A real-time AFM study on crystal nucleation and growth in nanodroplets of isotactic polypropylene

Isotactic polypropylene (iPP) nanodroplets were prepared by using the classical droplet method in this study. The formation of nanodroplets allowed the controlled observation of polymer nucleation as well as access to crystal growth at exceptionally high supercooling in iPP. Three cases including the heterogeneous nucleation and fast crystallization in iPP droplets, the formation of multiple independent homogeneous nuclei within a single droplet and a single nucleus within a single droplet were detected by using atomic force microscopy (AFM) during gradually cooling after remelting the nanodroplets. Moreover, it is found that when the volume of droplet is larger than the value of ca. 130000 nm3, the first case was observed. Otherwise, the latter two cases appeared. The temperature at which the onset of nucleation was observed in individual droplets was found to be mainly dependent on height of the droplets when the size scale of the droplet is comparable to the size of the critical nucleus in at least one dimension, which indicates the nucleation behavior under confinement.     

嵌段共聚物胶束薄膜空穴化结构形成的研究

用原子力显微镜研究了嵌段共聚物胶束薄膜的空穴化结构.结果表明,嵌段共聚物胶束薄膜的空穴化强烈地依赖于所用酸中氢离子的数目,只有使用一元酸时才能得到空穴化结构,而二元酸和三元酸都得不到空穴化结构.提出了形成空穴化结构可能的机理.运用选择性溶剂蒸气和一元酸分别处理胶束薄膜,得到了相同的表面形貌.