Crystallization and polymerization of 6-aminocaproic acid as simultaneous processes

Vapor of 6-aminocaproic acid (ACA) at a pressure of 0.12 mm Hg was observed to polymerize when placed in the presence of different types of surfaces, crystalline and amorphous, at temperatures around 170°C. Two clearly distinct stages of the process could be detected. The first was an induction period, during which the polymer phase must be nucleated. The length of this nucleation stage depended on factors not well understood. In the second stage, polymer was produced at a constant rate which seemed to be related to the vapor pressure of ACA. The polymer produced consisted of the characteristic radiating arrays of ribbonlike crystals known as spherulites. The spherulites, in turn, were made up of primary and secondary lamellae about 90 Å thick. Electron diffraction studies showed that the polymer chains were folded within the lamellae. Further it was proved by chemical and crystallographic arguments that adsorption and polymerization should be simultaneous processes.