Amines, multifunctional

Eor more demanding uses at higher temperatures, for example, in aircraft and aerospace and certain electrical and electronic appHcations, multifunctional epoxy resin systems based on epoxy novolac resins and the tetraglycidyl amine of methylenedianiline are used. The tetraglycidyl amine of methylenedianiline is currently the epoxy resin most often used in advance composites. Tetraglycidyl methylenedianiline [28768-32-3] (TGALDA) cured with diamino diphenyl sulfone [80-08-0] (DDS) was the first system to meet the performance requirements of the aerospace industry and is still used extensively. 

The polybenzoxazines (PBZs) provide a new class of phenolic resins that were first described by Ishida in 1998 (Ref. 15). Synthesis of the resins involves three components a phenol, a primary amine and formaldehyde. The first stage involves the formation of a multifunctional benzoxazine monomer Figure 23.30 a)). The monomer can then be ring-opened at elevated temperatures (160-220 C) to yield a polymeric stmcture (Figure 23.30(b)). 

An alkene activated by an electron-withdrawing group—often an acrylic ester 2 is used—can react with an aldehyde or ketone 1 in the presence of catalytic amounts of a tertiary amine, to yield an a-hydroxyalkylated product. This reaction, known as the Baylis-Hillman reaction, leads to the formation of useful multifunctional products, e.g. o -methylene-/3-hydroxy carbonyl compounds 3 with a chiral carbon center and various options for consecutive reactions. 

Where sodium sulfite is added as a component of multifunctional or one-drum products designed for smaller boilers, no cobalt catalyst is added because of the cobalt alkaline precipitation problem. Consequently, if the FW temperature is low this type of formulation is unsuitable because the sulfite requirement will be too high and the available reaction time too short. Probably a tannin-based, one-drum product would be more suitable (although here again there may be a problem because tannin-based products, unlike sulfite cannot be mixed with amines). 

Amines can be blended into multifunctional product formulations containing alkali, polymer, and phosphate and where sulfite- or hydrazine-based oxygen scavengers are part of the formula, but not where tannins are employed. Amines must be fed separately from tannins. 

PAMAM dendrimers are synthesized in a multistep process. Starting from a multifunctional amine (for example ammonia, ethylenediamine, or tris(2-amino-ethyl)amine) repeated Michael addition of methylacrylate and reaction of the product with ethylenediamine leads to dendrimers of different generation numbers [1,9]. Two methylacrylate monomers are added to each bifunctional ethylenediamine generating a branch at each cycle. Unreacted ethylenediamine has to be completely removed at each step to prevent the initiation of additional dendrimers of lower generation number. Excess methylacrylate has also to be removed. Bridging between two branches of the same or of two different dendrimers by ethylenediamine can also be a problem, and has to be avoided by choosing appropriate reaction conditions. 

Epoxy (Amine-Cured) Bisphenol A-based epoxy resins used for composite fabrication are commonly cured with multifunctional primary amines. For optimum chemical resistance these generally require a heat cure or postcure. The cured resin has good chemical resistance, particularly to basic environments, and can have good temperature resistance. 

Three factors determine the effectiveness of antioxidants in polymers, namely (i) intrinsic molar activity (ii) substantivity in the polymer and (iii) solubility in the polymer. Multifunctional AOs combine multiple functions in one molecule. Sterically hindered amine stabilisers (HAS), such as Chimassorb 944, Tinuvin 622 and Tinuvin 783 are prime examples. 

Normally the reaction Is useful for the conversion of alkyl halides to primary amines without concomitant formation of secondary amines.29 Treatment of polymer 17 with hexamethylenetetramine in a mixture of ethanol/THF afforded an insoluble resin. Using diazabicyclooctane (DABCO), we demonstrated that the reaction could be limited to attack by a single nitrogen in a multifunctional amine, so we did not anticipate crosslinking via bis-quat salt formation. Hydrolysis of 2 with anhydrous HC1 in ethanol generated free amino groups as evidenced by a positive ninhydrin test, but quantitative hydrolysis could not be achieved and the product remained insoluble. One would have expected a simple bis-quat to hydrolyse and open the crosslinked structure. 

A second method of immunotoxin preparation by reductive amination involves the use a polysaccharide spacer. Soluble dextran may be oxidized with periodate to form a multifunctional crosslinking polymer. Reaction with antibodies and cytotoxic molecules in the presence of a reducing agent forms multivalent immunotoxin conjugates. The following sections discuss these options. 

Figure 25.13 Polyaldehyde dextran may be used as a multifunctional crosslinking agent for the coupling of amine-containing molecules. Reductive amination creates secondary amine or tertiary amine linkages.

Sequential hydroformylation/reductive amination of dendritic perallylated polyglycerols with various amines in a one-pot procedure to give dendritic polyamines in high yields (73-99%). Furthermore, the use of protected amines provides reactive core-shell-type architectures after deprotection. These soluble but membrane filterable multifunctional dendritic polyamines are of high interest as reagents in synthesis or as supports in homogeneous catalysis as well as nonviral vectors for DNA-transfection (Scheme 18) [65]. 

Figure 19. Multifunctional nature of quinine as a catalyst. The various parts of the molecule fill the following roles (a) hydrogen bond forming ligand forming with metals (b) basic amine (c) aliphatic hydrocarbon—bulk (d) handle to modify (e,f) epimers available few conformers (g) aromatic hydrocarbon—bulk, polarizable (h) handle to modify steric and polar influence.

Ciba/Geigy NOV/AR 2 Multifunctional Novolac Aromatic Amine 100 46 10-11 254-279... 

Enantiomerically pure 3-amino alcohols which are important intermediates for many bioactive compounds can be directly synthesized by the ARO reaction of readily accessible racemic and meso epoxides with appropriate amines. Indeed, some simple and multifunctional p-amino alcohols have been obtained using this strategy by the promotion of chiral BINOL [30-32,88,89], salen [35,52], bipyridine [33,40,90-94] and proline-A,JV-dioxide based metal complexes [95]. However, none of these systems demonstrated the recyclability of the precious chiral catalyst. 

Figure 13.13 Multifunctional anticancer poly(amido amine) (PAMAM) dendrimers. Clockwise from top diol, taxol, fluorescein isothiocyanate, foUc acid, and acetyl groups.

In order to keep polyamides soluble in relatively apolar solvents, the use of flexible (macro)monomers such as a, co-(diaminopropyl)polydimethylsiloxane [52] or oligoethyleneglycol-based diamines [53, 54] has been proven to be a successful approach (Fig. 10). Poly condensations of dimethyl adipate with a variety of diamines were successful in bulk and at moderate temperatures between 60 and 100 °C (reaction A in Fig. 10). The low temperatures (60-100 °C) that suffice in these polymerizations also allow the use of monomers that are thermally instable, such as diethyl fumarate [53]. Moreover, multifunctional amines could be regioselectively polymerized up to molecular weights of 9 kDa, making lipase catalysts a valuable tool for the preparation of well-defined polyamides that can be further functionalized with active groups. 

It has been suggested in the literature that the a-amino radical is the species that initiates polymerization [210], This view is supported by our observation that, in spite of the relatively high quenching rate constant of Eosin triplet by triphenylamine (Table 5), the system Eosin-triphenylamine does not sensitize the photopolymerization of multifunctional acrylates. Thus, it is necessary that the amine contains a hydrogen at the a-carbon to be released as a proton after oxidation of the amine by the dye triplet. This deprotonation prevents the back electron transfer and forms a carbon radical that is sufficiently long-lived to be captured by the monomer. 

DIAMINES AND HIGHER AMINES, ALIPHATIC. The aliphatic diamine and polyaminc family encompasses a wide range of multifunctional. mullireactivc compounds. This family includes ethylenediamine I EDA) and its homologues. the polyethylene polyamines (commonly referred to as ethyleneainines). the diaminoprnpancs and several specific alkancdiamines. and analogous polyamines. The molecular structures of these compounds may be linear, branched or cyclic, or combinations of these. 

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