Preparation aromatic maleimide

As already mentioned, aromatic polymers are thermally stable but aliphatic portions of them are not as thermally stable. Typical maleimide resins have aliphatic units. This is inevitable because the Michael addition was used to prepare the maleimide-based oligomers. On the other hand, if an adhesive consists of a linear thermoplastic polymer, it is not usable at temperatures above its softening temperature. Introducing chemical crosslinking is one way to prevent thermal weakening of a material. 

Phosphorus containing poly(maleimide-amines) were synthesized from N,N -bisdichloromaleimido-3,3 -diphenyl alkylphosphine oxides and aromatic diamines or piperazine [144]. The polymers prepared from piperazine are soluble in DMF, DM AC, DMSO, etc., but have poor thermal stability and flame retardancy. 

Monomers 111 (a -d), were prepared from the common starting material 15 by a potassium phenate displacement of the aromatic nitro group. The yields of the keto-ether amine products ranged from 90 to 100% and were of sufficient purity after extractive work up to be utilized directly in the synthesis of the various maleimide monomers. Imidization of the aminobenzocyclobutenes was accomplished using standard reaction conditions (maleic anhydride to form the amic acid followed by cyclodehydration with acetic anhydride and triethyla-mine) and provided the maleimide products in yields ranging from 60 to 90%. 

However, due to the aromatic ring adjacent to its maleimide functional group, MBS displays less stability toward maleimide ring opening than SMCC (see this chapter Section 1.3). Unlike SMCC, MBS is therefore not recommended for preparing freeze-dried, maleimide-activated proteins, since during the processing necessary to purify and stabilize the derivative much activity can be lost by hydrolysis. 

A series of compounds of the type 120 was prepared by the condensation of ai-ferrocenyl aliphatic acids with aromatic o-diamines.115 The Diels-Alder reaction of 121 (R = H or CH3) with various N-substituted maleimides gave a series of compounds of the type 122.116 Only the endo isomers were formed. A number of additional nitrogen-... 

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]. 

Hoveyda et al. [262] prepared different N-aryhnaleimidobenzoic acids linked to SASRIN resin, whose double bond present in the maleimido moiety could act as a convenient dipolarophile in cycloaddition reactions. Thus, solution-generated a-iminoesters (from different aromatic aldehydes and aminoesters) were reacted vdth the supported maleimides (158) under Tsuge [263] conditions. Formation of the expected syn-endo cycloadduct (160) was observed after only 1 h at room temperature (Scheme 33). From structure-reactivity analysis, the authors concluded that the cycloaddition reaction is more sensitive to steric then to electronic factors on the azomethine yhde counterpart. The advantage of this procedure stems essentially from the fact that the iminoesters (159) are formed in situ. Aldehydes containing a-hydrogens could also be employed. Moreover, the resin in this case also plays the role of a protective group, because, in contrast with N-alkyl and N-aryl (see above) maleimides, N-unsubstituted maleimide is not suitable for 1,3 dipolar cycloadditions. 

The synthesis as well as the structure and properties of aromatic polyimides has been reviewed.This combination of synthesis, structure, and properties is a general characteristic of papers in this field. For example, the preparation of polyimides from di-isocyanates, poly(o-amino-o-carbonyl)amides, maleimides, and Af-(4-substituted phenyl)itaconimides, all follow this pattern. The preparation of polyimide fibres, wet spun from solution, has also been given. ... 

A number of polymers containing unsaturated imide side groups susceptible to cure by a thermal treatment (maleimide, nadimide, tetrahydrophthalimide), have been described [247,248]. The reactive side groups are generally introduced in this case by means of modified condensation monomers bearing reactive imide groups (Scheme 48). This approach has been applied for the preparation of cross-linkable aromatic polyamides and polyesters [248,249]. 

The condensation reaction between MA and aliphatic or aromatic polyamines has been used to prepare a large number of bismaleimides - - - and trismaleimides. """- "" Polystyrene has been treated with A-chloromethyl-maleimide, using a mild Friedel-Crafts procedure, to prepare polymer with pendant maleimide residues.Poly(vinyl alcohols) and alternating styrene-MA copolymer or polymers with pendent epoxide residues " have been converted to polymers with pendent maleimide moieties. All these multifunctional maleimides may be polymerized thermally, with peroxides, UV light, and y rays to obtain heat-resistant coatings or lami-... 

Because of the commercial availability and relatively low cost of the starting acid anhydrides, and the ease of preparation of the unsaturated imides, aromatic chain segments and low-M polymers end-capped with these reactive groups are most common. Although exotic unsaturated end-caps appear on occasion in the patent literature, the most common unsaturated reactive groups are maleimide [417-419,567-570], nadimide [417,419,567,571,572], methylnadimide [417,419, 567, 571] and itaconimide [573]. The maleimide end-group is prepared by the condensation of an amine with maleic anhydride, followed by cyclization ... 

Bis(maleimides) prepared from aromatic diamines (benzidine, p-phenylcne-diamine, o-tolidine, o-anisidine) were condensed with 1,8-diphenyloctatetraene and related bis(dienes). Polymers that softened above 300°C with molecular weights of approximately 3000 were obtained (18). A Diels-Alder polymerization has been described that yields a ladder polymer. The cyclic oligomeric esters [13] and [14] give low molecular weight polymer when heated in toluene (7). p-Benzoquinone has also been polymerized with [14]. A chloroform-soluble product with a molecular weight of about 2000 was obtained (7). 

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