CRYSTAL-STRUCTURES OF ISOTACTIC POLYSTYRENE ULTRAFINE PARTICLES

Ultrafine particles, with average equivalent diameters in the range of 60 similar to 330 nm, prepared by freeze-drying very dilute(about 2x1 0(-5)g/mL) solutions of isotactic polystyrene in benzene at 0 degrees C were studied by TEM and DSC, respectively. It was found that two dif ferent structures of widely different thermal stabilities can form at identical temperatures. One melt (mode A) at 220:degrees C just. as th e recognized structure of isotactic polystyrene(3(1) helix). The other (mode B) melt at 65 degrees C and produced distinct electron diffract ion patterns which, however, differ decisively from those provided by crystals A. The melting point of crystals B is also significantly lowe r than those of iPS dried gel crystals, which give an endotherm at 120 degrees C in calorimetric measurements. According to C-13 NMR measure ment, the material used in this Study should be practically fullyisota ctic.