High Performance Polymers

1, 3-Bis(3-aminobenzoyl)benzene (BAB), 1, 3-bis(3-amino-4-phenoxybenzoyl)benzene (BAPB) and 1, 3-bis(3-amino-4-biphenoxybenzoyl)benzene (BABB) were synthesized from 1, 3-bis(3-nitro-4-chlorobenzoyl)benzene. By using these three diamines and commercially available tetracarboxylic dianhydrides such as 3, 3′, 4, 4′-benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA), several kinds of poly(keto-imide)s were synthesized. Thermal properties and processability such as melt-flowability and solubility in organic solvents of the obtained poly(keto-imide)s were investigated by focusing on the chemical structures of their repeating structure units. Inherent viscosities of poly(keto-imide)s ranged from 0.54 to 0.75 dl g⁻¹. These poly(keto-imide)s displayed glass transition temperatures (T _g) between 219 and 256 °C, and only the poly(keto-imide) prepared from BAB and PMDA showed a melting point (T _m)at 451 °C. Melt-flowabilities of these poly(keto-imide)s except for BAB/PMDA poly(keto-imide) were observed between 285 and 330 °C. The poly(keto-imide)s having bulky pendent ether groups were soluble in chloroform, 1, 1, 2-trichloroethane, N, N-dimethylacetamide and m-cresol at ambient temperature.

Preparation and properties of the polyimide derived from cyclobutanetetracarboxylic dianhydride (CBDA) with diamines are investigated, focusing on the interfacial polycondensation of cyclobutanetetracarboxylic acid dimethylester dichloride (2a) with diamines.

Dimethylester was conveniently prepared from CBDA by refluxing in methanol solution. Dimethylester consists of two regio isomers; one is α-type (1a) with centrosymmetry, the other is β-type (1b) with plane symmetry. Separation of the mixture into each of pure 1a and 1b was successfully performed by fractional crystallization. The structure of the first fraction is 1a, which was determined by x-ray crystal analysis. The second fraction was necessarily assigned to 1b. 1a was converted into 2a by the reaction of thionyl chloride. The interfacial polycondensation of 2a with diamines afforded a high molecular weight polyamic ester. Polyimide was obtained only by heating the polyamic ester to about 230–280 °C. The cyclobutane polyimide thus obtained was thermally stable up to 400 °C, and less stable under hydrolysis than polypyromellitic imide.

The heterogeneous oxidation of N-(2-phenylthioethyl)benzamide in a dispersion of water was performed with twice the amount of hydrogen peroxide at 60 °C for 72 h as a model reaction of the oxidation of poly(amide-sulphide) (polymer 1), and the corresponding N-[2-(phenylsulphoxy)-ethyl]benzamide and N-[2-(phenylsulphonyl)ethyl]benzamide were obtained in 5% and 95% yields respectively. This suggests that the alkyl phenyl sulphide group was easily oxidized with time via the alkyl phenyl sulphoxide group into the alkyl phenyl sulphone group. On the other hand, when heterogeneous oxidation of diphenyl sulphide in a dispersion of water was carried out with twice the amount of hydrogen peroxide at 60 °C for 72 h, the corresponding diphenyl sulphoxide and diphenyl sulphone were obtained in 77% and 23% yields, respectively. Therefore, the oxidation rate of the diphenyl sulphide group was much slower than that of the alkyl phenyl sulphide group, and the heterogeneous oxidation of diphenyl sulphide with excess hydrogen peroxide in a dispersion of water primarily produced diphenyl sulphoxide under the same conditions. On the basis of these model reactions, the heterogeneous oxidation of polymer 1, which was prepared by the polyaddition of bis(4-mercaptophenyl)sulphide with m-phenylenebis(2-oxazoline), was performed with one to three times the amount of hydrogen peroxide in a dispersion of water at 60 °C, and the T _g of the resulting polymers gradually increased with reaction time from 111 °C to 165 °C. When the oxidization was carried out with three times the amount of hydrogen peroxide for 48 h, the polymer with major structure, poly(amide-sulphone) (polymer 3), was obtained. Polymer 3 was also easily prepared by the oxidization of polymer 1 with equivalent amounts of sodium periodate in a dispersion of water at 60 °C for 48 h.

Polyimide films were prepared from 2, 3, 3′, 4′-biphenyl tetracarboxylic dianhydride (a-BPDA) and 4, 4′-oxydianiline (ODA) by a two-step method (thermal and chemical imidization) and a one-pot method. In the case of the polyimide films prepared from polyamic acid solution by the two-step method, the molecular weight of the films decreased before achieving its final value. In the case of polyimide films prepared by the one-pot method, the molecular weight increased smoothly to its final molecular weight during cure. The inflection point in the viscosity curve was observed between 215 and 250 °C in the polyimide prepared by the two-step method, and the range of the inflection temperature was very different from the T _g of the polyimide (340 °C). So, this inflection of molecular weight was considered to be independent of the T _g of the polyimide. The films prepared from three methods had almost the same molecular weight and properties in spite of the different preparation processes. For this reason it is thought that the polyimide from a-BPDA/ODA has less crystallinity and less phase orientation.

Aromatic polyamide-imides having hexafluoroisopropylidene and isopropylidene groups in the main chain of the polymer were prepared by reacting 4-chloroformylphthalic anhydride (CPA) and fluorine or non-fluorine containing diamines using low-temperature polycondensation. Polyamide-imides were obtained with high molecular weight and high yield. Thermal decomposition temperature and glass transition temperatures of polymers were above 460 °C and 275 °C respectively. Fluorine and non-fluorine containing polyamide-imides were cast into transparent films which were characterized by mechanical and water absorption analysis.

A one-pot synthesis of aromatic polycarbodiimide from aromatic diamine has been developed. This method involves the preparation of carbamate by the reaction of 4, 4′-hexafluoroisopropylidenebis(p-phenyleneoxy)dianiline (6FPA) with phenylchloroformate, followed by the transformation of the carbamate with trimethylsilylchloride-triethylamine to diisocyanate, and then the polycondensation of the resulting diisocyanate in the presence of 3-methyl-1-phenyl-2-phosopholene-1-oxide. The polycarbodiimide (6FPCD) from 6FPA was obtained in quantitative yield having a number average molecular weight up to 5000. The thermal treatment of 6FPCD gave a crosslinkined polymer having a high glass transition temperature up to 200 °C.

A novel polyamide containing a naphthylurea moiety as the photoreaction site (Np Urea-PA) was synthesized by polycondensation of N-3, 5-dicarboxyphenyl-N′-1-naphthylurea and 4, 4′-oxydianiline (ODA). The model reactions, which consisted of irradiation by UV light of the low molecular weight aromatic ureas and isocyanate, suggested that the photochemistry involves an aromatic isocyanate intermediate. Np Urea-PA acts as the negativeworking resist, by UV irradiation through a quartz mask followed by development using aprotic solvents such as N, N-dimethylacetamide (DMAc). The contrast of the negative tone image was improved by using 20 wt% of p-xylylenediamine (pXDA) as a crosslinking agent.

Two types of siloxane modified polyimide were prepared as coating materials for microelectronics applications and their thermal, mechanical, electrical, adhesive and coating properties were characterized. The coatings prepared were classified as polysiloxane block (type A) polyimides and disiloxane modified (type B) polyimides. All of the polyimides showed excellent thermal, mechanical, electrical, adhesive and coating properties suitable for use in microelectronics coating applications. The type A polyimides have lower dielectric constants and good stress relaxation capability as compared with typical aromatic polyimides. The type B polyimides have excellent adhesive properties to silicon wafers. The polyimide prepared from 2, 2-bis[4-aminophenoxyphenyl]hexafluoropropane exhibited the lowest dielectric constant due to the presence of trifluoromethyl groups in the polymer backbone. Model encapsulated semiconductor devices coated with various polyimides were assembled, and the interface adherence between the polyimide and the encapsulant along with the reliability of the semiconductor devices were examined. Superior interface adherence between the polyimide passivant and the encapsulant was exhibited, resulting in improved reliability of integrated circuit chips. With the incorporation of siloxane moieties into the polyimide backbone these siloxane modified polyimides were shown to be good candidate materials for microelectronics coatings.

A new method to improve the thermal insulation of polyurethane rigid foam blown by a non-ozone depleting agent—an alternative to chlorofluorocarbon—has been developed. This method involves the reduction of the gas thermal conductivity for polyurethane foam by the conversion of gaseous carbon dioxide in the foam to an organic carbonate. We tried to perform the cyclization of carbon dioxide in foam with an epoxy compound, and then the reduction of the thermal conductivity of the polyurethane foam was ascertained as carbon dioxide was chemically fixed in the foam. Consequently, this method led to a reduction of about 10% in the thermal conductivity in comparison with that of the conventional foam including carbon dioxide. In addition, the degree of progress of reaction in the foam was investigated by a quantitative analysis of carbon dioxide, epoxide and the resulting cyclic carbonate in the polyurethane foam. It was observed that unnecessary reactions, which consumed epoxide other than for the fixation of carbon dioxide, existed in the process of urethane polymerization. The main unnecessary reaction was presumed to be a side reaction of epoxide with isocyanate. Furthermore, the unnecessary reactions were affected by the type of urethane catalyst, the selection of which has been of importance in this method.

A liquid crystalline polyimide (poly[1, 3-bis[4-(4-aminophenoxy)-α, α-dimethylbenzyl]benzene pyromellitimide]: PI-LC) was blended with two kinds of thermoplastic polyimide: poly[3, 3′-(4, 4′-dioxybiphenyl)diphenylene pyromellitimide] (N-TPI) which is a semicrystalline polyimide having a melting point of 388 °C and poly[2, 2′-bis(3, 4-dicarboxyphenoxy)phenylpropane-2-phenylene bisimide] (PEI) which is an amorphous poly(etherimide) having a glass transition temperature at 220 °C. The miscibility of N-TPI and PI-LC was evaluated by DSC using enthalpy relaxation, and the phase diagram of their blend was drawn above the melting point of N-TPI. The result indicated that the PI-LC-rich blend was miscible in a wide range of compositions. However, the extruded samples of their blend, which had been prepared under a flow of high shear, showed a phase separation structure. In the other combination of PEI and PI-LC, the blend was immiscible, but at low composition of PI-LC their blend fibre showed higher tensile properties than the original PEI fibre.

Polyimide/polyimide molecular composite (MC) films were prepared by blending precursor solutions of a rigid polyimide and a reactive oligoimide or a reactive polyimide that contains acetylene units in the backbone in a 7:3 ratio, followed by casting, drying and thermal imidization at 300 °C. 3, 3′, 4, 4′-Biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), p-phenylenediamine (PDA), oxydianiline (ODA) and 3, 3′-diaminodiphenylacetylene (m-intA) were used as acid dianhydride and diamine monomers for the preparation of polyimide. The rigid components were prepared from PMDA or BPDA and PDA. The matrix components were prepared from PMDA or BPDA and ODA or m-intA. The polyimide/polyimide MCs have exotherm on DSC due to the reaction of internal acetylene units, which indicates that the MC films are laminate processable. Tensile measurements revealed that the tensile modulus of the MCs utilizing reactive oligoimides is 20–30% higher than that of the MCs utilizing reactive polyimides. Viscoelastic analyses of the MC films showed that the crosslinking of the acetylene units gave polyimides that have a very high glass transition temperature.

We prepared the main-chain type of TP-n polyesters, which are based on the terphenyl dicarboxylic acid and alkane diols with the carbon number of n = 5–20. All the TP-n polyesters form a smectic liquid crystal, exhibiting the well known odd–even oscillation with respect to the thermodynamic parameters of transitions and smectic structure. From the x-ray patterns of the oriented fibres, the S_A and S_CA structures were identified for the even and odd series of TP-n respectively. The structural characteristics of the polymeric S_A and S_CA phases are presented by examining the variation of layer spacing with n in a wide range of n = 5 to 20.

We have prepared two classes of LC diblock copolymers, OcSt-b-LC and MeStb-LC, by living anionic polymerization. These are composed of the side-chain LC polymer as one segment and two different amorphous polymers, poly(octyl styrene) (OcSt) and poly(α-methyl styrene) (MeSt), as the other segment. OcSt and MeSt segments have glass transition temperatures of ⁻60 °C and 160 °C respectively, which are relatively lower and higher than the transition temperatures of crystal–S_A (∼90 °C) and S^A–isotropic (∼130 °C) in the LC segment. In OcSt-b-LC the lamellar domain size decreases gradually from that of the crystal phase to that of the isotropic phase, indicating that the global conformation of the backbone changes throughout the S^A temperature region. In MeSt-b-LC, in contrast, no change in the lamellar size is observed and the crystallinity of the LC segment is reduced in comparison with that in OcSt-b-LC while the liquid crystal is well formed. Such a distinction between two copolymer systems, arising from an interplay between the LC and amorphous segments, shows that the global conformation of the backbone is significant for understanding the phase behaviour and structure of side-chain LC polymers.

Mixtures consisting of polyamine (branched polyethyleneimine (PEI) and polyallylamine (PAA)) and n-alkanoic acid (Cn: n = the carbon number of alkanoic acid) were prepared and their thermal and liquid crystalline properties were examined. The occurrence of proton transfer from the carboxylic acid to the amine groups was found by IR measurement of the mixtures. The polyamines and Cn exhibited no mesophase. Also, PEI/Cn with n = 3, 4, 5, which are mixtures of PEI and Cn, did not show a liquid crystalline phase. However, PEI/Cn with n> 5 clearly displayed a lamellar fluid liquid crystal phase having a layer structure with low order inside the layer, due to ion–ion interactions. In the lamellar mesophase, PEI/Cn showed a focal-conic fan texture which resembles the fan-shaped textures in smectic A and C phases. PEI/Cn with 5 < n < 13 formed a bilayer structure in the lamellar mesophase. On the other hand, a tilted bilayer structure is proposed as a packing model of PEI/Cn with 13 < n< 19. PAA/C18 consisting of polyallylamine and C18 also showed a lamellar fluid mesophase and formed a similar layer structure to PEI/C18.

Anomalous solid structures formed by a thermotropic liquid crystalline polyimide (PI-LC) were investigated by thermal analysis, polarized light microscopy and x-ray analysis. It was revealed that PI-LC should undergo a phase transition from the crystalline to the isotropic phase through the smectic or nematic phase in the temperature range 277–300 °C. The PI-LC filament extruded at 280 °C, at which temperature the polymer was in liquid crystalline phase, was formed to have a structure similar to the smectic C phase, while that extruded and melt-drawn at 310 °C, at which temperature the polymer was in the isotropic phase, had a structure similar to the smectic A phase.

Novel thermotropic liquid crystalline (LC) semirigid homo- and copoly(imidecarbonate)s composed of a 3, 4, 3″, 4″-p-terphenyltetracarboxdiimide ring and aliphatic chains were prepared by melt polycondensation of a dihexanol derivative of 3, 4, 3″, 4″-p-terphenyltetracarboxdiimide and/or a dioxydihexanol of biphenyl taken in a definite molar ratio with hexamethylene diphenyl dicarbonate in the presence of zinc acetate, and their thermal and mesogenic properties were evaluated. The assigned structures of polymers were characterized by FT-IR and ¹³C NMR spectroscopy, and elemental analyses. DSC and TG-DTA measurements, polarizing microscope observations of textures and temperature-dependent x-ray analyses demonstrated that the polymers have wider LC temperature ranges (nematic phase) than analogous semirigid poly(ester-imide)s and are thermally stable up to 300 °C in air.