Morphology of mesophase and crystals of polyamide 6 prepared in a fast scanning chip calorimeter

Atomic force microscopy (AFM) has been employed to study the effect of the pathway of nucleation/crystallization on the morphology of the ordered phase of polyamide 6 (PA 6). Samples of PA 6 were crystallized or ordered at different supercooling of the melt, to obtain either α-crystals or γ-mesophase, respectively. For improved control of the nucleation pathway, samples for AFM analysis were for the first time prepared using a fast scanning chip calorimeter (FSC). It has been found that melt-crystallization at low supercooling is connected with the formation of lamellae, while the mesophase formed at high supercooling is of non-lamellar shape. In case of cold-crystallization, the final semicrystalline structure depends on the heating rate; slow heating first leads to formation of mesophase nodules which then reorganize to crystals at elevated temperature, while fast heating suppresses the formation of mesophase and allows direct transformation of supercooled liquid to lamellae. The general approach of using FSC for AFM sample preparation has been confirmed by analysis of the effect of the thermal pathway of ordering/crystallization on the structure of an isotactic polypropylene.