Two Growth Modes of Semicrystalline Cylindrical Poly(ε-caprolactone)-b-poly(ethylene oxide) Micelles
Two Growth Modes of Semicrystalline Cylindrical Poly(ε-caprolactone)-b-poly(ethylene oxide) Micelles
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DOI：
10.1021/ma301267k
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发表时间：
2012-12-25
期刊：
影响因子：
5.5
通讯作者：
Fan, Zhi-Qiang
中科院分区：
文献类型：
--
作者：
He, Wei-Na;Zhou, Bing;Fan, Zhi-Qiang
将聚（ε -己内酯）-b-聚（环氧乙烷）嵌段共聚物（PCL59-b-PEO113）的胶束在不同的混合溶剂中保持在53℃下5 mm，制备了具有不同胶束形态和胶束半晶种子量的种子溶液。采用高分辨率透射电子显微镜（HRTEM）和选择区域电子衍射（SAED）对种子胶束的结晶度进行了鉴定。结果表明，在H2O/THF （5/1 v/v）和H2O/二氧六烷（5/1 v/v）混合溶剂中加热胶束溶液形成的球状胶束多为非晶态，在H2O/DMF （5/1 v/v）混合溶剂中形成的球状胶束和短半晶圆柱形胶束的混合物，而在H2O/DMSO （5/1 v/v）混合溶剂中形成的圆柱形胶束多为短半晶。将种子溶液置于4℃下进行胶束生长。透射电子显微镜（TEM）观察发现，形成核心的PCL链在外延结晶的驱动下发生了胶束生长，并且随着时间的推移，生长的圆柱形胶束的长度增加。观察到两种生长模式。一是在水/DMF （5/1 v/v）的胶束溶液中，在半晶圆柱形胶束的活性端生长单晶（或非晶球形胶束）。另一种是圆柱形胶束在H2O/DMSO （5/1 v/v）中端对端耦合生长。胶束生长的动力学与生长机制密切相关。柱状胶束在H2O/DMF （v/v）溶液中的生长速度明显快于在H2O/DMSO （5/1 v/v）溶液中的生长速度。在长时间尺度上，在H2O/DMF （5/1 v/v）和H2O/DMSO （5/1 v/v）溶液中，半晶圆柱形胶束端到端耦合的胶束生长速度较慢，且在H2O/DMF （5/1 v/v）溶液中的生长速度比在H2O/DMSO （5/1 v/v）溶液中的生长速度更慢。
The micelles of a poly(epsilon-caprolactone)-b-poly(ethylene oxide) block copolymer (PCL59-b-PEO113) in different mixed solvents were held at 53 degrees C for 5 mm, and seed solutions with different micellar morphologies and amounts of micellar semicrystalline seeds were prepared. The crystallinity of these seed micelles was identified by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). It is found that mostly amorphous spherical micelles are formed by heating micellar solutions in H2O/THF (5/1 v/v) and H2O/dioxane v/v) mixed solvents, a mixture of amorphous spherical micelles and short semicrystalline cylindrical micelles is yielded in H2O/DMF (5/1 v/v), whereas mostly short semicrystalline cylindrical micelles are obtained in H2O/DMSO (5/1 v/v) mixed solvent. The seed solutions were placed at 4 degrees C for micellar growth. Transmission electron microscope (TEM) shows that micellar growth driven by epitaxial crystallization of core-forming PCL chains takes place and the length of grown cylindrical micelles increases with time. Two growth modes are observed. One is the growth of unimers (or amorphous spherical micelles) on the active ends of semicrystalline cylindrical micelles in micellar solution in H2O/DMF (5/1 v/v) at the initial growth period. The other is the growth by end-to-end coupling of cylindrical micelles in H2O/DMSO (5/1 v/v). The kinetics of micellar growth is strongly dependent on the growth mechanism. The growth of the cylindrical micelles in the H2O/DMF v/v) solution is much faster than that in the H2O/DMSO (5/1 v/v) solution. On long time scale, micellar growth by end-to-end coupling of semicrystalline cylindrical micelles occurs with slow rate in both H2O/DMF (5/1 v/v) and H2O/DMSO (5/1 v/v) solutions, and the growth rate in H2O/DMF (5/1 v/v) solution is even slower than that in H2O/DMSO (5/1 v/v).