Polyamides halogenation reaction

Some of the most familiar reactions falling into the polycondensation class are those leading to polyamides derived from dicarboxylic acids and diamines, polyesters from glycols and dicarboxylic acids, polyurethanes from polyols and polyisocyanates, and polyureas from diamines and diisocyanates. Similar polymer formations utilizing bifunctional acid chlorides with polyols or polyamines also fall into this class. The condensations of aldehydes or ketones with a variety of active hydrogen compounds such as phenols and diamines are in this group. Some of the less familar polycondensation reactions include the formation of polyethers from bifunctional halogen compounds and the sodium salts of bis-phenols, and the addition of bis-thiols to diolefins under certain conditions. 

Aliphatic and alicyclic molecules such as cyclohexane undergo photosubstitution with nitrosyl chloride (Pape, l%7). The reaction is of considerable industrial importance in the synthesis of 6-caprolactam, an intermediate in the manufacture of polyamides (nylon 6). (Cf. Fischer, 1978.) At long wavelengths a cage four-center transition state between alkane and an excited nitrosyl chloride molecule is involved, as indicated in Scheme 63. In contrast to light-induced halogenation, photonitrosation has a quantum yield smaller than unity, and is not a chain reaction. 

Work in Russia has shown that the use of elemental silicon plus tin chloride can enhance the flame retardancy of both polypropylene and polyamide 66 compounds. Silicon tetrahalides are formed in the gas phase of combustion and inhibit the chain reactions that develop in a fire. These silicon halides do not act like halogen hydrocarbons in the atmosphere so there is no likelihood of contributing to ozone depletion. 

An early example is the reaction of halogen-capped polymers with sodium azide. " A diazido-terminated PS prepared in this way could be fiirther reduced with tri(n-butyl)phosphine in THF in the presence of water (moisture) to yield a well-defined diamino-terminated polymer that, in turn, could be used in a step-growth process with terephtha-loyl chloride, leading to polyamides with controlled-length PS segments. The expansion of the ability to S3mthesize new materials by combining dick chemistry and ATRP has been reviewed.""" "... 

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