Amination reactions oligomer synthesis

In the case of phenol, with the free para position, due to the interaction between the phenolic group (acidic) and the aminic nitrogen (basic) of the amino alcohol, the ortho position is occupied first [9]. After the synthesis of Mannich bases, the water resulting from the reaction and the water from the aqueous solution of formaldehyde is distilled under vacuum, at 90-125 °C (preferably in the range 90-100 °C). A low range of distillation temperatures is preferred in order to avoid the tendency of the Mannich base to condensate to superior oligomers (with 2-3 aromatic nuclei), which increase substantially the viscosity of Mannich base and, of course, of final Mannich polyol. The mechanism of the Mannich reaction is considered to be a two-step mechanism. In the first step the reaction between formaldehyde and the primary or secondary amine (reaction 15.2) takes place, with the formation of an immonium cation [7-9, 22, 23]. 

The copolymer synthesis was carried out in a three neck round bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer and a condenser with drying tube. The stoichiometry was offset by using an excess of the polyimide oligomer. In every case, the calculated was 40,000 g/mole. The polyimide oligomer was dissolved in chlorobenzene and heated to -125 C. The amine terminated oligomer was added slowly and rinsed with chlorobenzene to bring the final reaction solids content to 15 percent. The reaction was stirred at -125 C for 2 hours. The solution was cooled to ambient temperatures and cast into films. The films were heated slowly in a vacuum oven and dried for at least 3 hours at 250°C. 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

An interesting procedure has been proposed for the synthesis of amylose-b-PS block copolymers through the combination of anionic and enzymatic polymerization [131]. PS end-functionalized with primary amine or dimethylsilyl, -SiMe2H groups were prepared by anionic polymerization techniques, as shown in Scheme 56. The PS chains represented by the curved lines in Scheme 56 were further functionalized with maltoheptaose oligomer either through reductive amination (Scheme 57) or hydrosilyla-tion reactions (Scheme 58). In the first case sodium cyanoborohydride was used to couple the saccharide moiety with the PS primary amine group. 

Additional work was carried out by the GE group on optimization of the reaction yield and to eliminate unwanted linear oligomers [14], Three side reactions which interfere with synthesis of cyclics were identified reaction of the amine with acid chloride to form an acyl ammonium salt, followed by decomposition to an amide (Equation (3.2)) reaction with CH2CI2 to form a salt (Equation (3.3)) hydrolysis of the acid chloride, forming carboxylate via catalysis... 

The key to a controlled molecular weight build-up, which leads to the control of product properties such as glass transition temperature and melt viscosity, is the use of a molar excess of diisopropanolamine as a chain stopper. Thus, as a first step in the synthesis process, the cyclic anhydride is dosed slowly to an excess of amine to accommodate the exothermic reaction and prevent unwanted side reactions such as double acylation of diisopropanolamine. HPLC analysis has shown that the reaction mixture after the exothermic reaction is quite complex. Although the main component is the expected acid-diol, unreacted amine and amine salts are still present and small oligomers already formed. In the absence of any catalyst, a further increase of reaction temperature to 140-180°C leads to a rapid polycondensation. The expected amount of water is distilled (under vacuum, if required) from the hot polymer melt in approximately 2-6 h depending on the anhydride used. At the end of the synthesis the concentration of carboxylic acid groups value reaches the desired low level. 

The alkyl-, alky laryl- and diarylcarbodiimides are the diimides derived from carbon dioxide, however, no direct formation of carbodiimides from amines and carbon dioxide is known. Interestingly, carbodiimides can be obtained from amines and carbon dioxide via a switteri-onic titanium complex (see Section 2.2.8). The major starting materials for the synthesis of carbodiimides are isocyanates, 1,3-disubstituted ureas or 1,3-disubstituted thioureas. The synthesis of isocyanates requires the use of the toxic carbonyl chloride or its oligomers. A book on the synthesis and reactions of isocyanates appeared in 1996. ... 

Synthesis of piperazine-terminated oligomers as prepolymers for interfacial membrane formation was also examined.46 48 Excess piperazine was reacted with di- and triacyl chlorides in an inert solvent such as 1,2-dichloroethane. The resulting amine-terminated polyamide oligomers had low solubility in the solvent system and precipitated. This served to limit the degree of polymerization of the oligomer. Even so, a portion of the product was insoluble in water and was filtered out during preparation of the aqueous oligomeric amine solution for the interfacial reaction step. 

The Effect of Amine Structure In order to evaluate the effects of eunine functionality and substitution on the crosslinking reaction/ several amine terminated urethane oligomers were synthesized by the same procedure as used in the synthesis of the LPUR. The oligomers were prepared in Urethane Grade MEX. These amines were evaluated with the allyl terminated unsaturated polyester as the unsaturation source. The composition and the properties of the oligomers are shown in Table IV. 

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