Silylated diamines

The utilization of N-silylated diamines as polyamide and polyimide forming monomers has recently been exhaustively reported by Kakimoto et al. [105] and Oishi et al. [106]. But their work is beyond the scope of this... 

The polymerization of aromatic diamines with acid chlorides in solution works well.7 914 35 The basicity of the aromatic diamine is low and acid binding can be achieved with several compounds and even solvents such as TV-methylpyrrolidonc (NMP) and dimethylacetamide (DMAc). The all-para aromatic amide poly(p-phenyleneterephthalamide) can be synthesized in DM Ac.7,9,14 To prevent precipitation of the polymer, a salt such as calcium chloride or lithium chloride can be added. It is also possible to react the acid chloride with a silylated diamine ... 

Acid chlorides are very reactive and at room temperature react readily with amines. Synthesis by interfacial and solution methods is possible. However, care should be taken that the hydrochloric acid produced does not react with unreacted amine groups. With the strong basic aliphatic diamines, the acid binder must preferably be even more basic. The attainable molecular weights are strongly dependent on the concentrations this is particularly the case for easily precipitated terephthalamide polymers. Possible problems with the acid binder can be overcome by starting with silylated diamines.33,34 A typical example for interfacial polymerization of terephthalamides is PA-2,T.66... 

Example 20. Poly(p-phenylene terephthalamide) by silylated diamines.33... 

Silylated diamines, 156, 187-188 Silylated monomers, 72 Silylation, distillation and, 338 6NT6 alternating polyesteramide, synthesizing, 189-190 6,6 -linked polymers, 480 Size exclusion chromatography (SEC) analyses, 90, 490 Slabstock foam, 233-234 Slow monomer addition, 57 Small-angle neutron scattering (SANS), 282... 

Mamyama et al.25 have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A,A 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoro-propane (25) with aromatic diacids and subsequent thermal cyclodehydration of the resulting poly(o-hydroxy amide)s in vacuo. In this method, aromatic diamines with low nucleophilicity are activated more positively through the conversion to the /V-silylated diamines, and the nucleophilicity of the fluorine-containing bis(o-aminophenol) can be improved by silylation. 

The diazepine 85 (tetramethyleneurea) has been prepared by a variety of routes. Among these are the treatment of tetramethylene diisocyanate with water,70-72 the rearrangement of the oxime (86) in polyphosphoric acid,73,74 and the reaction of 1,4-diaminobutane with sulfur, methanol, and carbon monoxide at high pressure.75 A novel preparation of 85 involves the reaction of 1,4-diaminobutane with 87 to give the silylated diamine (88). Reaction of 88 with phosgene and triethylamine yielded the bistrimethylsilyldiazepine (89) which was then hydrolyzed in aqueous ethanol to give 85.76... 

With certain silylated diamines, phosgene reacts to form the corresponding substituted urea. Equations (10.30) (n = 3 or 4) and (10.31) [197a]. However, for longer chains, viz. Me3SiNH(CH3) NHSiMe3 when n = 6, the expected diisocyanate, OCN(CH2)gNCO is formed [2133]. 

Preparations of poly-p-phenyleneterephthalamide by polycondensations with N-silylated diamine proceed more rapidly than with the parent diamine.In addition, the products have higher molecular weights than a similar commercial material made from the parent diamine and sold under the trade name of Kevlar. 

Silylated diamines can also condense with diphenyl esters of aromatic dicaiboxylic acids ... 

The reaction is kept between 120 and 200°C [91]. In place of isocyanates, it is also possible to use aldimines or ketimines, as well as silylated diamines. 

The N-silylated diamine method has several advantages over conventional condensation procedures ... 

The most widely employed synthetic route to aramids is based on the polycondensation of dicarboxylic acids with diamines in the presence of condensing agents. Good reviews on the synthesis of aramids have recently appeared (1-3). Recently, promising alternative synthetic routes to aramids have been reported and are described herein. These include the polycondensation of N-silylated diamines with diacid chlorides, the addition-elimination reaction of dicarboxylic acids with diisocyanates, and the palladium-catalyzed carbonylation polymerization of aromatic dibromides, aromatic diamines and carbon monoxide. 

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