Nylon-6,6 oligomers : Synthesis, characterization and relevance to the polymer.

The primary aim of this work is the investigation of potential routes for the synthesis of selected oligomers of nylon-6.6 and trial syntheses using these routes. Once a general synthetic route to pure oligomers is available it can be applied to the preparation of oligomers of increasing length, while maintaining purity for future characterization studies. It was soon found that the "nylon intermediates" are not readily amenable to the reaction conditions involved in more conventional syntheses due to solubility, lability etc. Because of this the project rapidly developed into a series of problem solving episodes.Although the project was intended only to deal with integer oligomers problems concerning the protecting groups arose. A new direction was temporarily taken involving the synthesis of non-integer oligomers. Here the need for selective deprotection was no longer a factor as chain-growth products would have identical end groups.With no satisfactory method for selective removal of the carbobenzoxy group, the doubling reactions on integer oligomers had to be carried out using unprotected andN-protected monomers. The presence of these two products in the synthesis of the dimer could obviously lead to over reaction. However in the mixed anhydride reaction the acid end group on the N-protected monomer is activated prior to the addition of the unprotected monomer thus eliminating, or certainly reducing, this potential problem. The scheme was successfully taken up to a D.O.P. of eight although the purity of the octamer was lower than would have been liked. IR, MS, NMR and GPC were used throughout the synthetic work to determine the purity and identity of each product.