Aromatic imides

Almost insoluble in cold water. Higher alcohols (including benzyl alcohol), higher phenols (e.g., naphthols), metaformaldehyde, paraldehyde, aromatic aldehydes, higher ketones (including acetophenone), aromatic acids, most esters, ethers, oxamide and domatic amides, sulphonamides, aromatic imides, aromatic nitriles, aromatic acid anhydrides, aromatic acid chlorides, sulphonyl chlorides, starch, aromatic amines, anilides, tyrosine, cystine, nitrocompounds, uric acid, halogeno-hydrocarbons, hydrocarbons. 

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

The competition at 200°C between an aliphatic and an aromatic amine toward the formation of an imide is a very selective reaction (Fig. 5.1) for the formation of an aliphatic imide.141 This reaction suggests that the reactive processing in extruder, for example, could be used to transform a melt-processable polyimide with an oligomer end capped with an aliphatic amine. In order to get a perfecdy alternate block polyimide-block siloxane, Rogers et al. used low-temperature transimidization.142 An oligomeric aromatic imide was end capped... 

The saiq>les studied were a BCB terminated aromatic imide oligomer and a BCB terminated imide monomer blended with a compatible bismaleimide (BMI) resin. Neat properties studied on both resin systems included the thersial and rheological properties of the uncured specimens subsequently used to determine appropriate cure conditions. Thermal and mechanical properties of the cured materials are also discussed. 

The structure formed through a linear addition of the molecules is Shown at the top of the illustration. The benzocyclobutene groups on either end of the BCB terminated resin molecules react with two other BCB groups as shown to form a poly(o-xylyene) strands. With BCB reactive groups present at both ends of the resin molecules, a double strand of poly(o-xylyene) is formed which is bridged by the aromatic imide chains. 

The double bond of maleimides in very reactive towards electron-rich dienes, to give a normal Diels-Alder cycloaddition. Thus BMIs were used to obtain linear polyimides by reaction with several kind of dienes [46-51]. However the dienes are often difficult to prepare [51] and functionalized dienes have been used. Furan terminated oligomers react with BMIs at 70 °C leading to an oxygen-containing cycloadduct [52-57] which can react with acetic anhydride to give an aromatic imide (Fig. 13) [58-59]. 

Aromatic imides are another type of product which can be synthesized by catalytic ammoxidation. o-Xylene is converted over vanadium-titanium oxide catalysts to tolunitrile and then, depending on catalyst composition and reaction conditions, phthalimide or phthalonitrile can be selectively synthesized (Scheme 20.3) [94]. 

Aliphatic and aromatic imides have relatively low reduction potentials (e.g. N-methylphthalimide —1.4 V relative to the SCE [147]) and absorb in the near ultraviolet region (260-320 nm). These properties have been widely used in synthetic transformations of imides and in catalytic processes in which imides serve as redox... 

Several new developments in silanes have been reported re cently. One deficiency of existing silanes was that they were not applicable to high-temperature polymers such as polyimides, either because they were not thermally stable or because they did not facilitate adhesion. A new aromatic imide silane was synthesized with two silane groups attached to the terminal phenyls in the molecule. A... 

Greenfield S. R., Svec W. A., Gosztola D. and Wasielewski M. R. (1996), Mnltistep photochemical charge separation in rod-like molecules based on aromatic imides and diimides , J. Am. Chem. Soc. 118, 6161-6111. 

The role of Structure Level II on membrane properties is not limited to RO membranes. In fact, the secondary structure is probably even more important in membranes that are intended for gas separations. Patents exist for gas separation membranes where Structure Level 1 is aromatic amide, aromatic ester and aromatic imide combined with Structure Level 11 of a precisely defined type (12, 13). For example, the repeating segmental unit (a) contains at least one rigid divalent subunit the two main chain single bonds which extend from it are not colinear, (b) is sterlcally unable to rotate 360° around one or more of the main chain single bonds, and... 

The facile reaction of an aromatic imide with an amine seemed surprising, perhaps because... 

Polyetherimide has a chemical structure based on repeating aromatic imide and ether units. High performance strength characterisitics at elevated temperatures are provided by rigid imide units, while the ether linkages confer the chain flexibility necessary for good melt processing and flow. 

N( per la 0gellate(j carbon atoms)+ 4 (BB aromatic imide groups)... 

The correction for aromatic imide groups (+41) is much larger than the correction (+17) for other types of aromatic heterocyclic fused rings, such as benzimidazole, benzoxazole, benzothiazole and quinoxaline rings. 

All LC-polyimides discussed in this review possess at least one phthalimide unit in the mesogenic unit and most of them contain an AT-phenyl phthalimide moiety. For a better understanding of the potential mesogenic character of aromatic imide groups it is useful to discuss briefly their stereochemical and conformational properties. 

By far the largest group of liquid crystalline polymers containing imide groups are copoly(esterimide)s (PEIs). These have been sub-divided into flexible copolymers containing aliphatic spacers and wholly aromatic copolymers. There are several reports of copoly(amide-imide)s and copoly(ether-imide)s (both thermotropic and lyotropic) and these are treated separately. There are only a few examples of wholly aromatic imide containing LCPs, as polyimides frequently melt well above their decomposition temperature. Successful attempts have been made to incorporate flexible spacers, but in most instances the spacers are based on ether units, and the polymer is more strictly classified as a poly(etherimide). 

In order to check whether aromatic imides in lateral positions are necessary for a high allosteric potency the phthalimide moieties were replaced with corresponding saturated imides and, additionally, the hexahydrophthal-imide was stepwise reduced to a succimide ring. 

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