B. , Patel Mohan M.
Published: August 2002

Polymers (RTT') were synmthesized by the condensation of resacetophe-none (R) with thiourea (T) and trioxane (T') in the presence of 2 Mu HC1 or 2 M H2S04 as a catalyst and varying molar proportions of reactants. The polymers were characterized by elemental analyses and IR spectral studies. The number average molecular weights of polymers were determined by vapour pressure osmometry and non-aqueous conductometric titrations in pyridine. Viscosity measurements were carried out in DMF Thermogravimetric measurements of the polymers have also been carried out.
Resacetophenone-Thiourea-Trioxane Polymer as an Ion Exchanger
Authors: Pancholi Hemendra B. , Patel Mohan M.
Published: August 2002

Ion-exchange properties of resacetophenone-thiourea-trioxane polymers were studied for Cu2+, Ni2+, Co2+, Mn2+, Zn2+, Fe3+ and UO22+ ions. A batchequilibration method was employed in the study of the selectivity of metal ion uptake. This involved measuring the distribution of a given metal ion between the polymer sample and the solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strengths. The polymer showed a higher selectivity for Co2+, Fe3+ and UO22+ ions than for Mn2+, Co2+, Ni2+ and Zn2+ ions.
Correlation between the Morphology and Permeability of Liquid Crystalline Polymer/Polyethersulphone Blends
Authors: James S. G. , Donald A. M. , Miles I. S. , Macdonald W. A.
Published: August 2002

Blends of polyethersulphone (PES) and a thermotropic copolyester based on hydroxynaphthoic acid and hydroxybenzoic acid residues have been examined. The permeability to oxygen of thin pressed films of a range of compositions has been studied. It is found that fairly modest additions of the liquid crystalline polymer (LCP) lead to a pronounced improvement in barer properties. This improvement is ascribed to the formation of a thin surface layer of the LCP. The existence of this LCP surface layer is supported by examination in the scanning electron microscope of dimethyl formamide etched samples: etching does not remove all the PES because it is protected from the etchant by the surface layer.
Glass-reinforced Polyimide Composites based on Poly(4-furanyl-butan-2-one)
Authors: Patel Hasmukh S. , Patel Harshad D.
Published: August 2002

A novel approach was used to develop a matrix resin for processable poiyimide-glass-fibre composites. Furfural-acetone (FAC) resin, poly(4-Furanyl butan-2-one), and various bismaleimides were polymerized at 140 + 10 and 180+ 10+C by in situ Diels-Alder intermolecular reaction into moderately thermally stable and highly cross-linked polyimide-glass-fibre composites without the evolution oQf by-products. The fabricated composites (i.e. laminates) were characterized by their chemical resistance and mechanical properties
Synthesis and Characterization of Epoxy Resin Containing Copper Acrylate
Authors: Anand Manjit , Srivastava A. K.
Published: August 2002

Novel epoxy resins containing copper have been synthesized by reacting copper acrylate with bisphenol A and excess epicholorohydrin. Values of as epoxy equivalent weight, hydroxyl content and hydrolyzable chlorine content have been estimated. The resins have been characterized by IR, 1H-NMR and 13C-NMR analysis. The cured resins were evaluated for thermal properties. The curing of resins has been carried out with polyamide at 30 °C and with phenacyl dimethyl sulfonium ylide mercuric chloride complex by heating at 150 °C for 8 h and at 180 °C for 3 h. The cured resins have improved electrical properties and excellent thermal and chemical resistance in comparison with the control resin. The reaction follows first-order kinetics with activation energies of 47 and 34 kJ/mol in the presence and absence, respectively, of copper actrylate. The copper forms a complex with bisphenol A, as indicated by spectroscopic studies, which increases the epoxidation rate.
Solid State 13C-NMR as an Indicator of the Microstructure of a Silicon Containing Dianhydride and Derived Bisimides
Authors: Dinan Frank J. , Wolfe Roger A. , Hojnicki Daniel S. , Schwartz Willis T. , Clair Terry St , Pratt J. Richard
Published: August 2002

The CP/MAS 13C-NMR spectrum of bis(3,4-dicarboxyphenyl)-dimethylsilane dianhydride (SiDA) as well as the spectra of the N-methyl and N-n-propyl bisimides derived from this dianhydride confirm the occurrence of solid state charge transfer complex (CTC) formation in these compounds. The proposed solid state alignment for SiDA was confirmed by X-ray diffraction spectroscopy. These compounds are monomeric models for polyimides and CTC formation in them supports the probability that such complexes form in polyimides.
Alginate Polyelectrolyte Ionotropic Gels-XVI. Kinetics and Chemical Equilibria Studies for Heterogeneous Ion Exchange of Polyvalent Metal Ions in Alginate Gel Complexes
Authors: El-Shatoury S. A. , Hassan R. M. , Said A. A.
Published: August 2002

The kinetics or chemical equilibria of exchange of Ca(II), Sr(II), Ba(I), Zn(II), Cd(II), Al(III), Fe(III), Se(IV), Ce(IV) and Th(IV) counter ions in alginate gel complexes by H+ ions have been investigated titrimetrically and conductimetrically at a constant ionic strength of 0.1 mol/dm3. The thermodynamic parameters have been evaluated and are discussed in terms of ionic radii and polarizability of the metal ions, coordination geometry, and stability of the gel complexes.
Polyimides containing pendent trifluoromethyl.groups
Authors: Havens S J , Hergenrother P M
Published: August 2002

Several new polyimides containing trifluoromethyl groups were prepared from the reaction of various aromatic dianhydrides and two new diamines containing trifluoromethyl groups, 4,4'.bis(3-amino-5-trifluoromethylphenoxy)biphenyl and 1,4-bis(3-amino-5-trifluoromethylphenoxy)benzene. The diamines were prepared from the aromatic nucleophilic displacement of the disodium salts of 4,4'-biphenol or hydroquinone with 3,5-dinitrobenzotrifluoride followed by hydrogenation of the resultant dinitro compounds. The thermally cured polyimides exhibited glass transition temperatures between 186 and 262 C. By thermogravimetric analysis, the polyimides exhibited 5% weight losses at 484-527 C in nitrogen and 452-506 C in air.
Dielectric and thermal characterization of fluorinated polyimides containing heterocyclic moieties
Authors: Mercer Frank W , McKenzie Martin T
Published: August 2002

A series of fluorinated polyinides and fluorinated polyimides containing heterocyclic moieties were prepared and investigated to determine their dielectric constants, dielectric constants as a function of relative humidity (RH) and thermal properties. Thle fluorinated polyimides containing heterocyclic moieties were prepared from diamines containing pyridine, pyridazine, oxadiazole or benzoxazole moieties. The properties of the fluorinated heterocyclic-containing polyimides were compared with those of fluorinated polyimides prepared from aromatic diamines. In most cases, the introduction of heterocyclic moieties caused an increase in dielectric constant, an increase in the dielectric constant as a function of relative humidity and a decrease in thermal stability compared with the polyimides prepared with aromatic diamines.
Sorption of methylene chloride vapor in polyimide films
Authors: Moylan Christopher R , Wade Christopher P , Swanson Sally A , Best Margaret E
Published: August 2002

Sorption of metbylene chloride vapor into thin films of three different polyimides was measured by means of a quartz crystal microbalance (QcM) apparatus. Rate laws for sorption and desorption were determined. Based on these data, it is concluded that methylene chloride vapor swells these polymers, and that sorption into a previously swollen film is quicker than initial sorption into a fresh film. The implication of these results for microelectronic packaging is discussed.
Studies of vinyl ester resins and their urethanized derivatives
Authors: Pachha R R , Thakkar J R , Patel R D
Published: August 2002

The epoxy resins diglycidyl ether of bisphenol A and triglycidyl p-amino phenol were reacted with acrylic acid to afford the corresponding acrylated resins. These vinyl ester resins were then reacted with toluene di-isocyanate to procure their urethanized derivatives. All these resins were characterized by their viscosity, number average molecular weight and infrared spectrophotometry. Curingconditions for these resins were established by differential scanning calorimetry. The results indicated that the curing reaction follows first-order kinetics, with activation energy in the range 53-84 kJ mol-. Styrene monomer was observed to lower the curing temperature of all resin systems when incorporated prior to curing.
Structure-property relationships in PMR-15-type polyimide resins: IIH. New polyimides incorporating triazoles, quinoxalines, pyridopyrazines and pyrazinopyridazines
Authors: Jigajinni V B , Preston P N , Shah V K , Simpson S W , Soutar I , Stewart N J
Published: August 2002

Polyimide oligomers (prepolymers) and resins of the PMR-15 type have been prepared from 5-norbomene-2,3-dicarboxylic half acid ester (NE), 3,3',4,4'-benzophenone tetracarboxylic diester (BTDE) and a series of diamines incorporating 1,2,3-triazole, quinoxaline, pyrido[2,3-b]pyrazine, pyrido[3,4-b]pyrazine, benzo[g]quinoxaline, pyrazino-[2,3]-d]pyridazine and bis(pyrido[3,4-b]pyrazino)benzene ring systems. Two tetraamines in the bis(pyrazino[2,3-d]pyridazino)benzene ring system were also employed. Selected diamine monomers from the above ring systems provde PMR-15-analogue resins of higher thermal and thermooxidative stability than PMR-15 itself. The physical behaviour during oligomerization and curing of PMR systems has been studied by dynamic mechanical thermal analysis (DMTA). Traces akin to that from PMR-15 are obtained using certain diamine monomers (e.g. triazole and pyrido[3,4-b]pyrazine containing) but a featureless thermogram is observed using tetraamines in the bis(pyrazino[2,3-dj]pyridazino) benzene system.
Amorphous Bisphenol A Based Poly(Arylene Ether) Modified Cyanate Ester Networks
Authors: Srinivasan S A , McGrath J E
Published: August 2002

Cyanate ester or triazine networks are receiving considerable attention as potential candidates for high-temperature adhesives and composite matrices. Low toughness is a major drawback with most cross linked thermosetting materials, including the cyanate ester networks. Considerable attention has been devoted to the aspect of toughening such brittle networks in our laboratories. Reactive functional thermoplastic toughness modifiers not only enhance toughness but also permit highly desirable stability to solvent stress cracking without seriously affecting the moderately high modulus. We have earlier reported on various aspects of this technology as applied to epoxy and bismaleimide systems. Careful control of the hetetophase morphological structure is necessary to achieve significant toughening. In the present work, we have focused on modifications of a specific cyanate ester network system based on bisphenol-A with thermoplastic modifiers of varying backbone molecular weight and chemistry. In particular, hydroxyl or cyanato functional bispheno]-A based amorphous poly(arylene ether sulfone)s and poly(arylene ether ketone)s have been successfully utilized. Blends of reactive and non-reactive polysulfones were also demonstrated to be useful tougheners, apparently by allowing phase size control. The use of polyarylene ether ketones (which are of lower polarity than the polyarylene ether sulfones) resulted in larger, well defined morphologies, which in turn afforded tougher networks. It was demonstrated that either hydroxyl or cyanato reactive end groups could be effectively utilized. Both were superior to non-reactive systems in terms of both mechanical performance and solvent stability..
The structural modification of epoxy resins by a liquid elastomer
Authors: Padma A , Rao R M V G K , Subramaniam C
Published: August 2002

A carboxy terminated poly-n-(butyl acrylate, acrylic acid, acrylonitryl) (PNBA) terpolymer was used as a modifier for three high-functionality epoxy resins, (i) epoxy novolac, (ii) triglycidyl-4-aminophenol (TGPAP) and (iii) tetraglycidyl diaminodiphenyl methane (TGDDM), used as matrix materials in polymer composites. The resin and elastomer were reacted using different amine catalysts at different temperatures. The progress of the reaction between the epoxy resin and elastomer was studied extensively by Fourier transform infrared (FMR) spectroscopy and differential scanning calorimetry (psc). The results show that hydroxy esterification and etherification occurred during the epoxy-carboxy group reaction. The possible reaction mechanism involved is discussed on the basis of the results obtained.
Synthesis and characterization of poly(p-phenylene terephthalate) crystals obtained by crystallization during polymerization
Authors: Kimura Kunio , Endo Seiji , Kato Yasuo , Yamashita Yuhiko
Published: August 2002

Poly(p-phenylene terephthalate) (PPTE) crystals were prepared by hightemperature solution polymerization via three different types of reaction as follows: bimolecular condensation of (1) 1,4-diacetoxybenzene and terephthalic acid and (2) hydroquinone and diphenyl terephthalate and self-condensation of (3) mono(4'-acetoxyphenyl) terephthalate. In spite of the reaction types, needle-like crystals are not obtained as found with poly(oxy-l,4-benzenediylcarbonyl) (POB) whiskers, under polymerization conditions identical with those used to produce POB whiskers. PPTE and POB have similar molecular structure that is, they comprise 1,4-phenylene groups and ester linkages. whereas the morphologies of the crystals obtained are quite different. From the structural study, PPTE crystals are single crystals, and polymer chains align perpendicular to the plane of the sheaf-like or plate-like crystal.
Structure-property relationships in addition polyimides. I: Resins from four-ring aromatic diamines containing carbonyl and methylene groups
Authors: Delvigs Peter , Klopotek David L , Cavano Paul J
Published: August 2002

In an effort to improve the processing characteristics of addition-type polyimide resins the use of flexibilized four-ring aromatic diamine moieties was investigated. A series of 12 diamines containing carbonyl and methylene, as well as oxo and thio bridging groups, was synthesized. The diamines were polymerized with the dimethyl ester of 3,3',4,4' benzophenonetetracarboxylic acid (BTDE). using the monomethyl ester of nadic acid (NE) as an end-cap. The effect of diamine structure on the solubility and rheological properties during cure was determined. This paper also describes the effect of diamine structure and formulated molecular weight on the glass transition temperature and thermo-oxidative stability at elevated temperatures after various post-cure regimes. The results indicate that polyimides from some of the diamines containing methylene connecting groups have potential as matrix resins for long-term applications at temperatures up to 300 C.
Preparation and characterization of some new diaminobisimides
Authors: Hawthorne D G , Hodgkin J H , Jackson M B , Loder J W , Morton T C
Published: August 2002

A series of stable diaminobisimides (DABIs) has been prepared as alternatives to simple aromatic diamines for use in the preparation of condensation polymers. These DABIs were prepared by reacting two moles of an aromatic diamine with one mole of a dianhydride under conditions that minimize side reactions and the formation of oligomers. In many cases, the pure DABI consisting of two moles of the diamine and one mole of the dianhydride (i.e. the 2:1 product) can be obtained free of oligomers (i.e. the 3:2, 4:3 etc products). The studies have shown that the major factor determining the yield and purity of a DABI is the extent of conjugation between the two amino groups in the starting diamine: to a lesser extent steric effects in the diamines also influence the product composition. The reaction conditions necessary to produce these new DABIs are described together with extensive characterization of these materials by FTIR,1H and 13C NMR and gel permeation chromatography. The results indicate that pure DABIs are more manageable materials than the impure. insoluble materials previously described in the literature and can be used successfully to produce useful high-temperature stable polymers.
The relative thermooxidative stability of a phthalindde against a phenylethynylphthalimide terminated polyimide
Authors: Hinkley J A , Jensen B J
Published: August 2002

An aromatic imide polymer was prepared both as a phenylethynyl terminated oligomer (LARCTM"PETI-5) and as the corresponding linear polymer with phthalic anhydride endcaps (LARCm-8515). After heating to cure/moulding temperatures, isothermal weight losses were measured for 134 h at four temperatures. Arrhenius activation energies were 169 + 6 kJ and 175 + 33 kJ for 8515 and PETI-5, respectively. Extrapolated lifetimes at lower temperatures were similar for the two materials.
Controlled molecular weight poly(arylene ether benzimidazole)s endcapped with benzimidazole and ethynyl groups
Authors: Smith J G , Connell J W , Siochi E J , Hergenrother P M
Published: August 2002

A series of controlled molecular weight poly(arylene ether benzimidazole)s (PAEBIs) endcapped with either benzimidazole, ethynyl or phenylethynyl groups was prepared and characterized. PAEBIs endcapped with either ethynyl or phenylethynyl groups were thermally cured to provide polymers with improved moisture and solvent resistance and higher glass transition temperature than PAEBIs without reactive endcaps. The synthesis and characterization of a series of PAEBIs endcapped with benzimidazole, ethynyl and phenylethynyl groups prepared at stoichiometric imbalances of 7 and 10 mol% are discussed.
Characterization of LARCTM-CPI 2 poly(amide acid) aging by gel permeation chromatography/differential viscometry
Authors: Siochi E J , Havens S J , Young P R , Hergenrother P M
Published: August 2002

A controlled-molecular-weight LARCr'-CPI 2 poly(amide acid) was synthesized to investigate solution property changes that result from aging'Both dilute and concentrated solutions were aged at five temperatures and periodically analysed over a 33 d period. Various molecular weight parameters were obtained by gel permeation chromatography in combination with differential viscometry. Chemical changes were also followed by Fourier transform infrared spectroscopy. The temperatures used allowed the calculation of the energy of activation associated with changes in weight and number average molecular weights.
A diphenylethynyl-terminated imide oligomer and its cured polymer
Authors: Bryant Robert G , Hergenrother Paul M
Published: August 2002

A novel amine end-capper containing two phenylethynyl groups was used to terminate an imide oligomer based on 4,4'-oxydiphthalic anhydride and 3,4'-oxydianiline. The properties of this cured di(phenylethynyl)-terminated imide oligomer (DPETI) were compared with the corresponding cured phenylethynyl-terminated imide oligomrner (DPETI). The initial results indicate that mechanical properties of these two systems are very similar. The cured DPETI displays a slightly higher Tg and better solvent resistance in methyl ethyl ketone than the cured PETI-1.
Separation of alcohol aqueous solution by pervaporation using asymmetric polyimide membrane
Authors: Yanagishita H , Kitamoto D , Nakane T
Published: August 2002

Asymmetric polyimide membranes were prepared by the phase inversion process by casting solutions composed of 25 wt% aromatic polyimide (PI-2080), 35 wt% N,N'-dimethyl formamide (DMF) and 40wt% dioxane. The membranes were annealed at 300C for 3 h in a vacuum oven and were measured for various alcohol aqueous solutions in pervaporation. The membrane exhibited separation factors of a(H20/EtOH) = 900 and a(H,0/2-PrOH)= I I000 with a flux of 0.45 kgm 2 h t for a 95 vol.% alcohol aqueous solution at 60C. The membrane showed stable membrane performance for 3 months for a 95 vol.% ethanol aqueous solution at 60"C.
Surface formation and environmental responses on polyurethane-polystyrene graft copolymers
Authors: Tezuka Yasuyuki , Araki Akitoshi , Shiomi Tomoo
Published: August 2002

The surfaces of polyurethane (PU)-polystyrene (PS) graft copolymers having a defined content of uniform-size polystyrene graft segments were studied in both dry and wet states. XPS inspection of PU-PS graft copolymer film samples indicated the enrichment of the PS component at the surface in the dry state. The sample films were then immersed in water, and the environmental response at the surface was examined by means of a contact angle measurement using a CCI4 in water technique. The contact angle underwent a slow, but measurable change from one near to that of the PS homopolymer toward that of the PU homopolymer within a 3 h period for the graft copolymer samples annealed at 80 C. On the other hand, the contact angle remained close to that of the PU homopolymer within a 3 h period for samples annealed at 120'C.
Thermotropic copolyesters from methylhydroquinone, 4,4'-dipbenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid
Authors: Inoue Toshihide , Yamanaka Toru , Tabata Norikazu , Okita Shigeru
Published: August 2002

Copolyesters from methylhydroquinone (Me-HQ), 4,4'-diphenyldicarboxylic acid (BB) and 2,6-naphthalenedicarboxylic acid (NDA) with various molar ratios were prepared and their thermal and mechanical properties were investigated. The modulus of as-spun fibres from Me-HQ/BB/NDA tends to increase as the orientation function of the nematic domains (F value) increases. As-spun fibre from a polymer with a molar ratio m/n=92.5/7.5 showed the highest modulus of 112GPa at F=0,91. However, the injection-moulded specimens did not show the same tendency and the highest modulus of 44 GPa was observed at the lowest F value of 0.56. From these results, it is assumed that the F value plays a predominant role in determining the modulus of the as-spun fibre, whereas other factors, such as rigidity of polymer chain. packing density of polymer chains and melt flowability, determine the modulus of the injection-moulded specimens.
Synthesis and properties of new aromatic-aliphatic homo-and copoly(ester-imide)s based on 3,4,3',4'-diphenylsulphone tetracarboxdiimide
Authors: Sato Moriyuki , Hirata Tomohiro , Kamrnita Tomoaki , Mukaida Ken-ichi
Published: August 2002

New aromrnatic-aliphatic homo-and copoly(ester-imide)s were prepared by the melt polytransesterification of a dihexanol derivative of 3,4,3',4'-diphenylsulphone tetra-carboxdiimide and'/or a dioxydihexanol of biphenyl with aliphatic dimethyl esters of various chain lengths (m=6, 8 and 18) in the presence of zinc acetate. The tetracarboxdiimide derivative was prepared by the methanolysis of the corresponding diacetylated compound derived from 3,4,3',4'-diphenylsulphone tetracarboxylic dianhydride and 6-amino-1-hexanol with acetic anhydride. The structures of the polymers were confirmed by means of FTIR and 13C NMR spectra, and elemental analyses. They had very good solubility in organic solvents such as chloroform and dichloroacetic acid. The thermal properties of the polymers were investigated by differential scanning calorimetry (DSC), and thermogravimetry and differential thermal analysis (TG-DTA) measurements. The thermal analysis data indicated that the polymers were thermally stable up to near 300C in air and had low phase transition temperatures based on glass transition, and melting and/or isotropization below 200C. Two biphenyl-rich copolymers were recognized to show thermotropic liquid crystalline nematic phases by optical texture observation and x-ray analyses at various temperatures.
The synthesis and characterization of liquid crystalline oligoimides and polyimides
Authors: Alder P , Dolden J G , Smith P
Published: August 2002

There are few examples of thermotropic polyimides reported in the literature. In the present article the authors report the synthesis and characterization of some novel oligoand poly-imides which exhibit mesogenic behaviour. The solution method of Yamazaki et al (Yamazaki N, Higashi F and Kawasaki J 1974 J. Polym. Sci., Polym. Chem. Ed. 12 2149) for the preparation of polyamides was successfully applied to the formation of imide compounds and oligomers. Liquid crystal phases were characterized by optical polarizing microscopy and by differential scanning calorimetry. Two anhydrides were employed which were considered to be suitable building blocks for preparing potentially mesogenic polyimides, namely biphenyl tetracarboxytic dianhydride and pyromellitic dianhydride. Low-molar-mass materials were first synthesized with monoanhydride units to endcap the chains. using nadic and maleic anhydrides. Nematic phases Awere observed in several nadic diimide compounds containing multicyclic cores and in some low-molar-mass diimides and polyimides which contained a biphenylene unit in conjunction with at least one other unsaturated ring When the nadlmldes were heated above 220 C cross-linking and decomposition occurred with loss of mesogenic properties. A fusible polyimide was synthesized containing a flexible chain which exhibited thermotropic behaviour below its decomposition temperature.
Heterocyclic polyamides with pendent imide groups
Authors: Hamciuc C , Hamciuc E , Bruma M , Stoleriu A , Diaconu I , Belomoina N M , Mercer F W
Published: August 2002

New poly(phenylquinoxaline-amide)s and poly(phenylquinoxaline-imide-amide)s containing pendent phthalimide or 3,4,5,6-tctrachlorphthalimide groups have been synthesized by low-temperature solution polycondensation of diaminophenylquinoxalines with diacid chlorides of two aromatic acids containing preformed imide ridgs. The inherent viscosity, solubility, thermal stability, glass transition tempratures, dielectric constants and mechanical properties of these polymers have been studied.
Partial Compatibility and the Formation of Thickened, Shrink-Resistant Thermoset Moulding Compounds
Authors: Bush S F , Methven J M , Blackburn D R
Published: August 2002

This paper describes a new class of thermosetting polymer blends. The blends are now used commercially in the manufacture of sheet moulding compounds (SMC) where they exhibit important advantages compared with conventional systems. The new compositions comprise a cross-linkable base resin and unsaturated monomer in which the base resin is dissolved and a saturated additive resin which has a crystalline melting temperature T m below the temperature T r at which cross-linking occurs. Between T r and T m the additive and base resin form a single liquid phase, which on cooling thickens reversibly to a leathery sheet with no bulk phase separation. The paper describes the mechanisms underlying this viscosity switch phenomenon and the partial compatibility criterion used to select the resin-additive combinations which exhibit this behaviour.
New Polymer Syntheses IV. Synthesis and Characterization of New Polyamides Containing Bis-Benzthiazolyl Sulphone Units in the Main Chain
Authors: Aly Kamal I , Kandeel Maymona M
Published: August 2002

Bis(2-aminobenzthiazolyl) sulphone (BABS) was used as a new starting material for preparing polyamides. These polyamides were prepared by reacting BABS with adipoyl, sebacoyl, isophthaloyl and terephthaloyl dichlorides, and also with 4,4′-azodibenzoyl chloride or 3,3′-azodibenzoyl chloride, utilizing the solution polycondensation technique at low temperature. In addition, the model compound was synthesized by condensing the BABS with benzoyl chloride. Characterization of the monomer, model compound and the polyamides was accomplished by 1H NMR, IR and elemental analyses. The polyamides had reduced viscosities of 0.25–0.63 dI/g in DMF or DMSO at 25 °C. All the polymers dissolved readily at room temperature in polar aprotic solvents. The thermal stability of the polymers was evaluated by TGA and DSC measurements.
Rheological and Spectroscopic Characterizations of the Properties of a Prepolymer for High-Temperature Applications: The IP960 System
Authors: Habas J P , Grenier-Loustalot M F , Peyrelasse J
Published: August 2002

Of the thermostable polymers on the market the American PMR-15 resin is a reference compound. Nevertheless, its defects have necessitated the development of new polymers such as IP960. The object of this work is to characterize IP960 which is soluble in the diglyme until the imide oligomer stage. HPLC and 1H NMR analyses of the prepolymer demonstrate its polymolecularity. Several isomer forms, due to possible conformations of the nadimide endcaps, are present in equal amounts in the medium. The combined use of differential scanning calorimetry and rheological techniques have allowed us to study and to explain the evolution of properties of the prepolymer with temperature (glass transition, crosslinking etc). Using FTIR spectroscopy, we have studied the structure of the polymer network. Our results seem to confirm the validity of the crosslinking diagram of nadic structures proposed by Wong and co-workers. Thermomechanical analysis of the crosslinked compound shows that the Tg of the polymer is close to 292 °C. It also reveals on the curb of the modulus G″, namely the presence of two peaks γ and β associated with secondary mechanical relaxations within macromolecular chains ( Tγ = −102 °C; Tβ =68 °C).
Average Dipole Moments of Aromatic Polymer Chains
Authors: Hinkley J A
Published: August 2002

Recently, certain aromatic polyimides with polar substituents were shown to exhibit piezoelectricity after poling. To help interpret these results, mean square chain dipole moments for model chains were calculated using a rotational isomeric state scheme. Average moments ranged from 1.7 to 3.6 debye2 per backbone link, and correlated well with the magnitudes of the piezoelectric coefficients within the series.
Rheological Study of a High-Performance Polyimide. Interpretation of the Secondary Mechanical Relaxations of a Nadimide Crosslinked System
Authors: Habas J P , Peyrelasse J , Grenier-Loustalot M F
Published: August 2002

Thanks to the study of model compounds, we have been able to determine the origin of three rheological transitions observed in the thermomechanical analysis of a crosslinked nadimide resin, in the thermal range (-150 °C–-400 °C). The first one, localized at about 300 °C, is attributable to the glass transition of the crosslinked compound. The two others (called γ and β) are respectively situated at -100 °C and 70 °C. They are due to localized motions of rigid segments comprising aromatic structures and imide rings.
The Enthalpic Relaxation of Amorphous Poly(Aryl Ether Ketone)s
Authors: Goodwin A A , Browne M M
Published: August 2002

The development of physical aging in four amorphous poly(aryl ether ketone)s at temperatures below the glass transition temperature, Tg, was studied using differential scanning calorimetry (DSC). The change in enthalpy lost on aging, determined by scanning through Tg, was used to determine the kinetics of the aging process through fitting to the Cowie–Ferguson model. The kinetics of aging were found to depend on the ketone–ether ratio as well as the substitution pattern of the polymers. The maximum enthalpy lost at equilibrium, Δ H∞, was found to be a linear function of the change in heat capacity at Tg, Δ Cp(Tg), and the degree of supercooling, Δ T. A composite curve incorporating Tg values from physical aging and dynamic mechanical studies, covering 15 decades, could be fitted to the Volger–Fulcher equation and demonstrated that physical aging is an extension of the glass forming process.
Poly(Amido-Imide)s Based on Amino-Terminated Oligoimides
Authors: Patel Hasmukh S , Patel Nilesh P
Published: August 2002

An amino-terminated oligoimide was prepared by Michael addition reaction of N, N′-1, 4-phenylene bismaleimide (PBM) and 4, 4′-diamino-diphenyl methane (DDM) at a PBM–DDM ratio of 1:2. The poly(amido-imide)s (PAIs) were prepared by condensation of this PBM–DDM oligoimide with various aliphatic bisesters. The resultant PAIs were characterized by elemental analysis, IR spectral studies, number-average molecular weight ( Mn), estimated by nonaqueous conductometric titration, and thermogravimetry. The curing reaction of the epoxy resin–, namely diglycidyl ether of bisphenol-A (DGEBA)–, PAI system was monitored by differential scanning calorimetry (DSC). Based on cure temperature, the glass- and carbon-fibrereinforced composites (i.e. laminates) of the PAI–epoxy resin system have also been prepared and characterized.