冰冻升华极稀溶液制备的iPS超细粉末结晶的结构与性质

Crystal Structures of Isotactic Polystyrene Ultrafine Particles

高分子在浓度低于动态接触浓度ｃｓ的极稀溶液中以单链形式存在［１，２］，用冰冻升华法将极稀溶液中的溶剂除掉可获得高分子的超细粉末．这些超细粒子与普通的聚合物相比，比表面积大，高分子链之间缠结程度小，有可能表现出特殊的物理性质．本文用示差扫描量热计（ＤＳ...

Ultrafine particles, with average equivalent diameters in the range of 60～330 nm, prepared by freeze drying very dilute(about 2×10 -5 g/mL) solutions of isotactic polystyrene in benzene at 0 ℃ were studied by TEM and DSC, respectively. It was found that two different structures of widely different thermal stabilities can form at identicaltemperatures. One melt(mode A) at 220 ℃ just as the recognized structure of isotactic polystyrene(3 1 helix). The other(mode B) melt at 65 ℃ and produced distinct electron diffraction patterns which, however, differ decisively from those provided by crystals A. The melting point of crystals B is also significantly lower than those of iPS dried gel crystals, which give an endotherm at 120 ℃ in calorimetric measurements. According to 13 C NMR measurement, the material used in this study should be practically fullyisotactic.