Creation of Polymer Nano-Particles from Solution Crystallization

Nano-structured spherical particles of polyamide-6 (N6) are generated by rapid mixing of a cresol solution of N6 with an aqueous solution of methanol. Their structures and morphologies are studied vs. relative compositions of N6 and solvent molecules. Very slow crystallization at compositions near the boundary of crystal-solution phase separation brings about precipitates of axialite-like or fiber-like morphology. On the contrary, rapid crystallization far from the phase boundary, thereby with much larger supersaturation, is found to generate spherical particles with peculiar nano-scale structures. Light scattering and small angle X-ray scattering from the particles show that the structure of the particle is similar to the usual spherulites in bulk N6, but with a smaller long period and a more ordered stacking of the constituent lamellae.