Materials dianhydride

Poly(phenylquinoxaline—arnide—imides) are thermally stable up to 430°C and are soluble in polar organic solvents (17). Transparent films of these materials exhibit electrical insulating properties. Quinoxaline—imide copolymer films prepared by polycondensation of 6,6 -meth5lene bis(2-methyl-3,l-benzoxazine-4-one) and 3,3, 4,4 -benzophenone tetracarboxyUc dianhydride and 4,4 -oxydianiline exhibit good chemical etching properties (18). The polymers are soluble, but stable only up to 200—300°C. 

Silicon-containing Pis, useflil as insulation and protective materials, demonstrate adhesion to fibers, fabrics, glass, quartz, and carbon (36). The synthetic method used is the reaction of the silicon-containing dianhydride with diamines. 

Uses. Pyromellitic dianhydride imparts heat stabUity in applications where it is used. Its relatively high price limits its use to these applications. The principal commercial use is as a raw material for polyimide resins (see POLYIMIDES). These polypyromellitimides are condensation polymers of the dianhydride and aromatic diamines such as 4, -oxydianifine ... 

Aromatic polyimides are generally produced by the reaction of aromatic dianhydrides with aromatic diamines to yield a material with the general stmcture... 

The pyromellitic dianhydride is itself obtained by vapour phase oxidation of durene (1,2,4,5-tetramethylbenzene), using a supported vanadium oxide catalyst. A number of amines have been investigated and it has been found that certain aromatic amines give polymers with a high degree of oxidative and thermal stability. Such amines include m-phenylenediamine, benzidine and di-(4-amino-phenyl) ether, the last of these being employed in the manufacture of Kapton (Du Pont). The structure of this material is shown in Figure 18.36. 

If trimellitic anhydride is used instead of pyromellitic dianhydride in the reaction illustrated in Figure 18.35 then a polyamide-imide is formed (Figure 18.37). The Torlon materials produced by Amoco Chemicals are of this type. 

Rather similar are the 5.5-dimethylhydantoin derivatives shown in Figure 26.18 (b, e). These resins are said to eonfer improved weathering resistance but also exhibit higher water absorption. Another trifunctional material is p-glycidyl-oxy-A,A/-diglycidylaniline. This has been recommended for adhesive systems in conjunction with benzophenonetetracarboxylic acid dianhydride, which is a room temperature curing agent in this case. 

Potyimides obtained by reacting pyromellitic dianhydride with aromatic amines can have ladder-like structures, and commercial materials are available which may be used to temperatures in excess of 300°C. They are, however, somewhat difficult to process and modified polymers such as the polyamide-imides are slightly more processable, but with some loss of heat resistance. One disadvantage of polyimides is their limited resistance to hydrolysis, and they may crack in aqueous environments above 100°C. 

In addition to the research on fluorinated and cardo polyimides, an important work was devoted to the semiaromatic cycloaliphatic polyimides. Volk-sen points out the potential interest of these materials in electronic industry.64 He reports that the simplest procedure to prepare these materials is to use a cycloaliphatic dianhydride and an aromatic diamine (Fig. 5.9) instead of an aliphatic diamine and an aromatic dianhydride, which leads to formation of gels. 

Different dianhydrides have been syndiesized or are commercially available, and some structures arc shown in Fig. 5.9.64-66 An improved method for preparation of cyclobutanetetracarboxylic dianhydride (CBDA) by photochemical dimerization of die maleic anhydride has been developed by Nissan.67 The polyimide obtained by condensation of CBDA widi oxydianiline gives a transparent and colorless material. The transmittance of 50-pm-thick film is 82% and the UV cutoff is 310 nm. 

Recently siloxane-imide copolymers have received specific attention due to various unique properties displayed by these materials which include fracture toughness, enhanced adhesion, improved dielectric properties, increased solubility, and excellent atomic oxygen resistance 1S3). The first report on the synthesis of poly(siloxane-imides) appeared in 1966, where PMDA (pyromellitic dianhydride) was reacted with an amine-terminated siloxane dimer and subsequently imidized 166>. Two years later, Greber 167) reported the synthesis of a series of poly(siloxane-imide) and poly(siloxane-ester-imide) copolymers using different siloxane backbones. However no physical characterization data were reported. 

In most of the studies discussed above, except for the meta-linked diamines, when the aromatic content (dianhydride and diamine chain extender), of the copolymers were increased above a certain level, the materials became insoluble and infusible 153, i79, lsi) solution to this problem with minimum sacrifice in the thermal properties of the products has been the synthesis of siloxane-amide-imides183). In this approach pyromellitic acid chloride has been utilized instead of PMDA or BTDA and the copolymers were synthesized in two steps. The first step, which involved the formation of (siloxane-amide-amic acid) intermediate was conducted at low temperatures (0-25 °C) in THF/DMAC solution. After purification of this intermediate thin films were cast on stainless steel or glass plates and imidization was obtained in high temperature ovens between 100 and 300 °C following a similar procedure that was discussed for siloxane-imide copolymers. Copolymers obtained showed good solubility in various polar solvents. DSC studies indicated the formation of two-phase morphologies. Thermogravimetric analysis showed that the thermal stability of these siloxane-amide-imide systems were comparable to those of siloxane-imide copolymers 183>. 

The raw materials from which di-D-fructose dianhydrides can be obtained in appreciable yield are readily available from comparatively inexpensive agricultural feedstocks. Thus, these compounds are attractive as chiral-starting materials for chemical synthesis. Their stability to acid and heat, and their relative rigidity, because of the conformational constraints covered here, are also features that might be exploited during syntheses.119 A series of variously substituted di-D-fructose dianhydrides has been prepared,119 starting from 6,6 -dideoxy-6,6 -di-halosucroses. The properties of these and other derivatives of di-D-fructose dianhydrides are summarized in Tables XIV-XX. Two of these derivatives, 48 and 56, exhibit thermotropic liquid-crystal properties.119... 

Biaryl derivatives bearing reactive groups have become increasingly important in industry. Uses for this class of compounds are constantly being developed in the production of high performance polymers. Materials such as 3,3, 4,4 -biphenyl-tetracarboxylic dianhydride 1 and 4,4 -biphenol 2 are monomers employed in the manufacture of high performance polyimides or polyesters. Applications for this family of molecules have also been found both in the dye industry and in the pharmaceutical industry. 

The primary starting material for the synthesis of perylene tetracarboxylic acid pigments is the dianhydride 71. It is prepared by fusing 1,8-naphthalene dicar-boxylic acid imide (naphthalic acid imide 69) with caustic alkali, for instance in sodium hydroxide/potassium hydroxide/sodium acetate at 190 to 220°C, followed by air oxidation of the molten reaction mixture or of the aqueous hydrolysate. The reaction initially affords the bisimide (peryldiimide) 70, which is subsequently hydrolyzed with concentrated sulfuric acid at 220°C to form the dianhydride ... 

Gasteiger et al. reviewed the best performing Fe-based catalysts in the literature up to 2004 1. Even the best of these catalysts (Fe on pyrolyzed peryle-netetracarboxylic dianhydride) showed a corrected turnover frequency of 7% and a volume activity density of 0.2% of Ft. More recent work has focused on optimizing the metal, nitrogen, and carbon composition of the materials. 

Benzenetetracarboxylic dianhydride (pyromellitic dianhydride) is a typical bifunctional acid anhydride, and it is a useful raw material for preparing many useful chemicals. Polyimides and polyimidazopyrrolons prepared from this dianhydride have excellent heat and chemical resistance, as well as excellent mechanical and electrical properties. Pyromellitic dianhydride is produced by the oxidation of 1,2,4,5-tetraalkylbenzenes such as 1,2,4,5-tetramethylbenzene (commonly known as durene) and 4,6-diisopro-pyl-l,3-dimethylbenzene. Durene, in particular, is a fundamental raw material for the production of the dianhydride 1-8). 

The methyl and ethyl ethers of the dianhydrides have properties which may make them useful as plasticizers. 2,5-Diallyl-dianhydro-sorbitol (XVII) and 2,5-diallyl-dianhydro-mannitol (XVIII) and the corresponding methallyl derivatives polymerize to resinous materials on being heated in oxygen.The allyl derivatives polymerize about five times as fast as the methallyl derivatives, to give products somewhat similar to that obtained by Nichols and Yanovsky by the polymerization of methyl tetraallyl-a-n-glucoside. 

Synthesis of PIQ. Very high heat resistance is required in order for a polymer film to be used as an insulator. This is because several heat treatments over 400 C are necessary in LSI interconnection and assembly processes. An aromatic polyimide (I), a reaction product of aromatic diamine and acid dianhydride, is one of the most heat resistant polymeric materials ... 

Analyses of Water Content. The water content of the PIQ starting materials was analyzed. The water content of amines was measured using a DuPont 321A moisture meter and those of the solvents were measured by Karl Fischer s reagent method. The water content of acid dianhydrides was measured by titrating the free acid. 

The water content in the starting materials was measured as follows. The water content of amines and solvents were measured using the DuPont 321A moisture meter and Karl Fischer s reagent methods, respectively. Since the water contained in acid dianhydride is considered to convert it to free acid. 

The results are shown in Table 1. The table shows that the greatest part of the water in the starting materials is present in the acid dianhydrides. This was verified by experimental results. That is, water content increases with time and that increase strongly depends on ambient humidity, as shown in Figure 5. Therefore, it is very important to keep the materials dry. 

In order to reduce the water content, dehydration of the starting materials were carried out as follows. Acid dianhydrides were recrystallized in acetic anhydride and dried by infrared lamp. Amines were recrystallized in butyl alcohol and dried. Solvents were distilled under reduced pressure. The water content of the dehydrated materials is also given in Table 1. A remarkable reduction in water content was achieved. 

The monomer 91 was prepared in a multistep process and the authors did not quote the yield obtained for the final product (Fig. 41). In the first step the dianhydride 87, was reacted with m-nitroaniline 88 to form the mono imide anhydride 89 without any of the bis imide product being reported. Once this material was isolated the remaining anhydride functionality was reacted with 4-aminobenzocyclobutene 60 to form the JV-benzocyclobutenyl imide, 90. The nitro group was reduced to the amine (H2,10% Pd/C) which in turn was reacted with maleic anhydride to afford the final AB monomer, 91. Polymerization of 91 was carried out in a DSC (10 °C/min to 450 °C) [14]. Monomer 91 had a melting point of 99 °C and the final homopolymer had a Tg of257 °C [14]. A TGA of the homopolymer indicated that at 508 °C the polymer suffered a 10% weight loss. 

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