摘要
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.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
1998年第9期1526-1528,共3页
Chemical Journal of Chinese Universities
基金
国家"攀登计划"
自然科学基金