BMI

BMI intermediate synthesis [COMPOSITE MATERIALS - POLYTffiR-MATRLO - THERMOSETS] (Vol 7) -coumarin reduction [COUMARIN] (Vol 7)... 

Other nootropic agents in some stage of clinical development include nebracetam (9), nefinacetam (10), and BMY 21502 (11). Nebracetam, an aminomethyl pyrrolidinone derivative, is expected to be approved in Japan in 1994 (73). In clinical studies involving patients having cerebrovascular or senile dementia of the Alzheimer s type, clinical symptoms such as spontaneous or emotional expression were enhanced in up to 71% of cases. Long-term treatment using nebracetam in patients with cerebral infarction also afforded marked improvement in most cases with few side effects (74). A review of this compound has beenpubUshed (75). 

Limited clinical data on BMY 21502 (11) suggest that some benefit may be provided to patients with dementia (87,88). This expectation is based on the abihty of (11) to increase the level of arousal and attention in patients with certain types of dementia. BMY 21502 enhances long-term potentiation... 

LTP) in hippocampal slices (89,90). LTP is believed to be a critical step in memory acquisition, and agents that possess the abiUty to augment this process in vivo are expected to be of benefit in memory enhancement. However, this compound has only demonstrated this property in vitro. In addition, because (11) does not appear to affect other neurotransmitter systems, as do other nootropics, the potential of BMY 21502 as a memory-enhancing agent is questionable. 

Obesity is a difficult condition to treat. Dietary restriction of caloric intake is the first line therapy and is optimally combined with an exercise program to promote loss of fat relative to lean body mass (17). For the grossly obese (BMI > 40), invasive mechanical measures such as jaw wiring, gastric banding, and gastric by-pass have been attempted with at least limited success (18). 

Bismaleimides are best defined as low molecular weight, at least diftinctional monomers or prepolymers, or mixtures thereof, that carry maleimide terminations (Eig. 3). Such maleimide end groups can undergo homopolymerization and a wide range of copolymerizations to form a highly cross-linked network. These cure reactions can be effected by the appHcation of heat and, if required, ia the presence of a suitable catalyst. The first patent for cross-linked resias obtained through the homopolymerization or copolymerization of BMI was granted to Rhc ne Poulenc, Erance, ia 1968 (13). Shordy after, a series of patents was issued on poly(amino bismaleimides) (14), which are synthesized from bismaleimide and aromatic diamines. 

A number of BMI resias based on this chemistry became commercially available through Rhc ne Poulenc for appHcation ia priated circuit boards and mol ding compounds and Rhc ne Poulenc recognized the potential of bismaleimides as building blocks for temperature-resistant thermoset systems. The basic chemistry, however, was not new, because the Michael addition reaction had been employed by Du Pont to obtain elastomeric reaction products from bismaleimides and Hquid polymeric organic diamines (15). 

The order of melting transitions for the diphenyhnethane bismaleimides is surprising (Table 6) because the 4,4 -MDA-BMI melts lower (155—157°C) than the 3,3 -MDA-BMI. The tetra alkyl-4,4-MDA-BMI also melts around 150°C. The BMI based on the isomeric diphenylindane diamine (24) is very low melting because it is a complex blend of various isomers. 

The BMT-biiilding blocks primarily used in commercial bismaleimide resins are 4,4 -bismaleimidodiphenylmethane, 2,4-bismaleimidotoluene [6422-83-9] 1,3-bismaleimidobenzene [3006-93-7J, and, sometimes, aUphatic BMIs based on alkanes. However, because of toxicity problems associated with MO A (4,4 -diaminodiphenylmethane) and other diamines with only one or two aromatic rings, polyaromatic diamines and BMIs based on them ate... 

The maleimide is prebuilt into the molecule in a separate step. Maleimidobenzoic acid [17075-07-7] or its acid haUde was used to synthesize maleintide-terrninated polyamides (16,17) or polyesters (27) from amino- or hydroxy-terminated polyamides and polyesters, respectively. The Hterature on bismaleimide prepolymers and bismaleimide building blocks is quite extensive (28), but only a limited number of BMI building blocks have been used for commercial resin formulations. 

Micha.elAdditions. The reaction of a bismaleimide with a functional nucleophile (diamine, bisthiol, etc) via the Michael addition reaction converts a BMI building block into a polymer. The non stoichiometric reaction of an aromatic diamine with a bismaleimide was used by Rhc )ne Poulenc to synthesize polyaminobismaleimides as shown in Figure 6 (31). 

Another approach to processible bismaleimide resins via a Michael addition chain extension, is the reaction of bismaleimide, or alow melting mixture of bismaleimides, with aminobenzoic hydrazide to provide a resin that is soluble in various solvents, such as acetone [67-64-1methylene chloride [75-09-2] and dimethylform amide [68-12-2] (33). The idealized chemical stmcture for a 2 1 BMI—aminobenzoic hydrazide resin is as follows ... 

The Michael addition reaction has attracted many researchers as a route to convert high melting BMI building blocks into resins with improved processibihty as compared with the BMI precursors. Heat-resistant resin compositions are prepared from BMI and para- or y /i7-aminophenol (38). The idealized stmcture of such a BMI—y -aminophenol adduct follows. 

BMI—y -aminophenol adducts can further react with epoxy resia and subsequendy be cured with imida2ole catalyst. 1 2 BMI—aminophenol adducts have been used as curing agents for epoxy resia (37). 

Bismaleimide Resins via EI E Reaction. The copolymerization of a BMI with o,o -diallylbisphenol A [1745-89-7] (DABA) is a resia coacept that has beea widely accepted by the iadustry because BMI—DABA bleads are tacky soHds at room temperature and therefore provide all the desired properties ia prepregs, such as drape and tack, similar to epoxies. Crystalline BMI can easily be blended with DABA, which is a high viscosity fluid at room temperature. Upon heating BMI—DABA blends copolymerize via complex ENE and Diels-Alder reactions as outlined ia Eigure 8. 

Reportedly, OjoCdiaHylbispheaol A is an attractive comonomer for bismaleimides because the corresponding copolymer is tough and temperature resistant (41). Toughness, however, is a function of the BMI—diaHylbisphenol A ratio employed. In one study optimized toughness properties were achieved when BMI and diaHylbisphenol were employed at a close to 2 1 molar ratio (42). In Table 9, the mechanical properties of BMI—bis(3-allyl-4-hydroxyphenyl)-7 -diisopropylbenzene resias are provided, showiag optimized properties for the 60/40 BMI—diaHylbisphenol composition. The 0,(9 diaHylbisphenol A is commercially available under the trademark Matrimide 5292. Another bisaHylphenyl compound is available from SheH Chemical Company/Technochemie under the trademark COMPIMIDE 121. 

Table 9. Mechanical Properties of BMI—bis(3-allyl-4-hydroxyphenyl)-/ -diisopropylbenzene Blends ...

---