New observations on the formation of "row-nucleated" structures of isotactic polystyrene

A unique 60 degrees C endothermic peak was found in the differential scanni ng calorimetry (DSC) measurement of freeze-dried isotactic polystyrene (i-P S) prepared from a 0.01 wt % benzene solution. While i-PS was melted before preparing a solution at a temperature beyond the equilibrium melting point , nothing could be observed around 60 degrees C. The endotherm can be attri buted to the melting of microgel crystals. Morphology observation revealed that ribbonlike films of i-PS were formed when the solution was spread on a cold water surface. After isothermal crystallization of the films, "row-nu cleated" crystals were grossly produced without any extensional deformation of molecular chains. It is suggested that microgel crystals may act as het erogeneous species to initiate the growth of "row-nucleated" crystals.